A Raised Bed Rebuttal: In defense of a common garden practice and soil health

One of the things I miss (and sometimes don’t miss) after my move from West Virginia to Nebraska is writing my weekly garden column for the Charleston Gazette-Mail newspaper.  It was a great way to always keep thinking about new things to talk about and a great way to connect with the public.

After I left, the newspaper replaced me with a team of 4-5 local gardeners who would take turns writing about their different gardening insights and experiences.  Some have been really good, like the ones who were my former Master Gardener volunteers.  However, sometimes I find the bad information and attitude of one of the writers off-putting and even angering.

Take for example this missive which equates sustainable agriculture (a term which is pretty well defined as a balance of environmental stewardship, profit, and quality of life) solely to permaculture and biodiversity while espousing an elitist attitude about “no pesticides, no fossil fuels, no factory farms, growing all you need locally and enhancing the land’s fertility while you’re at it.”  He got all this from an old photo of dirt poor farmers who were apparently practicing “permaculture” – which I’m sure was foremost on their minds while they were trying not to starve to death.  The fact is that our food system (and the food that today’s low income families) depends on comes from a mix of small and large farms. And most of those “factory farms” are actually family owned, and not everyone can afford to grow their own food or pay the premium for organic food (which still has been treated with pesticides and is in no way better or healthier than those conventionally grown).

Now, I know I no longer have a dog in that fight, but when I see bad information, especially when it is aimed toward an audience that I care deeply about I just have to correct it.  So two weeks ago when I saw his latest gem of an article berating a woman (and basically anyone) for using lumber (and those who work as big box store shills to promote them) to build raised bed gardens and should instead till up large portions of their yard for the garden I was aghast.  Putting aside the horrible advice to till up the garden (which we’ll talk about in a minute) or the outdated recommendation of double digging (proven to have no benefit), that advice is just full of elitist assumptions toward both the gardener and toward the technique. It is especially ridiculous and ill-informed to suggest that tilling up a garden and destroying the soil structure is much better ecologically speaking that using a raised bed (and we’ll talk about why in a little bit).

Don’t want to do a raised bed?  Fine, it isn’t for everyone.  But that doesn’t mean you should go out and till up a large patch of land that will degrade the soil, lead to erosion and runoff, and reduce production.  It does not do anything to improve drainage nor aeration.

So let’s do a breakdown of why I find this article, its assumptions, and bad science so distasteful:

Bad Assumptions (and you know what they say about assuming)

The gardener didn’t have a reason for a raised bed other than she had been told that’s the way you do it.

This assumption fails to take into account the many different reasons why a gardener may prefer to use a raised bed.  Does she or a family member have mobility limitations where a raised bed would provide access to be able to garden?  Or does she have space limitations for a large garden patch?  Would a raised bed make it easier for her to manage and maintain the garden?  Making a blanket pronouncement against the technique fails to use empathy to see if it actually would make gardening more accessible or successful for the gardener. Is she wanting a raised bed because the soil in the ground at her house is too poor or contaminated?  West Virginia is notorious for having heavy clay, rocky soil that is pretty poor for growing most crops.  It can take years of amending to get it even halfway acceptable for gardening.  Or perhaps she lives on a lot that had some sort of soil contamination in the past and she’s using raised beds to avoid contact with the contaminated soil.

Raised beds also have some production advantages – the soil heats up faster in the spring, allowing for earlier planting.  A well-built soil also allows for improved drainage in areas with heavy soil or excess moisture.

The gardener has access to equipment to till up a garden space, have the physical strength and endurance to hand dig it, or is she able to afford to pay someone to do it for her?

Raised beds can often be easier for gardeners to build and maintain, often not needing special equipment or heavy labor.  If the gardener isn’t supposed to benefit from these efficiencies, how will she go about tilling up the soil for her new garden.  Does she or a friend/neighbor have a rototiller or tractor she can use?  Is she physically capable of the often back-breaking work of turning the soil by hand?  Or does she have money to pay someone to do it for her?  So these “cheaper and easier” methods he describes could actually end up costing more and being harder than building a raised bed.

The raised bed has to be built out of lumber, which apparently only comes from the Pacific Northwest and is a horrible thing to buy. First off, raised beds can be built out of a number of materials.  The list usually starts with lumber.  Some people tell you to use cedar (which does primarily come from the PNW), since it is more resistant to decay, but plain pine that’s treated with a protective oil or even pressure treated is fine (it used to be not OK back before the turn of the century when it was treated with arsenic, but most experts now say it is OK since it is treated with copper).  The dig against the PNW lumber industry is as confusing as it is insulting, since there’s lots of lumber produced on the east coast, and even a thriving timber industry right in West Virginia.  Most lumber these days is harvested from tree farms specifically planted for the purpose or by selective timbering that helps manage forest land for tree health and sustainability.

The list can go on to include landscaping stone, concrete blocks, found materials like tree branches, and on and on.  These days, you can even buy simple kits you can put together without tools and with minimal effort that are made of high-grade plastic or composite lumber.  They’re getting cheaper every year, and can be especially affordable if you find a good sale or coupon.

Heck, a raised bed doesn’t even require the use of a frame at all….just a mound of well amended soil in a bed shape will do.  No need to disturb the soil underneath, just get some good topsoil/garden soil in bulk or bags from your favorite garden center, mix it with a little good compost, and layer at least 6 inches on top of the soil.  Use a heavy mulch on top if you are afraid of weeds coming up through the new soil.

The soil she’d buy is trucked in from Canada.

I’m guessing this has some sort of assumption that the soil a gardener should be putting a raised bed is like a potting mix composed primarily of peat moss. While many gardeners are trying to decrease the use of peat moss, which is a non-renewable resource harvested from Canadian peat bogs, the recommended soil for a raised bed is not potting mix or one that even contains a large amount of organic material.  The recommended composition of raised bed soil is largely good quality top soil, which is usually sourced locally, mixed with a bit of compost which could be from home compost, a local municipal composting facility or producer, or from a bagged commercial product that is likely from a company that diverts municipal, agricultural, and food wastes into their product.

Bad Advice based on Bad Science (or lack thereof)

Tilling or disturbing the soil is a common and acceptable way to prepare a garden.

More and more evidence is emerging that tilling or disturbing the soil is actually one of the worst things you can do in terms of both production and environmental impact in agricultural production.  First, tilling disturbs and in some cases destroys the soil structure.  Destroying the soil structure allows for increased erosion, especially when the bare soil is washed away during heavy rains or blown away in heavy winds.  Excess tillage and wind is what actually led to the dust bowl, which actually led to the early promotion of conservation tillage practices through government programs like Conservation Districts (and also gave us some great literature, thanks to John Steinbeck).  Aside from the soil particles that erode, having open, tilled soil leads to nutrient runoff that contribute to water pollution.

 One other structure negative is the production of a hardpan or compressed layer of soil that occurs just below the tilled area.  This results from the tines of a tiller or cultivator pressing down on the soil at the bottom of where it tills and can drastically reduce the permeation of water and gasses through the soil.

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Soil Aggregates and microbes

The aggregates in the structure of un-disturbed soil provide myriad benefits to soil health, especially in providing the capacity for the growth of good microorganisms.  Studies have shown that the population of soil microbes is drastically higher in agricultural soils that haven’t been tilled.  Therefore, tillage reduces soil biodiversity.

One of the reasons for increased soils microbes in no-till soil is an increase in soil organic matter.  No-till allows for some crop (roots, etc) to remain in the ground and break down.  Tillage also incorporates more air into the soil, which does the same thing that turning a compost pile does – it allows the decomposition microbes to work faster in breaking down organic matter.  This increased activity then decreases the amount of organic matter.  So tilling the soil actually reduces organic matter.  The structure and organic matter also allows no-till soil to have a higher Cation Exchange Capacity, or ability to hold nutrients.

When the carbon in the organic matter in the soil is rapidly depleted after tillage, it doesn’t just disappear.  The product of the respiration from all those bacteria and fungi is the same as it is for all living creatures – carbon dioxide.  The organic matter held in the soil therefore provides a great service (we call this an ecosystem service) in that it sequesters carbon from the environment.  This can help mitigate climate change   and even effect global food security.

Source

Double digging does a garden good.

Look through many-a garden book and it will tell you to start a garden bed by double digging, which is a term used to describe a back breaking procedure where you remove the top layer of soil, then disturb a layer beneath it and mix up the layers.  While it may not be as drastic as running a tiller or tractor through the soil, it still destroys the structure with the same negative outcomes as above.  Additionally, while many gardeners swear by it, there is evidence that the only benefit to come from it is to prove to yourself and others that you can do hard work.   It has no benefit for the garden and usually negative effects on the soul, psyche, and back of the gardener.

Large tilled up gardens are easier to maintain. One of the benefits of gardening in a bed, raised or otherwise, is that the close spacing allows you to grow more stuff in a smaller area. By reducing the area under production, you also reduce the labor and the inputs (compost, fertilizer, etc) that are used.  Using the old in-ground tilled up garden method where you grow in rows means that you have more open space to maintain and will be using inputs on a larger area that really won’t result in more production (it is really wasted space and inputs).

So, how do you start a garden if you don’t want to build a raised bed and know that you shouldn’t disturb the soil?

So you realize that tilling up the soil is really bad from both an ecological and production standpoint, but you don’t want to build a raised bed structure? That’s perfectly fine.  Gardening in a bed, raised or not, is a great, low-impact gardening practice.

To get started, you don’t have to disturb the soil at all.  Simply adding a thick layer of compost and topsoil on top of the soil in the general dimensions of the bed is a good way to start a bed.  No need to till or disturb.  And over time, the organic matter will eventually work its way down into the soil. If you have really heavy (clay) soil, you’ll probably want to start with a fairly deep (at least 6 to 8 inches) layer of soil/compost.

Just cover with your favorite mulch to keep it in place and reduce weeds (I prefer straw and shredded newspaper, but you can use woodchips as long as you don’t let them mix in with the soil – something I never can do in a vegetable garden where I’m planting and removing things on a regular basis). Keep in mind that a good width for a vegetable bed is about four feet and you want a walkway of at least two feet between them.  This allows you to not walk on the good soil, which can cause compaction.

If the spot where you want to put your bed is weedy, use your favorite method to remove weeds before laying down the layer of compost/soil.  This could be through herbicide usage (keeping in mind most have a waiting period to plant, though some are very short) or mulch.  If you are planning ahead (say at least a year), our Garden Professors head horticulturalist suggests a layer of woodchip mulch 8-12 inches deep that can turn a lawn patch into a garden patch.  They reduce the weeds and build the soil as the break down.

Are Soaker Hoses Safe?

By Cynthia Lee Riskin

With drought predicted for the west, southwest, and south through June 2015 (National Weather Service March 2015), many conscientious vegetable gardeners will try to conserve water by using soaker-hoses, those bumpy black hoses that weep water onto the soil through tiny pores.

Brussel sprouts and red lettuce
Soaker hoses are made from fine-crumb rubber, usually recycled from vehicle tires. Research strongly establishes that tire particles leach heavy metals, carcinogens, and mutagenics, among other toxins. Yet soaker hoses have not been studied for potentially increasing the toxicity of edible plants. Are they really safe to use safe on our edible plants?

Soil in the City
Urban soils already contain high levels of heavy metals (Murray et al. 2011) from years of household runoffs—chemicals from pesticides, cars, painting, cleaning, and more. Adding soaker hoses made of crumb tires might exacerbate the problem.

Rhubarb
Whether plants take up enough heavy metals to be toxic, however, is a complex equation, depending on a slew of interrelated factors, including:
• Soil pH (Costello 2003) and texture (Singh and Kumar 2006; Murray et al. 2011)
• Temperature (Murray et al. 2011; Lim and Walker 2009)
• The size of the rubber particles (Gaultieri et al. 2004)
• Chemical composition of irrigation water (Singh and Kumar 2006)
Furthermore, the plant species and even the cultivar can affect a plant’s uptake of zinc and other heavy metals (Murray et al. 2009 and 2011).

Growing Healthy Food
If you’re looking for the key to ensuring that your vegetable patch grows healthy food, however, I’m sorry to disappoint you. Too many factors are involved to predict the toxicity of what we grow in our gardens.

A good way to get more information is to contact your local extension agent for a list of laboratories that test soils not only for nutrient composition but for heavy metals. Although this information won’t guarantee you’ll be able to grow heavy-metal-free produce, it’s a step in the right direction while we wait for more research to be done.

vegetables_jpg.jpg
Cindy Riskin is a Master of Environmental Horticulture and freelance journalist raising edible plants, an unkempt ornamental garden, and elderly mutts in Seattle, Washington.

NOTE: This article is excerpted from a longer one soon to appear in Cindy Riskin’s upcoming blog, tentatively named Muddy Fingers Northwest. Please contact Cindy Riskin at cindyri@q.com for an advance copy or the blog’s web address.

REFERENCES
1. Costello, Laurence Raleigh. 2003. Abiotic disorders of landscape plants: A diagnostic guide. Oakland, Calif.: University of California, Agriculture and Natural Resources. P. 117.
2. Gualtieri M., M. Andrioletti, C. Vismara, M. Milani, and M. Camatini. 2005. Toxicity of tire debris leachates. Environment International 31 (5): 723–30.
3. Lim, Ly, and Randi Walker. 2009. An assessment of chemical leaching releases to air and temperature at crumb-rubber infilled synthetic turf fields. Albany, N.Y.: New York State Department of Environmental Conservation. http://www.dec.ny.gov/docs/materials_minerals_pdf/crumbrubfr.pdf.
4. Murray, H., T.A. Pinchin, and S.M. Macfie. 2011. Compost application affects metal uptake in plants grown in urban garden soils and potential human health risk. Journal of Soils and Sediments 11 (5):815–829.
5. Murray, Hollydawn, Karen Thompson, and Sheila M. Macfie. 2009. Site- and species-specific patterns of metal bioavailability in edible plants. Botany 87:702–711.
6. National Weather Service Climate Prediction Center. March 19, 2015. U.S. Seasonal Drought Outlook. NOAA/National Weather Service National Centers for Environmental Prediction. http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.html.
7. Singh, S., and M. Kumar. 2006. Heavy metal load of soil, water and vegetables in peri-urban Delhi. Environmental Monitoring and Assessment 120 (1-3):1–3.

Prepping Your Garden for The Next Growing Season

William H. McCaleb, Blog Contributor
Program Assistant for Agriculture and Natural Resources, Halifax County, VA. and Master Gardener

For gardeners in the eastern U.S., last year was a better than normal gardening season. Better than normal yield, better than normal precipitation, and in our case in Virginia cooler than normal which yielded excellent spring cool season crops as well as early summer crops.

But all good things must come to an end; that being the result of several heavy frosts.   With that said, I am looking forward to next year’s challenges and what I want to grow for our family. Oh, for the taste of one more summer ripened tomato, but for now, that is a dream and it is time to reflect on what grew well in the garden as well as what didn’t do so well.  Hopefully you have kept a garden journal to help you in this task. I find that writing down details of what is planted, the orientation, spacing, fertilization/liming rates and frequency, weekly rainfall amounts, production amounts, etc. is helpful as you start planning for the next season.

Like me, you should start thinking about what you want to grow in 2015. Take time to reflect on your 2014 garden production, care, and location. Also, evaluate what went right and what went wrong with the plants and varieties you planted and harvested. This will start you off in the right frame of mind in preparing for the next growing season. Good planning and preparation for next year gives you the tools to have an even better gardening season. A successful vegetable gardener is a happy well fed gardener!

I know, you too are already missing those fresh tomatoes, potatoes, peppers, squash, okra, and other great home grown vegetables we treated ourselves to this year, but the next season is ‘just around the corner’ so to speak. After all the days are getting a little longer. Spring can’t be far away!

If you just happen to live in an area that hasn’t had frost yet, take your prompt from your plants: when annuals and seasonal vegetables turn brown and begin to die back, it is time to clean up your garden.

Clean up the Garden
Your best action is to remove any spent or failing plant materials. Experienced gardeners know that many of the bacteria, fungi, and other disease-causing organisms that caused those diseases. Pathogens that are sources of those diseased plants this past season can survive over the winter in dead leaves, stems, roots, and dropped fruits that get left in the garden. Much like a piece of bread that is kept too long and looks like it has penicillin growing on it, garden debris also will carry the pathogens that can come alive with those same problems when the temperatures begin to rise in the spring. Prevention of diseases and insect infestation now, will keep you from a repeat of problems in next year’s garden.

A good leaf rake, given enough ‘elbow grease’, works well in getting the bulk of dead plant material out of your garden. If you experienced early or late blight or other tomato related diseases this past growing season, you want to make sure you reduce, to the best of your ability, the risk of repeating that problem again next year. Yes, there are many new varieties of vegetables available today that are ‘resistant’ to some of these diseases, but ‘resistant’ does not mean they are immune to them. You don’t want to take the chance of returning pathogens, so do a good job, cleaning and ‘sanitizing’ your garden now. Make sure, when removing the plant debris, that you totally destroy that debris so that no pathogens are left behind.

To Compost or Not!
Can you compost this dead plant material and use it next spring? Information that you find from Extension offices across the U.S. will recommend that you do not. The reason being is that most people do passive composting i.e. put it in a pile, and then using what compost develops, put the compost back in the garden for the next season. It is best to burn the plant material; this will destroy the pathogens and weed seeds as well and return some carbon back into the ground when you spread it out. Please check local/state laws prior to burning. Many states and/or localities have burn bans especially this time of the year. Another method, if your local law allows it you can bag the material and send it to the landfill. Each year there are more localities that ban yard waste from their landfills. If you are not sure, check with your locality to learn more about your local waste and recycling laws.

If you do decide to go with active composting; composting at a temperature 140°F, or higher, will destroy many of the disease organisms as well as many weed seeds. You will need a temperature probe to monitor compost temperatures.   It’s really not hard to source a compost thermometer either through the internet or local retail outlets such as garden centers or nursery supply stores. If in doubt about your compost pile reaching these high temperatures, it is best to side with caution and discard the material by properly bagging it or by burning based on your local ordinances.

Preventing Overwintering Pathogens
Some of our most notorious insects of the garden such as Mexican bean beetle, squash vine borers, European corn borer, cabbage loopers, can also overwinter in garden debris. Larvae will use debris as a safe harbor. Flea beetles and spider mites, as well, can find food and winter shelter in spent plant material and weeds.

After you have finished cleaning up the debris from your garden, it is time to turn over the soil to both aerate and break up any remaining debris into smaller pieces that will be turned under. A good rototiller will help make this job easier. Once buried, any plant material left will decompose more rapidly.

For some pests and pathogens, turning over the soil after removing spent plant materials is recommended as the main line of defense against overpopulation next year. Consider this information from “Home and Horticultural Pests: Squash Bugs and Squash Vine Borers,” from Kansas State University,

“A vigorous autumn… rototilling can physically destroy cocoons and larvae (of the squash vine borer). Brought to the surface, cocoons and larvae are more susceptible to predation by birds and exposed to cold winter elements, leading to their demise. Deep plowing physically destroys cocoons and larvae burying them deep beneath the soil surface so pupated moths become entombed underground.”

Steps to a Healthier Garden
If you haven’t done a soil test in three years or more, it is time to retest and determine the needs of your garden soils based on what you will be growing in the next season. Soil test kits and instructions are available from your local Extension Office. Also, in planning next year’s garden, rotation of your crops is a must do item. This simple action will help keep disease issues down.  If your soil test(s) recommend liming, you can go ahead and put down lime this time of year, allowing it to start adjusting the pH. If the ground is frozen already, wait until spring. As you add lime, you can also help build soil structure by incorporating compost or shredded leaves. These soil additives will also add beneficial micro-nutrients and beneficial organisms. If you want to further build the soil, you may want to consider putting in a cover crop that will not only hold soil, but when tilled in early spring, will further build a healthier garden soil. A legume such as white or red clover would be something to consider. Check with your local Extension Office for best cover crop recommendations for your area.

Prepping Your Garden for the Next Growing Season (pdf)

 References:

http://pubs.ext.vt.edu/426/426-334/426-334.html
http://www.ksre.ksu.edu/bookstore/pubs/mf2508.pdf

image sisters
“Three Sister’s Garden-Fall Clean-up “Southern Virginia Botanical Gardens” Photo by W. McCaleb 10/28/14 Corn, Beans, and Squash was grown here as the native Cherokee have done for centuries. Cleaned up and ready for spring 2015!

 

 

 

Let’s get (soil) physical…

We’ve had quite a bit of discussion this past week on the FaceBook page regarding Kelly Norris’s article in Fine Gardening on dealing with clay soils.  While Kelly’s article mainly addressed selecting plants for heavy soils, there was a side-bar on cultural approaches to dealing with clays; including the standard advice to avoid adding sand to clays.  This advice has been around for years.  The first time I recall hearing it was from Dr. Carl Whitcomb when I took his Arboriculture class nearly 30 years ago (Fall 1984 to be exact).  The rationale that is usually given is that adding sand to clay is the essentially recipe for concrete.  Technically, of course, this is not entirely true since making concrete also requires cement.  Nevertheless, trying to amend a clay soil with sand can lead to more problems than it solves.  The fundamental issue is not that clay + sand = concrete.  After all, there are plenty of highly productive soils in nature that have various ratios of sand and clay and they don’t form concrete.  The bigger issue is that tilling a clay soil (which you’d have to do to incorporate added sand) leads to a loss of soil structure.

 

So, what is soil structure?  Soil structure is a physical property of soil that describes its relatively ability to form aggregates.  Unlike soil texture, which can be quantified as percent sand, silt, and clay; structure is a qualitative soil physical property.  Common examples of soil structure are granular, platy or blocky.

 

 

While we usually think of clay as a negative thing (“Geez Jim, my wife just told me you have clay, I am so sorry…”); a well-structured clay soil can have excellent properties for plant growth.  Well-formed clay aggregates (referred to as ‘peds’) in a granular soil can function very much like larger soil particles in terms of water movement and drainage.  Soil structure is one of those things you have to experience to understand.  About the best description I can come with is that peds in a well-structured granular soil often have the consistency and texture of Grape Nuts cereal.

 

There are also soils out there that are sometimes referred to a ‘structureless’ soils.  These include single-grained soils and massive soils.  Single-grained soils are essentially pure sand.  In West Michigan these occur near Lake Michigan and are often called ‘blow sands’.  We have several seedling nursery operations in these areas.  Since there is no clay these soils have almost no nutrient-holding capacity – growers have to manage their fertility almost as it were a soilless system like a hydroponic or aeroponic system.  The advantage of growing in these soils is it makes lifting bare-root seedlings easy. Massive soils, on the other hand, are very dense soils where particles do not show any evidence of aggregation.  Repeated tillage can result in loss of structure and a soil (or portions of the soil) may show attributes of a massive soil including crusting or formation of hardpan.  The example below shows how structure (indicated by % aggregation) is lost through repeated cultivation.

 

 

 

Effect of soil tillage on soil structure.  Source (Greacen 1958, Australian J. Ag. Res. 9:129-137).

What can be done to improve or preserve structure?  This is a case where less is often better.  Natural processes such as freeze-thaw cycles and the action of earthworms and other invertebrates work to loosen soil and create aggregates.  The tips in the Norris article (avoid overworking soil and adding organic matter) are essentially the same advice I would give.

Container planting: intuition vs. reality

I’m just starting to think about getting my containers planted for the summer and happened to get an email on the topic from a blog reader. John was frustrated with a local columnist’s advice on using gravel in the bottom of the containers for drainage. When challenged, the columnist refuted John’s accurate comments with “logical thinking.” (You can find the posting and comments here.)

Here’s part of the post: “I like to cover the hole with a layer of gravel to improve drainage. Plants need to have their roots exposed to air in the soil to survive and thrive. If the container has no holes for drainage, it will fill with water and drown the plants very quickly. It is better to keep your plants on the drier side than to keep them constantly moist or wet. The big danger in using pots is drowning plants.” Later, he goes on to explain “The potting soil plugs up the drain hole and the water is trapped behind the plug. The layer of gravel creates an area for the water to drain through to escape. The creation of drainage commonly involves a layer of gravel.” This reasoning is part of what he calls “Logical thinking 101.”

As my husband pointed out, this isn’t logical thinking: it’s intuitive. It’s what we think is going to happen in the absence of any evidence. And in this case, it’s wildly inaccurate.

Jeff and I have both discussed the phenomenon of perched water tables in containers as well as the landscape in previous posts and on our Facebook page. The fact is, when water moving through a soil reaches a horizontal or vertical interface between different soil types, it stops moving. Here’s a photo from a very old research paper on the topic:

A layer of silt loam sits above a layer of sand, and water from an Erlenmeyer flask drips in. Intuition says that when the water reaches the sand, it will move more quickly through the sand because the pore spaces are larger than those in the silt loam. But intuition is wrong, as this series of photographs clearly demonstrate. Water is finally forced into the sand layer by gravitational pressure, after, of course, saturating the silt loam.

Intuition has its uses (I am quite proud of my own intuitive powers), but it doesn’t trump reality.

It’s raining, it’s pouring, it’s a good time for a site assessment…

April is turning out to be a soggy month for most of Michigan and our surrounding states.  While most homeowners are inclined to hunker down indoors and keep an eye on their sump pumps on these dark, dreary days; our current run of wet weather is a good opportunity to take a stroll around your property and make some notes.  In particular, note any areas where water is accumulating.

 

Poor drainage is one of the most common sites factors that limit landscape tree and shrub survival and growth.  Sites that retain water for more than a day or too after rains stop are especially problematic.  The challenge with wet areas is we usually wait to plant trees and shrubs until things are high and dry and it’s easy to forget where the wet spots are.

 

There are two primary strategies for establishing healthy trees and shrubs in flood-prone spots.  First, determine if the problem can be corrected.  In some cases homeowners may be able to re-direct water flow from downspouts or other sources to keep water form accumulating in one spot. Again, these kinds of problems are easiest to spot if you go out when it’s raining.  Re-grading the area or installing drain tiles are other options but these are usually require skills and equipment beyond the average do-it-yourselfer.

 

If correcting the drainage issue is not an option, the second strategy is to plant trees or shrubs that are tolerant of flooding.  Plants vary widely in their tolerance of soil flooding and, not surprisingly, trees and shrubs that grow naturally along riverbanks and other low areas are usually the most tolerant.

 


This low spot in my yard  was a good site for a Baldcypress 

There are numerous resources on flood tolerant trees and shrubs on the web.  Two of the better resources are from the Morton Arboretum and from Cornell University.  Please note the Cornell guide is a large (>6 MB) .pdf file.

 


These Michigan holly (Ilex verticullata) I planted a couple of years ago a doing fine even though they are periodically flooded each spring.

Wet areas on your property do not have to be a ‘dead zone’, but establishing trees and shrubs in low laying areas takes some planning.  The first step in the process is assessing your site and identifying the problem areas.  The best way to do this is to put on a raincoat and take a walk in the rain.

The invisible, insidious presence of heavy metals

I spent the last two weeks in Spain, combining business with pleasure.  It’s interesting when something that starts out as part of the pleasure ends up being business instead.


Charlotte translated this sign for me – it’s historical information. Note the brightly colored mine tailings in the background.

My daughter is teaching English in Mazarrón, a small town in the province of Murcia. The climate there is very similar to southern California, though drier and not as warm: it’s pretty much a scrubland ecosystem. Since we both enjoy hiking, we decided to take advantage of exploring the abandoned mine sites.  Unlike such sites in the United States, there are no restrictions to hikers and in fact there’s signage explaining the history of the mines. This is a popular hike after a rainstorm because of the unnaturally red pools that form in the landscape.

 
The abandoned mine works; these buildings are over 100 years old, though this area was mined since Roman times.

It took some Internet research to find out that lead, silver and zinc were the minerals of interest extracted from these mines.  For those of you who aren’t aware of how ore processing works, it includes adding various chemicals to crushed rock to solubilize and isolate the desired minerals. The leftover tailings are nearly always highly acidic and full of environmentally available heavy metals.  The various metal oxides and sulfides that formed at Mazarrón are vividly red, orange, and yellow, and there is a pervasive sulfur smell throughout the site. If this isn’t hell on earth, I don’t know what is.


Mountains of mine tailings

So it was really quite a shock to both of us that not only could we walk into this mine site, but that there were no warnings regarding exposure to whatever toxic chemicals might be in the soil and water.  We took pains not to touch anything – but others were not so cautious. Some hikers ahead of us watched their dog cavort through the largest of the pools, and later took photos of each other on the mine tailing spoils.


Visitors and dog and red pool of ????

Yes, the dog went in the water


And then a photo op on the side of Spoils Summit

This hideously beautiful landscape was unearthly, primarily because there was absolutely nothing alive in it.  No plants, no insects, no birds.  Along the edges of the mine tailings there were spring flowering shrubs, bees, and birds, just as one would find elsewhere in the region. (But not in the spoils.  What an apt name…)


A blood-red seep into the pond


Crystals forming as water dries in the pools


Just off the side of the tailings, life continues

How do the mines of Mazarrón fit into gardening?  Unlike this mine site, where the evidence of heavy metal contamination was clearly visible, it’s not so obvious in our garden soils. The residues of arsenic-containing pesticides, leaded gas, zinc from car tire wear, and other possible contaminants are unseen and unknown unless we have soil tests done to confirm their presence or absence.  Yes, it can be expensive to have these tests done, but if we are handling our soils, breathing the dust, and eating the plants that grow there, wouldn’t it be smart to find out what’s there first?

An unwanted bonus in your urban chickens

Longtime reader Ray Eckhart sent me a NYT story on urban chicken eggs and lead contamination.  As I’ve mentioned before on this blog, urban gardeners should have their soils tested for lead, arsenic, and other commonly found heavy metals before they plant edibles.  Chickens that are allowed to peck and scratch in metal-contaminated soils will pass that unwanted load on to you via their eggs.

So test your soils!  It costs a bit of money, but then you know exactly what’s lurking in there.  If your soils have significantly high levels of lead or other contaminants, you can still raise chickens as long as they don’t roam your garden.

Podcast #8 – Water Works

We’ve finally gotten our summer here in the Pacific NW and it’s been pretty hot for a few weeks. The plants weren’t really prepared for this, so we’ve had to irrigate quite a bit to keep all that lush foliage happy. So the topic of this podcast is Water Works – focusing on how water moves in the soil and through plants.

One of the more interesting tidbits I found this week is a recent USDA study on growing more potatoes with less water. Sound impossible? Listen to find out the one single, simple thing that increased water use efficiency by 12% and reduced fertilizer runoff as well.

I also debunk the common myth about using drainage material in container plants. Research from 100 years ago demonstrated that water won’t cross textural barriers – so putting gravel in the bottom of the pot will actually create a bathtub effect rather than helping drainage.

The interview this week is with my garden – primarily the sunny south-facing side. I thought I’d take you on a tour to see what’s happened in the last 11 years. The photos below will help you visualize the interview.


The front yard in 2003. We’ve started taking out the turf and moving around trees and shrubs.

The front yard in 2003 from another angle. We’ve removed the second driveway and covered the area in wood chips. By the garage you can see two of the roses I dug up from the shady back yard and moved to the sunny front.

The new front yard, with fencing, more plants, a pond, and no turf.

The rhody-hydrangea corner in front of the arbor vitae hedge

The new street garden, with a new retaining wall to hold back the soil that used to wash into the street.  Everything not covered in plants is covered with wood chips.

This is the last podcast of the first “season” of The Informed Gardener. We’re going to take off for about a month before starting the next series. If you’ve got ideas about future topics, you can email me or post a comment here. In the meantime, you can listen to archived podcasts found on this blog; just click on “podcasts” on the right-hand menu.

Our visiting GP takes on fertilizers

Like many readers of this blog, I’m like a kid in a candy store where plants are sold.  I try to justify the extra cost of a large annual pot instead of a scrawny 4-pack, or I imagine I’ll find room for that lime green Heuchera and my wife will learn to love it.  But unless I keep my blinders on and stick to the shopping list, I’ll probably leave with a fertilizer.  This year, I’ve purchased 12-0-0, 5-6-6, sulfur, and some 5-1-1 liquid.  Those go with my 6-9-0, 11-2-2, 9-0-5, 2-3-1, and 4-6-4.  I can explain why I ‘need’ each one.  I have a decent idea what my soil is like because I’ve had it tested (though I’m due for another test). But I’ve always questioned how those bags of fertilizer can know exactly what my garden needs.  The rates listed on the bag imply they’re universal under all circumstances and will give great results if the directions are followed.   Is that true?   And at what cost?

For example, 2 of the bags are listed as ‘lawn’ fertilizers (the veggie garden doesn’t care about that though).  But if I apply these to my lawn at the rate listed and 4 times per year, I’m adding 3-4 pounds of nitrogen per 1000 ft2.  That’s a reasonable rate if I irrigate and bag my clippings, but I don’t do either.  Therefore, I only need ~1 pound of nitrogen, not 3 or 4 (see this publication for more info). I just saved myself some money by disobeying the bag. That extra nitrogen isn’t useful for making MY lawn healthy.

One of my fertilizers is labeled ‘tomato’.  If I do exactly as the bag tells me for tomatoes, I would be applying the equivalent of 400 pounds of nitrogen and almost 500 pounds of phosphate per acre.  So what?  Well if I look at a guide for how to grow tomatoes commercially, I’d notice that the recommended nitrogen rate is 100 to 120 pounds per acre, and phosphate is 0 to 240 pounds per acre.  Yes, those are commercial guidelines, but they shouldn’t be too far off from garden recommendations. And of course, recommendations should always be based on soil tests.  But 4 times the N and 2 to infinitely more times the amount of phosphate than is required? That’s likely a waste of money at least. And yes, those recommended guidelines are real: you CAN grow food without adding phosphate or potassium-containing fertilizers.  If the plants you’re growing don’t need much and your soil has plenty, you don’t need to add any.

Say I’ve got an acre of onions (Fig. 1; not quite an acre). One of the bags of fertilizers, were I to follow its instructions for fertilizing ‘vegetables’, tells me that I should add 100 pounds of nitrogen and 120 pounds of phosphate and potash at planting (per acre), followed by half that partway through the season (next to the row). The commercial production guidelines tell me that the nitrogen rate is similar to what the bag of ‘vegetable’ fertilizer says, but I actually need about 7 times less phosphate and potash (based on my soil test results; I have quite a bit of P and K already in my clay-loam soil). I don’t want to add stuff my soil doesn’t need, so I use my shelf full of bags, a scale for weighing pounds of fertilizer per cup, and some math to come up with a custom fertilizer regime that suits my soil and the onion’s needs (see Table 1, and remember that the numbers are for MY soil, not necessarily yours).

One problem with using extra fertilizer may be in the extra cost (wasting nutrient the plant won’t use), but that depends on what fertilizer it is and how much it costs. Another problem may not be immediately apparent, and that is nutrient deficiencies. Too much phosphorus can cause zinc deficiencies, for example. Excesses of some nutrients can create greater chances for pest and disease problems. One big problem with using too much is the potential for these extra nutrients to go where they shouldn’t be, like in groundwater, rivers, lakes, and streams. And as Jeff has mentioned, phosphorus fertilizers won’t be around (cheaply) forever.

Do the work of figuring out what kind of soil you have and what’s in it, what your fruits and veggies need, and what kinds of fertilizers can do the job for you.  Heck, you can even organize your fertilizers based on “cost per pound of nitrogen” to see where the best bang for your nitrogen buck will be.  But none of us are THAT obsessed about our fertilizers, right?…. [$ per bag / (pounds per bag * (% nitrogen/100))].

As a reminder, the numbers on your fertilizers are percent nitrogen, phosphorous (as ‘phosphate’, P2O5), and potassium (as ‘potash’, K2O).  One cup is 16 tablespoons, and an acre is has length of one furlong (660 feet) and width of one chain (66 feet), or 43,560 square feet.  Side rant: metric rocks.