Standing up for (and lying down on) the environmentally sustainable lawn

If you’ve been reading this blog for a while, you might remember that I got rid of our lawn (getting rid of your lawn post) at our Seattle house . It took too much water to keep it green in the summer, and the resulting ornamental landscape was more ecologically diverse and aesthetically pleasing for such a small site.

On the way to replacing the lawn with landscape
And the same landscape a few years later.

But that was then, and this is now. In 2017 we moved back to the family farm, which has a full acre of landscape – including lawn. Although we are slowly reducing the vast expanse of lawn, we will keep part of it because (1) we are on well water and there is an irrigation system and (2) because we are allowing the lawn to become a diverse tapestry of different plant species – an ecolawn, if you will.

Farmhouse landscape with an acre of lawn!

When I was growing up, my father fought unsuccessfully to keep the moss and weeds out. I happen to LOVE the moss and the fact that it grows here has nothing to do with poor drainage or anything else. It grows here because the environmental conditions support its growth. I love the spongy feel of the underlying moss, and it reduces the amount of mowing necessary because it’s limited in height. And no fertilizers or pesticides are needed.

Mossy lawns are lovely for walking…and laying down on.

Speaking of mowing…I hate gas powered mowers. They’re smelly and noisy, they contribute to air pollution, and when something goes wrong you have to take it to small engine repair. These excursions are infrequently successful but always expensive. So imagine my delight is discovering newer battery-powered mowers! All you have to do is swap battery packs. They are quieter, there are no emissions, they don’t smell, and they have an electric engine! No small engine repairs, and they are also lighter for this reason.

A newer technology, battery-operated mower with rechargeable battery

I was even more excited to find compatible leaf blowers. We have tons of Oregon white oak leaves, and we blow them into the beds. We do NOT leave them on the lawn, because they interfere with some of our non-grass lawn inhabitants. They are perfect on the beds because their curly, rigid structure prevents compaction and they keep weeds out while allowing water and oxygen to penetrate.

Keep the leaves off the lawn and over the beds.
Our container violets have escaped into the lawn; covering them with leaves could kill them.

Finally, our ecolawn allows me to see and appreciate the reproductive structures of our mycorrhizal fungi. I don’t even pretend to know the species and whether they are edible. I just love the fact that they appear every fall after we’ve stopped mowing.

Some of our lawn mushrooms…
…and some others…
…and others.

Sometimes lawns aren’t appropriate, as we found in Seattle. But sometimes they are – and as long as they are cared for in an environmentally sustainable manner, they shouldn’t have to be something we apologize for.

Woodpeckers: Friends or Foes?

[This blog post has been provided by Bec Wolfe-Thomas, an administrator for the Garden Professors blog group on Facebook.]

Pileated woodpecker. Photo by Josh Laymon

Woodpeckers (Picidae) frequently get a bad rap from gardeners. It’s often their impression that the birds irreparably damage trees, but this is untrue. Most woodpeckers are insect eaters; they can hear insects under the bark and in the wood of trees. They then target their drilling with uncanny precision to get their meal. This removal of insect pests, such as emerald ash borer, benefits the tree.

Emerald ash borer larva. Photo by Pennsylvania Department of Conservation and Natural Resources.

And what about the feeding holes left in the tree? This is an exciting bit of tree physiology! Trees are able to compartmentalize or isolate the wounds. After the woodpecker has made a hole to retrieve the insects within, the tree starts compartmentalizing the wound. How long it takes for a tree to compartmentalize a wound and close it depends on species and climate factors.

Compartmentalization of decay in trees (CODIT). Photo from Wikimedia.

Below are photos of woodpecker holes in various states of compartmentalization, from freshly drilled to completely compartmentalized and closed holes. Woodpeckers help keep trees healthy by preventing large pest infestations. And while the small feeding holes might be an aesthetic concern to gardeners, they’re only temporary. They will eventually be compartmentalized and closed, and the tree will be healthier in the long run by having fewer pests.

This woodpecker hole is partially compartmentalized; you can see the edges are rounded, no longer rough. Photo by Bec Wolfe-Thomas.
This wound has fully compartmentalized and all that is left is a pucker on the trunk. Photo by Bec Wolfe-Thomas.

[Please note the larger holes excavated for nesting will compartmentalize but will not close over time.]

Soil or dirt? It’s really up to you

Dig up dirt. Treat like dirt. Dirt poor. Replace the word “dirt” with “soil” and you get phrases that make no sense. This is a roundabout way of explaining that “dirt” and “soil” are not the same things, either in idioms or in the garden. Yet many of us effectively turn our soils into dirt through poor garden practices.

This is dirt. (Photo from Wikipedia)

This is soil.

For the purposes of this post, we’re going to use a single criterion to distinguish between soil and dirt: one is a living ecosystem and the other is not. A thriving soil ecosystem contains sufficient water, oxygen, and nutrients to support bacterial, fungal, plant, and animal life. Regardless of soil type, about half of the volume in a living soil should be pore space and the other half soil particles. Half of the pore space should be filled with water and the other half with air. When we make choices about activities that affect garden and landscape soils, we need to be proactive in preserving both the particle-pore balance as well as connectivity between the soil and the atmosphere.

All soils have pore spaces regardless of their texture.

Pore size varies with particle size.

The only way pore space can be reduced is through soil compaction. So don’t do it.

  • No driving. If equipment must be brought in, put down a thick layer of wood chips to protect the soil, or at least plywood.

Not really the way to do park renovations.

These amenity trees quickly became liabilities, thanks to soil compaction during construction. {Photo courtesy of Jim Flott)

  • No naked soil. Bare soils are compacted soils. Mulch!

Basically dirt.

Wood chips covering real soil.

  • No rototilling. It grinds your living soil into dirt. Disrupt the soil as little as possible when you plant.

I have no words.

  • No stomping, pressing, or otherwise compacting the soil during planting. Let water and gravity do that work for you.

Let’s just press that pore space out of existence.

Mud it in! Let water and gravity settle new transplants.

The only way soil and atmosphere connectivity can be disrupted is by covering the soil with low permeability materials. So don’t do it.

  • No soil layering. Don’t create abrupt layers of soils with different textures. It interferes with water and gas exchange.

Soil horizons change gradually in natural soils.

Poor surface drainage indicates a perched water table caused by abrupt changes in soil texture (photo courtesy of Rich Guggenheim).

  • No sheet mulches. I’m sure you’re tired of hearing me say that and I am tired of saying it. Sheet mulches have less permeability than chunky mulches. That means oxygen and water have more difficulty getting through. Period.

The less porous the material, the more slowly gas diffuses through it. Read more about it in our recent article

Chips are great. Why ruin them with cardboard underneath?

Landscape fabric is even worse than cardboard, but the weeds love it.

And plastic? Dont even THINK about it.

Do use lots of groundcovers, chunky mulches, and hardscape in areas where there’s considerable foot traffic. They all protect the soil and are important parts of a well-designed, sustainable landscape.

Soils love all sorts of mulches.

Inorganic mulches protect soil, too.

If you just can’t get enough about soil science for gardens and landscapes, do check out this new publication by Dr. Jim Downer and myself.

Garden potions and notions to avoid

It’s Halloween and terrifying things abound – particularly at garden centers. Below you’ll find a pictorial approach to four frightful follies. Enjoy – and keep your garden safe!

Scary soaps. No. Not on your soil to aerate it. Not on your plants as part of some homemade devil’s brew. Soap stays in your house.

Scrubbing bubbles!

SOAP is not an acronym for Super Organic Agricultural Product

 

 

 

 

 

 

Petrifying phosphate. Not for flowers. Definitely not for transplanting. No matter how friendly and natural they look on the shelf, they are death to mycorrhizae and any aquatic system they wash into.

Mounds of mycorrhical mortality

“Bone meal” can be anagrammed to make “le bemoan.”

 

 

 

 

 

 

 

 

Murderous mulches. No cardboard. No plastic. And definitely no astroturf. The word “smother” does not conjure up a pretty picture for living soils.

The chips are great. The cardboard….not so much.

Cardboard’s so resistant to water you can make ponds out of it!

 

 

 

 

 

There are faster ways to kill trees.

Is it mulch? Or a tire graveyard?

 

 

 

 

 

Artificial lawn should only be used for indoor minigolf.

Zany zombies. These useless products live on in their science-free environments. Just…go…away.

Business is good even if efficacy isn’t.

Yes, because plants love stag’s bladders and cow mesenteries.

I can’t improve on this description.

 

 

 

 

You can find posts on these products by using the “search” box on the left hand menu. Or you can consult your Ouija board using this handy mulch planchette.

Will my tree survive? Ouija board says “Goodbye.”

 

Late summer pruning: what happens, what won’t, and why

In the fall a gardener’s fancy lightly turns to thoughts of pruning (with apologies to Alfred, Lord Tennyson).  In particular, people worry that pruning too late in the summer or early fall will stimulate plants to send out new growth, which is then damaged by freezing temperatures. Let’s dissect what actually happens when woody plants are pruned during this time.

Sumac leaves in full autumn glory.

First, we need to separate temperate trees and shrubs from tropical and subtropical species. For the most part, the latter don’t become winter dormant: pruning them at any time means you will have regrowth as long as there are sufficient resources. If planted in more temperate zones, they will continue to grow until they are killed by freeze damage. Instead, we’ll look at temperate species and how they are adapted to surviving winter conditions.

Tropical woody plants like this jade are not winter dormant species. Don’t leave them outside even if you think they are protected (lesson learned).

I wrote a couple of posts last year on cold hardiness (here and here), so I won’t repeat those discussions on how plants survive freezing. Instead, we’ll focus on the process of HOW plants enter winter dormancy and become cold hardy. It’s a two-step process that depends on two different environmental factors: one that never changes from year to year, and one that certainly can.

The first step to dormancy is initiated right after the summer solstice. Plants are exquisitely adapted to changes in the light-to-dark ratio, and days begin shortening after the summer solstice. The changes that occur are largely biochemical, but you can also see some changes in plants themselves. Many trees and shrubs slow their growth during this time so that fewer young leaves and shoots are produced. Instead, resources are put into the existing foliage, or flowers for summer bloomers. Excess resources are routed to woody parts of the plant for storage.

Light and dark ratios vary with latitude, but the seasonal changes are always the same time of year.

From a practical standpoint, this means that when you prune trees and shrubs where growth has stopped, you will NOT get regrowth. The vegetative buds below the pruning cut are dormant. The tricky thing is that the exact time when the switch is thrown varies by species and is affected by environmental conditions. Careful observation will allow you to estimate when the plants will no longer produce new growth.

Some temperate species naturally put on a spurt of late summer growth. The leaves on these new Japanese maple shoots generally die from cold damage, but the branches themselves survive.

The second step begins when night temperatures cool to near freezing, which is not a predictable date. Because many of the biochemical and physiological processes have already begun or are finished, the response to cold night temperatures is rapid and visible. Leaf colors change as the plant begins breaking down leaf materials for mobilization and storage elsewhere in preparation for winter dormancy.

This katsura has started the process of autumn leaf senescence.

This process, honed over millions of years, is unfortunately not infallible especially under abnormal environmental conditions. Two examples spring to mind:

  • High intensity street lights. If the normal light-to-dark ratio change is interrupted by significant levels of night light, the first step of dormancy is hijacked. You can see what happens in these previous blog posts here and here.

That street light in the middle has kept the nearby leaves green while those farther away are senescing.

  • Unseasonably cold weather. With climate change, we are seeing wild shifts in all sorts of weather patterns, including the date of the first hard freeze. Hard, early freezes are not the same as a light evening frost. You can see what happens here:

A hard freeze in early November fried the leaves on this hydrangea.

Given normal conditions, however, temperate trees and shrubs are well on their way to full winter dormancy by late summer and early fall. Pruning them is not going to induce new growth.

Landscape fabric – a cautionary tale

This isn’t the first time I’ve ranted about bad mulch choices and it certainly won’t be the last. But this pictorial cautionary tale is too important to pass up.

We already know that sheet mulches can be death to microbes, plant roots and animals living in the soil underneath. Our newly published research shows that landscape fabric reduces carbon dioxide movement between the soil and atmosphere about 1,000 times more than wood chip mulches do: plastic mulches are even worse. Oxygen movement will be likewise affected.  And while gaps and holes in these barriers can lessen the impact, the question remains: why would you use ANY mulch that reduces gas movement? Yet people persist in using fabrics and plastics, usually to “smother” weeds (and that verb should set off alarm bells for anyone thinking about collateral damage to soil life). But weeds are weeds for a reason, and they will eventually colonize the surface of sheet mulches as soil, organic matter, and water collect over time.

So without further ado, here is a case study of what happens when sheet mulch is used for landscape weed control.

These irrigated landscape beds are in Wenatchee, Washington, which has hot, dry summers. As you can see, bark mulch has been used to hide the shame of sheet mulching. And from a distance it looks…okay.

Upon closer inspection, you can see the shroud of death emerging from the bark mulch (which has no means of staying in place, especially on a slope).

And even close you can see the soil that’s blown in, along with the bark and other organic matter. Just add water, and you get weeds!

Weeds, weeds, weeds! Lots of weeds. Sunny weeds!

And shady weeds!

Border weeds!

Rocky weeds!

The weeds are thriving – but the trees are not. The crowns are dying…

…and the trunks are suckering.

But you’ll note that the trees in the first photo outside of the beds are thriving.

And it’s all because of that “weed control fabric.” Which is working so well that this landscape had to be treated with herbicide the day I was there – to control the weeds.

Why soil tests matter: lessons from my vegetable garden

Regular blog readers will remember that we moved to my childhood home a few years ago. With an acre or so of landscape I finally have enough room to put in a vegetable garden. My husband built a wonderful raised bed system, complete with critter fencing, and we’ve been enjoying the fresh greens and the first few tomatoes of the season.

Jim puts on the finishing touches to our first raised bed garden.

We filled these raised beds with native soil. During a porch addition I asked the contractor to stockpile the topsoil near the raised beds. The house was built almost 100 years ago and at that time there were no “designed topsoils” (thank goodness) – soil was simply moved around during construction. Some of this soil had been covered by pavers and the rest had been covered with turf. [You can read more about designed topsoils in this publication under “choosing soil for raised beds.”] There had been no addition of nutrients for at least 7 years so I was confident that this was about as natural a soil as I could expect.

Our native soil, ready for adding to our raised beds.

I’ve always advised gardeners to have a soil test done whenever they embark on a new garden or landscape project, so before I added anything to my raised beds I took samples and sent them to the soil testing lab at University of Massachusetts at Amherst (my go-to lab as there are no longer any university labs in Washington State for the public to use).

What I already knew about our soil was that it’s a glacial till (in other words it’s full of rocks left behind by a receding glacier). The area is full of native Garry oak (Quercus garryana), some of which are centuries old. The soil is excessively drained, meaning it’s probably a sandy loam. And that’s about all I knew until my results came back.

Some of our massive, centuries old Garry oaks.

Because nothing has been added to this soil for several years, and because I had removed all of the turf grass before filling the beds, I assumed that the organic matter (OM) would be quite low. Most soils that support tree growth have around 3-7% OM. Hah! Ours was over 12%! All I can figure is that centuries of leaf litter has created a rich organic soil.

I never expected this level of OM.

So here’s lesson number one: Don’t add OM just because you think you need it. Too much OM creates overly rich conditions that can reduce the natural protective chemicals in vegetation. This means pests and diseases are more likely to be problems.

I think these may be the lowest P levels I’ve seen in home garden soils.

I was pleased to see our P level was low. First soil test I’ve ever seen in my area where P was below the desirable range! Does that mean I’m adding P? No – because there is no evidence of a P deficiency anywhere in the landscape. And my garden plants are growing just fine without it.

No sign of any nutrient deficiencies here (though the mesclun mix got out of control).

Or here either.

Lesson number two: Just because a nutrient is reportedly deficient, look for evidence of that deficiency before you add it. It’s a lot easier to add something than it is to remove it.

Likewise, our other nutrient values are just fine, and I was pleased to see that lead levels were low. Given that this is an older house that had lead paint at one time, and given the fact that the soil being tested was adjacent to the house, I was prepared for lead problems.

Surprisingly low lead given the original location of this soil next to an older house.

However – we do have high aluminum in the soil. Exactly why…I don’t know. Perhaps the soil is naturally high in aluminum? There’s no evidence that aluminum sulfate or another amendment was ever used. In any case, that was an unexpected result that does give us some concern for root crops. I’ll be doing some research to see what vegetables accumulate aluminum.

The aluminum levels may bear some watching if I’m growing root crops.

Finally, note our pH – 4.9! This is completely normal for our area, which is naturally acidic. In addition, the tannic acid accumulation from centuries of oak leaves has undoubtedly pushed the pH even lower. Are we going to adjust it? Again, no. There is no evidence of any plant problems, and even our lawn is green. Why would we adjust the pH if there is no visual evidence to support that?

No, this is not a typo.

Which leads to lesson number three: Don’t adjust your soil pH just because you think you should. If your plants are growing well, the pH is fine. Plants and their associated root microbes are pretty well adapted to obtaining the necessary nutrients. If you have problems, don’t assume it’s a pH issue. Correlation does not equal causation! You’ll need to eliminate all other possibilities before attempting to change your soil chemistry. And remember it is impossible to permanently change soil pH over the short term. Permanent pH changes require decades, if not centuries of annual inputs (like our oak leaves).

The cat agrees – no pH issue with this lawn.

Will I test my soil again? Probably not. I have the baseline report and since I don’t plan to add anything I don’t expect it to change much. If I had a nutrient toxicity I would retest until the level of that nutrient had decreased to normal levels. But with everything growing well, from lawn to vegetables to shrubs and trees, there really is nothing to be concerned about.

Viburnum plicatum (I think) is one of many established shrubs on the property.

Lesson number four: Unless you have something in your soil to worry about, don’t.

Give me your huddled root masses yearning to breathe free

About this time last year I posted photos of the installation of my new pollinator gardens (all perennials). As you can tell from the photos below, all of these plants have not only survived but thrived with their midsummer rootwashing.

Garden 1. Robust perennials! Except for the the sad, tiny lavender in the lower right hand corner (discussed below).

Garden 2 is just like the other, except the strawberry groundcover is replacing the wood chips.

 

 

 

 

 

The only ones that didn’t make it were the six Lavandula stoechas ‘Bandera Purple’ (see above). They did fine through the summer and well into winter. But with our surprise snowstorm in February (along with a 20-degree temperature drop in one night – from 33 to 14F), all but one of these marginally hardy plants (USDA zones 7-10) gave up the ghost. I won’t make that mistake again. But I will continue to root wash ALL of my perennials before I plant.

It’s pretty easy to excavate this tree (planted months ago) since there is NO root establishment.

And since it’s Independence Day here in the US, I thought I’d continue with the “free your roots” theme and discuss the medieval torture system that passes for recommended B&B tree installation practices. I’m talking about the burlap, the twine, and the wire baskets that are left on the root ball and cunningly hidden underground to do their damage over the years.

THIS is what should be planted.

Not this.

 

 

 

 

 

There is a great deal of disagreement about what to do with all the foreign material that’s used to keep tree root balls intact during shipment. To be clear, that is the ONLY thing they are intended to do. There is no research that shows leaving them on benefits the tree at all. The reason they are left on is because it’s more economically feasible for the installation company to do it this way. Personally I think that’s a pretty crappy reason, particularly when you are looking at trees that can cost hundreds or thousands of dollars.

Does anyone seriously think this is a good way to plant trees?

Most studies that have addressed the issue have been short term: two or three years, rarely longer. Irreversible damage to roots can take years to develop. It’s useful, therefore, to look at the landscape evidence to see what happens with all these barriers to root growth and establishment.

Death row.

Arborist and landscape designer Lyle Collins recently excavated the remains of trees that had been installed in 1991. The trees had died years ago and certainly hadn’t grown much as evidenced by their trunk size.

Not much trunk growth in this tree.

But while the trees didn’t survive, the burlap, wire basket, and webbing were all still there almost 30 years later.

Basket and webbing are clearly visible (after washing)…

…as is the burlap (before washing)

 

 

 

 

 

 

 

The clay rootballs are nearly intact as well. That’s not what you want to see. Roots must establish outside the rootball into the native soil, or they won’t survive.

Intact rootball after 28 years

The same rootball after washing

 

 

 

 

 

 

 

Eventually I’m convinced long-term research will show the folly of leaving foreign materials on the rootballs of B&B trees. In the meantime, I’ll continue to plant trees in a way that ensures their roots are in contact with the native soil and free from any unnatural barriers to growth.

 

 

 

Cornmeal magic – the myth that will not die

Way back in 2010 (and then again in 2012) I wrote about a bizarre belief that cornmeal could be used to treat fungal diseases, from lawn spot to athlete’s foot. Rather than rehash what’s already been written, I’ll invite readers to read those posts for background. And of course look at the comments, which are…interesting.The weird thing is that this post from 2010 is the single most popular post on the blog. (Our stats are only for the last two years since we migrated the web site – who knows how many there were before May 2017?)

Blog stats over two years

The consistent popularity for the topic spurred me to publish a university fact sheet on the use of cornmeal and corn gluten meal in home landscapes and gardens. This fact sheet reviews the pertinent literature, and makes recommendations that are pretty much the same as those I made almost 10 years ago. Nothing has changed in the research world to support cornmeal as a fungicide.

But wait, there IS something that’s happened since 2010! Now cornmeal is being touted as an insecticide! In fact, if you go to Google and search for “cornmeal” and “insecticide” you’ll find thousands of hits.  As you might expect, there’s no research to support this notion: researchers in Maine, for instance, found no effect of cornmeal on fire ants. However, it is used as a bait to deliver actual insecticidal chemicals.

Way back in 1937.

But facts don’t get in the way of home remedies, such as Lifehacker’s eyebrow-raising advice.

Hmmm…

By refining the search to only include university websites (use “site:.edu” to do this), and swapping out “ants” for “insecticide,” you’ll find at least one Master Gardener group happily (and illegally) recommending cornmeal as an ant killer. The popular mode of action is either (1) they can’t digest cornmeal and starve or (2) the cornmeal absorbs water in their gut and they explode.

Boom!

This reminds me of yet another food product – molasses – recommended for killing ants. Since you’re already here, you might as well check out Molasses Malarkey parts 1, 2, and 3 too.

Might I recommend everyone use their cornmeal and molasses to make bread or cookies or pancakes? There are some delicious recipes on the internet.

Yum!

Bare Rooting – a guest post from a commercial landscaper

What are these trees and do they look like this? Read on to find out!

Today’s blog post is courtesy of Mary Blockberger of Sechelt, BC. As you’ll see, Mary and I go way back.  I thought it was important to our ongoing discussion to see how the industry can use the root-washing technique effectively and economically. Here’s Mary:

“Before I began managing the Sunshine Coast Botanical Garden in Sechelt, BC I had a small residential landscaping company.  By small, I mean that I was the employee of the month every month of the year!  One of our Garden’s mandates is to provide relevant and educational programs for our community.  Dr. Linda Chalker-Scott has been one of our most popular speakers several times.  One of her presentations dealt with the practise of bare-rooting perennials, shrubs, and trees prior to planting, and the tremendous advantages of following this method.

Root-washing and installing 36 Carpinus. November 2007.

“In November, 2007 I had a chance to try this technique out.  My client wanted a ribbon of Carpinus betulus ‘Fastigiata’ planted that would eventually be pleached into an interesting pattern.  [Pleaching is a formal tree training technique.] There was a total of 36 trees to be planted; most were container stock as I recall but there may have included a couple of B&Bs as well.  Working with another local landscaper, into a wheelbarrow of water went every single tree one at a time.  The dirt was clawed away from the root balls by hand with a final spray from the hose.  Honestly, it was a cold and miserable job, and I believe a few curses directed at Linda ensued.  However, once the roots were cleaned of all soil planting was a breeze.  It’s a lot easier moving trees without moving the soil too.

Carpinus are well established and pleaching is underway. April 2009

“Flash forward 12 years, and every single tree has flourished.  Bare rooting allowed us to identify and correct any problems before planting, and I’m sure this has a lot to do with the trees’ success.  It’s a time consuming and at times messy method, but the reward of a healthy row of trees is well worth the effort, IMHO.”

Pleached Carpinus hedge May 2019

And let me add to Mary’s account that a ZERO replacement rate is going to pencil out to long term economic success. I was able to see these trees earlier this year – that’s my photo at the top of this post.