Spring is off to a warm and fast start here in Michigan. March was unseasonably warm and the past week or so has seen temperature 20 degrees above average or more. Needless to say this is pushing all of our landscape trees and shrubs. Forsythia and saucer magnolia are in full bloom, at least two weeks ahead of schedule. The warm weather also has us scrambling to get some research projects in the ground as well. Today I was working with members of my lab to install a trial to look at the relationship between fertilization in the nursery and subsequent of shade trees in the landscape. For the past two years we’ve grown Acer miyabei (‘State street’ maple) and ‘Harvest gold’ Linden trees in 25 gallon containers as part of a trial on controlled release fertilizer. Interestingly, in the nursery we saw a significant increase in chlorophyll index and foliar nitrogen with fertilization (no surprise) but no difference in caliper or height growth (somewhat of a surprise). This indicates that in the nursery, fertilization induced ‘luxury consumption’ or an uptake of nutrients beyond what the trees need to meet their growth requirement. This observation provided the opportunity for our current, follow-up study. In the forest nurseries there is a growing interest in the practice of ‘nutrient loading’ seedling trees before they are lifted. Forest nursery managers deliberately induce luxury consumption by fertilizing late in the season. At this time seedlings have set a hard bud and won’t grow but can take up additional nutrients. Numerous studies, particularly by Dr, Vic Timmer and his associates at the University of Toronto have shown that nutrient loaded seedlings will outgrow standard seedlings when out-planted on reforestation sites; even though the seedlings are the same size when transplanted. How does this apply to large-caliper shade trees? We don’t know. There are certainly some underlying commonalities that are intriguing. Nutrient loaded forest seedlings have an advantage when planted on tough sites where follow-up culture is minimal – basically the seedling has to get by initially with its own energy reserves and resources. Shade trees planted as street trees often face the same hardship; once planted they may receive little or no after-care beyond an initial watering. Could nutrient loading provide a better internal nutrient reserve and jump start the re-establishment process for street trees like it does for the smaller forest cousins? We should gain some insights this summer and next.
There are people who are fascinated by plants and people who are fascinated by the science of growing plants. While I love plants I must confess that I consider myself to reside more firmly in the latter group that the former. I do love to see the beautiful flowers on an apple tree in the spring, but I’m more fascinated by the nitrogen, phosphorus, potassium and other elements that the tree obtains from the soil. I like to contemplate the complex ecosystem that surrounds the tree, including the tree’s pests and the possible things that we can do to protect the tree from pests. I love to learn about insecticides, herbicides and fungicides, and I especially love to learn about alternatives like beneficial insects that may be used to control pests. Histories that cover fertilizers and pesticides are pleasure reading.
One of the most important things to ever happen to the world as we know it was the discovery of a process to take nitrogen from the air so that we could use it as a fertilizer. During the 1800s we discovered that applying nitrogen to our soils made plants grow really fast. Though this nitrogen could be supplied with manure we quickly learned that Peruvian Guano and Chilean nitrates had more concentrated nitrogen and so less needed to be added to fields to get bigger responses. Incidentally we could also use the nitrogen from these sources for bullets and bombs. Nitrogen is a cornerstone of most conventional explosives. Unfortunately these sources of nitrogen did have a drawback, they are not renewable resources. You may say — Hey, Guano’s renewable! — But you’d be stretching the truth. You see, guano is aged manure where the nitrogen has had a chance to become concentrated.
Anyway, by the time the 20th century rolled around we had used up much of the nitrogen available from South America and so we (and by we I mean the world in general) were hurting for nitrogen — particularly Germany. Germany had a feeling there was going to be a war and she needed a way to get nitrogen other than sailing all the way to Peru or Chile. So she put money into research. Pretty soon two researcher, Haber and Bosch, came up with a method to take nitrogen directly out of the air and make it into ammonia. Once present in ammonia it could then be used to make any number of other nitrogen based compounds, from fertilizers to bombs.
Coincidentally, Haber is also known as the father of chemical weapons. He led the German poison gas program and had a hand in developing such things as mustard gas. He was considered to be a patriot, but, born a Jew, the rise of Hitler wasn’t good for him and he was forced to leave in the early 1930s.
The story of Haber and Bosch is absolutely fascinating, not only because of the colorful characters, but because their discovery is, arguably, the most important factor in the increase of the worlds population over the last century. The best book that I know of on this topic is Enriching the Earth by Vacliv Smil. It’s a great book, but it does get a little technical. But my dad (he’s a chemist) showed me another book yesterday that is much more entertaining and readable than Smil’s book while retaining most of the pertinent science. It’s called The Alchemy of Air by Thomas Hager and, if your interested in fertilizers and the people who first developed them, then this is a must read.
This time of year is very exciting for the students in my plant propagation class because now is when they all get to try grafting. In particular, they get to place buds from an apple tree onto a rootstock. There is nothing like placing a bud from one tree onto another to make a person feel as though they’re a horticulturist (NOT HorticulturALIST — that’s not a real word). Especially if that bud successfully grows on the plant where it was placed and produces a happy new tree — What a warm fuzzy feeling!
There are all kinds of things that a rootstock can offer to the bud placed on it. The rootstock can make the tree a dwarf, it can be resistant to certain diseases which the bud isn’t, it can even add some degree of cold hardiness. In return, the bud produces a cultivar that the grower wants such as ‘Honeycrisp’ apple. Additionally, the bud also offers an older tree. This probably doesn’t make sense at first, so think about it for a second or two. The bud that was grafted onto the rootstock came from a mature tree and so it may be more mature than the rootstock (which may have come from a seed — if the rootstock came from something besides a seed — like cuttings — then the rootstock may also be quite mature). Because the bud from which the top of the tree will grow is more mature than the base the tree will usually come into bearing sooner than if it were grown from seed.
Tree age is a funny thing. Though you wouldn’t expect it, the base of a tree is actually the youngest part of the tree physiologically while the older portion of the tree is at the top from which most new growth comes. The reason for this is that the bottom of the tree was laid down first as the tree first emerged from the soil and so the bud from which that growth came hadn’t had the chance to age much yet. After a few years of growing up the terminal bud developed more and more “age” and so the top of the tree is more mature. Confusing? It confuses me too — and I’m oversimplifying things quite a bit here. Making it even worse, no two tree species seem to age in exactly the same way.
I grew up on a small farm (30 or so acres) near Tacoma, Washington. We raised our own Herefords, I gathered eggs from my frizzle chickens, and we all enjoyed apples, plums and cherries from our fruit trees. Neither of my parents were farmers by profession, though my grandfather owned a dairy farm in Oregon. Eventually, my husband and I hope to move back to the family farm, if for no other reason than preserve it from the surrounding encroachment of houses.
I’ve been thinking about things I might do for fun or profit on the farm. Home grown beef for sure. A veggie garden – finally – on some of the only native soil left in the area. We’ve got lots of options and the space to try them out.
Now back to the question in the title: organic or local? Our family property has been managed gently since we moved there in the late 1960’s. Nothing’s been added to the pasture soil other than what the animals deposited themselves. We’ve had the apple trees sprayed yearly (a requirement because of apple maggot), but this is a targeted application with little affect outside the trees. The cattle were never treated with hormones or other additives – they were about as free range as you can get.
I’ve heard from others that organic certification standards have become increasingly difficult to meet and some growers think they have become increasingly meaningless. On the other hand, locally-grown products are becoming more available.
Is it time for a new standard – locally grown, with some requirements (e.g. soil tests) to demonstrate safety?
Recently, Rebecca Finneran, an MSU Extension Educator from the Grand Rapids area sent me a cool photo. The tree is a large Norway spruce near the Kent country Extension office.
This is a great example of witch’s broom. Witch’s brooms are growth anomalies that occur on various trees, most commonly conifers, Brooms can be caused be a variety of factors including diseases, aphids, environmental stress and random mutations. In some cases the growth defect is only present when the casual agent, say, a pathogen is present. In others, however, the growth mutation can be propagated by grafting scion wood from the witch’s broom onto a regular rootstock. In fact, this is the origin of many forms of dwarf and unusual ornamental conifers. Because of this, brooms are often a prized commodity and ‘Broom hunting’ is an active past-time for conifer enthusiasts such as members of the American Conifer Society. ACS members that find their first brooms are sometimes referred to as ‘Baby broomers’. Broom hunters are a focused lot and have been known to screech to a halt on major interstate in their relentless pursuit of conifer conversation pieces. So keep an eye out for brooms – and broom hunters!
With the late Chub Harper and the ‘Merrill broom’ tree at Hidden Lake Gardens, Tipton, MI
One of the hallmarks of science is that our view of the world evolves and changes as new evidence comes to light. When I was a grade-schooler following the Apollo missions, for example, I knew all the planets in order from Mercury to Pluto and how many moons each one had; Jupiter was the champ with 12. Today, Jupiter has as many as 63 moons depending on who’s counting. And Pluto, let’s not even go there. Likewise, our view of plant science has changed over the years. As I’ve mentioned before, when I took introductory Botany as an undergrad thirty-some years ago we learned that there were 16 essential plant nutrient elements. Since then we’ve learned that nickel is also essential at least for some plants.
If you took your plant science more than 10 years ago, you also learned that nitrogen is taken up from the soil as either ammonium or nitrate. This view is now being revised due largely to evidence from the ecological literature. Ecologists have found that in northern boreal regions where soil temperatures are cold and mineralization and nitrification rates are low, plants will take up intact amino acids from the soil (Nashholm and Persson, 2001; Kielland et al., 2006). Recent studies have extended these observations to temperate forests (Gallet-Budynek et al., 2009) and horticultural crops. (Ge et al., 2009), indicating that a range of plants may be able to derive a portion of their N requirements directly from organic sources.
So what does this have to do with the Garden Professors and the science of landscape horticulture? First off, this is pretty cool stuff and certainly will cause a lot of re-evaluation of some established paradigms. From an applied perspective, fertilizing with amino acids and related organic source has some potential benefits. In warm, well-aerated soils, nitrate-N predominates. When plants take up nitrate, it must be reduced via nitrate reductase and nitrite reductase before it can be assimilated into amino acids. These steps require metabolic energy. In theory, amino acids could bypass the reduction and assimilation processes and provide a more efficient means of fertilization. At this point, most of the scientific focus is on quantifying how much organic N can be directly taken up from the soil. Evaluating efficiency of uptake and utilization is a couple steps down the road. Amino acid fertilization could potentially provide another benefit over nitrate fertilization by reducing nitrate leaching.
Of course there’s a potential downside as well. A quick Google search of ‘amino acid fertilizer’ reveals sites shilling all manner of concoctions for fertilizing plants; many of dubious value. One of the first sites I hit proclaims that, unlike inorganic fertilizers, their product provides the 70 elements needed for plant growth. Seventy?! Well that’s close to seventeen. Point is be prepared for an ever increasing barrage of claims about organic fertilizers. There is no doubt that compost and similar organic sources can provide essential plant nutrients and effective fertilizer sources. As always, however, be skeptical of spectacular claims and secret, proprietary ingredients and pay close attention to the cost of amino acids compared to conventional fertilizers. There is some science here; clearly many plants have the capacity to take up amino acids directly. Beyond that we’ve still got a lot to learn.
Gallet-Budynek, A., E. Brzostek, V.L. Rodgers, J.M. Talbot, S. Hyzy, and A.C. Finzi. 2009. Intact amino acid uptake by northern hardwood and conifer trees. Oecologia 160:129–138.
Ge, T., S. Song, P. Roberts, D.L. Jones, D. Huang, and K. Iwasaki. 2009. Amino acids as a nitrogen source for tomato seedlings: The use of dual-labeled (13C, 15N) glycine to test for direct uptake by tomato seedlings. Environmental and Experimental Botany. Volume 66: 357-361.
Kielland K, J. McFarland, and K. Olson. 2006. Amino acid uptake in deciduous and coniferous taiga ecosystems. Plant Soil 288:297–307.
T. Näsholm and J. Persson. 2001. Plant acquisition of organic nitrogen in boreal forests, Physiol. Plant 111: 419–426.
A paper was recently published in the Proceedings of the National Academy of Sciences which discussed the dangers of one of the most commonly used weed killers in the United States, atrazine. This paper was written by Tyrone Hayes and colleagues and was immediately embraced by the media because it showed something scary (which the media loves — in case you were wondering). In a nutshell this study showed that frogs were changed from males to females when they were exposed to relatively small amounts of the herbicide atrazine. The next day in class I had a student come up to me and ask me about it and what I thought. I gave him my short answer (class was about to start). Here’s the longer one, but first I want to present you with some notes which will be important as we proceed.
Science does not provide values, instead it is a tool to use with your own personal value system. Some people may put a high value on cheaper production of important food crops such as corn, while others may put a high value the absence of potentially dangerous chemicals. That doesn’t matter to science. Remember that — science doesn’t give a poop what you care about. Furthermore, science doesn’t care what past experiments have found — what one researcher finds another may not find. Who knows why? That’s just the way things happen. On with the story.
Atrazine has been around since 1959. It’s a preemergent herbicide (which means that it kills weed seeds as they germinate) used on a variety of crops, but most frequently on corn. One of the advantages of atrazine is that it works extremely well in no-till growing systems which are used to reduce erosion. Another advantage of atrazine is that it’s cheap. Generally atrazine is considered to have a low toxicity (lower than caffeine for example). Additionally, though there is some data out there showing that it may cause cancer, this is grossly outweighed by data demonstrating that it isn’t carcinogenic. But there is data showing that atrazine is a hormone disruptor potentially affecting such hormones as estrogen and testosterone — and this effect is generally considered real — in other words not many scientists dispute it.
Over the years this hormone effect has been seen as a Bad Thing, but not bad enough to warrant banning this useful herbicide. Then along came Tyrone Hayes — and he started looking at how atrazine affected frogs — despite the recent news surge he has been doing this work for a long time (about 10 years) and has published much of that work. In a nutshell he is showing that atrazine, and to some extent other chemicals, cause hormone problems in frogs, particularly male frogs. Sex change and/or hermaphroditic frogs ensue! Unfortunately (or fortunately depending on how you look at it) other researchers have not been able to show the same things — at least not it the dramatic way that Dr. Hayes has (I’m not implying that they haven’t found problems with atrazine — they have — Dr. Hayes findings just tend to be more dramatic. Speaking of which, if you ever have the opportunity to see Dr. Hayes give a talk GO! He is an amazing public speaker and his slides and words make his findings even more dramatic). There is little to no direct evidence that hormone disruption caused by atrazine is currently affecting humans though many news sources are trying to draw that link. Indirect evidence is pretty weak too — but not nonexistent. The European Union banned atrazine in 2001. Should we follow?
My value judgement follows — yours might be — in fact it probably should be — different.
Here’s what I think. Ban atrazine, or at least regulate it more tightly. Why? Because there are many weeds resistant to it (that’s what happens to old herbicides…). Because there are options which are safer for our ecology (though they are somewhat more expensive). Because this stuff is showing up in groundwater at rates higher than what we’d like to see, and these concentrations will probably continue to rise — a direct result of using the stuff for so many years. Look, we don’t need to cut farmers off from this stuff right now, lets start a phase-out program and get rid of it over the next five years. Why not? If we NEEDED it to produce crops I’d probably be on the other side of the issue, but we don’t, so I reside firmly on the “let’s be cautious about this” side.
First of all, who we are and what we do. All of the Garden Professors are in the business of the science of Horticulture. What’s Horticulture? The standard definition of Horticulture is the art and science of tending a garden. Horticulture is clearly more than science but science is the foundation and underpinning. For anyone that needs convincing that Horticulture is an art as much as a science I suggest the following exercise. Go to a major research university and wander through their Botany or Plant Biology greenhouses. Observe the plants. They look like crap. The people working there are on the cutting edge of plant science; they sequence genes, they elucidate biochemical pathways but they can’t grow a plant to save their lives. Now wander through the Horticulture greenhouse; plants are thriving, flowers are blooming. What’s the difference? The horticulturalists not only have the science, they have the art. There is no denying that art and intuition play a role in growing plants, especially in ornamental horticulture where we deal with hundreds of species and cultivars, each with its own subtleties and nuances. But as educators, especially public funded educators, how do we teach intuition? It’s very difficult. What we teach are principles developed through systematic scientific inquiry. How do we know there are 17 essential elements needed for plant growth? Repeated experiments over the years. And our knowledge continues to evolve based on the scientific method. I’m old enough that I learned 16 essential elements as an undergrad; the need for nickel by some plants had not yet been established. As extension educators our role is to disseminate science-based information. For some of us that phrase is even in our job description. We can try to impart our experience and intuition but it’s a difficult thing.
It can be especially difficult when we deal with alternative systems for which a long-term knowledge base may be lacking. Despite perceptions to the contrary, we are not apologists for the status quo. Overuse and misuse of pesticides and fertilizers are rampant, especially in ornamental horticulture. A lot of our current research and extension programming deals with reducing water and nutrient usage to reduce run-off and to reduce leaching. I spend a lot of time telling growers things they don’t really want to hear. How do we know growers are potentially impacting water resources? Because we and others have done the scientific research. We’ve set out plots, we’ve fertilized, we’ve sampled leachate, we’ve measured run-off. And we’ve conducted extension programs teaching growers that they can back off fertilization and irrigation rates without reducing crop growth.
Where we get concerned is that some assume or take on faith that because a nutrient source is ‘organic’ or ‘natural’ it’s automatically better or safer for the environment. Is the nitrate from Chilean nitrate less likely to cause blue baby syndrome then nitrate from ammonium nitrate? Dr. Corey Reams developed his principles as revealed to him through divine revelation. Unfortunately most of us are not blessed with such experiences. Instead we rely on systematic scientific investigation to develop knowledge that we share with our clients. Personally I do not believe that faith and science are mutually exclusive. Some of the most brilliant scientists I have met in my career have been people of deep and abiding faith. But we need to keep each in its context. Science is knowledge gained through systematic inquiry. Faith is a belief system. The central tenets of most Christian denominations are stated in the Nicene Creed which begins, “We believe in one God…” Note it doesn’t start “We know…” or “We can prove…” In their liturgy Catholics, “proclaim the mystery of faith; Christ has died, Christ is risen, Christ will come again.” Not only can they not prove these things they celebrate the fact that it’s a mystery. Faith does not demand proof. Science does.
Occasionally one of the GPs will blog about a book that’s particulary good – or not. I was given a copy of Ruth Stout’s No-Work Garden Book a few years ago and frankly hadn’t given much more than a passing glance. But last week I thumbed through it and was immediately struck by the quality of science this self-taught gardener brought to her writing.
Much of Ruth’s gardening practices included the use of organic mulch on vegetable gardens, and she regularly wrote to scientists to ask for their interpretation of “expert” advice. Here’s an excerpt from a letter written 50 years ago by Dr. Arthur Pratt from Cornell:
“Yes, leaves, hay, straw, etc. that are not decayed or that are only partially decayed will rob the soil of nitrogen if they are mixed into the soil. But when used on top the way you use them, I have never seen a nitrogen shortage as a result of the mulch.”
So, we’ve known for at least 50 years that organic mulches don’t cause nitrogen deficiencies. Why does this misconception persist, especially for woody mulches?
Ruth also challenged the use of plastic mulches, then relatively new to the garden product market. She understood the benefits of a no-till approach to maintaining healthy soils. She has a whole chapter entitled “Make Mine More Mulch.”
So here’s to Ruth Stout, the original “Mulch Queen.”
Yes, not my day to post, but I just received an email with a link to a new product called Packing Pearls. These are polystyrene balls that fill the bottom of large containers so they aren’t so heavy. They are promoted as “improving water drainage and oxygen flow.” You can find a link here
The “pearls” are separated from the soil and plant roots with a pot liner (composition unknown). We’re told that the roots can’t grow through the pot liner. So now my question: can a material that “improves water drainage and oxygen flow” be impervious to root growth? Doesn’t it sound as though you’d be waterlogging the soil by installing this liner?
I honestly don’t know the answers to these questions, and the web site is not detailed (nor does it contain any links to research). The emailed advertisement states “Tests show that flowering plants bloom two to three months longer when grown in containers with a base of Packing Pearls. Plants are also visibly healthier and hardier.”
Anyone used this system before?