Thought I’d throw up a quiz today. In the work that I do I frequently see trees and other plants damaged by herbicides. The plant in the picture below was accidentally hit with an herbicide very similar to 2,4 D, but one that is not currently labeled for general landscape use (clopyralid). Can you guess what type of tree it is?
When I first started reading extension recommendations for plants around 15 years ago now, I read a lot about “balanced fertilizers”. Today I still see balanced fertilizers recommended, but not nearly as frequently, which is a good thing.
At this point you may be asking yourself “what is a balanced fertilizer?” A balanced fertilizer is one that has three numbers on its label which are the same — such as a 10-10-10 or a 14-14-14 (Nitrogen, Phosphorus and Potassium are the three nutrients indicated by
these numbers). Although it might seem like equal numbers would mean equal amounts of these nutrients, these numbers actually indicate percent Nitrogen, percent P expressed as P2O5 (in other words, if you took all of the phosphorus present in the fertilizer, made it into P2O5 and then added it back to the fertilizer and figured out what percent of the fertilizer that made up — that would be the second number) and percent potassium expressed as K2O (basically the same as the phosphorus example you saw previously).
But here’s the problem. The amount of phosphorus, and often potassium, that is added when you use a balanced fertilizer is typically out of line with the amount that the plant needs. This is because fertilizers are usually applied based on the amount of nitrogen that a plant needs. The reason that a balanced fertilizer was usually recommended was that phosphorus and potassium levels in these fertilizers is high enough that they provide all of those elements that a plant needed without being toxic to the plant. The problem is that, while the levels of these nutrients added might not be toxic, they are in excess of what is usually needed.
OK, so we’re adding excess phosphorus and potassium, what’s the problem? Well, for the potassium the problem isn’t usually that big a deal. In fact, a fertilizer bag with the first and third numbers equal may be what’s called for in many cases — fruits and nuts in particular often like a higher level of potassium. Additionally, the world has a pretty big store of potassium so we’re not likely to run out any time soon. Phosphorus, on the other hand, is a little bit different.
Phosphorus is a bit more hard to find in large quantity than either of the other elements in a bag of fertilizer. Because of this it is often the element that limits the growth of plants, for example algae. When phosphorus runs off into a lake or other body of water it can allow algae to go crazy and use up all of the oxygen in the water killing fish and other creatures (actually it’s the dead algae that do this — bacteria use oxygen while breaking the algae down). Most of you are familiar with this and know that it’s the reason why Minnesota and now Wisconsin have banned the use of phosphorus fertilizers on lawns without a soil test.
But here’s what you may not know. Most of the phosphorus which we use for fertilizers comes from rock phosphate. Rock phosphate is mined in only a few places around the world, Florida being one. Just as it is a foregone conclusion that we will run out of oil someday, it is also a foregone, but lesser known, conclusion that we will run out of rock phosphate. Estimates are that we will reach “Peak Phosphorus” (in other words maximum phosphorus production.) in 20 years or so and that we will run out in 50 – 100 years. Here’s an interesting article on the situation http://www.foreignpolicy.com/articles/2010/04/20/peak_phosphorus
So conserve our natural resources and skip the balanced fertilizer. When asked for a general use fertilizer recommendation I usually recommend something with a ratio of roughly 5-1-2, with a higher potassium content if you’re growing fruits or nuts.
Last month Linda posted on the need for horticultural knowledge for those trying to restore native habitats or at least establish native plants. There seems to be a pervasive notion that if we plant natives all we have to do is stick them in the ground and walk away. They’re native, right? Don’t need irrigation; don’t need fertilizer; all that good jazz. Well, often there is lot more to it than that.
A case in point. Over the past couple of years I’ve been watching an unintended experiment near the State Capitol grounds in Olympia, WA. The State opened up a vista so that the south end of Puget Sound and the Olympic Mountains were visible from the Capitol campus. It’s a lovely view. As part of the development, a switchback trail was established on the steep hillside to connect the Capitol grounds with the park surrounding Capitol Lake below. A great idea. Along the trial the hillside was planted with an array of native plants such as Oregon grape, salal, alder, and western redcedar. Another fine idea. Now comes the problem. Near as I can tell, there was no plan for maintaining these native plants. In fairly short order the hillside has become overrun with grasses, dandelions, and Himalayan blackberries – not exactly the desired effect. And therein lies the rub. Everyone is on board to plant natives but who’s on board for the hard work to maintain them. Keeping weedy species from this planting by hand would take an army volunteers. Burning is likely out due to the proximity of the Capitol and probably wouldn’t promote the desired species. The answer? Most likely a combination of hand-weeding and herbicides. It is interesting that when the end justifies the means, herbicide is not such a dirty word anymore. So there you go. In order to effectively establish and maintain native plants, not only do we need to know about Mahonia aquifolium, Gaultheria shallon, and Alnus rubra; but it also helps to know about glyphosate, flumioxazin, and triclopyr.
OK, now we know why we usually leave the puzzles to Linda: mine are too easy! As several folks correctly noted the photo in my yard was an example of the "dog vomit fungus" or, more correctly "dog vomit slime mold" Fuligo septica. Either way, it’s fairly disgusting and fairly common. My expereince has been it that it often shows up shortly after I lay dowm some fresh mulch (ground pine bark in this case) and then we get rain and warm temps. Although sometimes it shows up when I give our dogs too many treats… Hmmm…
Thanks to all those who chimed in with comments and links. Here’s one more link with some interesting tidbits.
http://botit.botany.wisc.edu/toms_fungi/june99.html
Was on the road earlier this week and missed my regular post. Thought I would slide in here with a Friday puzzler. This one is from my very own yard last week. Know what it is?
Today I was reading an interesting gardening website with a wide variety of advice, some good and some not so good. As I analyzed the website in my mind to figure out why some stuff was good and some stuff was bad it occurred to me that the problem was that a lot of the stuff that the author was recommending was based on testimonials. And then it occurred to me that many of you out there might not know what a testimonial is and why recommendations based on testimonials shouldn’t be recommended — and then viola! I had a blog post.
A testimonial is testimony presented by one person about their experiences with something. It’s like when a friend tells you that dryer lint controls slugs in a flowerbed. Don’t laugh, this is a real suggestion on one website! This person decided that it was appropriate to put dryer lint around their garden, and when they did, slug damage appeared to be reduced. Good for them. But is it good for you? The answer is maybe.
The problem is that this person is missing the two things that we need when assessing whether a particular thing works. First, we need a a control, and second, we need replication. Let’s use the dryer lint example.
We have no idea whether, if we hadn’t put out the dryer lint, the slug population might not have dwindled anyway. To find out whether it might have we need to treat only a portion of our garden with dryer lint and then see if the treated portion has more or less damage than the untreated portion after a few weeks. The untreated part of the garden is called a control and it is necessary for a good experiment. But it isn’t the only thing necessary for a good experiment, so is replication.
It is possible that the part of the garden which was treated with the lint had less slug damage than the control portion of the garden for some reason besides the lint — for example, perhaps the area where the lint was applied happened to be further from the sprinker than the other section — and slugs like it moist. So to combat possible problems like this you need to conduct your experiment more than once. In other words, you need to replicate your trials. This might be done by doing this experiment over multiple years, by having other people in your gardening club try it too, or by dividing up sections in your garden into six or so equally sized sections so that three randomly selected sections get treated with lint and three don’t. Or, best of all, do all of these things — multiple years, multiple gardens, and multiple plots within a garden! If we did more testing like that I have a funny feeling that we’d have fewer crappy products for sale.
Testimonials are interesting, but don’t get fooled into thinking that they prove anything. They don’t. You need control and replication to demonstate that something really works.
Hydrangeas are in full bloom this time of year. I snapped these photos yesterday of several hydrangeas, all planted along the same strip of land. Just look at the different colors:
Why so many colors? Most of you probably know that genetics play a role, as does soil pH. But there’s much more to it than simple soil chemistry and genes.
1. pH: Strongly acidic soils produce blue hydrangeas, while slightly acid to slightly alkaline soils favor pink or red flowers. Soil pH can be modified by adding lime to raise soil pH or ammonium sulfate to acidify the soil.
2. Aluminum: Aluminum, a toxic heavy metal, is required for blue hydrangeas. Like other metallic elements, aluminum binds tightly to clay particles under alkaline conditions. As the pH becomes more acidic, aluminum becomes soluble and can be taken up by plant roots.
3. Nutrients: Relative concentrations of phosphate, nitrogen, and potassium have significant impacts on the uptake and activity of aluminum.
4. Pigments: Blue hydrangea flowers depend on the formation of a complex among three partners: an anthocyanin called delphinidin with a sugar attachment, a phenolic acid co-pigment, and aluminum. Co-pigment differences among species and cultivars will influence flower color.
And here’s an interesting factoid about hydrangeas: ever notice that they are rarely bothered by insects or other animals? Accumulation of a toxin like aluminum in their tissues may be the reason.
[And I don’t mean “greatest hits”, I mean “Mafia hit”]
Gardeners, yardeners, and designers are on a perpetual lookout for a good hedge species. Hedges are useful in so many ways: providing backdrop for a border, making good neighbors, containing football players, etc. In reference to the latter, the field at Sanford Stadium at the University of Georgia (cue woofing!) is known as “Between the Hedges”. In the extensive lore of UGA football, everyone makes like it’s some sacred plant, but (gasp!) it’s just plain ol’ privet. Aside to Jeff, my fellow UGA alum: CNN just reported the dubious distinction that Georgia is the #1 party school in the country (again). Maybe this is why I can’t remember the Krebs Cycle.
Variegated Chinese Privet in all its shrubby glory; photo from University of Arkansas Cooperative Extension.
Back to privet. Designers of D.O.T. landscapes such as medians and interchanges seem especially enamored. Clouds of variegated privet (L. sinense ‘Variegatum’) dot interstates throughout the South. Yes, it’s tough, useful, variegated, and touted as “wildlife friendly” by some leading gardening resources. The berries are indeed good bird food; therein lies the problem. Seeds pooped out by birds results in the green, non-variegated version – much more vigorous and deposited everywhere. For the record, the variegated form also reverts like crazy.
My family’s farm in northeast Georgia is bordered by the North Fork of the Broad River. Over the years, the river bottom, and then the fence lines at all elevations, have filled with privet. It is, pardon my language, a total bitch to remove and almost impossible to eradicate. The State Botanical Garden of Georgia in Athens has an entire squad dedicated to eliminating it from acres of river bottom; ironically, only a few miles from Sanford Stadium. Thought of mostly as a Zone 7-9 plant; we have lots of it in the woods here in the mountains – an entire zone cooler.
Distribution of L. sinense; USDA PLANTS Database http://plants.usda.gov/
Ligustrum sinense is on at least two official Invasive and Noxious Weeds lists by the Southeast Exotic Pest Plant Council and Florida Exotic Pest Plant Council as well as several international lists. Nursery growers and landscapers across the South know these things. So why, why, why, do they continue to produce and spec it? “Variegated foliage sells. People see it, like it, and then ask for it. It’s a bread-and-butter item.” This comment came from the owner of a fairly large nursery that sells to independent garden centers.
Our industry yelps whenever a state or federal mandate threatens to impose restrictions on a best-seller (Hedera helix, for recent example). There are LOTS of terrific woody plants out there, people. The Dirr book is now up to 1250 pages – thumb through and pick a few alternatives. Cease and desist with the Chinese privet.
OK, this Friday’s quiz is the real deal: everyone gets to play “Extension Specialist for a Day”. I am stumped on this and so are my colleagues here at MSU. I used to work for a guy who liked to say, “None of us is as smart as all of us”. Let’s put it to the test.
The photos below come from a nursery here in Michigan. The trees are container-grown Red sunset maples. Pretty routine crop around here. The trees look fine: good color, full crowns, growing well. The only problem is that nearly all of the trees have bumps along the bottom 8” or so of the trunks. The grower is concerned, and rightly so, about consumer acceptance of the trees. The trees have been examined by a highly qualified pathologist – no evidence of fungal disease; and by a highly qualified entomologist – no evidence of insect activity. The grower is sitting on several hundred of these trees. What should I tell him?
NOTE: The name of the nursery is confidential – they just used the calipers from Schumacher’s in the photo.
Last week’s column on “why do nurseries sell this plant?” struck a chord with many readers as well as with Holly! So here is this week’s submission: that ubiquitous vine, English ivy.
First of all, we’ll stipulate than many ivies are sold as English ivy (Hedera helix) but may be entirely different species. Genetic research on invasive ivy populations in the Pacific Northwest identify most as H. hibernica (aka Atlantic ivy), with H. helix making up only 15% of the invading populations. Regardless of their species identity, it’s obvious that Hedera is a genus with the potential to escape gardens and invade remnant forests or other environmentally sensitive areas. It grows so vigorously that it can create monocultural mats on forest floors; it grows into trees where its sheer weight can break limbs and in some cases topple entire trees.
But what about other regions of the country – or the world, for that matter? In colder climates, Hedera spp. are much better behaved, dying back to the ground every winter and rarely able to flower and reproduce. The absence of a seed bank means the vine can be kept in check more easily. And it does tolerate tough environmental conditions where other groundcovers might not succeed.
Yet consider another invasive: kudzu (Pueraria montana var. lobata) For decades this noxious weed was thought to be too cold sensitive to expand past the American Southeast. Yet populations have been found in Maine, Oregon, and most recently in Ontario, Canada. Plants adapt!
So – is it worth the risk to buy a plant known to be invasive elsewhere, simply because it’s not a problem yet?
And why oh why do nurseries in Washington state continue to sell Hedera spp. as ornamentals?
