The Garden Professors™

Modern day torture stakes

Torture stakes were used centuries ago as a slow means of executing prisoners. Unfortunately, the practice lives on every time someone incorrectly stakes a newly planted tree. Though I’ve written about tree staking before (click here to read more), I’ll use today’s blog to demonstrate another unintended result of improper staking – decapitation. A normal tree develops taper as it grows. At eye level, a tree trunk is narrower than it is at ground level: that’s taper. As the trunk flares out and morphs into roots (Figure 1), a buttressing structure is created that allows trees to remain upright, even under windy conditions.

Figure 1. Trunk flares as it meets soil and roots begin.

A tree that’s been staked too high, too tightly, and/or for too long does not have this structural protection. Instead, the staking material creates an unnatural pivot point, which is not structurally capable of withstanding wind. When the inevitable windy day comes along, the trunk snaps at this point (Figures 2-3):

Figures 2 and 3. Tree decapitation, up close and personal.

Unlike the victims of the original torture stakes, trees don’t necessarily die after breakage. They are, however, permanently deformed and have little aesthetic value. If trees need to be staked at planting (and many times they do not), staking needs to be low and loose to allow taper to develop normally. (More information on proper tree planting can be found by clicking here.)

Fabulous Sporobolus!

“Where have you been all my life?!!”

Every once and a while, I come across a plant and simply fall in love.

I am not alone on this particular species, and the bandwagon is getting mighty crowded. Sporobolus heterolepis is the object of my affections…it even has an intriguing common name – Prairie Dropseed. It’s native to much of North America, short of the West Coast. Though most widespread in the Midwest, there are isolated populations in Virginia, North Carolina, and Pennsylvania. It’s even hardy up in the Arctic North (where Jeff and Linda live).

Sporobolus shows off some fluffitude while Echinacea tennesseensis look on in amazement. Author’s garden.

Now on to the juicy description: fine, green foliage forms fluffy mounds or tussocks up to one and a half feet tall and up to two feet wide. I describe it to my students as “pet-able” – one just wants to run their fingers through the flowing locks… The tiny, fragrant flowers appear in late summer form a fluffy cloud above the foliage and wave about on slender stems, even with the slightest breeze. I think the flowers have a coriander scent, have also heard buttered popcorn and vanilla. Seeds form and then drop to the ground around the plant (hence the common name), at which point the birds scarf them up. There is very little actual germination; the species is in fact endangered or threatened in several states (USDA Plants Database). As the weather cools, the fall color can range from bronze to orange to apricot – just gorgeous – and then turns to a tawny buff for the remainder of the winter.

Newly-planted in the Hahn Horticulture Garden at Viginia Tech – check out that fabulous fall color!

As with many prairie natives, this a very tough character once established – puts up with lousy soil, little rainfall, and is definitely drought-tolerant. We’ve added more than 100 of them to our campus meadow garden. At my favorite public garden, Chanticleer (Wayne, PA), they’re planted in huge drifts and are managed in the “natural” way, with controlled burns in the early spring.

Doubt you’d find it at a big box store, but it should be available at an independent garden center near you! Please note this one of those species that does NOT look very exciting in the pot, especially in the spring (green, grassy, that’s it). But give it a season or two in your garden and…[cue romantic violins…].

Global Warming, Carbon Dioxide, and Plants

There was an article published recently that traced the melting of glaciers in the US over the last 50 years. This study showed, pretty convincingly, that the glaciers are, indeed, melting, and melting rapidly. Meanwhile, in our atmosphere, levels of carbon dioxide from humans burning fossil fuel are increasing in a manner roughly correlated to the increase in temperature that’s melting the glaciers. But is the carbon dioxide actually causing the warming? Believe it or not this is still an area of discussion among scientist, and the answer isn’t as simple as many newspapers make it out to be. Almost all of the scientists that you care to talk to, even those skeptical of the role of carbon dioxide in global warming, admit that increasing carbon dioxide is going to cause a net increase in global temperature. But there is a decent amount of research out there showing that solar and geothermal activity (in other words things that we can’t control) may cause anywhere from 15 to 75% of the warming that we’re seeing. To be honest, based on what I’ve read (and I’m no climate scientist), I tend to side with those who believe that global warming is mostly caused by human releases of carbon dioxide, but I also think that to accept that theory as proven is a mistake.

In my humble opinion we’re missing the more compelling reason to reduce our emissions of carbon dioxide (besides the fact that we’re running out of fossil fuels of course). Plants. Most people simply assume that, temperature increases aside, increasing carbon dioxide in the atmosphere is going to be good for plants, and that’s just not the case. True, some plants, like Canadian thistle and many other weeds, love the increase in carbon dioxide, but other plants, such as many grasses, just don’t respond to it that well. The ironic thing is that, for those plants that respond strongly to CO₂, nutrients like nitrogen and potassium are taken up quickly from the soil (as you’d expect with a rapidly growing plant) and then, as the nutrients in the soil run out, the growth of the plant is drastically reduced. In other words, CO₂ causes unfertilized soils to become more rapidly depleted. So what does this all mean? It means that as we increase CO₂ levels in the atmosphere we’re changing the world’s ecosystem, including the fields that grow our crops. Indeed, we’re actually adjusting the atmosphere to alter which plants are most appropriate for certain situations. There are even those who argue that, because of our CO₂ emissions, we’re encouraging invasive plants to take over our native forests because these plants tend to be able to handle high CO₂ (and high temperatures) better than the plants that are already there.

To me this is the more important reason to reduce our carbon footprint.

The other side of nurseries

As some of you know, my background is somewhat different from most faculty members in Horticulture in that my roots (no pun intended) are deepest in forestry. I’m sometimes asked to compare and contrast various aspects of horticulture and forestry. There are certainly differences – some of which I’ll get into in later posts – but there are also a lot of similarities. One of the truisms that seems to pervade both fields goes something like this: “When all else fails, blame the nursery”. Whenever a tree dies, whether it’s a 2-0 bare-root seedling or a tree that was spaded in with 60” tree space, the first reactions is “Must’ve been bad nursery stock”. Um, could it have been that the tree planting crew left the bundle of seedlings in the 90 degree sun all afternoon or that 5” caliper red oak really doesn’t belong in a bathtub? I bring this up because often we see suspicion, if not downright hostility, aimed at landscape nurseries. I thought of this as I was touring J. Frank Schmidt and Sons nursery this week near Boring, Oregon (yes, there really is town called Boring). J. Frank Schmidt and Sons is one of the largest wholesale producers of shade trees in the country. If you walk into virtually any garden in the northern half of the US, chances are you will see trees that began their life in the Schmidt’s fields under the shadow of Mt. Hood. J. Frank Schmidt nursery is among the most progressive nurseries in the industry, investing in new plant development, in-house research, and supporting university research through the J. Frank Schmidt Family Foundation and donating thousands of trees for research trials. During the tour, our host. Jim Ord, was excited to show us an air-slit container that Schmidt had developed for to reduce circling roots in container-grown trees. As I mentioned at the outset, we are often quick to blame nurseries for causing problems, here’s an example of a nursery working to solve problems. And this is just one example, Schmidt and other nurseries are working to develop and promote new elms and other species to provide a wider array of trees to replace ash trees in the wake of the Emerald Ash Borer. In some ways Schmidt is unique due its size and progressive stance but other ways it is very similar to a large majority of wholesale nurseries which with I interact. While there are certainly issues that trace their roots to problems in nursery production, most nurseries take great pride in their products and work constantly to refine and improve their growing techniques.

What’s in YOUR soil? (with apologies to Capitol One)

Urban environments are always challenging for landscape plants just because they are anything but “natural.” Temperatures are higher, water is often less available, and compacted soils have all the nourishing qualities of concrete. The single most important thing you can do to ensure long-term success of landscape trees and shrubs is to get their roots well established in the soil.

I’m going to leave the topic of soil amendments to another day (but you can find my myth columns about them at http://www.theinformedgardener.com under “Horticultural Myths”). What I want to focus on is our propensity for fertilizing landscape trees and shrubs without really knowing why, or when, or if we should be adding any particular plant nutrient.

The smartest $13 you can spend is to have a soil analysis done before you add anything to your soil. My favorite soil testing lab is the University of Massachusetts at Amherst. That $13 will buy you a complete standard analysis of the available nutrients in the soil, plus a measurement of the soil’s organic matter content. Of course, there are many other soil testing labs you can use, but UM’s Amherst lab is only providing you with information – not a sales pitch for amendments and fertilizers.

Why is this so important? Let’s say you go to a nutritional supplement store, buy every possible supplement, and take them all. Do you need all of these? Probably not. It would be smarter to talk to your doctor and find out what you’re missing, right? It’s the same with your soils. Don’t assume your soil needs a lot of phosphorus, even though transplant fertilizers are loaded with this element. Non-agricultural soils often contain abundant levels of this nutrient, and too much phosphorus will hurt mycorrhizae and contribute to water pollution. Take a look at this portion of a soil test for an organic demonstration garden:

Figure 1. Note the high level of organic material in this soil, which contributes to the nutrient overload.

The trick to fertilizing landscape soils is understanding that landscape soils are not agricultural soils. You’re not harvesting crops (an activity that depletes the soil of its plant nutrients). Urban landscape soils usually have high enough levels of most nutrients to sustain plant growth. But you’ll never know unless you have your soils tested.

What I Learned This Summer (part 2): Pot Recycling, a Photo Essay

A big “score” at a great garden center or nursery results in guilt. Not about the money I spent, but the giant pile of pots and tags left in the wake of the planting frenzy. I plan to provide a more thorough review/discussion on this topic in the future – but for now, I want to share what I learned in a visit to the Missouri Botanical Garden’s (MOBOT) recycling center in St. Louis (part of the Perennial Plant Association’s annual conference). As one of the public gardening world’s leaders in conservation and sustainability, their program is truly revolutionary and apparently very successful. In place since 2006, they’ve kept hundreds of thousands of pots out of the landfill.

Dr. Steve Cline,recycling guru and dynamic Director of MOBOT’s Kemper Center for Home Gardening, explains the system to our group.

Start with your basic pile o’ pots, knocking out loose soil, beer bottles, whatever they’ve accumulated.

Deliver them to either a participating garden center (there are several) or the garden’s recycling location and place in the appropriate bin.

If off site, pots get hauled to the garden’s Monsanto Center for recycling. Garden staff and volunteers then send them off to the great and loud Pot Chipper in the Sky…

resulting in pot confetti…
Woo hoo! (flings in air)

…which gets shipped to manufacturers of cool things like plastic lumber!

Voila. Guilt relieved; IF you garden in the greater St. Louis area. I’ll be talking about alternatives for the rest of us in a future post!

The Pile Of Ash On My Floor

Part of the problem with being a professor is that companies assume that I have a bottomless supply of funds to test their products and that it is, in fact, my duty to do so. And of course they assume that this testing will ultimately find their product useful.

The truth is that I do love to test things, but I don’t have the funds to do the comprehensive tests that these companies usually want, at least not without them helping out at least a little – and most of them don’t want to spend money on tests! But many times, even if I tell them on the phone that I’m not likely to test what they’re selling they’ll send along a sample anyway, hoping that I’ll be curious enough to give the stuff a shot. And I usually let them because, well, why not?

Anyway, that brings me to this pile of ash that is currently sitting on my floor. A guy from a company (which I will decline to name) called me on the phone and convinced me to accept about 25 pounds of rice hulls that had been burned to ash while being used to fuel something or another (I can’t remember what and there was no note in the box). This ash is supposedly the cat’s meow for helping the media in containers to retain water and this guy wants me to test it. I told this guy that I was unlikely to have time for it, but he was insistent. I guess he thought that if the stuff sat on my floor long enough eventually I’d get curious, open the box, and try it out.

Turns out he was right.

So I get this box full of ash, open it up and am immediately hit in the face with black dust which I wisely (and accidentally) inhale. Lovely. Then I take out the MSDS sheet (Material Safety Data Sheet – required for most chemicals) and read about the problems with this product. It turns out this stuff contains crystalline silica (no surprise there, rice hulls are full on silicon), which can cause a rapid onset of silicoses as well as being a cancer hazard (crystalline silica is a known carcinogen if it’s inhaled).

Now I don’t want to blow the danger of this stuff out of proportion. I have little doubt that my exposure to it wasn’t enough to do anything terrible to me (just as I’m pretty sure that the two packs of cigarettes or so that I smoked during college aren’t going to eventually lead to lung cancer). And I’m all in favor of using industrial byproducts for other purposes whenever possible. But my goodness, this stuff is ash! It just flies into the air! I just can’t see how, even with the recommended protection, nursery workers could avoid inhaling this stuff on a daily basis if they were using it to pot up plants (perlite is pretty bad – but this stuff is worse) — which just seems like a heck of a bad idea. In terms of the ability of this stuff to hold water….well, I put some into a plastic container with some water which the ash absorbed none of. All that said, it might be possible that this stuff helps container media to hold more water, but for an unintended reason. This ash is extremely fine. When we mixed it with container media it quickly found its way into all of the pore spaces between the media particles making the media more like clay than media. This did potentially increase the media’s ability to retain water, but decreased its ability to hold air – which is not a good thing for young roots. So the quick and easy summary is that rice hull ash is not the best idea for containers.

Bad roots and deceptive marketing

I guess today’s blog should be entitled “The Cranky Garden Professor.” Really, I’m not always cranky, and when I am I go outside to do something constructive in my garden. Last weekend I finally tackled a 5-gallon container of lavender that I’d bought several weeks ago. I had intended to wait until fall to transplant it, but I was watering it every day to keep it from wilting. I figured I might have better luck getting it into the soil where a good mulching would help keep the soil moist without daily watering.

So I carefully slid the lavender out of its pot and into my root-washing tub (Figure 1). (If you’re not familiar with root washing trees and shrubs, be sure to check out my web page. I’ve got a fact sheet and some myth columns on why it’s important to bare-root containerized and B&B woody plants before installing them in the landscape. Please visit www.theinformedgardener.com to access the entire site, or this link for a fact sheet.

Figure 1. Five little lavenders.

As I worked the potting media out of the root mass, I suddenly discovered why I was using so much water to keep the lavender happy. It wasn’t one plant. It was 5 separate lavender plants all placed in the container to LOOK like one large plant. Worse, all 5 plants had some of the crummiest root systems I’ve ever seen (Figures 2-6). They were poked into the pot like little carrots. Most of the pot was filled with untouched potting media.

Figures 2-6. The beehive is back!

What you see in these figures are root systems that look like upside down beehives. They were obviously left in their original small pots too long and developed circling root systems. So rather than growing outwards into the soil, they stayed in these little spirals and eventually would fuse into woody knots. They don’t miraculously straighten out when they’re put into larger containers (or the garden). If they did, they would have rapidly spread throughout the big container to soak up all that water I was pouring on daily.

Sigh. Now I was cranky again. These lavender roots were just like those I’d seen on hundreds of landscape plant failures over the last 10 years. Since these roots were so tightly woven together there was little hope of untangling them. So I made one vertical cut through each of the root masses (Figure 7), spread them out horizontally (Figure 8), and planted them (Figure 9).

Figure 7. The cut. Figure 8. The spread. Figure 9. In the ground.

This is the worst possible time of year to transplant trees and shrubs (it’s August, after all) and I most definitely put a world of hurt on these roots. But I will say that since I moved them I have been able to reduce irrigation, since the soil holds moisture better than the potting media. I’ll keep track of their progress through the next 12 months. I’m hoping they make it through this summer – if so, they stand an excellent chance of growing a decent root system over the fall and winter.

Back to the cranky part. I really resent nurseries that deliberately bunch small shrubs together in one pot to make them look like one big plant. It certainly cost more to buy this one pot than to buy five smaller pots. If this isn’t deceptive marketing I don’t know what is.

Evaluating ‘Scientific’ Claims

Whenever I give talks to landscapers or gardening groups some of the most common questions that come up deal with various products promoted to provide ‘miracle’ results in the garden. These are usually various soil amendments; fertilizer additives, bio-stimulants, mycorrhizae, and the like. My initial reaction to these inquiries is, “What does your current basic plant maintenance look like?” Are you mulching? Irrigating when needed? Fertilizing if needed? Pruning properly? Have you matched the tree to the site conditions?

As a culture we seem oblivious to the tried and true and gravitate to the quick fix. Look at late-night infomercials for weight loss products. Hoards of people are willing to shell out $39.95 (plus shipping and handling) for a bottle of pills guaranteed to miraculously ‘melt away pounds’. Apparently “Eat less and exercise more” is a tougher sell. For garden products claiming to produce bigger, better plants there is sometimes a grain of scientific rationale and for a few, such as mycorrhizae, there are specific situations where they can be a benefit. Nevertheless the basic rule of caveat emptor is the best guide. Remember, just about anyone can get on PowerPoint and develop some slick looking 3-D bar charts and put together a glossy brochure or cool-looking website. Here are some things to consider when evaluating ‘scientific’ claims.

English 101

Words such as more, greater, bigger, faster are comparatives. They compare one thing to another. They need to be followed by a ‘than something’. Without an object they are meaningless. Advertisers use this all the time: “New Shill gasoline gives your car more power!” More power than what? Not putting any gas in your car at all? So what does a claim that a stimulant produces ‘more and stronger blossoms’ really mean?

What’s compared to what?

Some manufacturers go further and compare their product to an untreated control. This is a step in the right direction but can still be somewhat misleading. A common example is various bio-stimulant products, which often contain various enzymes and nutrient elements. Compared to an untreated control these may indeed improve plant growth. But is this due to a unique and patented blend of dung beetle excrement and papaya extract or simply the fact that a product contains essential plant nutrients? A better comparison would be to compare plants receiving the miracle product and plants receiving a conventional (and less expensive) fertilizer containing similar nutrient elements.

The bottom line, as always, is if something sounds too good to be true, it probably is. Before reaching for an exotic concoction of eye of newt and wing of bat, consider the basics of site selection and landscape plant management. Chances are there is a lot more to be gained from mundane matters such as putting the right tree in the right place than from trying to remedy the situation by sprinkling some magic dust over the roots.

Mulch Volcanoes

After Linda’s post yesterday I just had to add my own 2 cents about gator bags. I use ’em and I like ’em. But, that said, I never allow gator bags to sit against trees for an extended period of time (Maybe 6 weeks when the tree first goes in). That’s just asking for trouble! But looking at those bags got me thinking about a project which we’re finishing up this year. Volcano mulching. Believe me, it sounds a lot cooler than it is. Volcano mulching is when you make a big pile of mulch along a tree’s trunk, as in the picture below.

The reason we’re looking at volcano mulching is that everyone says it’s bad, but no-one has really proven that it’s bad. The reasons that volcano mulching are supposed to be bad are twofold: First, the mulch could cause rot on the tree’s stem (as with those gator bags) and second, because it might be possible for a tree’s roots to grow up into the mulch, potentially surrounding the stem, which might lead to the roots choking the stem as the tree grows larger. Not a good situation. Anyway, early in 2007 we took a field of maples and cut squares in their trunks, as seen below, and then either did or didn’t mound up mulch around these tree’s stems.

What we expected to see was that, over time, the wounding and presence of a mulch volcano would lead to diseases in the stem. Instead what we found is that, for many of the trees, deeper mulch actually led to the wounds closing more rapidly. The image below is of a wound that was covered with mulch.

While this next image is of a wound that wasn’t covered with mulch.

Of course some of the wounds without mulch closed fine as well, as you can see in the next image. (Why isn’t anything ever cut and dried?)

So what does all this mean? Well, nothing yet. Research is a funny thing: it rarely gives you quick and easy answers. I won’t recommend mulch volcanoes because we still haven’t examined those roots that may enter the mulch and surround the stem. And before I say that the volcanoes didn’t affect stem rot in this study I want to take a closer look at those wounds by cross sectioning the tree which we’ll probably do this fall. Plus we’ve got to run statistics on all the different trees….. and then it would be great if someone else would take a stab at this study to confirm what we see…. I tell you what, nothing’s easy.