Cool Research – Page 7 – The Garden Professors™

Two new postings on compost tea efficacy – and safety

We just don’t have enough excitement on the blog, so I thought I’d bring up two new items that just crossed my virtual desk. The first is today’s Garden Rant posting from Susan Harris. I won’t spoil her well-written blog, but if you’ve been following the debate on the disease-control properties of compost tea, you’ll be interested in reading it.

The second was in an email from a colleague at the EPA on a new journal article. Here’s what he said:

More potting soil and Legionella, this time in Scotland. (Eurosurveillance, Volume 15, Issue 8, 25 February 2010). Note that “other countries where L. longbeachae outbreaks have been reported” includes the U.S. but there is no required labeling here, though it is in Australia, New Zealand and possibly much of Europe. Also note the association of Legionella mainly with droplets, and the possible connection to compost sprays as seem popular among do-it-yourself pesticide makers.

“The exact method of transmission is still not fully understood as Legionnaires’ disease is thought to be acquired by droplet inhalation. The linked cases associated with compost exposure call for an introduction of compost labeling, as is already in place in other countries where L. longbeachae outbreaks have been reported.”

A rose by any other name…

This past week I got to spend three days doing one of my favorite things; talking about conifers. Wednesday I was a last-minute guest lecturer for a landscape design class and Thursday and Friday I did my ‘Conifers for Connoisseurs’ talk for our MSU Extension ‘Plants of Distinction’ program. One of my favorite conifers and one I often recommend as a large specimen tree is Alaska yellow-cedar (the name I learned in Mr. Chance’s Botany class at Olympia High School) or Nootka false cypress (the usual common name for the tree in this part of the world). Notice that I didn’t give a scientific name, like a good garden professor should. The reason? I’m not 100% sure what the scientific name for Alaska yellow cedar is any more.

Xanthocyparis nootkatensis at Daisy Hill Farm, DeWitt, MI

Prior to 2000 it would have been easy: Chamaecyparis nootkatensis. Then a team of international scientists including members of the Kew Royal Botanic Gardens and the Missouri Botanical Garden discovered a rare conifer in northern Vietnam, which was previously unknown to science. The new species was described in a 2002 article by Farjon et al as Xanthocyparis vietnamensis. A conifer still unknown to science at the end of the 20^th Century, that’s pretty cool. But, in addition to describing and naming the new species, the authors’ also reclassified Chamaecyparis nootkatensis with the new species as Xanthocyparis nootkatensis. While this news was mildly disappointing to those of us who love the tree and thought Chamaecyparis nootkatensis was about the coolest scientific name ever, the name change was not entirely surprising. Within the genus Chamaecyparis, nootkatensis was always the proverbial red-headed step-child. At one point the species had been grouped in the genus Cupressus. The change to Xanthocyparis also required a change for Leyland cypress, an intergeneric hybrid between Alaska yellow cedar and Monterey cypress (Cupressus macrocarpa). Under the new nomenclature ×Cupressocyparis leylandii becomes × Cuprocyparis leylandii.

Now, as if all this weren’t confusing enough, subsequent work by Damon Little based on molecular markers groups all of the Cupressus species in North America and the two Xanthocyparis species under one genus, Callitropsis. Little et al’s re-classification and rejoinder by Mill and Farjon (2005) demonstrate the schism which has developed between taxonmists that rely heavily of cladisitcs and molecular tools and those that rely on morphology and evolutionary relationships. Their debates are far testier than any barbs traded between Linda and the Brothers Horvath. Check out this link for a taste of the action:

http://urhomology.blogspot.com/2009/03/myths-that-evolutionary-taxonomists.html

Xanthocyparis nootkatensis at MSU Horticultural Gardens

So what about us poor horticulturists and foresters who just want to know what to call the damn thing? I suspect the taxonomic battle lines will deepen before anyone offers a peace offering. And this will extend far beyond Xanthocyparis (syn. Callitropsis). Get used to seeing lots of synonyms next to scientific names in the future. Remember when you took your first Botany class and learned we used scientific names to eliminate confusion over common names? Sigh… Alaska yellow-cedar sounds pretty good to me.

Farjon, A., N.T. Hiep, D.K. Harder, P.K. Loc, and L. Averyonov. 2002. A new genus and species in Cupressaceae (Coniferales) from northern Vietnam, Xanthocyparis vietnamensis. NOVON 12:179-189.

Little, D.P., A.E. Schwarzbach, R.P. Adams, and C.-F. Hsieh. 2004. The circumscription and phylogenetic relationships of Callitropsis and the newly described genus Xanthocyparis (Cupressaceae). American Journal of Botany 91(11): 1872-1881

Mill, Robert R. and Farjon, Aljos. 2006. Proposal to conserve the name Xanthocyparis against Callitropsis Oerst. (Cupressaceeae). Taxon 55(1):229-231

Better Red than Dead!!!

David, one of our newer readers, asked why his red-stemmed roses seem to be more cold hardy than the green-stemmed cultivars. So today’s blog will be dedicated to a brief discussion of why it’s better to be red than dead.

The brilliant red, blue, and purple colors seen in flowers and fruits are due to anthocyanins (and the closely related betacyanins). These water-soluble, non-photosynthetic pigments are also commonly found in stems, leaves and other vegetative tissues. In 1999 I wrote a review article exploring the reasons that leaves and stems might turn red. A few years later I wrote another review, more specifically looking at how anthocyanins might influence plant water relations. (This last phrase is plant physiology-geek jargon, and I have to admit that the class I took on this topic during my PhD work was the hardest, and probably most hated, of all the classes I took. And now it’s turned out to be one of the most valuable. Go figure.)

While you hard-core types can read the review articles that I’ve hot-linked above, what I’ll try to do is summarize my hypothesis for why leaves (and stems) turn red. Some leaves are red when young, then turn green when older. Green, deciduous leaves turn red before they fall off in the autumn. And some plants are genetically programmed to have red leaves all their lives.

The environment can also influence leaf reddening. Drought, nutrient deficiency or toxicity, salts, heavy metals in soils, cold temperatures, low soil oxygen, whew! All of these environmental factors have been attributed to temporary reddening. What do these factors have in common?

It turns out that all of these environmental stresses directly or indirectly affect the ability of plants to take up and/or retain water. Because anthocyanins are water-soluble, they effectively dilute the concentration of water in the plant. Look at it this way: any limited area will only hold so many water molecules. A test tube of pure water has the maximum number of water molecules possible. A test tube of water plus sugar (or salt, or anthocyanins for that matter) will have fewer water molecules, because the other substances take up space, too. So effectively, anthocyanins reduced the apparent concentration of water in plant tissues.

Why is this important? Well, anthocyanins in leaves helps reduce water loss, because the concentration of water in the leaves is reduced and evaporation slows down. They also could serve as antifreeze compounds, allowing red leaves (and stems, David!) to be more cold hardy. And if anthocyanins aren’t amazing enough already, they also (1) bind and transport sugars during fall leaf color change, (2) protect tissues against high levels of solar radiation, and (3) are natural antioxidants. (That’s why you’re supposed to eat red fruits!)

I could go on and on, but I hope this might help explain why David’s red stemmed roses might be more cold hardy than the green variety. (And my thanks to my daughter Charlotte for allowing me to use her photos here.)

Pop Quiz!

Bet you weren’t expecting this on TUESDAY, eh?
Heh, heh.

Situation: these photos are from a grad student project. We wanted to create, observe, and record nutrient deficiency symptoms, so we grew the plants hydroponically in a made-from-scratch nutrient solution, containing everything except one particular nutrient. There were 12 separate batches of solution, one missing each essential mineral nutrient (N,P, K, Ca, Mg, S, Fe, Mn, Cu, B, Mo, Zn – couldn’t exclude Cl as it’s too common in salts). As my research interest is herbaceous perennials, some common perennial taxa served as our victims, er, subjects.

Here’s the set up for the Verbena ‘Homestead Purple’ experiment – rooted cuttings were placed in the little buckets and secured by the lids. The nutrient solution was constantly aerated. For most elements, symptoms appeared between two and four weeks after the start of the project. Symptoms, depending on the elemental deficiency, included chlorosis (yellowing) of old or new leaves, leaf curl, speckling, stunted growth, and in one case, some excessive growth.

Below are results from day 42 of the study. We lifted the lids, hanging-basket style, so we could examine the roots. The control (received a complete nutrient solution) is on the left; Rapunzel there, on the right, lacked a nutrient. Quiz question: What element was missing in this particular case? What made you come to this conclusion?

Hint: If you have a rudimentary knowledge of garden fertility, be it veggie or ornamental, you can probably figure this out. I’ll go ahead and rule out the pesky micronutrients.

(L) Control: received complete nutrient solution (R) Deficiency solution

Wonderful wood chips

I’m in love…with arborist wood chips. These are not your beauty barks or other packaged mulches, but the chipped branches and leaves fresh from the tree crews. It’s a great way to keep this resource out of the landfill – and don’t even get me started about using this great mulch material for a “biofuel!”

I’ve written about wood chip mulches a lot, but thought today I would post some photos to show you how well they work in suppressing weeds and promoting growth in restoration sites. We published a paper on this in 2005, though we’ve been using them in ornamental and restoration landscapes for about 10 years.

Here’s a recent project: a wetland buffer enhancement was being installed in an area that was covered in Scot’s broom (Cytisus scoparius) and blackberry (Rubus discolor):

We had a brush cutter mow it to the ground, then put a foot of wood chips down. Later, we planted poplar, ash, willow and alder on the site:

We had to keep records, both written and photographic, for the county who monitors wetland projects. So we took photos every year at the same points for comparative purposes. Here’s what part of the site looked like immediately after planting and then after 5 years:

That’s not to say that we haven’t had to battle resurgent blackberries. They migrate over from the wetland itself (which we can’t touch) and tip root. But the increasing shade and competition from the trees has weakened their ability to take over, and the Scot’s broom has been gone for years.

So that’s one reason I love wood chips. I’ll do a follow up some week showing how they can be used in the home landscape.

My Favorite Class Project

Every year I teach a class called nursery management. In this class students have the opportunity to try all kinds of different growing techniques out in the nursery. They get to use a tree spade and prune and all kinds of other stuff. But something else that I have the students do is to make hydroponic systems for growing plants. No, hydroponics is not a common technique for growing plants in a nursery, but to grow plants hydroponically you need to know what you’re doing, and so this is a convenient way to make the students think about the plants they grow and what these plants need to prosper.

To start this project I give the students a water pump and an air pump (courtesy of our friendly neighborhood drug dealers — no, seriously — when the cops bust pot growing operations they give us the equipment that they’ve confiscated after they’re done using it as evidence. Much of the equipments is new, some is very high end.) Then I divide the students into a few groups, tell them what they’re growing, and give them two weeks to come up with a growing system and a nutrient solution to grow their crop (I do allow them to use our stock hydroponic solution, which will grow the plants, but won’t win anyone any prizes — most groups choose to use this as a base solution and then add to it.). The group whose plants grow the largest after twelve weeks wins a modest bonus to their grade.

So, what do we have for set-ups this year? Some very, very cool ones! First, we have a number of groups who went with a simple, non-circulating system, as seen below. Basically just an air-hose and a container filled with nutrient solution.

Another group decided to use a flood and drain system. They use a timer to trigger the water pump to fill a tray with nutrient solution for five minutes every few hours. This hydrates the containers which hold the extremely well drained ceramic beads in which the plants are held.

And finally, one group decided to use a capillary action system where the base of the container is filled with nutrient solution which is wicked up into a well drained media (a combination of rockwool, vermiculite, and perlite) into which the plants are placed. This group decided to lay their plants on their sides to encourage extra root growth.

I’ll let you know in about 12 weeks which group wins!

Eat your veggies! (But not the arsenic, or the chromium, or the lead…)

The last few years have been a perfect storm for the resurgence of home vegetable (and fruit) gardens. Grapevines are trellised along sidewalks, herbs replace the grass in parking strips, and tiny gardens of carrots and lettuce are shoehorned into any available spot. It’s all good – but we need to be particularly careful about what those plant roots might be taking up along with nutrients and water.

1) Contaminated soil. Many urban (and suburban, and even rural) soils are contaminated with heavy metals, pesticides, and/or industrial wastes. Lead is commonly found in soils near roads (from the old leaded gasoline we used to use) or from old lead-based paint chipping away from houses. Arsenic is a very real problem in North Tacoma soils, for instance, thanks to the smelter that operated there for decades. Overuse and incorrect use of home pesticides will leave residues in the soil for years.

2) Contaminated compost and soil mixes. Many of the same contaminants mentioned above can be found in unregulated composts and soil mixes. (More on this topic here.)

3) Treated lumber. The old treated lumber (CCA = copper, chromium and arsenic) is no longer being sold, but it’s out there. These timbers should not be used around vegetable gardens, as they will leach their heavy metals into the soil. Vegetables vary in their ability to take up and store these metals. (More on this topic here.) Likewise, rubber mulches may leach unwanted chemicals into the soil and should not be used around food plants. (More on this topic here.)

treated%20lumber_jpg.jpg

What can you do to avoid these problems? A few things are quick, easy and cheap:

1) Have your soils tested. I’ve mentioned this in an earlier blog on urban soils. It’s the best way to find out exactly what you have in your gardens – the good and the bad.

2) Use only certified composts and soil mixes.

3) Plant in containers if your soils aren’t safe for food. This is especially easy to do with perennial herbs, which can be kept like any other container plant on your deck or porch for years.

4) You can also replace the soil in your vegetable garden. This isn’t quick, easy, or cheap, but is a solution for some people.

Shoot your favorite ash

One of the biggest issues facing urban and community forestry in the eastern half of North America is the Emerald Ash Borer (EAB). As most people are aware, EAB was accidentally introduced in Michigan some time in the late 1990’s. By 2002 when the insect was found and identified, thousands of ash trees in and around Detroit were dead or dying. Since then the insect has continued to spread, partly by natural dispersal but also by hitchhiking on logs and firewood. As of July 2009, EAB now occurs in 13 states and 2 Canadian provinces. To date, researchers have not found any indication of resistance to EAB in North American ashes. This includes green ash and white ash. Based on our current understanding of the insect, EAB has the potential effectively eliminate the ash genus from North America, similar to effect of chestnut blight on American chestnut or Dutch elm disease on American elms. To help stave off the demise of ash to EAB a veritable army of university and government researchers are conducting wide array of trials to identify chemical or biological controls that can save ashes. Several insecticides can be effective but so far are only feasible for use on high-value landscape trees due to the cost of application and the need to re-apply treatments every 1-3 years depending on the chemical.

To help build awareness of the destructive potential of EAB and the impact of losing ashes in North America, I invite readers of the Garden Professor’s blog to share photos of their favorite ash. Photos can be e-mailed to me @ cregg@msu.edu and I will post them on the blog. Include any pertinent information about the tree(s). To get things started I have included photos of ash trees surrounding the Gateway arch in St. Louis. In the early 1970’s over 500 ‘Rosehill’ white ash trees were planted along the sidewalks in the park area surrounding the arch, which was completed in 1967. The ash trees frame the famous ‘Gateway to the West’ and provide shade to cool visitors during St. Louis’s sweltering summers. Unfortunately, the ashes may ultimately serve as a cautionary tale of the perils of monoculture in landscape design if they are lost to EAB. The National Park Service, which manages the Gateway Monument grounds has begun to plant new trees from a variety of species. However it will be years before those trees will be anywhere near the size of the existing ash trees. To date, EAB has only been found in Missouri in an isolated outbreak in the southeast corner of the state but the insect has a firm foothold in Illinois and is moving westward. The ashes in the Gateway monument are being monitored for EAB and presumably the Park Service will begin treating the trees with trunk injections of systemic insecticide if EAB are detected in or near the Monument.
Ash trees frame the Gateway to the West

Over 500 'Rosehill' ash trees line the walkways at the Gateway National Monument

Voles are Pickier Than You Think

…and it’s not just the scientifically-proven inverse correlation between the price of the mail-order perennial and likelihood it will get chomped within six months. The prairie vole (Microtus ochrogaster) is notorious throughout central and eastern North America for laying waste to many a well-tended garden. Much of what’s out there in regards to herbivory of ornamental plants (said chomping by deer, voles, bunnies, etc.) is simply anecdotal, yet repeated ad nauseum as fact. So it’s exciting to see some new research in that field, published in a recent HortTechnology journal.

Dr. William Miller’s research focus is bulbs, and his group at Cornell University set up feeding trials with thirty common garden bulb species to quantify the prairie vole’s preference thereof. Tulips topped the list as the colony’s favorite (but you knew that already). In fact, “the voles became accustomed to this feeding schedule, and would vocalize and get excited when we entered the laboratory to prepare the bulbs…”

The voles showed the least interest in daffodil (Narcissus), grape hyacinth (Muscari armeniacum), Italian arum (Arum italicum), ornamental onions (several Allium species) and snowdrop (Galanthus nivalis). These bulbs were evidently high in the sort of secondary metabolites that, among other things, cause plant tissue to taste bad. There were even preferences shown as to different cultivars within each species – they were wild about tulip ‘Apeldoorn’ yet ate half as much of the species Tulipa turkestanica. Note to the vole-ridden…the daffodil ‘Ice Follies’ registered barely a nibble.

Apparently voles love apples more than anything, so the researchers also mixed dried, ground bulbs with applesauce to make them even more appealing. The point of this slightly eludes me, but the take-home message was 1) voles will eat anything except onions when mixed with applesauce, and 2) don’t dip your bulbs in applesauce prior to planting. Now if only Dr. Miller would work on vole feeding preferences by price point…

Source: Curtis, B, D. Curtis, and W. Miller. 2009. Relative Resistance of Ornamental Flowering Bulbs to Feeding Damage by Voles. HortTechnology 19:499-503.

Take it all off (cue bow-chicka-bow-bow music)

OK, I know there are skeptics out there including many of my dear colleagues. Though it seems that at least some of my photos are making an impression. So here is another little photo tour through bare-rooting – this time with a bigger tree.

This demonstration was given at the 2006 ISA conference in Washington. This is a good sized tree…

…that we plopped into a Rubbermaid watering trough after removing the burlap…

…and washed off all the clay. It is deceptively easy to do.

Oh! I almost forgot! We put some duct tape around the trunk just above the burlap before we started this procedure. Look where the tape ended up:

So there is another really compelling reason to bare root trees. Had we not, this tree would have been planted 10 inches below grade. But I do have to say the burlap made pretty patterns on the tree:

Another plus – with the clay gone, these trees are really easy to pick up and move around!

And it didn’t need staking once it was mudded in…

And it looked great seven months later with little to no maintenance and lives happily ever after. The end.