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Can cultivars be considered native plants?

One of the questions that arise in discussing native plants is the question of whether ornamental cultivars (e.g., ‘October golory’ red maple) can or should be considered ‘native’. In short, my answer is ‘No.’

Here’s my rationale on this. First, when we think about natives we need to put political boundaries out of minds and think about ecosystems. Political boundaries – a ‘Michigan native’ or ‘an Oregon native’ – are meaningless in a biological context. What’s important is what ecosystem the plant occurs in naturally. In addition to taking an ecological approach to defining natives we also need to consider its seed source or geographic origin. Why is it important to consider seed origin or ‘provenance’? Species that occur over broad geographic areas or even across relatively small areas with diverse environments can show tremendous amounts of intra-species variation. Sticking with red maple as an example, we know that red maples from the southern end of the range are different from the northern end of the range. How are they different? Lots of ways; growth rate, frost hardiness, drought tolerance, date of bud break and bud set. Provenances can even vary in insect and disease resistance.

Native range of red maple

If we’re dealing with an ornamental cultivar, do we know the original seed source or provenance? Sometimes yes, sometimes no, sometimes maybe. Think for a minute how most ornamental cultivars come to be. Some are developed through intentional crosses in breeding programs. The breeder may or may not know the geographic origins of the plants with which they are working. Or they may produce interspecfic hybrids of species that would not cross in nature. Some cultivars are identified by chance selection; an alert plantsperson finds a tree with an interesting trait (great fall color) in the woods or at an arboretum. They collect scion wood, propagate the trees and try them out to see if they are true to type. If the original find was in a native woodlot and the plantsperson kept some records, we may know the seed source. If the tree was discovered in a secondary location, such as an arboretum, it may not be possible to know the origin.

So, if a breeder works with trees of known origin or a plantsperson develops a cultivar from a chance find in a known location AND the plants are planted back in a similar ecosystem in that geographic area, we can consider them native, right? As Lee Corso would say, “Not so fast, my friend.” We still need to consider that matter of propagation. Most tree and shrub cultivars are partly or entirely clonal. Cultivars that are produced from rooting cuttings; for example, many arborvitae, are entirely clonal. Cultivars that are produced by grafting, like most shade trees, are clonal from the graft union up. The absolute genetic uniformity that comes from clonal material is great for maintaining the ornamental trait of interest but does next to nothing to promote genetic diversity within the species. From my ultra-conservative, highly forestry-centric perspective, the only way to consider a plant truly native, it needs to be propagated from seed and planted in an ecosystem in the geographic region from which it evolved. Few, if any, cultivars can meet that test.

The New Evidence Against Glyphosate

This past week Susan over at Garden Rant asked me about a paper which she had recently read which “proved” that Round-up caused birth defects. This study was interesting because it took embryos of chickens, exposed them to glyphosate (the active ingredient in Round-up) and then looked at the problems which the embryos had. Indeed, there were problems at concentrations of glyphosate much lower than what you’d see in normal agricultural applications. This is similar to other studies which “prove” how toxic glyphosate is which have been conducted over the years where various types of cells have been removed from human bodies, exposed to glyphosate, and then the resulting cellular damage has been taken as an indication that this herbicide is incredibly dangerous to us.

Studies where embryos or cells removed from the human body are tested against poisons have a glaring weakness which needs to be appreciated before we go off the deep end thinking that they prove that glyphosate is killing us. They’re conducted in a system that isn’t at all natural. That’s not to say they have no importance, but it’s like saying that, because it’s known that an air bubble in your bloodstream will kill you, air is dangerous. Or like saying that, because salt injected into your bloodstream is deadly, you shouldn’t eat it. Both air and salt can be deadly if they are in your bloodstream above a certain level, but we need to be careful to look at the specific situation with which we are dealing and take that into account when we make our judgments about how toxic particular things are to us.

I can’t argue that glyphosate can be toxic to people. This morning I did a little literature search on it and actually found cases where people had committed suicide by drinking agricultural formulation of glyphosate – mostly in the Eastern world. It would be a nasty way to go too – you’d need to ingest a lot of the stuff and the primary problems would be that parts of your gastrointestinal system would be corroded. Ouch!

If you’re going to use a glyphosate herbicide use it carefully and in accordance with its label. Don’t go splashing it around willy-nilly. Don’t drink it. Don’t get it on anyone. Don’t use more than you need to. To do any of these things is not only dangerous, it’s also stupid. That said, I can’t find any reason to think that glyphosate is anything but what it appears to be – an effective weed killer that is on the safer end of the spectrum relative to other chemical weed killers (and here I’m including organic weed killers too – Ever been exposed to those 20% acetic acid vinegar herbicides? I tried one this summer — Just being near it made my eyes burn.)

How to Kill Buckthorn

Last year we completed a small research study on how to kill buckthorn. If you live in the upper Midwest then you’re familiar with this plant as a shrub which has escaped cultivation, been spread by birds, and generally made a nuisance of itself, particularly at the edges of forested land.

Buckthorn is notoriously difficult to kill after it gets more than about a foot high. It laughs at single applications of roundup. If it’s pulled out of the ground any roots that don’t come with it have a good chance of sprouting shoots themselves, and it seems to enjoy being treated with organic herbicides like vinegar. So, to try and kill bucktorn, we used an herbicide which had the active ingredient triclopyr. This is an active ingredient which is usually great against all manner of weedy vines like poison ivy. This herbicide is labeled for homeowner use and is available in most garden centers.

We applied this herbicide to buckthorn in the spring, summer and fall, and we used a few different application methods including painting the herbicide onto cut stumps and spraying it onto the leaves of uncut bushes, as well as painting the product onto the lower portion of stems. Some of these application methods were experimental. Do not attempt to apply an herbicide in any way besides that which is listed on the label!

That said, we found that the fall was by far the best time to apply the herbicide and that spraying the foliage wasn’t nearly as effective as other application methods, particularly painting the cut stem with the product after cutting it down.

Sheet mulching – benefit or barrier?

Alert reader Matt Wood pointed out a recent article in the NY Times on mulching with newspaper and wondered about my take on the topic.

For use on landscapes, I do not like sheet mulches of any stripe. They tend to hinder to air and water movement, most especially in unmanaged landscapes like restoration sites. A classic example is the use of cardboard or newspaper covered with wood chips. The chips are easily dislodged, exposing the sheet mulch which quickly dries out and becomes hydrophobic. Thus, the roots of desirable trees and shrubs lose out on the water, while the weeds surrounding the edges of the mulch benefit from the runoff:

Published research on sheet mulching in landscape settings confirms the drawbacks of sheet mulching. But the article in the NY Times is about vegetable gardens. This is a different situation – more akin to agricultural production than to landscape horticulture. Vegetable gardens are routinely managed during planting, thinning, weeding, and harvesting. Newspaper sheet mulches in these situations rarely dry out and, when kept buried and moist, do break down quickly.

So – keep the sheets on the (vegetable garden) bed where they belong!

Another W.O.W.

We’ve been beating up nurseries over Why-Oh-Why (W.O.W) do they sell things like Scot broom. Here’s one of my favorite W.O.W’s from the landscape side (Homeowner division).

Why-oh-Why do people think grass clippings make a good mulch?! This photo comes from near my home. The homeowner put the clippings down about two months ago. All the trees were dark green and healthy before the clippings were put down. Note how chlorotic the trees in the middle have already become and the dead lower limbs where the trunks were covered. We’re all for mulch but this ain’t it!

Are Fertilizer and Insecticide Spikes a Good Idea?

One of the products that I often hear gardeners raving about are their fertilizer / pesticide combination spikes which are supposed to not only feed your plants, but also kill all of the insects which attack them. I, personally, have not used these products, but I’m generally the kind of person who says “If it works for you then keep using it”. Still, these spikes bug me a little. Here’s why.

First of all I should point out that I’m not opposed to fertilizer spikes by themselves. I’m a little concerned that fertilizer should be spread out instead of concentrated in one place, but still, I don’t consider them that bad. The insecticides used for these spikes is where I have the problem. Once upon a time these spikes were made with a chemical called disulfoton (aka disyston) which is bad news. It’s a water soluble chemical which is highly toxic to people. If you have an old package of fertilizer / insecticide spikes around there’s a good chance they were made with this chemical. Do yourself a favor and get rid of them. This stuff is really toxic and not to be messed with. On the other hand, if you’ve purchased fertilizer / insecticide spikes recently, then the active insecticide in those spikes is probably imidacloprid. Imidacloprid is a mixed bag when it comes to safety. It’s not nealy as toxic as disulfoton, but it’s not non-toxic. It has been banned in Europe for a variety of reasons, the most important of which seems to be that it was implicated in the collapse of bee hives (imidacloprid is systemic insecticide so it will get into a plants pollen where honey bees could eat it). At this point it hasn’t been ruled out as having something to do with hive collapse here in the states — though if it does have a role it does not seem to act alone. It can also affect other beneficial insects who feed on pollen. Additionally, it has been known to control some pests while allowing mites to go crazy — in fact, it may even increase the rate of mite egg laying.

But imidacloprid is an effective insecticide which works against a wide range of insects which you that you might find on your plants. It is much safer than many of the older systemic insecticides, and it isn’t readily translocated to fruits (a problem that many people are concerned about with systemic insecticides is the movement of these insecticides into the fruit itself where it can’t be washed off — Imidacloprid is translocated to fruits –just not that much — it moves in the xylem and fruit takes up mostly phloem).

So these spikes are one of those things that I’m wary of. Not to say you shouldn’t use them, but be aware of what they are and what they could do before you buy them.

Volunteering for duty

One of the advantages of having a couple acres (and not being especially fastidious about weeding) is that sometimes you get your landscape plants for free. I always keep an eye out for interesting plants that may turn up on their own – or a least get left behind by our bird friends. Here are some volunteers that have shown up recently at Daisy Hill farm that I’ll work into the landscape.

Sassafras (Sassafras albidum) are notoriously difficult to transplant. I’ll leave these sassafras volunteers where there are and relocate the shrubs in the bed. I’m looking forward to some awesome fall color in a few years.

The native range of redbud (Cercis canadensis) only extends into the southernmost counties of Michigan but they generally do fine here in the Lansing area (just north of the end of the native range). We have an old redbud in the front of our house so we get volunteers from time to time. This one is on the edge of our patio so it’s easy to keep an eye on. I’ll let it grow on another year or so and then find it home.

Most people probably wouldn’t get too excited about eastern redcedars (Juniperus virginiana) showing up on their own. When I was with the US Forest Service, my grad student and I did research on seed germination of eastern redcedar and Rocky mountain juniper (J. scopulorum). Ironically they can be difficult to grow as seedlings in nurseries because the seed are doubly dormant (they have a tough seed coat that requires scarification and the embryo is dormant and requires cold stratification). I’m planting conifers as a screen on the south side of property. I’ll move these guys and a couple of their friends in the spring.

Further decline of “public” education

“The Texas A&M University System is moving ahead with a controversial method of evaluating how much professors are worth, based on their salaries, how much research money they bring in, and how much money they generate from teaching, The Bryan-College Station Eagle reports. Under the proposal, officials will add the money generated by each professor and subtract that amount from his or her salary to get a bottom-line value for each, according to the article.”

This bodes ill for faculty like myself who have Extension appointments. For those of you who aren’t familiar with how Extension works, Extension specialists educate citizens outside university classrooms. But with declining state support for universities, their administrators in turn focus on income generation from grants and tuition. Extension specialists do get grants, but for those of us in areas outside food and fiber research (which is what the USDA funds), there’s not much money available.

Bottom line? According to this model I’m not just worth nothing – I’m worth less than nothing. I’m not worried about my job (I have tenure after all), but for the direction that outreach education is heading. What will happen is that Extension specialists will be pushed back into classroom teaching, leaving no time for educating the rest of the state citizens. Outreach education will become little more than an afterthought.

The ironic thing about this trend is that Extension is one of the biggest bargains states get from their land grant universities. Extension education includes Master Gardeners as well as other programs tailored to local state and county needs.

It’s sad that Texas A&M puts so little value on outreach education. What’s even sadder is that this economic approach will undoubtedly be adopted by other state universities.

Rubber mulch – the discussion continues

Almost a year ago I posted my complaints about rubber mulch (you can find the posting here). This week I was contacted by Jesse, a purveyor of rubber mulches. We’ve had a very civil discussion about the topic, and he asked me to review his fact sheet.

Which leads me to today’s assignment. I have no personal experience with rubber mulch, so I’d like to hear from you about your experiences with this product. Specifically:

1) Have you seen fungi growing on rubber mulch?

2) Have you had issues with the heat captured by the product – either to your feet or to your plants?

3) Does the mulch continue to smell, especially when hot?

4) How quickly do you notice degradation of the product?

Obviously this is anecdotal, not scientific, evidence. But the scientific literature regarding rubber mulch is thin, and anecdotal evidence can often indicate directions that science should explore. Perhaps this can be the beginning of such a study.

Confessions of a carbon sequestration skeptic

One of the potential environmental benefits that came up in our discussion of the pro’s and con’s of turfgrass was carbon sequestration. The basic premise of carbon sequestration is to take CO2 out of the atmosphere and ‘lock it up’ in a form that won’t contribute to further global warming. One of the fallacies floating around these days is that any plant that photosynthesizes, takes up CO2 and thereby sequesters carbon. What we need to realize is that leaves give off CO2 at night via respiration and all non-photosynthetic (non-green) plant parts such as roots and stems give off CO2 virtually all the time. Turfgrass has some potential to sequester carbon, primarily as soil C. If we consider that a 7” deep layer of soil weighs 2 million pounds, increasing soil carbon by 1% can sequester 20,000 lbs of C per acre. How long does it take turfgrass to increase soil C by 1%? Don’t know, but I’m sure it takes awhile. Also, there is a limit to amount of carbon a give soil can store as C is respired away by microbial activity so eventually a steady state will be reached. (Plus we haven’t even subtracted out fossil fuel carbon to maintain turf). Some plants, such as trees, do have the capacity to sequester carbon in wood for long periods – think redwoods, sequoias and redcedars. But these trees cover only a small fraction of the world land area. Intensively managed forestry plantations can take large amounts of carbon out of the atmosphere and sequester it into wood. The question then becomes what do you do with the wood? If we burn it for biomass energy; Foof! All that C is right back in the atmosphere. Still better than burning fossil fuels but also a little less than carbon neutral at best. We can build houses with the wood from the plantation – the carbon will be sequestered as long as the house lasts. My home and barn were built in the 1890’s so the carbon taken out of the atmosphere by those trees is still locked up. If we really want to get serious about carbon sequestration, however, our best strategy would be to convert the entire Upper Peninsula of Michigan to fast growing poplar plantations, harvest the wood every 15 years, and sink the logs in Lake Superior where the cold water will prevent decay. Sound funny? I’m not the only person thinking this way. See Strand and Bedford 2009. Ocean Sequestration of Crop Residue Carbon: Recycling Fossil Fuel Carbon Back to Deep Sediments Environ. Sci. Technol., 2009, 43 (4), pp 1000–1007. http://pubs.acs.org/doi/abs/10.1021/es8015556

Bottom line: carbon sequestration is a very complex process and sequestering carbon for more than a few decades takes more creativity and brain-power than most of us can muster. However, trees and landscape plants do have important role to play in mitigating climate change and it doesn’t require heroic feats of engineering. Trees and landscape plants can effectively cool buildings, thereby reducing air conditioner use and save fossil fuels – see the USDA Forest Service Urban Forestry Research site for a few examples http://www.fs.fed.us/psw/programs/cufr/research/studies.php?TopicID=3 ultimately this is landscape horticulture’s contribution to climate change. Carbon sequestration? It’s a drop in a very big bucket.

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