Managing for growth

In a previous post (A bit more about cultivars, Feb 3) I promised to come back to the topic of managing for growth. All that I’ve seen in our plantations suggests that rapid seedling growth (increasing height, expanding DBH) leads to more rapid physiological maturity, and that this in its turn is displayed as fruit setting (nutting). At the core of management for early growth will be weed control, and if you plant, as I did, in old pastures or hay fields, this means grass control. Grasses are particularly pernicious, if you’ll forgive the alliteration. A little while ago I gave a talk to a local woodlot association, where I was tackled about my use of glyphosate. “Why” I was asked “didn’t I mulch my trees?” Laziness, I suppose, though economists would probably interpret that as awareness of an infinitely low return to labour were I to do so, because I am not inherently lazy. The difficulty lies in the number of trees we have – we would have to mechanize the mulching process if we wanted not to have to work around the clock. Let me first, though, defend myself to the purists. In the early years, I did work around the clock, using a Honduran sickle (don’t ask right now) to control grass and weed growth manually. The trees didn’t grow. I also used plastic brush mats (inorganic mulch, if you like). The trees didn’t grow. So I bought myself a backpack sprayer, having seen the local CN maintenance crews spot-spraying for brush control along the local railroad track. I even bought the same model. The trees began to grow. By this time I had 1,500 trees, and found that I could spot-spray the lot in one good day’s hard work. Much better than bending over for several days with my old Honduran friend in hand, without result. The trick was to lower a piece of old 15cm stovepipe over each tree, for protection, while whipping the spray-wand around it. That tells you how undeveloped they were, because even a 50cm seedling can develop enough branches that you’d need a 50cm diameter stovepipe if you were to lower it over the tree quickly.

So the trees grew, and outgrew my technology. Then I picked up an old orchard sprayer from my local machinery dealer, and gravitated to band spraying (switching a tractor-mounted sprayer off between trees requires more dexterity, accuracy, and even controls, than I had, and doesn’t do the machinery much good). Though by this time the trees were getting to the point where a continuously clear band was only going to be good for expanding root growth, so I didn’t begrudge them that extra bit of herbicide. They grew wonderfully. So the lesson in this is that herbicides can be very useful and, if the sums were done, probably far more economical (let alone effective) than mulching. And in case you believe ‘herbicide’ and ‘conservation’ shouldn’t be mentioned in the same breath, or the same sentence, just try g**gling them together, e.g. http://www.appliedeco.org/conservation-research/prairie-restoration-research, or http://www.ecologyandsociety.org/vol7/iss1/art6/
So, let me finish this post off with a couple of photos. The first is courtesy of the Ontario Ministry of Natural Resources and dates from the early 1980s when a lot of work on hardwoods, especially black walnut, was being done. The photo shows the contrast in tree growth between herbicide (background) and no herbicide (foreground). When I find the booklet (it’s lost in my files somewhere) I will confirm the herbicide (simazine, I think) and the agency involved (Canadian Forest Service, I think). Fred Van Althen was the principal researcher. I think the photo speaks for itself about grass effects on black walnut.

The second is from our farm, and dates from 2004. Two years before, these trees were very much like the trees in the foreground of the previous photo. Glyphosate sprayed at the recommended level of active ingredient per hectare gave the grass control you can see here. Some of these trees nutted in 2004, which does not speak to an immediate herbicide effect but rather that the previous spot-spraying was itself effective. Now, I only spray seedling trees under establishment (mainly the selection blocks). My current weapon of choice (not used in this photo) is an ATV-mounted Enviromist Sprayer, with a 60cm spraydome. I can now do hectares of plantation per hour.

Let me mention some of the other consequences of vegetation, mainly grass, control with herbicide. As I generally spray only once, in the spring, there has been an interesting proliferation of broad-leaved species, with an accompanying increase in insect and bird diversity. Note that I say broad-leaved ‘species’, rather than ‘weeds’. The definition of a weed is ‘any plant growing where you do not want it to grow’. While I was quite surprised by the influx of milkweed, and of some other species, it is only ragweed that I truly dislike. Ragweed, apart from its noxious asthmatic-inducing pollen, is a plant with no redeeming features, and can be as oppressive to young black walnut as grass can be. So a second application may be called for. The remaining vegetational diversity I value, as it co-exists with the trees without direct competition. As the trees grow they quickly shade the other species, and I am now mowing beneath them as some grass has returned. There seems to be no juglone intolerance in these broad-leaved species, as I see no major species-difference where they grow between fields with trees or without.