Friday, June 6, 2008

Bonsai as Ecology

It occurs to me that a useful start to my ecological/botanical blog would be to take a systematic look at some convenient microcosm and discuss it thoroughly. My bonsai trees seem tailor-made for this. So here we go with a series of essays on "How Bonsai Grow."

In the front courtyard under the shade of an old Photinia tree along the portal, I display my ragged little collection of mostly temperate bonsai during the spring, summer and fall. In winter they all get packed away in the back of the garage underneath a friendly skylight. Right now they're all doing well except a Ponderosa pine I harvested from the wild two months ago and a Taxus that has been struggling to hold on in New Mexico's low humidity for more than a year.

The tropicals usually find them selves on the back porch where they get higher temperatures, a good shot of morning sun, and some dappled sunlight in the afternoons. In the winter they must come all the way indoors, being secreted all over the house.

Bonsai means "growing in a tray," referring to the generally low profile of the traditional pots. Some styles, notably cascades and semi-cascades, use pots with higher aspect ratios, but by and large one is looking for a pot that is roughly the same height as the thickness of the tree's trunk.

Meanwhile, the volume of the pot is going to be approximately 1/3 of the volume of the tree's canopy. The pot's proportions are dictated by traditional formulae for esthetics and their relationship to the height and width of the branches. As you can guess, this doesn't leave us much room to work with.

So, back to the topic at hand, how do bonsai grow? Fortunately, there are only four mechanisms in plants and one of those is restricted to monocots, which are rare in bonsai. These are:
  1. Primary apical shoot meristems -- the growing tips of the branches, producing new shoots, flowers, and leaves (some would count floral meristems separately)
  2. Primary apical root meristems -- the growing tips of roots
  3. Intercalary meristems and primary thickening -- the means of increasing height and diameter in horsetails and monocots; primary thickening meristems are found in arborescent monocots, palms and such
  4. Secondary thickening meristems -- lateral meristems or cambium that increase the diameter of the plant (these produce xylem and phloem as well as bark)
Of course, the object of growing bonsai is, as an art form, to evoke an emotion in the viewer. Usually the bonsai artist attempts to capture the age and grace of a vast and ancient forest dweller in miniature.

This in turn usually means that we want relatively short trees (typically under 3 or 4 feet) with very wide trunks. The Japanese term that describes a desirable wide flaring of the trunk into obvious surface roots is nebari.

To grow trees with these characteristics, one has two choices: harvest a naturally formed beauty from the wild or to carefully cultivate nursery stock to develop the desired form. Therefore, we must control growth such that secondary thickening of the trunk is encouraged and primary apical growth is limited.

We'll continue in a later posting on the topic of the control of meristematic activity, what stimulates them and what suppresses them. This will lead us to shoot-root balance, control of primary vs secondary growth, and plant nutrition.

1 comment:

Mom Thumb said...
This comment has been removed by the author.