Monday, January 14, 2013
Seeds v. Starts 3—Trees and Shrubs
Our Landscape Management teacher at RCC told us that a small tree will outgrow a large tree within just a few years, and for the most part I’ve found that to be true: a gallon tree will generally outgrow a 5 gallon or larger tree within 5 years. An exception is small, slow-growing trees like weeping Japanese Maple. Faster-growing trees become quickly root-bound, and the root balls on larger trees are smaller in proportion to the size of the tree than on smaller trees.
Another exception is exceedingly small trees, such as the ten trees given “free” by the Arbor Day Society in return for a $10 “donation” or conifers sold by state forestry department for 50 cents or a dollar apiece, which are lucky to survive their first year. Even under good garden conditions, such trees often have less than 50% survival. They may well outgrow larger trees if they do survive, but they won’t outgrow a seed that starts within a year or two.
A seed-started tree that grows where it sprouts will always outlive and outgrow a transplant in the same spot, because its roots are never broken or distorted by transplanting. The very small conifers sold by the state are grown in narrow tubes, in which they grow roots longer than the tube that fold up and down within it; they have to be cut to be planted in a shovel-deep hole. They are rarely spread out over a cone of soil in the planting hole, and even if they are, they can never match the form of roots that grow without disturbance.
The best time to plant either trees or shrubs in Southern Oregon is fall, as the roots can grow all winter and spring before the summer heat. This goes double for most tree seeds, as most of them require stratification, soaking in cold water or freezing and thawing, to crack their seed coats and get them to sprout. The seeds that need to spring planted, like Amur maple or box elder, are obvious, as they hang on the tree until spring.
Some seeds require heating from a fire or being eaten by birds to sprout; these are not so easy to plant by seed. Madrones are always a gift from the birds, as they need their stomach acid to sprout, don’t survive transplanting at any size, and can’t live in a pot. Fortunately, the birds spread them widely, particularly under trees and along fences.
Shrubs follow much the same rules as trees, but people are only likely to want one to grow fast in the beginning, to fill the space allotted to it. After that, the problem is often keeping it within that space. Here again, a 1-gallon shrub will fill the space faster than a 5-gallon shrub, and be healthier thereafter.
And here again, it pays to buy a larger plant if it is slow-growing, or if its root system is shallow and fine, rather than deep and thick. Blueberries are a case in point. They don’t root more than about 6” deep, even in a deep pot. Their fine, spongy roots do not get root-bound, and they grow slowly. So buy the 3-gallon blueberry; it will give you blueberries that much sooner. They are an almost perfect landscape shrub; they grow slowly, need no pruning, and have great fall color, and provide fruit that you can leave for the birds if you are lazy.
Published at Yahoo Voices under The Natural Gardener #13.