PROPAGATING MINIATURE TREES AND SHRUBS
This is one of my favorite addictions. I can’t resist planting any seeds that come my way, can’t bear to discard an evergreen or a broken branch of cotoneaster, can’t resist the impulse to root cuttings. As a result, our rather small nursery bed is closely populated with small, young shrubs and trees of all kinds. I doubt that we’ll ever find space to plant them once they’re grown; and I imagine I could be rather popular could I ever bring myself to give them away.
Propagating trees and shrubs is predominantly a trial-and-error proposition because each variety has its own preferred method of reproducing itself. Some are difficult to raise from seeds, some won’t propagate any other way; some root readily from cuttings, some take three years; some are amenable to layering, others are not. For me this guesswork is a good thing. If all my seeds and cuttings took root and grew into bushes and trees, there’d be no challenge, no fun, and no place to put them.
We always keep a propagating box handy—a shallow box or flat with sides and top of glass or polyethylene. In summer it rests under a tree; in winter it may be on an unheated porch, in the cold frame, or in the greenhouse. The propagating medium may be Pelonex or perlite; a three-way mixture of peat, vermiculite, and perlite; half-and-half sterilized leaf mold and sharp sand (peat packs too hard for me); or clean sharp sand alone. The medium is kept constantly moist but not soggy and is never allowed to dry out. Cuttings are inserted in rows, and removed for potting as soon as the roots are an inch or so long. Sometimes seed is sown in part of the box, or we may rig up a second box when we have a goodly number to plant. The glass, or plastic, sides and top preserve moisture and keep the air humid.
Seeds
Most types of shrubs and trees are rather slow to grow to maturity from seed. And seeds of miniatures produce all-miniature seedlings only when the seed-bearing parents are natural species with natural miniature characteristics. Small varieties of larger species, “sports” or mutations, can’t always be counted on to produce small offspring.
Seeds vary in the time they take to germinate (three weeks to three years, depending on the plant) and in germination requirements. Some need warmth, some cool temperatures, some darkness, some light. And some need a period of dormancy or “after-ripening” before they are planted. In a process of “stratification” seeds are stored in moist sand for several months, usually at about 40 degrees or slightly less. However, some types (cedar, mugho pine) need to be frozen; a few others are stratified in warmth. Some seeds that you buy have already been stratified. The package will tell you so.
Fleshy seeds, such as chestnuts, are usually planted as soon as they ripen and fall. When seeds are covered with a fruity coat, like holly berries, for example, the berry should be soaked in water for a few days until the seeds can be squeezed free of the pulp. Hard-coated seeds need to be gently cracked, or nicked, to hasten germination, and can be sown outdoors in the fall to germinate the following spring, or even the spring after that. Most winged seeds of conifers need to be stratified (remove the wings) in moist sand all winter at 35 to 40 degrees and are planted in the spring. Fine seeds, as for rhododendrons, can be harvested from the split pods in fall and stored cool and dry until spring.
These are, of course, generalizations. When I am in doubt about how to handle seeds, and if my reference books don’t give me the information I need, I plant them several different ways. It is surprising how often they’ll germinate, regardless of method.
There is, of course, one inviolable rule about planting seeds of any sort—the planting medium should never dry out from the moment of planting, through germination and up to transplanting time.
Softwood Cuttings
Take the ends of this year’s growth when it is half ripe, in summer, or longer sections that can be cut into pieces with at least two buds or “eyes.” Make the cut just a little below the node. Or on slow-rooting plants, pull off the cutting with a sliver of the main stem (a “heel”) attached to the rooting end. Remove the leaves at the base, and dip the cut end in one of the hormone rooting powders if you wish. Check the formula on the label to make sure you have the correct one for that type of cutting, and follow the directions precisely. Insert cuttings in rows in the propagating box and firm the medium around the stem ends.
Almost all deciduous trees and shrubs can be propagated from summer softwood cuttings, and so can evergreens—both the needle-leaved and the broad-leaved varieties. Needle-leaved evergreens can also be produced from similar cuttings taken in late fall, but they seem to take longer to make roots. With mild bottom heat in the greenhouse, however, the process is fast enough so the cuttings are rooted before time to set them out in the nursery in the spring.
Hardwood Cuttings
When deciduous trees and shrubs have dropped their leaves, and this year’s growth has had additional ripening from a few sharp frosts, take cuttings of the ends of branches that seem fairly thick and sturdy. Cut off any immature tips, and trim the cuttings (of miniatures) to four to six inches long. Tie a dozen or so into a bundle with covered wire, or some similar tie that will neither rot nor injure the bark. Bury the bundles (some growers bury them standing, some in a horizontal position) so they are completely covered with soil in a cold frame, or use a box that can be kept where the temperature will be cold but not freezing. In spring, unbundle the cuttings and root them like any others in a propagating box, greenhouse, frame, or nursery bed.
Grafting
There are several different methods of attaching a stem or branch of one tree or shrub to the roots of another until the two parts grow together as one plant. So far, I’ve willingly left this field to the professionals, or to amateurs who are seriously interested and make a thorough study of it. I haven’t found the patience or free time for it.
Layering
Here is a foolproof method that guarantees a healthy new plant almost every time. Although some root faster than others, there’s hardly a tree or shrub with long or low-hanging branches that can’t be layered. Of course, the safety lies in the fact that the new plant is part of, and supported by, the parent plant until it is well rooted and strongly established.
In spring, when the plant is growing vigorously, select a low-hanging branch that can be pulled down to the ground. At that spot nick the bark, or slit the branch, to encourage rooting. Pin it down with a forked twig, a hairpin, or a clothespin and cover the tip with a little soil. When roots have formed and the tip is growing lustily, cut the branch between the new plant and the parent, then pot or transplant as you wish.
Air Layering
Plants that do not have a low branch are air-layered by nicking a stem or branch three or four inches from the tip, covering the nick with a ball of moist sphagnum moss, and wrapping the ball tightly in polyethylene, which is tied tightly at both ends. Hormone rooting powder can be applied to the nick with a small brush if you wish. Make sure the moss doesn’t dry out. When you see several good-sized roots, cut the stem below the ball, remove the plastic, and transplant or pot as you wish. Rooting speed varies with different plants. Some take only six weeks; some, several years.
Air layering can be done in spring, using ripened wood of last year’s growth, or in summer with new growth that is not yet woody and hard.