This creates an alluring adventure which the amateur gardener is warned to approach with great restraint and caution. He must be careful not to try to introduce new varieties unless they combine qualities that are better than any already existing, and on the excellence of these qualities he should be sure to have the judgment of truly experienced growers. He may find real pleasure in the development of new varieties, solely as a hobby, for his own garden, but must conscientiously eradicate those that are not as good as existing varieties.
Most perennials seeds may be sown in spring or soon after midsummer for bloom the next year. Seeds of a few plants must be sown immediately on ripening or they will not germinate. Phlox is one of these.
Some perennials give their best blooms the first year after they are sown; others bloom only one year; these are biennials treated as though they were perennials. It is well to sow the seeds of these species each year to make young plants available each season. Such plants include sweetwilliam, hollyhock, and foxglove. Although they complete their growth and produce seed within a year, two growing seasons are required for them to yield flowers.
Rich soil, not too heavy, is best for many of the perennials that grow readily from seed. The soil must be well drained but moistureretaining. It should be light and crumbly and the seedbed well supplied with humus-rotted manure should be spaded in well. Row planting is advisable, making it easier for the gardener to tell weeds from seedlings.
Don't plant the seeds to a depth greater than five times their diameter, firm the soil about them, and water well. To keep moisture uniform in summer plantings it may be helpful to put boards over the seed beds for a few days, but they must be taken up before the seeds start to grow. Sand is also an excellent covering.
Transplant or thin the seedlings as soon as they show their first true leaves and give them plenty of space at all times. In areas in which fall transplanting is advisable, young plants may be moved to their permanent location in their first fall, but those which have heavy taproots are better left until spring as they may heave badly.
In general it is a good idea for a beginner to buy hardy perennial plants from a nursery and get some experience in growing them before starting to do his own plant propagation. When the gardener succeeds with vegetative propagation he may pridefully regard himself as well past the beginner class.
Propagating by division means simply dividing the roots or crowns. If the gardener digs up a plant and cleans the roots of earth he will see that it can be cut into pieces, each of which has some stems, buds, or leaves with some roots. Each such piece may be planted with a good chance that it will grow.
These pieces should be planted in the spring; in sections in which fall transplanting is successful they should be put down at least 3 months before freezing weather.
Leaf or stem cuttings
Cuttings of herbaceous plants should be made from leaves or stems. Leaf cuttings usually are used to reproduce plants which have thick, fleshy leaves containing a large quantity of plant food either in the body of the leaf or in its larger ribs. Use the whole or a part of a healthy, fully developed leaf that includes a small piece of stem.
Fill a flat with sand, make a small hole in the sand for the stem, and firm the sand around it. Press the leaf gently to lie flat on the sand, water well, and cover the flat with glass.
The flat, thus covered, becomes a selfwatering device. The humid air condenses on the glass and the water drops back on the leaf, which has a strong chance of taking root quickly. There are several commercial preparations for treating the sand to promote the growth of roots.
In working with softwood cuttings the gardener may show a real professional flair. A slip, bearing several leaves, is cut from the end of a stem. Make a diagonal cut to provide the largest possible feeding area. It is planted in a sand-filled flat.
Since a number of slips are planted in the same flat, its preparation is important. If it is possible, use a strip of glass for one sidewall of the flat. Water the sand thoroughly, treat it with a commercial preparation for promoting root growth, and cut parallel furrows in the sand.
Stick the slip into the sand to a depth sufficient to cover the two lower nodes, from which the leaves have been removed. Insert the slips at a slight slant; this leaves more room for working among the cuttings. Compact the sand gently, sprinkle again, and cover with a piece of glass.
Do not be impatient for the slips to take root. Some take longer than others. The really certain way to determine root development is to lift a slip out of the sand for examination, but there is little chance that this one will do well if reset. Thus the reason for the glass wall of the flat. If one slip is inserted in the sand right up against the glass the gardener has a constant subsurface view of root development. When the roots have grown, lift them from the flat and plant them in thumb pots filled with loamy soil with a large proportion of sand. Put the pots in a coldframe. Cuttings should be reset to the same depth to which the slips were covered in the sand beds in which they were started.
The vegetative propagation of bulbous plants is by division of old bulbs or by use of the bulblets which grow along the stem near the old bulb or at the root line of old bulbs.
Bulbs should be planted at a depth below the surface equal to the bulb's longest axis. This gives them a firm grip in the earth, from which the plants can stand up against winds that would topple more shallow plantings.
Roots should be planted with the crowns well covered with soil. There is no general rule. Experience will guide the gardener in the depth to which to plant specific roots.
In propagating shrubs, there are several types of hardwood cuttings that may be used. In a simple cutting a straight part of a shoot or cane containing two or more buds is used. The lower end is cut off just below a bud, for roots develop most readily from a joint. The top is cut off a few inches above the highest bud.
A heel cutting is the lower part of a branch containing two or more buds and severed so as to carry with it a small section of the parent branch, which forms the heel.
A mallet cutting, so called because of its appearance, is obtained by cutting off the parent branch just above and just below a shoot.
These multiple-bud cuttings are planted in a trench, leaving only the topmost bud above the surface. Since they provide several buds from which the roots may form, their chances of successful rooting naturally are greater. The difficulty in using them is that only one such cutting may be obtained from each lateral branch.
When it is necessary to obtain the largest number of cuttings from a limited supply of stock, a single eye cutting is used. This is simply a piece of branch bearing only one bud. In setting it in the trench the bud is placed an inch below the surf ace.
Layering is bending a shoot down and covering it with soil to take root while it still grows from the parent plant. The simplest method is to bend a branch or shoot into a trench, cover it with earth, and leave the end above the surface. Bruise the branch beneath the buried buds, where the roots form, and pin it down with a stone or a forked stick before covering with soil. When the roots are formed, cut away from the parent plant and set the new plants in the trial garden or, if they are strong enough, in their permanent location.
Air layering is simply this process of propagation above the ground. A branch, in the position in which it grows, is slit or bruised near a bud. The slit or bruise is covered with a ball of peat moss and soil, which is held in place with a wrapping of spagnum. moss and raffia. When roots develop in the ball of soil and peat moss the branch is cut and planted, ball and all. The raffia and spagnum moss wrapping must be kept moist while the new roots are forming in the air.
Compound layering differs from simple layering only in that a shoot is buried and exposed in a series of undulations, so that it loops into the ground with one bud and out with the next.
Weeping and overhanging plants, such as forsythia and vines, are well suited to such methods of propagation.