Propagating Plants

Plants are generally propagated by seed, cuttings or grafting/budding.

SEED-If you are producing a plant from seed you must gather the seed when it is mature but before it is eaten or loosed from the plant. Most seed is produced in summer or fall. Knowing when in this time period the seed is ripe is crucial to successful gathering. Once seed is gathered it can be sown directly into a prepared section of soil or stored for later use. Because there are so many different plants it is hard to generalize about when and how to plant. Many hardy perennial plants(trees, shrubs, herbaceous perennials, etc.)need a period of cool moist conditions, called stratification, to break dormancy. For most species planting directly into the soil in fall is ideal, as this gives the seed the conditions needed to break into active growth in spring. A warning however; animals such as squirrels and mice can smell seeds and will dig them up. This is particularly true of nuts (oak acorns, walnuts, hazelnuts, etc.). A covering of 1/2in galvanized metal hardware cloth that is weighted down will help prevent predation. Seeds should be planted at a depth approximately three times the diameter of the seed. Nuts are best positioned so the tip is pointed horizontally in the hole. There are many exceptions to this rule, particularly among the perennials. Some are simply pressed into the surface so that light can trigger germination. Some seed does not require stratification and can be planted whenever convenient. Such seeds can usually be stored in a cool dry place in sealed jars. Each species will differ in the amount of time it can be safely stored. As you can see there are many differing conditions for good germination. A search online or in books that details the conditions needed for the species in question can save a lot of grief.

SOFTWOOD CUTTINGS-Many species of trees, shrubs and perennials can be propagated by taking cuttings of the new growth in mid-summer. Cuttings should be gathered when still soft but not flabby. In our area (New Brunswick) the ideal time is early July. Cuttings should be gathered in early morning when they are most turgid (filled with water). Generally a cutting is made using 3-5 leaf bearing nodes. The basal leaves are stripped and the very tip of the cutting is dipped in a rooting hormone. Note only the cut surface at the base of the cutting is dipped in the hormone. Rooting hormone above the base will only burn the tissues and will cause it to rot. Most softwood cuttings root well using a #2 rooting hormone. Some, such as rhododendrons, require a stronger #3 hormone. Once prepared, stick the cuttings to a depth of 2.5-5.0cm (1-2in) in a rooting medium of either 3parts perlite to 1part peat moss or a medium of sand with a small amount of fine peat moss incorporated. A very small amount of slow release fertilizer can be used in the mix to provide nutrients when the cutting roots. If only doing a few cuttings they can be placed in a container with a clear plastic cover supported so that the cuttings do not come in contact with the plastic. Keep the container in incidental light but not direct sunlight, which can cause overheating in the chamber. Humidify the chamber with a water bottle spritzer just enough so it does not dry. Too much water is just as bad as too little. Balance is the key. Larger amounts of cuttings can be rooted in a low coldframe placed on the north side of a building or in a similar light situation. These can be made using boards for sides and old windows hinged at the back so the cuttings can be checked and later opened slightly to allow for the conversion to lower humidity levels. In such a chamber sand makes an ideal medium. Generally cuttings will root in 2-3 weeks. Resist the temptation of constantly checking them by pulling them out and re-sticking. You will know they have rooted when growth commences from the buds. After growth begins, leave the cuttings for a week or more to allow the roots to grow to a size that will support the plant when transplanted. Remember that the cuttings are used to high humidity and low light levels. You must gradually condition them to drier conditions and higher light levels. The process is simple but every detail is critical for success.

HARDWOOD CUTTINGS-Some species such as willow, poplar and currant can be stuck directly into the soil. Use wood from the last year’s growth cut into sections around 15cm (6in) long. These are plunged into the soil so that only the top bud shows. This prevents the cutting from drying before rooting occurs. Ideally, leave rooted cuttings for the rest of the season and harvest in early spring to plant into their final location. Conifers such as cedar, juniper, microbiota, false cypress and others are often rooted in the winter. The trick here is to keep the top of the cuttings cool and the rooting medium warm (21c/70f). The cuttings are prepared using the last year’s wood, or sometimes a bit of two year wood at the base. The bases are stripped and the tip dipped in rooting hormone (most often #3). Usually a plastic tent is placed over the cuttings and enough water used to keep the chamber humid. Avoid overwatering. Rooting can take up to two months.

GRAFTING AND BUDDING-Fruit trees and several ornamental species are propagated by placing a section of the last year’s wood (a scion) onto a rootstock. By using this method plants that have unique characteristics (cultivars) can be maintained. Often these plants are difficult to root. Some, such as weeping trees, are grafted at a height that allows for easier nurturing or to provide an enhanced form. Grafting usually takes place in early spring. Budding can be accomplished in summer (usually August in our area) or spring if using a chip bud. The secrets to success are to match the cambium layers (thin green layer below the bark) of both rootstock and scion and to protect the graft from drying out before the union is complete. Images of one of the more popular techniques are presented in the grafting section of Our Tips.