Growing trees and shrubs from seed

Growing tree and shrub seedlings at home is similar to growing garden plants for transplanting as the seedlings are delicate and require careful attention. Growth is slow but with proper care the seedlings will attain sufficient size within a few years to enhance your property or be ready for sale.

Obtaining Seed:

The first step in seedling production is to obtain good quality seed. It is essential that seed, either purchased or collected, be from locations similar in climate and latitude to the one in which the plants will eventually grow.

When collecting your own seed try to collect the seed from plants with superior traits such as disease resistance, hardiness and form. Collect the seed when it is ripe (see attached table) and label the seed with the name of the species, source of seed and date of collection.

Tree and shrub seeds have specific processing requirements depending on seed type. Coniferous cones are picked before dispersal and spread in a thin layer in a well ventilated, warm room until the scales open. The cones are then gathered together and shaken to release the seed.

Fleshy fruits such as chokecherry and Saskatoon are handpicked or shaken from the tree or shrub. The seeds are extracted by mashing the fruit to a pulp and then separating the seeds from the pulp by flotation. Small quantities of fruit can be macerated in a blender. The sound seed will settle to the bottom of the blender and the water and pulp can be poured out.

Dry fruit, such as caragana or lilac, can be spread thinly on a bench in a warm, ventilated room. The fruit will split open releasing the seeds which can be separated from the debris by shaking through a mesh screen.

Seed Germination:

When tree and shrub seed does not readily germinate following ripening, it is said to be dormant. Dormancy is a protective mechanism that prevents newly germinated seed from being destroyed by the cold of winter. In nature dormancy is overcome by changes in temperature and moisture or by passing through digestive systems of birds or animals. The degree and type of dormancy varies with the species. Mature seed of elm, poplar, caragana and Scots pine exhibit little dormancy and germinate readily, whereas, ash, chokecherry, maple and White spruce have an embryo dormancy and require a cold period or stratification to ensure germination. The attached table outlines stratification requirements of common trees and shrubs grown in the prairies.

Dormancy of many species can be overcome by sowing in the fall immediately following seed collection. Fall sowing takes advantage of cold winter temperatures which satisfy stratification requirements. The seed will germinate the following spring as temperatures increase.

When it is desirable to sow seed outside in the spring or inside in pots, the seed of hard to germinate species must be stratified in a medium such as moist sand at 5 C for various length of time depending on the species. The media used for stratification should be sterilized in an oven at 80 C for a few hours to prevent buildup of mold. The sand is then cooled and water is added at 10% of the dry weight. The volume of sand should be five times that of the seed. The moist sand and seed is mixed, placed in a sealed container and stored at 5 C (a household refrigerator is adequate) for a specified period (see Table). The seed should be checked frequently during the stratification period to determine if the sand is too dry, the seeds are sprouting, or mold is developing.

Preparing the Seedbed:

Proper seedbed preparation is essential for successful establishment of seedlings. The seedbed should be in a well drained location with a sandy-loam soil. To facilitate drainage, beds are often raised by furrowing or erecting side boards. Conifers require shading in their first growing season which can be provided by ereting side boards and covering with snowfence. Deciduous trees and shrubs generally do not require shading. The size of the bed will vary but generally a 1 m x 3 m bed will be adequate for approximately 1,500 seedlings.

Sowing:

Conifer seed can either be broadcast or sown in rows. Rows are easier to maintain. If sowing by hand, shallow trenches 2 cm wide and 15 cm apart are made. The seed is sown at approximately 150 seeds per metre and covered to a depth two to three times the diameter of the seed with fine sand or soil. After sowing, shading is required and the seedbed should be kept moist until germination occurs. Seedlings are usually left in the seedbed for two years before being transplanted to a larger area.

Deciduous seed can be sown in rows or broadcast. Seeds are generally sown at a rate of 90 seeds per metre and to a depth approximately three times the seed diameter. Irrigation stimulates germination and hastens growth. The seedlings usually reach sufficient size for planting in a permanent location in two years.

The preceding provides a brief introduction to growing trees and shrubs from seeds. For more information on this subject you may wish to obtain some of the following publications:

1. Agriculture Canada. Nursery propagation of woody and herbaceous perennials for the prairie provinces. Pub. 1733E, Ottawa, Ont.
2. Alberta Department of Agriculture. Propagation and production of woody ornamentals in a small nursery. Agdex 275 116, Edmonton, Alta.
3. Hartmann, H.T.; Kester, D.E. Principles and practices of plant propagation. 3rd ed. Englewood Cliffs, J.: Prentice-Hall Inc.; 1975.
4. United States Department of Agriculture. Seeds of woody plants in United States. Agriculture Handbook No. 450. Forest Service, Washington, D.C.; 1974.

GROWING TREES AND SHRUBS FROM SEED

* Species listed as "difficult" require long stratification at various temperatures or acid soaking.

+Stratification temperature 5º C.