Growing trees and shrubs from seed takes time, but has its own rewards

Planting seeds is a satisfying way to grow trees and shrubs, and gives you a special affection for the plants.

Don't be put off by how long it takes. Unless you are interested in flowering or fruiting, you can expect plenty of shoot growth from most young trees and shrubs. And even if years are required, shouldn't some aspects of gardening be a long-term proposition?

VARIETY IS THE SPICE OF ...

Seed-grown plants, unlike cuttings and grafts, are not genetic replicas of their parents, so each new plant is a genetic individual, just like each child in a human family.

With some species, such as green ash, each seedling may be noticeably different from the others in form or leaf colour. At the other extreme is Amur honeysuckle, all seedlings of which appear almost identical to each other, superficially at least, and to their parents.

You can buy tree and shrub seeds mail-order or collect them yourself. In the case of a tree or shrub with a wide natural range, increase the likelihood that the seedlings will be adapted to your backyard by choosing seeds from plants growing under similar weather and soil conditions as those in your yard.

OVERCOMING INHIBITIONS

Obtaining seed is just the first step in growing a tree or shrub. Most seeds need pretreatment before they will sprout and grow.

Seeds that ripen in autumn generally just sit after planting until they experience enough cold that they feel winter is over. If they grew immediately, the tender young seedlings would be killed by the first frosty night.

You can fool such seeds into sprouting by giving them an artificial winter. Pack them into plastic bags along with slightly moist potting soil, then put the bags in a refrigerator for a couple of months. Of course, you also could give the seeds a real winter, sowing them directly in the ground outside, but that exposes them to squirrels, birds, flooding and other natural hazards.

Another common roadblock to germination is a hard seedcoat that's impervious to water. Make such seeds permeable to water by nicking them with a file, or soften them by packing them into plastic bags with potting soil for two or three months at room temperature.

Some seeds - honeylocust, locust and Kentucky coffeetree, for example - sprout right after this treatment. Others, such as redbud, juniper and hophornbeam, need the cool, moist treatment after their seedcoats are made permeable.

And then there are those tree and shrub seeds that sprout without any pretreatment at all. Catalpa and sycamore ripen in autumn, but sprout almost as soon as they touch ground - which may not happen under natural conditions until spring. Seeds that ripen in the spring, such as silver maple and red maple, also need no treatments.

PLANT WITH FORETHOUGHT

Once seeds are ready for planting, perhaps already sprouting, they are ready to plant outside. If outdoor weather is still too cold, hold back growth by keeping the seeds refrigerated, or pot them up in containers in potting soil.

Keep growing plants in containers in a cool room exposed to as much light as possible. When it comes time to move a potted tree or shrub outdoors, acclimate the plant gradually, with increasing exposure to sun, wind and cold, just as you would with tomato seedlings.