MOST of us gave up studying science when we left school. But whether we are aware of it or not, we gardeners regularly use and exploit scientific know-how in many of our day-to-day gardening practices.

I was reminded of this fact last week, while discussing the propagation of Sorbus with some fellow enthusiasts apparently the brightly-coloured pith of rowan berries contains a growth inhibitor which must be removed before the enclosed seed will germinate.

In the wild, this happens as the seed passes through the acid of a bird's stomach. In the nursery, the pith must be carefully washed off in order to tempt the seed to germinate.

Here are some more interesting scientific facts relating to plants and gardening: Seeds of many trees and shrubs will not germinate until they have been exposed to a period of cold temperatures. You can break this dormancy artificially by keeping seeds in the fridge for a few weeks before sowing.

The green parts of a plant are positively phototropic (they grow towards the light) and the roots are negatively phototropic (they grow away from the light). Geotropism is the response of roots and shoots to gravity, and haptotropism is the response of stems and leaves to touch or rubbing, such as when clematis leaves and vine tendrils coil around supporting vegetation.

Thermonasty is the response of a plant to the external temperature. For example, tulip flowers open with rising temperatures, which stimulate cell growth on the inside of the petal, while celandine flowers close up when the sun is not shining as cooling temperatures stimulate cells on the under-surface of the petals.

The top-most, or apical, bud of a shoot has dominance over all the lateral buds below it. This apical dominance is something we encourage when we train a leader into a small tree in order to produce a tall, straight specimen, and something we remove every time we clip a hedge.

By laying the stem of a climbing rose or the branch of an espalier apple tree horizontally, we are encouraging plant hormones to accumulate on the upper side of the stems. These will stimulate the plant to produce many more flower buds than if it had remained upright.

Short day plants' such as chrysanthemums will not flower until the day-length is shorter than a critical amount. Long-day plants' like petunia will not produce flower buds until the day-length exceeds a certain amount.

Pollination can often affect the longevity of flowers; carnations and many species of orchids, for instance, will fade rapidly once they have been pollinated. Unpollinated examples will last much longer.

Lowering the temper-ature around stored fruit, such as apples and pears, helps to preserve it by reducing the rate of respiration.

Jobs for the week

Plant hedges small plants are cheaper and will generally establish more quickly than larger plants, provided the soil is in good heart and they are kept well weeded.

Begin raking up autumn leaves from lawns and pathways. Save yourself a job and benefit wildlife by leaving those that fall under trees and shrubs to rot down naturally.

Dig up and split any overgrown or very large clumps of herbaceous perennials. Replant smaller pieces after enriching the soil with compost or rotted manure.