Climate and Its Relation to Gardening
The relationships between the surrounding physical conditions (the climate) and the growth of plants are very complex and by no means fully understood. Nevertheless it is important that a good gardener should appreciate the principles involved.
First of all there is the general climate of the area where you live, the details of which will be found in officially published statistics. The next is the local climate, which is a further modification of the general conditions—for instance if you live at the bottom of a hill, you are more likely to experience frosts than your neighbors at the top because cool air travels downhill.
Finally there is the microclimate, the exact conditions surrounding each growing plant, and over which you can exert some influence—a screen against wind, a delicate plant on the sheltered side of a hardier specimen, and so on.
Main Weather Conditions
The most important forms of weather which will affect your plants are soil moisture, sunlight and temperature. Wind is also important.
Plants need moist soil to enable their roots to take up the essential nutrients from the earth. Soils vary in the amount of moisture they can hold. Coarse sandy soil drains very fast indeed, and you will need to add lots of water holding humus. Rich soils can hold up to twice as much moisture as sandy, and will make watering a less arduous task.
Sunshine provides energy and light. Different plants need very considerably different amounts of light and shade, and it is important to match the plant with its appropriate conditions in your garden when you plant it. I used to live in the UK and the sunniest places in the British Isles are those nearest the coast, and especially the south and south west. On higher ground there will be less hours of sun.
In summer, plants transpire water in hot sunny weather, and nearly all gardens will need the water balancing maintaining by artificial irrigation.
The best rainfall from the point of view of a garden is that which occurs fairly steadily throughout the year. Not very much will survive months of drought followed by torrential monsoon-type rains. The UK is a good place for a gardener for this reason, although some years will always be exceptional for the amount of rainfall or the lack of it.
The temperature of the air and the soil in which a plant lives are of vital importance in its development. Temperature controls the rate, if at all, at which seeds germinate, the period when the leaves give way to flowers and fruit, and the progress towards maturity.
Average temperatures decrease with the height of the ground above sea level, so that if you live in a hilly area you must accept that you will not have the same choice of outdoor plants as those lower down. On the other hand, there are plenty of plants which actually prefer cool conditions.
Very cold winters are the worst threat to all other than annual plants, and the worst problems occur when a mild spell which encourages plants to start into growth is followed by a sudden return to wintry conditions. It is always worthwhile having sacks, polythene sheets and cloches available to protect tender plants at short notice. The temperature in summer will determine whether a plant will reach full maturity; warmth is as important for most plants as is the length of the growing season.
Frost causes two different kinds of damage. It can break the plant tissues, or it can freeze the moisture in the ground and thus prevent it reaching the roots. The average date of the last frost of any area is an unreliable guide to the time at which you can plant out tender subjects.
If you do not know your area well, ask around amongst the neighbors or at a local college, and see if they are able to tell you the frost patterns in the area. Of course you cannot wait forever to plant out your half-hardy and tender plants. It is almost certain to happen sooner or later that some will be caught by an unusually late or severe frost. A little local knowledge though should mean that planting out is successful in most seasons.
The simplest way to protect your plants against frost is to keep the soil moist, free from weeds and as compact as possible. This will mean that heat rises during the night, thus warding off frost.
Everyone has seen the damage to fields, trees and hedges caused by gales, but even moderate winds can cause considerable havoc in a garden. If your garden is small, hedges will give the best protection if they are placed to the windward side of the plot. If you have a larger area, tree shelter belts will perform the same function even more effectively.
Hedges and trees provide shelter for a distance of about seven times their height; if you have room for neither, and have to settle for a wall or fence, this will give you protection to a distance of five times its height. Shelter is always most necessary near the coast where off-sea winds cause heavy damage.