Weather Effects
Plants and Soil

Heat and Humidity

High temperatures and bright sunlight can be very damaging, and are often combined with low moisture levels in the soil. Heat damage causes wilting, scorching, and ultimately withering of the plant due to moisture loss from both plant and soil. Add organic matter to the soil to encourage moisture retention, and choose plants that tolerate sunny, hot, or dry conditions – these plants have leaves that retain moisture well.

Certain plants need high humidity to grow well – tropical plants and ferns are examples – but this often causes a multitude of problems. When the air has a high moisture content, more moisture is retained by plants leaves, encouraging diseases such as mildew and fungal scab infections. The soft growth of the plant is also more prone to damage and attack by pests.

Rain

Rain is essential for the survival of all plants; it also helps to keep foliage and flowers free of dust and other deposits. Too much rain can pose problems since it leads to waterlogged soil (where the amount of water entering the soil exceeds the amount of draining out) and leaching of nutrients, thus preventing plants from growing properly. If plants are exposed to waterlogged conditions for long periods, the roots may become “asphyxiated” and die. Few plants, except specially adapted marginal water plants, will establish well on permanently waterlogged sites. To improve the soil in waterlogged areas, try adding organic matter and grit or, in extreme cases, putting in a drainage system. You can also choose plants that are specifically suited to moist conditions (see “Plants for a Bog Garden”). Avoid walking on waterlogged soil since it is easily compacted.

Storm Damage

On slopes, soil may be washed away by torrential or heavy rainfall, and the soil structure may also be quite severely damaged elsewhere in the garden. The force of heavy rain can sometimes bruise or even tear soft, tender foliage and flowers. More extreme problems may be caused by hail, which can literally puncture foliage. Lightning damages or kills any trees that it strikes.

Wind

Some air movement is needed to reduce humidity and lower air temperatures; it also keeps many diseases at bay, and helps to disperse pollen. However, excessive wind can scorch foliage and flowers, distort growth, and may even break or uproot plants, as well as dry out soil. Salt-laden coastal winds can cause severe scorching, and salt from sea spray can kill plants if it reaches their root systems. In windy conditions, spraying against pests and diseases is difficult. Fewer fruits may set since pollinating insects are less active.

A windy site can usually be planted successfully behind a living or artificial windbreak, this must allow about 50 percent of the wind to blow through to be most effective. See "Wind Tunnels".