Sunday , November 19 2017

All vital plants processes: photosynthesis, transpiration, respiration and growth are affected by temperature. Each plant species has a minimum and a maximum temperature beyond which these precesses fail to take place. For most plants, the maximum temperature is around 35 Celsius degrees (96 F), while the minimum is highly variable. When extremely low temperatures occur, plants tissues may be physically destroyed.

Air and soil temperatures are the most important climatic factors influencing the onset and breaking of dormancy in plants and also the length of the growing season.

Temperature

Air temperature
Sunshine produces radiant energy that rises the ambient or air temperature significantly. In temperate and cooler climates, a site in the garden that is sheltered and benefits from the warming effect of full sun, can be used to grow plants from warmer regions that might not otherwise thrive.

Altitude also has an important effect on air temperature. At the same latitude, highland sites are cooler than lowland ones. For every 300 m increase in altitude the temperature drops by 0.5 Celsius degree (1 F). From this reason, high-altitude sites have a shorter growing season, which combined with the cooler temperatures affects the range of plants that can be grown in that area.

Soil temperature
The temperature of the soil is important for good, healthy, root growth and affects the rate at which plants are able to absorb water and nutrients from the soil. The successful germination of seeds and development of shoots also depend on suitable soil temperatures.

The speed at which soils warms up and the temperature maintained during the year depend on soil type and the aspect of the site. For example sandy soils will warm up more quickly than clay and well-drained, fertile soils stay warm longer than the ones that are compacted or infertile. Soils from the sites with a natural, gentle incline towards the south warm up quickly in spring because they gain more benefit from the sun than the soils from a level site or north-facing ones. From this reason the south-facing grounds are ideal for early vegetable crops. North-facing slopes stay relatively cool and may be used for growing plants that require cooler conditions.

Dormancy
Plants become dormant to limit their exposure to winter weather, most of them heaving at least a short period of full dormancy. Woody plants start their dormancy by shedding their leaves in autumn to avoid excessive transpiration. Most herbaceous and bulbous plants dye down completely in winter and remain dormant below the ground.

The temperature of the soil and air are the most important factors involved in the onset and braking of dormancy. As a gardener it is possible to exploit this knowledge for your own interest. For example if you grow bulbous plants in pots you can awake them from dormancy and bring them into early flowering by placing them in a warm greenhouse.

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Wind

Wind, especially strong ones, often damages plants. But wind has also some benefits. It plays an important role in pollen and seeds dispense and may also be useful in cooling plants down, provided that they have enough water to prevent desiccation. Gentle winds prevent the development of a stagnant atmosphere and deter plants diseases that might otherwise thrive.

Strong winds may discourage beneficial insects and make it difficult to control pests, diseases and weeds. Spraying is less effective in windy conditions or damaging to non-target plants due to spray drift. Many other problems are caused by the wind, but there are various ways to protect the plants.

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