Microclimates in the garden

 Alan Jolliffe

One of the more interesting aspects of gardening is the identification of areas in the garden which have different climates. In these locations, we can grow plants that may be different from those of our neighbours and friends. Identifying microclimates also allows gardeners to plan their garden for the best results.

To understand microclimates is to understand your garden, its orientation, soils, slope (if any), shelter, setting of the house, buildings, and anything else that directly effects the site. Gardeners also need to understand the microclimates of rainfall, sunshine hours, prevailing winds, wind types, temperature variation and the like.

It is the combination of these factors which creates microclimates in the garden. Every garden has microclimates.

Here is a description of some of the factors.

Soils vary greatly. Fine, clayey soils have the ability to be highly fertile, but they are also wet soils hard to cultivate and slow to warm up in spring. Sandy soils on the other hand are easy to cultivate, low in fertility and fast to warm up in the spring. Know which soils you have, what their attributes and weaknesses are and use that to advantage.

The amount of sunshine that reaches the garden will be an influencing factor. This will determine where sun loving and shade loving plants will be grown. It may also dictate the style of gardening and the landscape design.

In home gardens sun plays an important part in the temperature of the microclimate. Areas of the garden on the north side of a building (house) will be considerably warmer as both the soil and building heat up during the day and release the heat slowly at night. These are often frost-free areas that can be used to advantage. This phenomenon varies around buildings as each side faces a different direction each receiving more or less sun than another. Different exterior finishes on buildings also affect this.

There are several ways parts of the garden can receive shelter. Fencing and similar structures provide shelter from wind - both warm winds cold winds. Many plants grow a lot better without the constant battering by wind. However some gardens may have to be designed to cope with wind and good plant selection is needed in these situations.

Large trees also provide shelter from sun and frost. Even deciduous trees provide shelter so that half-hardy plants can be grown under them.

Manmade items such as pergolas, roofs, glasshouses and house eaves can also provide shelter from extreme conditions.

Land contours are important as they affect airflow. Cold air is heavier and will roll down a slope and congregate at the bottom where cold, cool and often wet conditions exist. It will be possible to grow different types of plants at the bottom of the slope from those grown at the top.

Identifying microclimates for a brand new garden is more difficult as there are a limited number of factors on the section to influence microclimates.  As shelter is added, suntraps created, soil modified and plants grow there is more opportunity to identify and create microclimates around the home. In more developed gardens it is much easier to identify microclimates.

Deliberately creating microclimates requires the adjustments of the factors (soil, shelter, contours, sun etc) to create the right microclimatic conditions that are required in the garden. Understanding the basics means that adjustments are easier to make to create a desired microclimate. The interaction of all these factors may be necessary for some microclimates but others may only adjustments of one or two.

Creating and using microclimates helps gardeners create the type and style of garden that they want.