Spring arrives for some, and struggles in for others…
March is a very variable month. The weather can change greatly from day to day, and indeed, year to year.
After plants’ winter rest, most begin to grow when the daily mean temperature rises above 6°C (43°F). One obvious sign of this is that the lawn begins to grow again and will need mowing.
Spring usually arrives by mid-March for much of southern England, as well as the Midlands and the coastal regions of northern England and Scotland. Gardeners on the Lizard may have already been enjoying spring weather for some weeks. The Pennines and Highlands often have to wait until April at least before plants start back into strong growth.
Frequent sunny days provide the opportunity for an increasing range of gardening tasks. You can now sow and plant a wide range of vegetables and flowers - outside in many areas - local weather permitting. Roses can be pruned, and a few crops can be harvested.
Temperature
The sun’s rays are growing stronger, causing temperatures to rise. In the Midlands, peak March temperatures now average 10°C (50°F), but at night temperatures can still drop to around 2-3°C (36-37°F), frost being common. Average night-time temperatures in western Scotland are similar, although eastern Scotland sees nightly dips as low as 0°C (32°F). Peak temperatures in Cornwall and south Devon are much warmer, 12°C (54°F) being common, and lows dipping only to 2.5-4°C (36-40°F). Frost here is extremely unlikely.
Bear in mind that towns and cities remain several degrees warmer than the open countryside, which allows some tasks to be done earlier than would otherwise be advised in a northern region, for example.
Continue to check greenhouse and conservatory heaters to make sure they are working properly (a maximum-minimum thermometer is a useful checking device).
The last three years have seen above average and even exceptionally above average temperatures in March. This year, with northern Europe being affected by the negative North Atlantic Oscillation, temperatures may be more unpredictable, and late frosts could be likely.
Rain
There are widespread showers this month, but usually less total rainfall than earlier in the year. The last three years have seen below average rainfall in March for most regions of the UK (Northern Ireland being the only exception). As a result, soil water reserves are low. As temperatures rise and rainfall lessens, the soil begins to drain and become more workable. This is often a good time to cultivate clay-based soils. The drying process can be speeded up in wet areas by covering the ground with plastic and fleece. This increases the number of days of fieldwork (i.e. the number of whole useable days in the garden) possible this month.
Heavy showers and melting snow continue to wash nutrients out of the soil, which will benefit from a mid-spring application of fertiliser.
Actual averages for March rainfall vary from 43mm in East Anglia, to 65mm in southeast England, 100mm in south-west England, 90mm in northern England and eastern Scotland, and140mm in western Scotland.
Wind
North-westerly winds often bring cold, strong breezes. And, like the saying ‘March winds will blow and we shall have snow’, snow, sleet and hail are also likely.
Winds can reach gale-force, particularly along the western coast of the UK. Make sure that tree stakes are securely in place, and that plants are tied firmly to supports. If large trees are damaged, it is best to prune off the damage. Small branches are manageable for most gardeners, but more major work will require the help of an arborist or tree surgeon.
Light
The days are now longer and light is beginning to reach adequate levels, even in northern regions. There is an average 30 per cent increase in sunshine levels across the UK in March, with 90-100 hours being an expected broad average across the UK. South-east, south and south-west England usually fare better than northern England and eastern Scotland, which in turn fare better than western and northern Scotland.
Despite the general increase in sunlight, it is still a good idea to keep glasshouse plants well spaced, and to keep the panes clean, in order to maximise light on dull days and in northern districts.
Recent years have seen an overall trend towards increased March sunshine levels than long-term averages would lead us to expect. March 2005 was an unusually dull month, but March 2003 and 2004 saw sunshine levels up to 70% above average in some regions. Let’s hope for a sunny March 2006.