Spring planting and the cold greenhouse
This blog for February gives me the ideal opportunity to discuss best use of the spring planting season and a cold (i.e. unheated greenhouse) if you have one. Gardening writing, including mine, regularly talks about ‘early spring’ rather than specifying a particular month because the advent of increasing temperatures varies so much from place to place even within south east England and from year to year; and more so in this era of unpredictable weather.
The spring planting season, at least until late April, is the time to add, split or transplant Hardy plants to your garden. Hardy meaning that the plants will survive temperatures below freezing without serious impact. And I suggest that if you are buying new plants to either ensure that they have been grown outside or go through the hardening off’ process, outside during the day and with a little protection for a few nights. Just because a plant is described as hardy does not mean that an individual specimen that has had some winter protection will be entirely happy planted out immediately before a frosty spell. Although once we hit April in the Kent/Sussex borders regular frosts are rare, the occasional air frost as late as early May can knock back newly breaking buds and the top growth so plants that are not completely hardy. Keeping some fleece handy and checking the weather forecast can be a plant-saver (the voice of bitter experience from many years ago!).
Despite all this gloom though, there are very good reasons to plant through the spring. Whatever the temperatures, day length is increasing – March 21st is the spring equinox when daylight and darkness balance out at 12 hours each. Plant growth is temperature sensitive: quicker growth at warmer temperatures, but daylight is the energy source through photosynthesis without which there is no growth at all. Also as spring progresses the soil starts to warm (this can be helped by placing empty cloches or fleece over areas where you want to plant) whilst there is still plenty of moisture in the ground and this promotes root establishment while cooler air limits the plants attempts to put out new stems and leaves.
If you cannot wait until the end of spring to start sowing seeds outside then the solution could be a cold greenhouse. This is one that is not heated so provides a level of protection for plants (and gardeners) in winter, especially if it is insulated on the inside. But the night time temperature will only be 3-4o above the outside and relies on warmer and/or sunny daytimes to rewarm the inside. If the days are also freezing and dull then the effectiveness of your greenhouse will drop off.
However, even a few degrees of warmth and the all-round light in a greenhouse do allow you to sow seeds earlier than you would in open ground. And you can control the amount of water in a pot or tray of compost to avoid seeds rotting off in waterlogged vegetable plot. I will now offer the same advice that I (and every other gardening advisor) do every February: Do not start to sow seeds now in a greenhouse or windowsill that cannot be planted out until the last frost. Even if you can keep them warm enough, seedlings will become spindly if left in seed trays or you will have hundreds of potted on plantlets to accommodate.
But there is plenty to plant and sow now if you take a little time to plan your gardening campaign.
Happy Gardening from Alison