It’s that time of the year when social media posts are full of “should I start sowing some seeds or is it too early?” There’ll be pictures of long leggy seedlings and people asking what to do with them. Of course, the answer is far from simple and depends on where you live in the country. The trick is knowing the dates of the last frosts where you live. Once you have managed to germinate your seeds where will you be able to grow them until the danger of frost is finished?
As you can see from the chart above the only months we haven’t recorded any frost over the last 15 years are June, July, August, and September. The tricky month is May. A frosty night in May will normally damage any potato shoots that have emerged but with protection from some fleece plants usually survive in the greenhouse. I don’t normally start any tender plants such as tomatoes before the beginning of April. The hope is that by the time they are ready to move into the greenhouse the keenest of frosts will have finished.
We germinate lots of our seeds under an indoor propagator. It does have a light to stop the seedlings from becoming leggy but it isn’t heated. However, from here the seedlings have to be transferred to our cold greenhouse until they are big enough to be planted in the allotment.
Our earliest sowings last year were onions and shallots. These were sown in the middle of February last year and they survived any cold weather and went on to produce some decent onions and shallots.
Our first brassicas were sown at the end of February and are pictured growing in the propagator in the photo above. These too went on to produce some decent cabbages although the cauliflowers were a little less successful due to dry weather conditions later into spring.
Therefore, based on successfully producing a decent crop of onions and shallots from seeds sown in the middle of February last year, the same varieties have been sown again this year on the 15th February. Time will tell if the sowings turn out to be as good as last year’s sowings.
I agree with your comments Steve. At the allotment potatoes are the vegetable crop to suffer from late frosts. Our early potatoes often seem to be caught by the last frosts of spring but always seem to recover. I think the cropping date is just delayed. Generally, all our other vegetable crops cope okay with any late frosts. We grow strawberries, apples, pears, plums and greengages and late frosts certainly cause damage to these crops but there’s not much I can do to protect trees from frost damage. Some years the crops are good and sometimes not but there are lots of other factors that come into play with fruit crops not only late frosts
I’ve never really understood the focus on last frost date Martyn, it’s not relevant to heat loving crops, which need 10c overnight and it’s not relevant to cold tolerant crops like alliums, brassicas, lettuce and spinach. We can still be having plenty of frosts in April and May, but light levels are excellent at during both months and so plants can be growing exceptionally well in the ground from March onwards, with only a little protection from cold winds and a layer of fleece or poly provides a huge boost in daytime temperatures. As a result I’ve basically ignored all ‘last frost date’ constraints and focused on light levels instead and I’ve never been disappointed. You can see the results in my monthly summaries https://steverichards.notion.site/Reference-information-eb1f6a760b9c4b5d8e9683502dfec7d0?pvs=4. Like you though I do find early sowings, over winter, benefit from 14-21 days under grow lights : All the best – Steve