Sometimes, spring comes early. It can encourage us to sow seeds and plant out seedlings into our polytunnels. Unfortunately, sometimes we have been lulled into a false sense of security. Late cold snaps in early spring can pose a problem for gardeners who have imagined that spring has truly arrived. But if a sudden cold snap is forecast, there are ways to protect tender seedlings in your polytunnel, so they are not damaged or killed by frost.
Horticultural fleece is sold online or at garden centres. This is an affordable fabric that can be draped over plants to protect them from sudden cold temperatures. You can double it up to make it thicker, and can also erect a tent like structure over seedlings to prevent them from being crushed by the fabric. To support your tent, you can use branches, garden canes, or other materials – such as reclaimed plastic piping, for example.
If a cold snap strikes suddenly, however, you may not have time to purchase horticultural fleece. You may be able, however, to give your plants protection with things that you might have lying around. Bubble wrap that comes as packaging round parcels can be useful for adding an insulative layer above or around plants in a late cold snap. Other similar packaging can also be used in a pinch.
Cloches can be expensive to buy, but you can also make these with things you may have lying around. Plastic drinks bottles cut in half can make free cloches that will help to keep plants safe in a late cold snap. Other plastic packaging such as plastic trays may also help to protect tiny seedlings on a temporary basis.
Organic materials can also help to protect plants. Spreading straw in a thick layer of mulch around plants will help to keep the soil from becoming frozen and can protect roots from a surprisingly cold early spring. The straw will slowly decompose, radiating heat as it does so and staving off hard frosts, adding to the protection from cold temperatures already offered by your polytunnel.
Bracken is another abundant material that can be beneficial as a thick mulch in a similar way to straw. If this is a common natural material where you live then this could also be an easy solution to keeping plants and seedlings safe in a sudden late cold snap.