Rows of young plants under a polythene cloche

Protect young veg plants in spring

Protect young plants from late frosts and cold winds in spring to get them off to a good start.

Vegetable plants and bedding should be planted out after all risk of frost has passed, but sometimes a late cold spell can cause problems and put all your hard growing efforts at risk, even if your plants are in the greenhouse or cold frame. Most plants need an average night temperature of around 10ºC to thrive. Without extra protection, low temperatures, frost and cold winds can damage plants’ leaves and check growth.

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Don’t worry, there are plenty of things you can do to protect young veg plants from spells of cold weather, whether you’ve planted them in an unheated greenhouse or cold frame, or outside on the veg patch or allotment. The first rule of thumb is to always have some protection handy – such as a cloche or some horticultural fleece – as  you can use these to quickly pop over your plants if cold conditions are forecast.


Protect plants with cloches

A polythene tunnel cloche over rows of seedlings

Cloches provide instant protection to young plants – both in an unheated greenhouse or outside. Flexible polythene and wire hoop cloches are the quickest and easiest to use, while sturdier plastic cloches provide additional protection from wind. Ensure they sit firmly in the ground to prevent losing them in high winds. If possible, keep any ventilation holes slightly open during the day and close them at night, as this prevents the air from getting too hot during the day, which can damage plants, as well as prevent a build up of condensation, which can lead to fungal diseases.

In a greenhouse, plants are already protected from outside conditions, but temperatures can still fall below the desired 10ºC and so a cloche can provide additional protection – up to around 5ºC in some instances, which can make all the difference. Invest in a min-max thermometer to help you decide when you need to give plants a helping hand, and have cloches on hand to use when you need to. Again, it’s best to keep ventilation holes open during the day but closed at night.

Moneysaving tip: if you don’t have cloches, raid your local recycling bin and cut the ends of 2L plastic bottles. These can be used as individual cloches over plants. Keep the lids to use to increase or decrease ventilation, to keep your plants as snug as possible.


Protect plants with a heat mat

Placing pepper plants on a heated capillary mat

In a greenhouse, if you have access to electricity, pop plants on a heated mat at night to protect them from the worst of the cold temperatures. There are many types of heated mat available, with some also providing irrigation options. Simply turning the mat on at night and off again in the morning will help to protect the plants without providing them with too much heat, which can make them ‘leggy’.


Cover plants with fleece

A tunnel of horticultural fleece supported by wire hoops, its edges weighted down with bricks

Rows of bedding plants and veg, along with the fragile blossom of fruit trees, can be protected with horticultural fleece. If possible, support the fleece using wire or cane hoops. This will ensure a good air flow around plants and can be left in place for a few days. Otherwise, just throw a couple of layers of fleece over the plants at night and then remove in the morning.

Moneysaving tip: instead of fleece, use a few layers of old net curtain to protect your plants instead


Protect plants in an unheated greenhouse

Fixing bubble wrap to the greenhouse frame
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Plants in an unheated greenhouse can be protected with cardboard, old curtains, bubble wrap or anything else to hand you can drape over the plants to protect them from the coldest temperatures. Suspend heavier materials on bamboo canes if you need to. If you have stones, bricks or pieces of slate, you can place these in the greenhouse to warm up during the day and give off heat at night. This may not make a huge difference, but every bit helps.