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How to use a tomato plant cover

Updated: October 2026

You use a tomato plant cover after the forecast allows the plant out, not on the day the parcel arrives. In much of the UK, air frost still occurs in May. The Met Office notes that it tends to finish earlier in the south and on coasts, and later further north and on higher ground. A film house does not cancel that pattern. The Products Compared editorial team read the RHS growing guidance and the amazon.co.uk listings on 16 October 2026. This page is the season order. The [tomato plant cover comparison](/hub/plant-accessories/tomato-plant-cover) is the table. There is no ranking here. If you buy through our links, we may earn a commission at no extra cost to you.

You use a tomato plant cover after the forecast allows the plant out, not on the day the parcel arrives. In much of the UK, air frost still occurs in May.

Our top picks

VOUNOT VOUNOT tomato grow house, white

Best overall

VOUNOT VOUNOT tomato grow house, white
9.0/10about £23.49
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DIVCHI DIVCHI tomato growhouse

Best value

DIVCHI DIVCHI tomato growhouse
8.2/10about £15.47
View offer
Tierra Garden Haxnicks pop-up tomato cloche

Alternative

Tierra Garden Haxnicks pop-up tomato cloche
7.8/10about £20.99
View offer
On this page
  1. 1.When to put tomatoes under the cover
  2. 2.How to peg it before the wind
  3. 3.How to water and when to vent
  4. 4.What the cover does not change

When to put tomatoes under the cover

Plant outside once temperatures are reliably above 16°C, which is the RHS tomato guidance. Tomatoes do better when nights stay above 10°C. A cover can take the edge off a cool breeze and keep a shower off the leaves. It is not a date you can bring forward because you own plastic. If the night forecast still drops to frost, leave the plants indoors. Northern and upland gardens often wait longer than southern and coastal ones. Harden for two to three weeks before the plants live under the cover full time. An RHS May-jobs note also mentions 10 to 14 days. This page uses two to three weeks and does not average the two lines. Bring the pots in if a frost is forecast, and only then set them in the grow bag under the film. Sizes are on the tomato plant cover buying guide.

How to peg it before the wind

Put the stakes in before you trust the afternoon. Buyers of the tall film houses, the pop-up cloche and the low tunnel keep saying the supplied fixing is too light. On an open site, add longer stakes or a tie to a fixed point you are allowed to use. Do not screw a frame to a balcony you do not own. The VOUNOT bullets name four ropes, ground stakes and nylon ties, and reviews still say people add more. The DIVCHI box list does not name pegs. The Haxnicks listing includes pegs, and one buyer found them missing. A low tunnel in this set has no pegs listed, and one review said it blew away. A frame that stays up can still steam the plant if you leave it shut.
VOUNOT VOUNOT tomato grow house, white

Testsieger

VOUNOT VOUNOT tomato grow house, white
9.0/10about £23.49
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How to water and when to vent

Water the compost at the base. The RHS links swinging moisture to split fruit and to blossom end rot, and container plants may need water every day in hot weather. Under a film cover the path can be wet while the bag is dry, because the rain is on the plastic. On the 150 cm houses, the roll-up door is how you get there. Open it, water, and close it only if rain is coming and the air inside is not already stale. On the Haxnicks cloche, buyers say there is no watering opening, so the cover comes off. Open the door or the vents when the sun is on the film, when condensation beads inside, and when the plants are flowering so insects can reach the flowers. The RHS says high humidity and soft growth under cloches encourage grey mould unless ventilation is efficient. If there is no stated vent, leave the door ajar. Drop it before a shower.

What the cover does not change

The cover does not replace the forecast or hardening off. If frost is still in the forecast, a 150 cm house on the patio is not a reason to plant. Further north or on higher ground, that frost window runs later than on a southern coast. It does not add a temperature you can print on a label. The RHS figure of about 2°C is for heavier fleece, and these film covers were not measured that way. If the spots might be blight and you have potatoes in store, use the RHS blight pages. The detail is on tomato plant cover and blight.

Common questions

When can I put tomatoes under a cover outside?
Wait until days are reliably above 16°C and nights hold above 10°C. Air frost still happens in May, later further north and on higher ground. The cover is not a frost-proof room.
Does the cover replace hardening off?
No. Harden for two to three weeks and bring the plants in if frost is forecast. An RHS May note of 10 to 14 days is a different line. Do not split the difference.
How do I peg a tomato growhouse so it stays up?
Stake it before the wind. VOUNOT lists ropes and stakes, and buyers still add more. DIVCHI does not name pegs. Haxnicks includes pegs, and you should check they are in the bag.
When do I open the door or vents?
Open them when the sun is on the cover, when condensation is on the film, and when the plants are flowering. Drop the door when rain is due. A permanently shut house holds humidity, which the RHS links to grey mould.
Should I shut the film on a hot day?
No. A closed cover on a hot day traps heat and wet air. Open the door or a vent. Put the film back over the leaves when rain is coming.
Can I plant earlier in the north because I bought a cover?
No. Frost finishes later further north and on higher ground. A cover does not rewrite that. Use the same 16°C and 10°C lines, and your local forecast.

Related pages

Best tomato plant cover

Tomato plant cover

Tomato plant cover and blight: what a film cover can do

Tomato plant cover buying guide: height, film and door

Tomato greenhouse or cloche: a 150 cm house or pop-up

Sources

Public UK sources checked for this comparison, plus the amazon.co.uk listing facts in the display file on 16 October 2026. Shelf prices and star lines are those UK figures. A cover in this set does not prove a temperature lift or that blight is stopped.

  1. RHS: Cloches (retrieved 16 October 2026)
  2. RHS: Fleece and crop covers (retrieved 16 October 2026)
  3. RHS: Tomato blight (retrieved 16 October 2026)
  4. RHS: Grow your own tomatoes (retrieved 16 October 2026)
  5. RHS: When to plant out tender plants (retrieved 16 October 2026)
  6. Met Office: Why frost can still occur in late spring (retrieved 16 October 2026)
  7. Gardeners' World: How to grow tomatoes (retrieved 16 October 2026)
  8. Gardeners' World: Tomato blight (retrieved 16 October 2026)