Top Of The Crops - Tomatoes

Growing Tomatoes in a Polytunnel

Tomatoes are a summer crop that smells and tastes great from the smallest cherry variety to large beefsteaks hanging on the vine. It isn’t summer without gorgeously fresh tomatoes eaten straight from the garden.
Home-grown tomatoes taste completely different from the flavourless supermarket offerings, so they are more than worth the effort it takes to grow them - which is considerably lessened with a polytunnel.


Tomatoes originate from South America and they aren’t too keen on our chillier climate. Tomatoes will grow outside during a hot summer, but more often than not they struggle to ripen. A polytunnel can make the difference between tasty ripe tomatoes and hard green ones only good for chutney.
A polytunnel warms the soil beneath it, so you are able to plant out your tomatoes at an earlier date. Warmer soil means quicker, healthier growth. Cold, bare soil doesn’t have the same knack with young tomatoes.
At season end a polytunnel extends the time you have so tomatoes are more likely to ripen. On average a polytunnel adds 6-8 weeks to your growing season.
A polytunnel will also keep the damaging rain and wind at bay but let in all the light they need to fully ripen. Rain rots stems, roots, flowers, and fruits if it doesn’t dry off. This leads to fungal infections such as blight and poor growth. The wind can damage tomatoes by blowing them over, snapping off productive stems and freezing the tender plants.

Polytunnels shelter your tomatoes from the elements in a cosy atmosphere. Too much cold damages plants on a cellular level, but polytunnel protection helps maintain a steady temperature for healthy plants.
This steady temperature keeps the ground moist too, so if you’ve planted directly into the soil water won’t immediately evaporate or hang around in puddles if it’s chilly.
Polytunnels can also help keep off pests. Cats and birds dislodge new plants and all kinds of aphids want to eat your tomatoes if you don’t protect them.

Slugs and snails are persistent so peg the polytunnel down well. A weighted net or fine mesh on either end can keep pests at bay, but fine mesh means the pollinating insects can’t get in. Netting also allows air to circulate and prevent fungal infection such as blight.
You’ll need to check inside your polytunnel for pests even if it’s netted because if they manage to slip in they’ll enjoy the warm conditions and feast of tasty tomatoes enough to breed.
If you’re a fan of cherry tomatoes it’s easy to grow them in hanging baskets, but if you prefer the warmer and safer conditions of a polytunnel choose the smaller, cost-effective mini tunnels which are perfect for small bush varieties.


Tomato seeds are cheap and there are many varieties to choose from but they are all best grown in a warm pot and transferred to a polytunnel or greenhouse in warm weather.
Sowing tomato seeds in pots:

  • It’s a good idea to start early with tomato seeds so they have reached a good size when the sun arrives. Plant seeds on a sunny windowsill or in a heated propagator during January and February.
  • Sprinkle tomato seeds on a seed tray of loose potting compost and cover them with a thin layer of soil. Keep them moist but not waterlogged. Standing pots in a saucer of water is a good way to keep them damp but prevent dislodging the seeds - a fine rowed watering-can will do the trick too.
  • Within a week or two you’ll see germination. When the young plants are large enough to handle re-pot them into larger flowerpots and bury them to the first set of leaves. Hold the young plants by leaves which will grow back if you accidentally snap them.

Sowing tomatoes direct:

  • Tomatoes need good soil to thrive so dig in some compost, mulch, or organic matter for a real boost before planting. If you’ve already planted them out, dig mulch around the base being careful not to disturb the roots.
  • Once the risk of frost has passed, plant them in a polytunnel deeper than they were in the pots. Tomatoes regenerate extra roots on the buried stem to suck up more nutrients.
  • Growing tomatoes directly in a compost bag is a popular technique, but they do need constant watering.

Growing tomatoes:

  • Give them room to grow. Large varieties will need a few feet of space to stretch out their stems and vines.
  • Cherry or bush tomatoes will support their own weight without stakes, but larger vine varieties need support. Use stakes, trellis or a cage around the plants - it’s a good idea to put this system in place before the plants grow too big. Tie on trusses with soft twine and re-tie as they swell and grow.
  • Tomatoes need lots of water, but only around their roots. In hot spells you may have to water every day, this can be time-consuming so consider a seep hose or irrigation system. Poor watering can mean tomatoes don’t ripen or the flowers ‘dry-set’ meaning no fruit at all.
  • Feed is also important once the flowers set. Use a tomato feed once a week in summer - they grow quickly and need lots of food. Try not to get plant food on the leaves as this burns them and introduces infection like blight.
  • If you’re using a polytunnel pests are less likely to attack but be vigilant for whitefly in particular. If tomato leaves are curling at the edges it’s likely you have an aphid infection. You can use an insecticide or a citrus-soaked water to deter them.
  • Organic gardeners grow marigolds around the tomatoes as the scent deters flying pests whilst encouraging the ones that eat damaging aphids.
  • If you’re growing vine-staked tomatoes nip out the main growth at the top of your supports when flowers appear and continue to pinch out the extra leaves that appear between trusses. This ensures all its energy diverts into the fruits. Cherry/bush type tomatoes don’t need nipping out though.
  • As the season draws on it can help to remove some of the leaves so all the light shines directly on your tomatoes and ripens them up.



Picking ripe tomatoes encourage more to ripen, so pick them when they are ready, don’t hold back. You can usually start harvesting in July, though cherry varieties come earlier.

Starting picking when the fruit is ripe - the size and colour will depend on the variety. Most tomatoes are red but you can also get orange, green, yellow, and purple varieties.
Pinch out tomatoes at the stem but don’t squeeze the fruit as this creates a bruise. Scissors or secateurs can be useful.  Begin at the bottom of the plant if you are able and work your way up.
If you pick a tomato that isn’t entirely ripe, put it on a sunny windowsill to continue the ripening process. They smell divine as they heat up in the sun, and your kitchen will smell amazing.
You can put all fruit that hasn’t ripened by the end of the season on the windowsill or in a drawer with ripe fruit such as a banana. The gas that ripe fruit releases encourages quick ripening of other fruits around it.
If you are lucky, and especially if a polytunnel is involved, you may have a glut of tomatoes. Give them away or freeze them for winter strews or rich bolognese sauce.

Sowing Time

January to February indoors
Plant out in a polytunnel in April or May

Harvesting Time

From June to late August

Tomatoes are one of those crops that taste completely different from the garden - supermarket versions simply don’t compare.

Vine and bush tomatoes will grow faster and are more likely to ripen in a polytunnel or greenhouse, so if you’re a tomato fan it's worth getting them undercover for a reliable and tasty crop.  

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