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Growing in a Polytunnel in May

What to sow, plant and harvest from your polytunnel in May

May is the most exciting month in your tunnel or greenhouse. This is the time to plant out your summer crops – your tomatoes, peppers, aubergines, cucumbers and basil.

Take good care of them and give them a fabulous soil and they will reward you with a bounty of delicious sun-ripened fruit. Once the busy spell of planting is over you can start to relax again.

May Polytunnel

Show Growing Carrots in Barrels in Polytunnel

Planting into beds

You will appreciate now all the hard work of preparing the beds in the previous months. There is no shortcut: only a well-prepared and well-fertilised bed can sustain the demands of the heavy yielding summer crops.

All the summer crops can be planted now:

  • Aubergines
  • Basil
  • Courgette
  • Cucumbers
  • Melons (only in warm districts)
  • Peppers and chillies
  • Tomatoes

You can also plant out into the tunnel or greenhouse the seedlings you sowed last month on your heating bench:

  • French Beans
  • Celery
  • Lettuce
  • Scallions
  • Dill
  • Coriander
  • Chervil

Sowing into modules/pots (18-20 degrees C)

In May you can sow the following vegetables into modular trays or pots and place them in your propagator or warm, south facing windowsill in the house.

  • Basil (Sweet Genovese) – 4 seeds per cell
  • Celery (Victoria F1) – broadcast in a tray for pricking out later
  • Courgette (Defender F1) – 1 seeds per 7cm pot
  • Cucumber (Passandra F1 and Styx F1) – 1 seed per 7cm pot
  • Coriander, Dill and Chervil – 5 seeds per cell each
  • French beans (climbing and dwarf) – 5 seeds per 9 cm pot
  • Florence fennel (Rondo F1) – 1 seed per cell
  • Lettuce (various types) – 1 to 3 seeds per cell
  • Melon (Emir F1) – 1 seed per 7cm pot
  • Sweetcorn – 1 seed per small pot

General greenhouse/polytunnel maintenance

  • Water more frequently and more heavily now.
  • Ventilate as much as possible.
  • Dig out potatoes and early cabbages to make room for summer crops.
  • Keep a watch out for pests, especially slugs and snails on newly planted salads, aphids on a variety of crops and fleabeetles on brassica salads.
  • Spray aphid susceptible plants with a garlic spray every seven to ten days.
  • Prick out and pot on plants as necessary.
  • Harden off your summer crops that are nearly ready for planting (tomatoes, peppers, aubergines, cucumber, melons, peppers) by taking them off the propagator.
  • If you haven’t fed the beds for the summer crops, do so now.

Further Information & Polytunnel Articles

This Article is by Klaus Laitenberger, expert on Polytunnel Growing.

Klaus grows in the challenging conditions of Ireland and has experience and knowledge of growing under shelter in polytunnels and greenhouses.

He’s the author of Vegetables and Herbs for the Greenhouse and Polytunnel

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