What to Sow in May – 2024

“Remember – always sow the seeds.  You can catch up on everything else, but if you get behind on that, then there’s nothing you can do about it.” – A great piece of advice I was given many years ago!

French beans and Sweet Corn are just two of the reliable and delicious crops you could sow now directly into polytunnel soil.

Although in theory we can sow almost everything outside in the garden now – except tender veg. like cucumbers etc. – our weather is so variable now that we must keep an eye on soil temperature and weather conditions!

Unless you have had ground covered with cloches or polythene so that the soil is dry and warm – and the space is relatively slug-free – then it’s always much safer to sow in modules undercover in a greenhouse, polytunnel or cold frame to be sure of guaranteed results and to save wasting expensive seed.  Doing this means you will have well grown plants ready to plant out as soon as the weather improves. Also don’t make the mistake of sowing too deep – this is one of the main reasons for seeds not germinating. Never sow any seed at more than twice its own depth – and some seeds like celery and alpine strawberries prefer to be sown on the surface of compost, or only very lightly covered with something like vermiculite or sharp sand, which allows light to filter through. 

The soil in many areas is still very wet, and also cold after recent frosts. A late frost could destroy newly emerged seedlings of tender crops like French beans even under cloches, even if they germinate in the cold soil – which is unlikely. Seed is expensive and you can’t afford to waste it!  You can’t afford to waste time now either, by possibly losing any sowings made in poor conditions at this time of year.  More seed of the varieties you want may not be available now, with many more people growing their own food due to shortages, supply chain issues and adverse weather throughout Europe and the UK affecting imports. So treat seeds like the valuable resource they are.

Many important staple winter and storage crops need to be sown this month – and if they fail it may well be too late to sow them again.  Although the sun is strong now and sunny days are warm, there can still be seriously damaging night frosts this month, depending on your location.

In a heated propagator, in a warm place, or directly in tunnel soil when it’s warm enough – for polytunnel or greenhouse cropping, or for planting outside under cloches or fleece at the end of May you can now sow:

Cucumbers and tomatoes for tunnel/greenhouse crops.  Super-fast bush tomato Maskotka is the earliest-fruiting tomato in the world, and if sown now, will produce delicious and abundant crops of small to medium-sized cherry tomatoes from late July. Also, French beans, runner beans, sweet corn, courgettes, edamame (soy) beans, chickpeas, cucamelons, gherkins, pumpkins, summer squashes, marrows and melons. Also, Florence fennel and ‘soft’ herbs such as basil, coriander, dill, Greek oregano (best for flavour), lovage, mints, parsley (giant flat-leaf Italian best flavour) Perilla (or Japanese beefsteak plant) and fennel, Alpine strawberries (Reugen is a good large-fruited, everbearing variety). 

Sow half-hardy single flowers such as Tagetes, single French marigolds, nasturtiums etc. for bees and butterflies – and to attract other beneficial insects like hoverflies etc. to help with pest control and pollination, under cover in a greenhouse or polytunnel and out in the garden. 

It’s really important to shade propagators and young seedlings from strong sun now at all times now to stop seedlings from cooking! – You can also switch off propagators during the day to save energy – even if shaded, on sunny days they will be plenty warm enough – but do make sure you remember to turn them on again well before it gets chilly in the evening, in case of unexpected frost..


Sow in modules if the weather is still too cold, in a seedbed for transplanting, or in the ground where they are to crop – if the weather and your ground conditions are suitable:

 Asparagus, globe artichokes, beetroot, broad beans, carrots, all varieties of peas, savoy and other autumn/winter cabbages, all varieties of sprouting broccoli including calabrese and purple sprouting, cauliflowers, salad onions, Hamburg parsley, land cress, lettuces, perilla, orache, chicory, kohl-rabi, kales (those for cropping overwinter outside from the middle of May onwards), parsnips (early May) radishes, rocket, salsify, Swiss chards, spinach, turnips and swedes, summer purslane, lamb’s lettuce, salad mixes and perennial hardy herbs including sorrel. Asparagus peas, Cardoons, Good King Henry and New Zealand spinach can be sown outside under cloches now, and also from the middle of May, if the soil is warm enough, sweet corn, French and runner beans. Marrows, courgettes, pumpkins, ridge cucumbers and squashes can all be sown outside under cloches at the end of May, in warm areas.

Also sow some single annual flowers such as Sweet Alyssum (perennial in polytunnels, and will sow itself freely), limnanthes (poached egg flower), cosmos, calendula, Californian poppies, Convulvulus tricolour, nasturtiums, phacelia, sunflowers etc.  All of these will attract beneficial insects like hoverflies, lacewings and ladybirds which will help with pest control, and also attract bees which help with crop pollination. 

Sow fast-growing green manures like buckwheat, mustard (a member of the brassica/cabbage family, so make sure it fits into your rotations), lupins & red clover (legumes) and phacelia, to protect and improve soil by adding humus, encourage beneficial microbes, ‘lock-up’ carbon and feed worms (after digging in), on any empty patches of ground that won’t be used for 6 weeks or more. Never leave ground empty! 

In polytunnels and greenhouses you can plant tender veg like sweet potato ‘slips’ in pots this month – or in the ground if it’s reliably warm enough, but I always prefer to get mine growing really well in pots first, as it gives them a better start. They need a long season because they don’t bulk up until late autumn, are very frost tender and hate cold, wet ground. 

You can also plant Oca and Mashua tubers in pots now – again to plant out later, at the end of May or early June – or to plant directly into tunnel soil.

The small growing tubers of Yacon can also be planted now in the tunnel or in pots to plant outside later. They are just starting into growth now.