What to do now - May

It's that time of year...



The weather is getting warmer, the days are getting longer and it is time to plant and sow outdoors. Cropping really gets started in early summer as the first potatoes, peas and soft fruits become ready to harvest. But watch out for frost during May, keep plants watered as we move into summer, and keep slugs and other pests at bay.

May and June are the months that transform our plots from mostly soil to an almost complete array of vegetation. They are very important months for keeping on top of weeds – these will be taking advantage of the longer days and warmer weather (by June there should be no risk of frost). They will be competing with crops for light and heat so regularly hoe and hand pick out weeds.

Earth up your spuds – applying earth around the base of potato stems will reduce tubers’ exposure to frost as well as keeping them in the dark to stop them turning green. Thin out direct-sown crops such as spinach, carrots and lettuce. Move leeks and brassicas to their final positions.

Keeping grow bags and potting compost in direct sunlight (or even in your greenhouse) will warm them up and give your seeds a head start in the growing cycle.

Keep an eye on your crops for early signs of pests or nutrient deficiency – e.g. if the leaves on your tomato plants turn yellow this is a sign of magnesium deficiency. This can be caused by overstimulating growth by using fertilisers with high content of other nutrients. This can be overcome by adding epsom salts (20g per litre, ½ oz per pint) to water every two weeks. 

Remember to ventilate your greenhouse on warm days, and consider using blinds or shades to avoid excessive temperatures, and damping down pathways to maintain moisture levels (and discourage mites).



Allotment tasks - May


Sow Now

Outdoors - Carrots, beetroot, French and runner beans, lettuce, peas, sweetcorn, cauliflower, sprouting broccoli

Under cover - tomatoes, basil, beetroot, Brussels sprouts, cabbages, carrots, courgette/squash/pumpkin/cucumber


French and runner beans, lettuce, peas, sweetcorn, cauliflower, sprouting broccoli

(aubergines, pepper undercover)    




Harden off plants by leaving them outside during the day and under cover at night.

Ensure that plants do not dry up – remember that occasional thorough watering is often better than more frequent light watering.  

Keep an eye on pests – slugs/snails, aphids. 

Weed beds regularly, pick off any young caterpillars (and leave in shallow containers where birds can feed on them), thin out seedlings


 Broccoli, kale, cauliflower, lettuce, spinach, chard, spring cabbage, asparagus   

Planning for Root Crops

Early spring is the time to plant root crops, and carrots can even be planted outdoors under cover during February. And a little preparation before they are planted can make a big difference to crop.

Carrots naturally grow in well drained sandy soil. They are not well suited to heavier clay soils where their development is hindered by solid clay or stones and the wet ground can increase the likelihood roots rotting. This can be overcome by growing them on raised beds and/or by selected short root varieties. 

Whilst root vegetable take nutrients from the soil, too much goodness can cause them to fork. Carrots, for example, tend to have greatest success when grown in a bed that was well manured for the preceding crop.

They are sometimes grown for competition in plastic tubes containing a soil/sand mixture. 'V-shaped’ channels in a bed to the depth of a spade head, filled with a mixture of sand, coffee grounds and spent soil from grow bags can also help to reduce obstructions to root growth, and prevent forking.



Planting Potatoes

Potatoes are a versatile vegetable, and the process of preparing the ground and growing potatoes helps to break up the soil. By now, seed potatoes should be well chitted – with several short, plump roots sprouting from their ‘eyes’.

Before planting them, ensure that some well-rotted compost or manure has been dug in. The potatoes should be planted in ‘V’ shaped trenches at least 12cm (5”) deep. Trenches should be at least 30cm (12”) apart for early varieties, 37cm (15”) for maincrop varieties. 

When to plant and harvest:

  • First Earlies – plant in late March, harvest June-July
  • Second Earlies – plant early to mid-April, harvest July-August
  • Maincrops – plant in late April, harvest August- October

Water the potatoes during dry weather and apply a liquid feed every few weeks to increase the yield and the quality of tubors. As soon as the green shoots start to appear, earth up to cover the stems with a ridge that is ~15cm (6”) high – this is stop light reaching the potatoes.

Controlling Slugs

In almost any year Slugs are the most troublesome pests on our plots. 

A cubic metre of soil can hold up to 200 slugs. Most of these are below ground during the day only surfacing in the evenings.

The best way to keep them in check is to tackle them on several fronts: 

  • removing them by hand at dusk when it’s damp, 
  • applying barriers of bran/sharp sand/egg shells around vulnerable seedlings, 
  • fitting copper bands to flower pots
  • setting slug-traps (sunken pots filled with (cheap!) beer, and 
  • slug pellets (ideally environmentally friendly ferrous-phosphate varieties).