Wondering which seeds to sow in May? Read on for my top tips on what to sow, and useful planting advice.

Is there anything quite as satisfying as growing your own fruit and vegetables? And is there anything more confusing than knowing what seeds to plant when? Let me help. Here are the seeds to sow this month – either directly in the soil, or for starting off undercover, or in heat – as well as handy growing tips for each plant.

Treat this sowing guide as a general guide.  Some years the typical growing season might be a few weeks out of kilter.  If it feels a little bit too cold outside, you might instead want to wait until later in May to sow outdoors.  Alternatively, sow indoors or undercover, or else be ready with a fleece in case of any cold nights still ahead of us.

Person sowing seeds with blue text box that says the seeds to sow in May for a bumper harvest.

I originally made the guide image-based, but I’ve recently updated these with the text below in case any readers are visually impaired and use a text reader. 

What Seeds to Sow Outside In May

seeds to sow outside in May

French beans, beetroot, cabbage, kale, leeks, turnips, lettuce, runner beans, broccoli, cauliflower, chicory, peas, kohlrabi, swedes, and spring onions can all be sown outside. Here are some handy tips:

French beans

Sow seeds 5 cm deep into the soil.  Space the seeds 15 cm apart, with 45 cm between rows.


Sow your seeds 1cm deep into the soil. Space the seeds 10 cm apart, with 30 cm between rows.


Sow at a depth of 2cm, 25 cm apart.  Leave 30 cm between rows.


Sow at a depth of 1 cm, leaving 60 cm between seeds and rows.


Sow at a depth of 1 cm, 15 cm apart.  Leave 30 cm between rows.


Sow at a depth of 1cm, leaving 30 cm between rows.


Sow thinly at a depth of 1cm, leaving 30 cm between rows.

Runner beans

Sow two seeds at the base of a cane.  Plant them 5cm deep and space them 15 cm apart.


Sow three seeds 2cm deep, leaving 30cm between each row.


Sow seeds thinly at a depth of 2cm. Depending on the size of the variety you’re growing, rows should be between 15 cm apart for small varieties to 60 cm apart for larger ones.


Sow seeds thinly at a depth of 1cm, in rows 30 cm apart.


Make a flat-bottomed trench around 5cm deep and 15cm wide. Sow the seeds evenly in the trench about 7.5 cm apart, before covering them with a light layer of soil.  If you sow a second row, space it at a distance equal to the height of the final pea crop.

Kohl Rabi

Sow seeds, 1 cm deep in rows 30 cm apart.


Sow 2cm deep in rows 38cm apart, and thin to 23cm apart.

Spring Onions

Sow thinly at a depth of 1cm in rows 10 cm apart.

What Seeds to Sow Undercover in May

seeds to sow undercover in May

Sweetcorn, courgette, marrow, and pumpkin can all be sown undercover right now.


Grow sweetcorn in a warm, sheltered, sunny position, protected from strong winds.  I find a polytunnel works best. Sweetcorn is pollinated by the wind, therefore seeds should be sown in blocks rather than rows, 45cm apart. Try sowing two or three seeds at each point, then thin out the extra seedlings to leave just the strongest one.


Sow two or three seeds in the centre of a 2.5 cm deep hole. Cover with a glass or plastic cloche, and leave the covering in place for at least two weeks. If more than one seed germinates, remove the smaller, weaker seedlings to leave just the strongest one.


Similar to courgettes, sow two or three seeds at a depth of 2.5cm and cover with a cloche for at least two weeks.  Then thin the seedlings to leave the strongest one.

Pumpkin – follow the advice for both courgettes and marrows.

What Seeds to Sow in Heat in May

seeds to sow in heat in May

Aubergine, chilli peppers, sweet peppers, cucumbers, and tomatoes should all be grown in heat right now:


Sow at 18-21°C in small pots.

Peppers (chilli peppers and sweet peppers)

Sow seeds in small pots.  Place the pots in a heated propagator at about 18–21°C, or on a warm windowsill.  If you don’t have a heated propagator, cover your pots with a clear plastic bag or clear lid to trap moisture and warmth.  Transplant your seedlings into 7.5–9 cm pots when two true leaves have formed.


Sow cucumber seeds on their side, at a depth of 1cm, in small pots. Keep them warm in a heated propagator, greenhouse, or on a sunny indoor windowsill.


Sow in small pots, then either place in a propagator or cover each pot with a clear plastic bag and place on a sunny windowsill. The seedlings need to be kept at around 18°C. Once two true leaves have formed, transplant them into 9cm pots.

What Seeds Are You Sowing In May?

what seeds to sow in May

As always, I’m curious what seeds you are sowing this month! I’m definitely getting my kale seeds planted to enjoy later in the year.

I have lots of other useful gardening guides on Moral Fibres.  From some great sustainable garden ideas to why you should choose peat-free compost. and how to attract bees to your garden.

ps: if you’ve found this page through Google then for future reference you may be interested in my March and April sowing guides!  Bookmark them for next year!

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