What to Sow and Grow in May: A Complete Guide
May is a fantastic month for gardeners, with warmer soil and longer days providing perfect conditions to sow seeds and plant young plants. Below, we’ve put together a detailed guide on what you can sow and grow right now.
Seeds are available from molesseeds.co.uk, and young plants can be purchased from gardenerskitchen.co.uk.
Each entry includes handy gardening tips and notes on pests and diseases to watch out for.
Vegetables to Sow from Seed in May
Carrots
- Tip: Sow carrots directly into well-prepared soil that’s free from stones. Thin seedlings to avoid overcrowding.
- Pests/Diseases: Carrot fly is a serious pest. Use fine netting or companion plant with onions to deter them.
Courgettes
- Tip: Sow seeds indoors in pots and transplant after the risk of frost. Alternatively, sow directly outside in late May.
- Pests/Diseases: Slugs and snails can decimate young plants—use organic slug pellets or crushed eggshells around plants.
Garlic
- Tip: May is late for garlic, but spring-planting varieties can still succeed if planted in light, well-draining soil.
- Pests/Diseases: Watch for rust (orange spots on leaves); improve air circulation by spacing plants well.
Leeks
- Tip: Sow in modules or a nursery bed and transplant when pencil-thick into dibber-made holes.
- Pests/Diseases: Leek moth and onion fly are common pests. Cover with fine mesh and practice crop rotation.
Melons
- Tip: Sow seeds indoors in individual pots. Keep very warm (ideal temperature 20-25°C).
- Pests/Diseases: Aphids can be an issue; wash off with a blast of water or use insecticidal soap.
Onions
- Tip: Sow thinly in rows; thin seedlings as they grow.
- Pests/Diseases: Onion white rot and onion fly can cause problems—rotate crops annually to avoid build-up.
Pak Choi
- Tip: Sow in partial shade for tender leaves. Water regularly to prevent bolting.
- Pests/Diseases: Flea beetles love young pak choi—protect with fine mesh.
Parsnips
- Tip: Sow directly into soil as they dislike transplanting. Be patient; germination can take several weeks.
- Pests/Diseases: Canker affects parsnips. Avoid sowing into wet, poorly drained soil.
Peas
- Tip: Sow every two weeks for a continuous crop. Provide support early on.
- Pests/Diseases: Pigeons and mice love peas. Netting young seedlings is essential.
Peppers
- Tip: Sow indoors and keep very warm for germination. Transplant into large pots or greenhouse beds.
- Pests/Diseases: Aphids and spider mites can infest plants; mist regularly and monitor for pests.
Potatoes
- Tip: Plant second earlies and maincrops in trenches, covering emerging shoots (‘earthing up’).
- Pests/Diseases: Watch for blight; good spacing improves airflow and reduces risk.
Pumpkins
- Tip: Sow indoors in large pots or directly outside if it’s warm enough.
- Pests/Diseases: Powdery mildew often affects pumpkins; water at the base rather than overhead.
Spring Onions
- Tip: Sow little and often for fresh onions throughout summer.
- Pests/Diseases: Root fly can be an issue—use horticultural fleece to protect crops.
Sweet Potatoes
- Tip: Plant slips (young plants) in sunny, sheltered spots in ridges for best growth.
- Pests/Diseases: Whiteflies can infest plants; encourage natural predators like ladybirds.
Tomatoes
- Tip: Sow indoors for later planting in greenhouses or sunny outdoor spots.
- Pests/Diseases: Blight and aphids are the biggest threats. Avoid overhead watering and use blight-resistant varieties if possible.
Broccoli
- Tip: Sow seeds indoors or directly outside, and plant out when they have 4-6 leaves.
- Pests/Diseases: Cabbage white butterfly larvae can decimate plants—net crops or hand-pick caterpillars.
Vegetables to Grow from Young Plants in May
If you want a head start, buy and plant these young vegetable plants:
- Cauliflower
- Celery
- Lettuce
- Spinach
- Swede
- Asparagus
- Sweetcorn
Tip: Harden off young plants by leaving them outside during the day and bringing them in at night for 7-10 days before planting permanently outdoors.
Pests/Diseases: Young plants are especially vulnerable to slugs and snails. Protect them with copper tape, organic pellets, or beer traps.
Herbs to Sow from Seed in May
Fresh herbs are easy to grow from seed this month:
- Basil
- Dill
- French Tarragon
- Lemon Balm
- Lemon Verbena
- Marjoram
- Mint (Moroccan)
- Oregano
- Parsley
- Rosemary
- Sage
Tip: Sow in pots using seed compost. Basil prefers warmth; others like mint and oregano thrive even in slightly cooler weather.Pests/Diseases: Aphids and powdery mildew are the main threats. Keep plants well-spaced to allow air movement.