15 x gardening tips for May

Published on 3 May 2020

May is the month when the garden starts to get going, and there’s plenty to do. And while you’re following our top 15 May gardening tips, don’t forget to take some time just to relax and enjoy watching your garden grow.

Top 15 May gardening tips

Now’s the time to start hardening off potted-up half-hardy plants like dahlias and cannas before planting them out. Place the pots outside for gradually longer spells during the day and bring them back inside at night. Do this for at least a fortnight before planting them.
In milder parts of the country, it’s time to start planting out summer bedding in borders, pots and hanging baskets. In colder areas, wait until June.
Mix sowing sunflowers, nasturtiums, poppies and cornflowers for a riot of summer colour.
Get going in the vegetable garden. Sow courgettes, runner beans and French beans in modules or in individual pots. They will be ready for planting out in a few weeks.
Keep earthing up potatoes to give you a bumper harvest. If you still have any seed potatoes left, plant them this month.
Plant tomato plants in greenhouse beds or grow bags now, but if you’re growing tomatoes outdoors, wait until the night-time temperature is reliably above 12 deg C to plant them. Remember to harden off outdoor-grown tomatoes before planting them.
Sow basil seeds in pots in a greenhouse or on a warm, sunny windowsill.
Plan ahead for a good supply of winter vegetables. Sow kale seeds in pots in the greenhouse, and sow parsnips and Brussels sprouts directly where they are to grow.
Be water-wise. In hot, dry weather, water the garden early in the morning or late in the afternoon, always watering the soil and not the foliage. If you can, install a rainwater butt.
It’s not just plants that are starting to grow – weeds are too! Keep on top of things by running a hoe over beds regularly to clear annual weeds. Use a hand fork or dandelion grubber to tackle perennial weeds like docks and dandelions.
Watch out for pests like Viburnum beetle larvae, lily beetles and aphids. Tackle pests and diseases promptly.
Mow the lawn regularly to keep it looking neat, and trim border edges with edging shears.
Take care when trimming hedges, and always check first that you’re not going to disturb any nesting birds.
Prune spring-flowering shrubs like Forsythia, Japanese quince (Chaenomeles), flowering currant (Ribes) and Mexican orange blossom (Choisya). Once flowering has finished, prune Clematis montana to keep it to size, and tie twining climbers like honeysuckle and clematis into supports
Water container plants regularly and feed fortnightly with a balanced liquid feed. Top-dress permanent container plants by removing the top 5cm (2in) of compost from the pot and replacing with fresh compost.