Garden Diary: May

Bulbs and flowers

This month sees some of the fastest growth of the whole year, so get on top of perennial weeds as they start to show, dig out or treat with a systemic weed killer.

Keep watch for pests, especially on young shoots and tips. Wash off any aphids with soapy water.

Lift , divide and replant any big clumps of the primula family now.

At the end of the month, cut back hard pulmonarias that have finished flowering for a new flush of clean foliage.

 Feed the borders with granular food.

Continue to plant summer bulbs and new perennial plants.

Give tulip and other spring bulbs a liquid feed as they start to go over.

Sow seeds of hardy annuals directly into any empty spaces.

Greenhouse and containers

Start hardening off plants growing under glass. Bring out during the day and take in at night for a week or so. Then be prepared to cover with fleece if there is a cold spell.

Prick out seedlings and continue to succession-sow salad leaves.

After mid-month, hang up planted baskets in a sheltered spot to allow them to acclimatise.

Pot up tomato plants into large pots or grow-bags.

Check regularly for pests and diseases and take speedy action to control.

Make sure the greenhouse doesn’t overheat. Open vents on warm days.

Top dress and feed container plants. Don’t forget evergreens like box and bay, if they are looking a little jaded, they will green up well with some high nitrogen food.

Start feeding houseplants now and feed regularly ‘til autumn. Wash the winter dust from their leaves to allow them to breathe!

Trees and Shrubs

If you spray, start treating roses for blackspot now. Wash off, or spray, greenfly.

Mulch around trees and shrubs to keep in moisture.

Feed acid lovers: rhododendron, azalea, pieris and camellia with ericaceous food.

Continue to plant new shrubs. Keep well watered until established, especially in dry windy weather.

Prune the early clematis after flowering if you need to control their size.

Continue to tie in climbers including roses. Training horizontally will encourage more flowers.

Trim lavenders, if not done last year after flowering, cutting off any old flower heads and about 2.5cm (1 inch) of the current year’s growth.

Continue to prune any shrubs that have flowered this spring.

Fruit and Vegetables

Hang pheromone traps in apple and plum trees to reduce problems with moth larvae.

Spray peaches and nectarines with fungicide to prevent peach leaf curl.

Continue sowing vegetable seeds, most can be sown outside now. Cover with fleece to give them a good start.

Give strawberries a dose of tomato feed.

Put up runner bean supports and pea sticks, ready for next month.

Tie in new soft fruit shoots to wires or canes.

Start earthing up potatoes. It keeps the frost off and stops them going green.

Start picking rhubarb, but leave some stems to grow on.

Lawns and other jobs

Dig out perennial weeds or treat with a specialist lawn weed-killer.

Plant pond plants now and keep control of any duckweed before it multiples.


 Think about choosing plants that are good for wildlife – berry-bearing shrubs for birds and perennials with broad, open flowers for bees.

Keep bird-baths topped up for drinking and bathing.