Action for May Borders
Jobs that'll give instant results
Remove faded flowers from pansies and violas to prolong flowering. Deadhead azaleas, rhododendrons, camellias, irises and tulips so they can put their energy into next year’s display.
Tidy up tulips after flowering, once the foliage has died down. If your soil is free draining, the bulbs can be left in the ground. If it’s heavy, lift bulbs and store them in a cool, dry place for replanting in November.
As early flowering bulbs die back, insert short canes or sticks around their clumps to mark their position – this will help prevent you accidentally damaging dormant bulbs.
What to prune now
Clip over the new growth on box and conifers with a pair of topiary shears, cutting back to just above the old growth.
Cut back ivy on fences and walls, and from windows, roof tiles and gutters, allowing for at least a season’s growth (30cm-60cm).
Remove most of the flowering growth from spring-flowering evergreen ceanothus (eg Ceanothus ‘Burkwoodii’ and C. impressus) that have finished flowering.
- Check tall perennials are adequately supported.
- Pinch out the growing tips of garden chrysanthemums to encourage branching and more flowers.
Jobs to do now; you'll see the rewards later
Sow fast-growing hardy annuals...
Such as calendulas, candytuft, clarkias, cornflower and nasturtiums, to give a splash of colour.
From perennials such as Michaelmas daisies and other perennial asters, delphiniums and penstemons. Use the new shoots at the base of plants when they have reached 5cm-10cm.
Continue to plant bulbs
Plant summer-flowering bulbs, corms and tubers such as dahlias and gladioli.
Get ahead for next year
Sow biennials such as Canterbury bells and sweet williams for next year’s spring bedding plants.
Pests and diseases
Cats and squirrels
Protect new plantings from cat and squirrel digging - surround with a frame of pea sticks, chicken wire or upturned hanging baskets. Download our squirrels factsheet for more information.
Slugs and snails
Delphiniums, hostas, strawberries and lettuces are particularly vulnerable to slugs and snails. Pick off and destroy any that you find or use a slug and snail repellent (see our factsheet on slugs and snails). A greener option for slugs is the biological control Nemaslug.
Check for aphids. Squash or treat them with a spray containing bifenthrin or pyrethrins.
It does most damage in late spring, caused by the larvae, which are creamy yellow with black markings. Greyish-brown adult beetles feed on the leaves from late July to September. Spray the plants with bifenthrin.