What to do in your garden this month

This monthly guide is geared to London gardens and their unique conditions. Compiled by the RHS Wisley Plant Centre team
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Lilium Pink Perfection Group
© RHS/Mike Sleigh
Lilium Pink Perfection Group
If the soil in your garden is warm enough:

1. Sow vegetable seeds such as cauliflower in trays for planting out in June. Brussels sprouts can be sown directly into seed beds now.

2. Plant summer flowering bulbs such as lilies and gladioli in pots and/or beds. Remove faded flower heads from bulbs, and remember to incorporate bulb feed to give them a good healthy start for next year.

3. Plant chitted main crop potatoes at least 6cm deep in pots or vegetable plots, along with late onion and shallot sets.

4. Give lawns, if they are dry, the first mow of the year, on a high setting if required.

Lilium 'Orriolo'
© RHS/Carol Sheppard
Lilium 'Orriolo'
5. Check slug prevention around herbaceous and alpines where new growth is appearing.

6. Prune forsythia as soon as it has finished flowering to give it enough time for new buds to form for next year.

7. Finish hardening off bedding plants in cold frames, and keep checking to protect from late frosts.

8. Water seedlings prior to transplanting.

Planting Lily bulbs
© RHS/Tim Sandall
Planting Lily bulbs
9. Place supports such as bamboo, pea sticks or plastic coated metal around herbaceous perennials such as delphiniums, paeonia, alstroemerias, asters and lupins. Doing this now provides support at all stages of growth and prevents damage to root systems.

10. Weed around fruit trees and shrubs, carefully removing all perennial types such as dandelion, creeping thistles, brambles, ground elder, hedge bindweed. A hand trowel will ensure safe removal of all roots. Dispose in normal household waste not in general compost. Also, hoe off annual weeds such as sow thistles, chickweed, orache, canadian fleabane.

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