Late May is one of the most important moments in the garden calendar. Spring growth is in full swing, summer is approaching fast, and the decisions you make now will determine how your garden performs through the warmest months. This guide covers everything you need to do in your South East London garden this late May.
1. Lawn Care: The May Essentials
By late May, your lawn should be growing vigorously. Weekly mowing is now essential — but avoid cutting too short. A height of 25–40mm is ideal for most London lawns. Cutting too short stresses the grass and makes it vulnerable to drought and weeds.
Edging: Clean lawn edges make the entire garden look sharper. Use a half-moon edger or a spade to redefine borders that have become ragged over spring.
Feeding: Apply a balanced lawn fertiliser if you haven't already. A slow-release granular feed applied now will sustain the lawn through summer without causing excessive soft growth.
Watering: London's clay soil retains moisture well, but newly seeded or turfed areas need consistent watering. Water deeply and infrequently — this encourages deep root growth and drought resilience.
2. Pruning: What to Cut Now
Late May is the right time to prune spring-flowering shrubs that have finished blooming. Pruning immediately after flowering gives the plant maximum time to produce new growth before next year's flower buds form.
- Forsythia: Cut back flowered stems by one third. Remove any crossing or dead wood.
- Lilac (Syringa): Remove spent flower heads and any weak stems. Avoid heavy pruning.
- Weigela: Prune out one in three of the oldest stems at the base to encourage fresh growth.
- Clematis (Group 1): Lightly tidy after flowering. Remove dead or damaged stems only.
What NOT to prune in late May: Avoid pruning summer-flowering shrubs like Buddleja, Hydrangea paniculata and late-flowering Clematis (Groups 2 and 3). These are still building up to their flowering season.
3. Hedge Trimming: First Cut of the Year
Late May is the ideal time for the first formal hedge trim of the year. Most hedges — box, privet, laurel, hornbeam — have put on their spring flush of growth and are ready for shaping. Cutting now encourages dense, bushy regrowth through summer.
Important: Check for nesting birds before trimming any hedge. It is illegal to disturb an active nest in the UK. If you find a nest, wait until the birds have fledged before cutting.
Box hedges: May is the best time for the first box trim. Use sharp, clean shears or electric trimmers. Wipe blades with disinfectant between plants to avoid spreading box blight.
4. Planting: What to Put In Now
Late May is prime planting time. The soil is warm, frosts are (mostly) behind us, and plants establish quickly. This is the best window to plant summer bedding, tender perennials and warm-season vegetables.
- Summer bedding: Petunias, Begonias, Busy Lizzies, Verbena and Salvias. Plant after the last frost risk has passed (mid-May in London).
- Tender perennials: Dahlias, Cannas and Agapanthus can all go out now. Water in well and mulch around the base.
- Evergreen shrubs: Container-grown evergreens establish well when planted in late spring. Water regularly for the first 6–8 weeks.
- Ornamental grasses: May is the ideal time to plant grasses like Stipa, Miscanthus and Hakonechloa. They establish quickly in warm soil.
5. Weed Control: Stay Ahead
Weeds grow fast in late May. The key is to hoe or hand-weed little and often — removing weeds before they set seed prevents the problem from compounding. A sharp hoe used on a dry day is the most efficient tool for border weeding.
Mulching: A 5–7cm layer of bark mulch or garden compost applied to borders now will suppress weeds, retain moisture and improve soil structure. This is one of the highest-impact tasks you can do in late May.
6. Patio & Surface Maintenance
Before the outdoor entertaining season begins in earnest, give your patio, decking and paths a thorough clean. Algae and moss that built up over winter can make surfaces slippery and dull-looking.
- Porcelain paving: Pressure wash and re-point any joints that have been disturbed over winter.
- Composite decking: Wash with a specialist composite cleaner. Avoid pressure washers at high pressure — they can damage the surface.
- Timber decking: Sand any rough areas and apply a fresh coat of oil or stain. This is essential annual maintenance for timber.
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