What to Do in the Garden in May | UK Gardening Jobs
Discover what to do in your garden in May, including the Chelsea Chop, lawn care, planting, fruit and vegetables, watering, weather advice and plants to enjoy.
What to do in my garden in May
May is one of the most rewarding months in the UK garden. Trees are in full leaf, herbaceous borders are filling rapidly, lawns are growing strongly and an increasing number of plants are coming into flower.
It is also an extremely busy gardening month.
Warmth and longer days encourage rapid growth, but the same conditions also bring weeds, pests and increasing demand for water. Plants that seemed small at the beginning of spring can double in size surprisingly quickly, so staking, tying, pruning and general maintenance can suddenly become important.
May is also a major planting and sowing month, although gardeners should remain cautious about tender plants. Late frost is still possible, particularly in northern, inland and exposed gardens.
The priority during May is to keep ahead of growth. Deal with weeds before they seed, support perennials before they collapse, monitor newly planted trees and shrubs for water and gradually introduce tender plants to outdoor conditions.
Top 10 tips
1. Keep newly planted trees and shrubs watered
May can bring warm, dry and windy conditions.
New trees, hedging and shrubs have limited root systems and may require thorough watering even when established plants appear perfectly healthy.
2. Keep on top of weeds
Weeds grow extremely quickly during May.
Remove them while they are small and before they flower and set seed.
3. Mow lawns regularly
Grass is usually growing strongly by May.
Regular mowing encourages a dense, healthy lawn and maintains a neat appearance.
4. Carry out the Chelsea Chop
Selected late-flowering herbaceous perennials can be cut back around the time of the RHS Chelsea Flower Show.
This can produce shorter, bushier plants and may help extend or stagger flowering.
5. Watch for late frost
Do not assume frost is impossible simply because daytime temperatures are warm.
Tender bedding, vegetables and recently emerging plants can still be damaged by a cold night.
6. Harden off tender plants
Plants raised in greenhouses or indoors need to become gradually accustomed to outdoor conditions before being permanently planted outside.
7. Stake tall-growing plants
Support peonies, delphiniums and other tall perennials before they begin to lean or collapse.
Early supports are much less conspicuous once foliage grows through them.
8. Check for pests
Slugs, snails and aphids can multiply rapidly during May.
Inspect young shoots and vulnerable plants regularly.
9. Deadhead spring flowers
Remove faded flowers from suitable plants to improve appearance and, in some cases, encourage further flowering.
Allow bulb foliage to die back naturally.
10. Start preparing for summer
Check outdoor taps, hoses, irrigation systems, garden furniture, lighting, water features and outdoor entertaining areas before they are required regularly.
Herbaceous Perennials
May is when herbaceous borders begin developing their summer character.
Perennials are producing substantial growth and early-flowering varieties may already be providing strong colour.
Complete any remaining division of suitable plants as soon as possible before conditions become too warm and dry.
Recently divided plants should be watered carefully until established.
Tall-growing perennials may need support.
Plants that commonly benefit include:
Peonies
Delphiniums
Lupins
Campanulas
Asters
Rudbeckias
Echinacea
Heleniums
Positioning supports before they are needed allows plants to grow naturally through them.
The Chelsea Chop
Late May is traditionally associated with the Chelsea Chop, named because it coincides approximately with the RHS Chelsea Flower Show.
Selected late-flowering herbaceous perennials are cut back to encourage shorter, bushier growth.
Depending upon the plant and the technique used, this can reduce the likelihood of plants flopping and can delay or extend flowering.
Plants sometimes suitable for the Chelsea Chop include:
Sedum/Hylotelephium
Phlox
Helenium
Echinacea
Rudbeckia
Asters
Nepeta
Not every perennial should be treated this way.
One useful approach is to cut back only part of a clump, potentially creating different flowering heights and extending the overall flowering period.
Continue removing weeds and mulch bare soil where appropriate.
Monitor young foliage for slugs and snails.
By May, most deciduous trees and shrubs are in active growth.
Recently planted trees require particular attention.
The combination of fresh foliage, warm sunshine and drying winds can create significant water demand.
Water deeply rather than applying small quantities to the surface.
The aim is to encourage moisture to penetrate into the root zone.
Continue checking:
Tree stakes
Underground anchoring
Tree ties
Rootball stability
Mulch
Soil moisture
Do not allow mulch to accumulate directly against tree trunks.
Spring-flowering shrubs can be pruned after flowering where appropriate.
Forsythia and other shrubs that flower on growth produced during the previous season can often be pruned after their display has finished, allowing new shoots to develop for next year's flowers.
Evergreen hedges may begin producing substantial fresh growth.
Check for nesting birds before undertaking hedge cutting. Active nests must not be disturbed.
Remove suckers and unwanted basal growth from trees and shrubs where appropriate.
May is still suitable for planting container-grown trees and shrubs, but the need for aftercare increases as temperatures rise.
May is one of the main lawn-growing months.
Regular mowing will usually be required.
The exact frequency depends upon weather, grass type and the finish required.
Avoid removing excessive growth in a single cut.
Frequent moderate mowing is generally preferable to allowing grass to become very long and then cutting it extremely short.
May lawn jobs can include:
Regular mowing
Feeding
Overseeding thin areas
Repairing bare patches
Aerating compacted ground
Controlling weeds
Redefining lawn edges
Newly seeded areas must be kept consistently moist while germinating and establishing.
Where possible, water early in the morning rather than during the hottest part of the day.
If May becomes particularly dry, established lawns may begin slowing their growth.
Do not panic if an established lawn loses some colour during prolonged dry weather. Grass is remarkably resilient and often recovers once rainfall returns.
Avoid excessive watering simply to maintain an artificially lush appearance unless this is genuinely required.
May is a critical month for fruit development.
Many fruit trees have finished or are finishing flowering, and small developing fruits may now be visible.
Late frost can still damage blossom and newly developing fruit.
Monitor forecasts carefully, particularly in frost-prone gardens.
Apple and pear trees may naturally shed some young fruit during the coming weeks.
This is normal and is often referred to as the June drop, although it can begin earlier.
Check fruit trees and bushes regularly for pests and disease.
Recently planted fruit trees require careful watering during dry weather.
Strawberries are developing rapidly.
Keep plants watered and consider placing straw or another appropriate material beneath developing fruits to keep them away from wet soil.
Netting may eventually be required to protect soft fruit from birds, but ensure any netting is installed safely and does not unnecessarily trap wildlife.
Tie in new raspberry growth and maintain supporting wires.
Mulch fruit bushes to retain moisture and suppress weeds.
May is one of the busiest months in the vegetable garden.
Successive sowing can continue to provide a steady harvest rather than producing too much of one crop at once.
Depending upon conditions, crops that may be sown outside include:
Carrots
Beetroot
Radishes
Lettuce
Peas
Spinach
Chard
Spring onions
Turnips
French beans
Runner beans
Tender vegetables require greater caution.
Plants such as:
Courgettes
Pumpkins
Squashes
Cucumbers
Sweetcorn
Runner beans
French beans
should generally be hardened off before being planted outside once the danger of frost has sufficiently reduced.
Tomatoes, peppers, chillies and aubergines grown under glass will require increasingly regular watering and feeding as they develop.
Earth up potatoes as shoots grow.
Hoe regularly between vegetable rows to control weeds while they are small.
Watch for slugs and snails around young seedlings.
Provide supports for peas and climbing beans before plants become difficult to manage.
The herb garden becomes increasingly productive during May.
Established herbs such as chives, mint, oregano, parsley, thyme, rosemary and sage can provide regular harvests.
Many annual herbs can be sown outside as conditions warm.
These may include:
Coriander
Dill
Parsley
Chervil
Basil in suitably warm conditions
Basil remains sensitive to cold temperatures and is often better kept protected until conditions are reliably warm.
Regular harvesting of many herbs encourages fresh growth.
Mint can become extremely vigorous and may need containing.
Remove flower buds from herbs grown primarily for their leaves where flowering would reduce the quality or quantity of the harvest.
Container-grown herbs require more frequent watering than plants growing in open soil.
Mediterranean herbs should still be grown in freely draining conditions and should not be kept unnecessarily wet.
Water features become increasingly active during May.
Rising temperatures increase evaporation and encourage aquatic plant growth.
Check water levels regularly.
Clean filters and inspect pumps to ensure water is circulating correctly.
Remove excessive blanket weed where necessary, taking care to check removed material for aquatic wildlife.
Pond plants can grow rapidly during late spring.
Thin excessive vegetation where appropriate while retaining sufficient cover for wildlife.
Avoid making dramatic changes to wildlife ponds during periods of intense activity.
Check:
Pumps
Filters
Water levels
Reservoirs
Pipework
Fountains
Rills
Grilles
Lighting
Contemporary water features may require more frequent topping up during warm or windy weather.
Clean visible surfaces carefully if algae begins to develop.
Water features can become increasingly important visually during May as surrounding planting grows around them and begins softening their edges.
By May, patios, paths and terraces become much more heavily used.
Inspect surfaces and deal with outstanding winter maintenance before summer.
Clean paving where required using a method appropriate to the material.
Check:
Porcelain paving
Natural stone
Steps
Paths
Driveways
Paving joints
Garden walls
Retaining walls
Drainage channels
Manholes
Raised beds
Remove weeds from joints before they become established.
Check drainage channels and gullies for debris.
Warm weather can also highlight drainage problems around outdoor taps, irrigation equipment and water features.
Inspect steps and level changes carefully, particularly where planting has begun encroaching onto walking surfaces.
Cut back vegetation that creates a trip hazard or restricts access.
Clean and prepare patios and entertaining areas ready for regular summer use.
May is when climbing plants can begin covering garden structures remarkably quickly.
Tie new growth onto:
Pergolas
Trellis
Wires
Arches
Screens
Use suitable soft ties that will not cut into expanding stems.
Check structures before they become hidden beneath foliage.
Inspect:
Pergolas
Fences
Gates
Privacy screens
Gazebos
Garden buildings
Raised beds
Trellis
Arches
Check timber for decay and ensure fixings remain secure.
Gates and doors that moved during winter may require adjustment.
Paint or treat timber structures before surrounding planting makes access difficult, following the product manufacturer's instructions.
Check outdoor furniture and clean it ready for summer use.
Parasols and other seasonal structures can also be inspected before being returned to regular use.
May provides excellent growing conditions for many house plants.
Longer days and warmer temperatures mean watering and feeding requirements increase.
Check plants regularly rather than relying on a fixed watering schedule.
Actively growing plants may benefit from appropriate feeding.
Continue repotting root-bound specimens where necessary.
May is also an excellent time for propagating many house plants from cuttings or division.
Check regularly for:
Aphids
Spider mites
Mealybugs
Scale insects
Fungus gnats
Strong sunlight through windows can scorch sensitive foliage.
Plants that tolerated a south-facing window during winter may require moving slightly further back as sunlight intensifies.
House plants may benefit from increased ventilation, but avoid exposing tropical plants to cold draughts.
Some house plants can eventually spend summer outdoors, but they should be acclimatised gradually and only moved outside when temperatures are appropriate for the species.
May Garden Weather
May weather can range from cold and unsettled to conditions that feel almost like midsummer.
This makes it important to remain flexible.
Late Frost
Frost remains possible.
Tender bedding plants, vegetables and young shoots are particularly vulnerable.
Monitor local forecasts rather than relying solely on traditional planting dates.
Warm Sunshine
Strong sunshine can rapidly dry containers and newly planted borders.
Check soil moisture regularly.
Plants against walls and beneath roof overhangs may receive much less rainfall than expected.
Dry Weather
Prolonged dry periods can occur during May.
Prioritise watering:
Newly planted trees
Newly planted hedges
Shrubs
New perennials
Containers
Vegetable seedlings
Newly seeded lawns
Established plants with deep root systems generally require less frequent intervention.
Heavy Rain
Warm temperatures combined with heavy rainfall create ideal conditions for rapid plant and weed growth.
Slugs and snails can also become particularly active.
Strong Winds
Warm, drying winds can remove substantial moisture from foliage and soil.
Recently planted trees and large-leaved plants may require additional monitoring.
Plants to enjoy in May
Border and rock garden
Allium
Ornamental onions begin producing their distinctive spherical flowers during May.
They work particularly well emerging through grasses and herbaceous planting.
Aquilegia
Aquilegias provide elegant flowers in a wide range of colours and work beautifully in informal and cottage-style planting.
Geranium
Many hardy geraniums begin flowering during May and can provide useful ground cover through borders.
Iris
Bearded and other garden irises can provide dramatic flowers and strong architectural foliage.
Lupinus – Lupins
Tall flower spikes create strong vertical accents within late-spring borders.
Euphorbia
Acid-green and yellow-green flower heads remain an important feature in many planting schemes.
Camassia
Camassias provide tall blue, purple or white flowers and are particularly effective in naturalistic planting.
Dicentra/Lamprocapnos
Bleeding heart produces distinctive arching stems carrying heart-shaped flowers.
Geum
Geums begin producing bright flowers in shades including yellow, orange and red.
Nepeta
Nepeta begins producing its characteristic blue-purple flowers and aromatic foliage, creating an excellent companion for roses and other early-summer plants.
Trees and shrubs with foliage of interest
Acer palmatum
Japanese maples provide delicate foliage in shades of green, bronze, red and purple.
Cotinus coggygria
Smoke bushes provide striking foliage, particularly purple-leaved and golden cultivars.
Photinia × fraseri 'Red Robin'
Bright red new growth remains highly prominent during May.
Cercis canadensis
Cultivars of Cercis can provide dramatic heart-shaped foliage in green, purple, red or golden tones.
Fatsia japonica
Bold evergreen leaves provide architectural contrast against softer herbaceous planting.
Pieris japonica
Colourful young foliage may remain highly attractive as it develops.
Sambucus nigra
Dark-leaved cultivars can provide an almost black-purple backdrop to lighter planting.
Hostas
Hostas are now developing their full foliage display, providing green, blue, gold and variegated leaves for shaded borders.
Trees with colourful fruit
May is generally too early for mature ornamental fruit, but it is an important month in the development of the autumn berry display.
Many trees and shrubs are flowering or setting their first small fruits.
Malus – Crab Apples
After the spring blossom fades, tiny developing crab apples begin to form.
These will gradually develop into colourful ornamental fruits later in the year.
Sorbus – Rowan
Clusters of spring flowers are followed by developing berries that will ripen during late summer and autumn.
Crataegus – Hawthorn
May is traditionally associated with hawthorn blossom.
These flowers eventually develop into the familiar red haws of autumn.
Pyracantha
Masses of small white flowers provide an important source of nectar for insects and are followed by spectacular autumn berries.
Cotoneaster
Spring flowers attract pollinators and later develop into red or orange fruits.
Ilex aquifolium – Holly
Small holly flowers may appear relatively insignificant, but successful pollination of female plants is essential for the winter berry display.
Greenhouse plants in flower
Greenhouses are increasingly colourful during May.
Pelargoniums
Pelargoniums can now provide abundant flowers and strong growth.
Fuchsias
Early Fuchsias may begin flowering under protected conditions.
Begonias
Greenhouse-grown Begonias can provide increasingly strong displays as temperatures rise.
Streptocarpus
Cape primroses can produce colourful flowers over a long period under suitable conditions.
Orchids
Numerous orchid species and hybrids can flower during May.
Bougainvillea
In sufficiently warm, bright conditions, Bougainvillea may begin producing its intensely coloured bracts.
Abutilon
Flowering maples can produce colourful bell-shaped flowers in protected conditions.
Preparing the Garden for Summer
May is the month when spring begins to merge into summer.
The garden is filling rapidly and many of the decisions made now will determine how manageable it remains later in the season.
Get supports around perennials before they fall over. Deal with weeds before they seed. Check irrigation before prolonged dry weather arrives. Tie in climbers while their shoots are still flexible and keep newly planted trees and shrubs properly watered.
It is also worth looking beyond individual plants.
Prepare seating areas, clean patios, check garden lighting, bring water features fully into use and make sure the garden is ready to be enjoyed.
May is not simply about maintenance. It is one of the finest months to spend time outside and appreciate the transformation that has taken place since winter.
A little regular attention now will help keep the garden healthy, structured and attractive as it moves towards the abundance of early summer.