May Gardening Tips

Pots & Borders


  • Time to plant up your hanging baskets and containers. No time? Let us do it for you!
  • Harden-off annual bedding plants ready to plant out soon. Put them in a shady spot, keep well watered but bring them back inside if frost is likely. Keep a close eye on them and they will be toughed up ready to plant after about a week.
  • Be ready to cover tender plants with horticultural fleece if frosts are forecast. Check out the forecast every day this month.
    • Order Slug nematodes and rid your plants of this pest the natural and safe way.
    • Stake border perennial varieties that are tall growing and that tend to flop over. Either use pea sticks [tree and shrub prunings are good] or use purpose made support systems that we have available.
    • Cut Aubretia back hard when it has finished flowering and give it a feed. They will produce new growth soon and remain more compact if this is done each year.
    • Plant out Cannas and Cosmos [chocolate plant], Dahlias and Begonias.
    • Trim foliage off early flowering perennials to encourage fresh new leaves. Lungwort [Pulmonaria] responds particularly well.
    • Regularly tie in sweet peas and remove unwanted side shoots.
    • Hosta divide well this month. Lift clumps and split them up making certain that each shoot has plenty of root attached.
    • Wait until spring flowering bulb leaves die back naturally before removing them.
    • Watch out for scarlet lily beetles. This pest can eat your lily leaves in a few days! Control with Bayer Greenfly Killer or a pyrethrum based spray.
  • Give some of your border perennials the ‘Chelsea Chop’. If you cut some of them back by about half now it will delay flowering but extend the display longer in your garden.

Trees, Shrubs, Roses, Conifers, etc.


    • Prune early flowering shrubs back now so that they have time to make new growth and flower buds for next year. Large Forsythia can be cut back hard, flowering Currants trimmed a little and Camellias can be trimmed to reshape them. Spirea arguta, Chaenomeles, winter jasmine, Kerria, Choisya and Viburnum tinus will benefit from careful pruning and still have plenty of time to set flower buds for next year.
    • Large over-grown early flowering Clematis such as montana, alpine, macropetala and winter flowering species can be pruned surprisingly hard when they have finished blooming.
    • Ensure all recently planted trees, shrubs etc are thoroughly watered regularly and staked securely
    • Watch out for Viburnum beetle and spray with Provado Ultimate Bug Killer as soon as seen.




    • Lift and dry off tulips ready for replanting in the late autumn. Other bulbs can be left in the ground.
    • Plant out Dahlias and Begonias plants but protect from late frosts.




    • Start feeding greenhouse tomatoes with a high potash feed such as Westland’s Gro-Sure Tomato Food, as soon as you can see the first visible tiny fruit. Vibrate flowers regularly to improve fruit set.
    • As plants grow larger and days get longer and hotter you will need to increase the amount and frequency of water that you give.
    • Increase ventilation on bright days. It may be necessary to open vents very early in the morning and close late in the evening. Leave open a little on very warm nights.
    • Side shoots should be removed from cordon type tomatoes [most varieties] before they get too long. Thin out side shoots on bush varieties. Support both.
    • Apply shade [Coolglass] to the roof of your greenhouse to keep temperatures down.
    • Open greenhouse vents and doors on warm days.
    • Damp the floor down regularly to raise air humidity if your crops suffer from red spider mite attacks in the past. Don’t do it late in the day.
    • Plant marigolds as ‘companion plants’ to encourage natural predators in to control pests.


The Inside Garden


    • Some houseplants can be moved outside for summer this month. Put them in a shady spot until they get used to the brighter light outside and make sure they get watered regularly. i. e. Cymbidium, Yucca, Aralia, Aspidistra, ivies, ferns, etc.
    • Citrus plants will benefit from being outside from now until late August. Once acclimatised they will relish the sunshine! Some orchids, such as Cymbidium, are happier outside than in too.
    • Watch out for pest attacks such as from aphids, scale, red spider mite and mealy bug. Push Scotts Bug Clear Ultra spikes in the compost; they control pests and feed your plants.


Grow Your Own Food


    • Sow Sweet Corn directly into well cultivated soil outside. Sow or plant out in blocks, not long rows, as it is better wind pollinated that way. Choose ‘super sweet’ varieties such as ‘F1 Swift’ or ‘F1 Applause’.
    • Sow Courgettes, Marrows, Ridge Cucumbers and Melons in individual pots. When germinated, plant the Melons under glass or polythene as they will need all the heat you can give them. All like lots of organic matter so plant them with lots of compost.
    • Sow turnips, Swedes, cauliflowers, leeks and other late winter vegetables now.
    • Sow borage, nasturtium and other edible flowers for use in salads.
    • Order slug nematodes and rid your plants of this pest the natural and safe way.
    • Buy and hang out pheromone traps for apple and plum maggots at end of May. This will reduce those annoying maggots in the fruit.
    • Plant out basil but this herb is best grown in a very sheltered spot in pots. It may even pay to grow them in between your greenhouse tomatoes.
    • Earth up early potatoes and keep a watch out for late frosts ~ cover with horticultural fleece if frost is likely.
    • Tie in soft new shoots of trained fruit trees and canes. Flexi-tie is the perfect material to use.
    • Hoe off raspberry canes that appear between the rows.
    • Check gooseberries [and Solomon’s Seal] for sawfly larvae. If left unchecked they will strip the leaves in a few days. Use Provado Ultimate Bug Killer or Westland Plant Rescue.
    • If necessary, prune stone fruits now. [cherries, plums, nectarines, peaches, etc]
    • Remove strawberry runners as they develop. Lay straw under fruit trusses to prevent mud splashing. Cover with bird netting.
    • Check autumn sown broad beans for blackfly. Use Provado Ultimate Bug Killer. Simply removing the plant tops sometimes works too.
    • Continue successional sowing of lettuce, carrots, beetroot, spring onions, radish.
    • Support runner beans with canes or poles and strings. Make sure that they are well watered at all times.
    • Support peas and mange-tout with pea sticks, tree prunings or netting.
    • Outdoor tomatoes, pumpkins, squashes and cucumbers can be planted out late this month. Give them cloche or tunnel protection to start with.
    • Spray Ashton Garlic Wonder to keep caterpillars and most pests off your food crops the safe way.


Lawns, Hedges, Paths and Drives


    • Treat those lawn weeds with a good lawn weed killer like Verdone Extra now. This is the best time to do it. Don’t use the cuttings for composting until the fourth cut after applying weedkillers.
    • Mow lawns weekly.
    • Sow new lawns after thorough soil preparation. Lay turf this month too.
    • Check for nesting birds before cutting hedges. Delay until nestlings have fledged.


Bits & Pieces


    • If you haven’t done it already, install a rainwater butt. If you have, install another!
    • Mix your grass clippings with drier materials such as shredded prunings, cardboard and newspaper. Add Garotta compost accelerator to each layer. Turn and water heaps regularly to make the best compost!


Soils, Mulching, Weed Control, etc.


    • Regularly hoe off weeds.
    • Apply mulch to trap in moisture and minimise weed growth.
    • If not done earlier, control weeds on paths and drives with Weedol Pathclear Season Long weedkiller.
    • Bindweed shoots begin to appear now so treat them with Roundup or Resolva 24h.


Ponds, Wildlife, Pets and Bog Plants


    • Plant water plants this month. They should get away very quickly.
    • Divide and plant water lilies now.
    • Regularly clean water filters. Use bags of barley straw if the water turns green.
    • Plant waters edge plants and oxygenating plants now.
    • If deer are getting into your garden and eating your roses, apple shoots and other plants, try one of our sonic pest control systems. If badgers and foxes are coming in and causing damage, these sonic emitters work well on them too.
    • Continue to feed birds but avoid feeding peanuts and other large food from feeders that allow the adults to take complete seeds to their young. Feeding fat balls is a good alternative. It is important to continue to support birds at this crucial time.
    • Provide a regularly cleaned and refilled bird bath so that birds can drink, bathe and entertain you!
    • Keep some areas of longer grass and even some weeds as wildlife sanctuaries. Piles of old logs can make a brilliant home for wildlife. A small sheet of corrugated iron may encourage slow worms and grass snakes into your garden. In return they will eat many of your pests.
    • Feed hedgehogs with a little cat food but take care that you aren’t encouraging too many foxes.
    • Encourage plenty of insects into your garden. These will provide food for wildlife and pollinate your crops.