Garden jobs for May

Garden jobs for May

  • Continue to stake or support plants before they need it. This is essential for herbaceous plants which get tall or for those, like peonies, that produce heavy blooms.
  • Keep on top of weeds in beds, borders and containers.
  • Sweet peas need training and tying in to their supports to encourage them to climb and make a good display. Once they start flowering, cut them regularly and have these sweet smelling blooms in the house.
  • Continue to tie in shoots on vigorous climbers, such as clematis, roses, honeysuckle and jasmine.
  • Deadhead remaining spring bulbs. Give the leaves a feed and let them die back naturally thereby feeding the bulb which stores energy to produce next years flower. Divide clumps of ‘blind’ daffodils, dig them up and plant them in a new spot.
  • Towards the end of May, think about the ‘Chelsea Chop’ on perennials which have a habit of getting tall and unwieldy, including some Sedum, Rudbeckia, Helenium, Veronica and more. By cutting or pinching back plants by half you will create bushier plants that flower later in the season and often flower more prolifically.
  • Keep watering any recently planted shrubs and trees, including fruit, even if it has been raining. They won’t have had time to get their roots down yet, so are vulnerable to dehydration.
  • Thin out direct sowings of hardy annuals. This is best done in two or three stages at fortnightly intervals.
  • Lift clumps of Forget-me-nots as they fade and before they set too much seed.
  • Trim back spreading plants like Aubretia and Alyssum after flowering to encourage fresh growth and flowers.
  • Mulch beds and borders with a good organic compost, after weeding and watering the ground underneath. The worms and other bugs will take the nutrients down into the soil, and the mulch will help with water retention and weed suppression.

Container gardening

  • Now is the time to clean containers and plant containers for the next few months.
  • Plant up troughs, pots, window boxes and hanging baskets with summer bedding for months of glorious colour. Incorporating water retaining crystals and slow release fertiliser in the compost will help to ensure a continuous display throughout the summer. There is a wide range of plants which will flower from now until the autumn. Combinations of trailing and upright plants will make a great display - choose from Nemesia, Geranium, Petunia, Calibrachoa, Fuchsia, Lobelia, Felicia, Diascia and many more.
  • Herbs make attractive container plants. Plant some favourites near the back door, or on the balcony… there’s nothing better than stepping out to cut a handful of fresh herbs to to use in the kitchen. Use Mediterranean herbs such as rosemary and thyme in a sunny spot, and mint, parsley, tarragon, coriander and dill in more shaded surroundings.
  • If you’d like to plant a container to last for a few years, choose herbaceous perennials to suit the position - long flowering Erysimum Bowles Mauve, grasses, Sedum, Nemesia, lavender, Agapanthus and many more will work in a sunny spot. In shade, you could try combinations of Hosta, ferns, Heuchera, Vinca or a shade loving shrub.
  • Specimen plants: an individual plant can be given the planting conditions it needs and look fabulous in a container. Trees and shrubs: try an Acer, a patio fruit tree or bush, Hebe, Daphne, Pittosporum, Pieris, hardy Fuchsia and Rose - all are good container possibilities.
  • Set a routine of watering your containers in the cool of the morning or evening, and get to know how much different plants need. In sunny or windy weather, you will need to water more.
  • Start a feeding regime. You can boost plant growth and health tremendously with the right fertilisers, either by using slow release fertiliser when you plant, or with a weekly fertiliser when you water.

Pruning

  • Early flowering Clematis such as C. montana C. Alpina and C. armandii can be pruned after flowering to keep in check, and this may lead to another flush of flowers later.
  • Prune overgrown Camellias once they finish flowering and start putting on fresh growth. Cut to young side shoots, which will flower next spring. Feed with an acidic fertiliser.
  • Evergreen hedges and topiary can be lightly clipped to keep them neat. Make sure shears are clean and well-oiled before use. Pick an overcast day, or wait until the sun moved on to avoid leaf scorch. Ensure that birds aren’t nesting, and if necessary wait to do the pruning until the young have fledged.
  • Cut out any plain green shoots on variegated shrubs and trees.
  • Thin Spirea when the flowers have faded removing up to a third of old wood.
  • Cut back the flowered stems of Choisya to encourage a second flowering in the autumn.

Planting

  • The ground is warming up and is ready for planting. The lengthening days of spring are a perfect time for plants to get their roots down and top growth up.
  • Plant with the right compost and drainage.
  • Always remember, right plant, right place. Choose plants which will thrive in the conditions - lavender loves a sunny spot, but will be lank and sulky in the shade. Ferns, Tiarella and Vinca will thrive in partial or full shade, but may risk being frazzled in full sun.
  • Climbers provide coverage on a wall, fence or trellis, or can provide height in a border either with a wigwam of cans or sticks or with an elegant obelisk. Try annual climbers such as Lophospermum, Rodochiton, Thunbergia or ever popular sweet peas.
  • Plant lupins, foxgloves, peonies, delphiniums, alliums, geraniums, grasses, ferns, roses, shrubs, trees, lilies… there’s so much choice!
  • Have a look at our Planting Instructions for advice on planting if you aren’t sure.

Vegetables and herbs

  • This is the month to really get going with the vegetable garden.
  • Plant out vegetable and salad crops in containers or the vegetable garden for tasty home grown crops later in the summer.
  • Lots of vegetables can be sown outside this month, as the temperatures rise. Try french beans, courgettes, squashes, quick and easy radish, sweet corn and many more.
  • Crops such as rocket, lettuce, basil, coriander and others can be sown successionally every 10 days or so for continuous cutting over the summer.
  • Pot on tomato and other young vegetable plants into larger pots. Make sure there is a well-developed root system - if not leave them for a bit longer before moving them into individual pots.
  • Harden off all young vegetable plants before planting out, in a cold frame, or by placing them outside during the day and under cover at night. You can cover them in pots or in the ground with a layer of horticultural fleece.
  • Vegetables and herbs can be grown in the smallest of spaces, in the ground or in a variety of pots, trugs and other containers. Find a sunny spot for tomatoes, chilli and peppers, but if sun only reaches an area for a few hours a day, go for a green crop of lettuce, rocket, pac choy, spinach or other green leafy delicacies.
  • Pinch out the growing tips of herbs such as lemon balm and mint to stop them flowering and encourage bushy growth.
  • Devise a routine of feeding and weeding your vegetable garden and containers, and water regularly.

Fruit

  • Keep fruit plants and trees well watered in dry spells to ensure good setting and fruit development.
  • Harvest rhubarb, picking no more than a third of stems at one time.
  • Cover strawberry beds with straw. Feed every couple of weeks with tomato fertiliser.
  • Mulch around fruit trees and bushes to discourage weeds and retain moisture.
  • If you don’t have space for an orchard, there are fruit trees and soft fruit which can be grown in containers very successfully. Have a look at our guide to growing Fruit in containers

Companion planting

  • Companion planting, where plants are positioned to benefit neighbouring plants, can help in the battle against pests, and help with pollination.
  • Many herbs have nectar rich flowers which will attract beneficial insects to the garden.
  • Some herbs have strongly scented leaves which can repel unwanted insects, so can be useful planted around the garden. Try planting sage next to cabbage-family plants to repel cabbage white butterflies, chives next to apples to prevent apple scab, or next to roses to prevent blackspot.
  • Nasturtiums are one of the plants which will attract blackfly away from precious crops.
  • Carrot fly will start to appear in May. Sow carrots with annual flowers such as Love-in a-mist and Cornflowers in a roughly 50:50 ratio to discourage them.

Lawn maintenance

  • This is a perfect time to sow new lawns, or to lay new turf. See our instructions for Laying turf
  • Continue with your lawn maintenance routine this month, increasing the frequency of cutting as long as the weather allows you to.
  • Keep the blades high for the first few cuts, and always leave grass longer in shady areas.
  • If using a ‘feed and weed’ product on your lawn, ensure it has been very well watered in, either by luckily timed rain or by hand with a hose or watering can.

Garden pests

  • Box tree caterpillar feed within webbing and can completely defoliate box plants. See our notes on this relatively new pest. (add link)
  • Guard against slugs and snails - here are some steps to try:
  • Rake over soil surfaces to expose slugs and their eggs to predators.
  • Think about growing hostas and other susceptible plants in pots, raised off the ground, with copper tape below the rim.
  • Use a mulch of gravel or grit on pots and around plants and seedlings.
  • Encourage natural predators, such as birds, into your garden, who will happily munch on molluscs! Keep bird feeders topped up, and put up nesting boxes.
  • Frogs and toads will eat slugs, and a pond (however small) will encourage these amphibians to take up residence.
  • Look out for Scarlet Lily Beetle and squish them when you find them.
  • Viburnum beetle larvae can damage the leaves of evergreen and deciduous Viburnum. Keep a sharp eye on them.
  • Aphids can multiply rapidly during mild spells. Remove early infestations by hand, spray with a soap solution, or treat with a pesticide.
  • Watch for blackspot on roses and treat with a systemic fungicide.
  • Adult vine weevil chew notches in leaves of plants such as rhododendron, camellia and olive. However it’s the vine weevil larvae which do the worst damage to plants in containers, eating the roots. Tip out the rootball of suspect plants, and look for the creamy, orange headed maggots, which tend to curl up into a C shape. If you find them, take very swift action to eradicate them, with chemical or biological controls, or by disposing of the compost and starting afresh.

Wildlife

  • Remember to keep feeding the birds as they begin to nest and raise young. Leave water for them too.
  • Sow or plant wildflowers to encourage insects, butterflies and bees.
  • Plant single flowers which are easier and better food sources for insects than double blooms.

Reference sites

  • There are many books, magazines and websites to help with choosing plants and designing borders and containers.
  • Use a website such as the Royal Horticultural Society (RHS) rhs.org.uk to identify plants, diagnose problems and for general gardening advice.
  • We have a number of our own advice sheets which you can find on our website How to guides or by the till in the shop.
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