May gardening tips
Summer is on its way.
As bulbs fade and herbaceous borders grow in leaps and bounds, summer is definitely approaching. Sowing and planting out bedding can begin, depending on regional weather variations, and you can take softwood cuttings. It’s also time to get back into the lawn-mowing regime, as the lawn will love the warmer temperatures this month brings.
Protect tender plants. Frost can affect many plants, and is particularly damaging to tender new growth and blossom in the spring. Cover plants with suitable protection when frost is forecast.
Plant out summer bedding at the end of the month (except in cold areas).
Water early and late to get the most out of your water, recycle water when possible.
Clip evergreen hedges, but check for nesting birds first.
Tie in climbing and rambling roses. Laying the stems horizontally will help to produce more flowers.
Lift and divide overcrowded clumps of daffodils and other spring-flowering bulbs. Apply a liquid fertiliser to spring bulbs after they have flowered, to encourage good flowering next year, and help prevent daffodil blindness. Allow the foliage of daffodils and other spring-flowering bulbs to die down naturally.
You can still divide herbaceous perennials now to improve their vigour and create new plants.
Prune out frost damage from affected evergreen shrubs.
Ensure newly planted trees and shrubs do not dry out.
Check roses for signs of blackspot, aphids and leaf-rolling sawfly damage.
Inspect lilies for red lily beetles as the larvae can strip plants in days.
Continue to protect lily, delphinium, hosta and other susceptible plants from slugs and snails.
Keep tubs, hanging baskets and alpine troughs well watered.
Weed borders to prevent annual and perennial weeds from spreading and seeding themselves.
Mow lawns weekly, and feed with a high-nitrogen spring/summer fertiliser. If moss is a problem, choose a combined fertiliser and moss killer when feeding the lawn.
Use a stiff-bristled brush or pressure washer to remove algae from paths.
Remove dirt and algae from walls, paving and patios.
IN THE VEGETABLE GARDEN
May is still a perfect month for planting asparagus, seed potatoes and the new autumn maturing rhubarb.
Sow vegetable seed outdoors. The warmer weather has raised the soil temperature meaning that seed will germinate quickly. Sow after the risk of frosts. Sow carrots, lettuce, peas, beetroot, french beans, runner beans, radish, spinach and turnips.
Earth up potatoes, once shoots have reached 23cm (9in) tall, earth up to prevent greening of potatoes.
Harvest asparagus spears when they are no more than 18cm tall.
Harvest rhubarb, picking only a third of the total amount of stems.
Harden off outdoor tomatoes, courgettes and pumpkins for planting early next month.
Plant out brassicas and leeks to their final positions.
Plant herbs in containers. Put them on your patio where they are easy to get to from your kitchen. Sow basil and coriander once all frosts have passed. Thyme, rosemary, parsley, chive, mint, sage, oregano are all hardy.
Weed around your onions and garlic to reduce competition for nutrients and water. Applying an onion fetiliser will boost growth.
Be vigilant with weeding – weeds will compete for precious water, light and nutrients.
IN THE FRUIT GARDEN
Keep young fruit trees well watered whilst they are putting on rapid growth.
Remove blossom and fruits from newly planted fruit trees to allow them to establish properly during their first year.
Surround strawberries with straw to protect fruit. Net them to keep birds off of the fruit.
Strawberries grow very well in hanging baskets. They look pretty and the fruit is away from slugs and snails.
Protect fruit blossom from late frosts. Strawberries, blackcurrants, and cherries can be damaged by frosts so protect by covering with horticultural fleece.
IN THE GREENHOUSE
Apply shade paint to the outside of the glass or use blinds on sunny days to prevent temperatures from soaring.
Open doors and vent on greenhouses to increase ventilation on warm, sunny days.
Damp down the floor of the greenhouse regularly on hot days, to increase humidity levels. This benefits plant growth and also reduces the risk of pest problems.
Don’t forget to give greenhouse plants more space as they put on new growth. This will help to prevent disease, and to contain early pest infestations.
Harden off your half-hardy bedding plants that were started off early under cover. By placing them outside for a short period only, at the warmest time of day, and then gradually increasing the length of time they are outside.
Check plants at least every few days, to see if they need watering. Seedlings will need daily attention.
Continue to prick out and pot on new seedlings and cuttings.
Plant tomatoes, peppers, chillies, and capsicum in the greenhouse borders, or in pots or grow bags in the greenhouse.
Hang flytraps throughout the greenhouse to monitor levels of whitefly, thrips and other pests.