Essential tasks for May Everything is picking up pace this month. Seedlings are growing strongly, plants and shrubs are bursting into flower and annual weeds are popping up. Keep on top of your gardening jobs with our guide to essential tasks this month.

Hardy annuals

Finish sowing hardy annual flowers outside in May. Later sowings will result in later blooms. Learn the best way to sow outside with our guide to sowing outdoors.

Feeding

Sprinkle general purpose fertiliser around clumps of spring-flowering bulbs. Ensure permanent shrubs and hedging are given a generous feed using this or rose fertiliser. Hoe it into the soil's surface and water in before covering with a mulch of garden compost. Follow Alan Titchmarsh's advice on feeding plants.

Support plants

Place support frames over tall perennials, or those with a floppy disposition. Remember to put eye guards on top of any canes used.

Hellebores

Prune back the flowering stems of hellebores, such as Helleborus argutifolius, as soon as blooms are past their best. Cut back to their base to make room for new shoots. If seedlings are required, leave a stem to set seed, then collect and sow it when ripe. Learn more about these wonderful spring plants with our plant profile.

Tidy alpine plants

Lightly trim off dead flowers of moss phlox, saxifrage, aubrieta and other alpines once they have faded. Excessive growth should also be trimmed to keep plants tidy. Rooted portions can be potted up separately. Follow the progress of the Gardeners' World team's own alpine garden at Berryfields.

Penstemons

Now that the danger of frost has passed, cut down last year's growth from perennials such as penstemons. This will encourage new flowers to bloom during the later summer months.

Watch Alan's tips for successful penstemon pruning.

Chrysanthemums

Plant out young chrysanthemums raised from cuttings in early May, planting each one next to a tall cane. Our plant profile has more tips on growing these attractive plants.

Greenhouse

Seed sowing

Continue sowing seeds of summer bedding plants. Thin out those in trays, or prick them out individually into pots.

Hanging baskets

Plant up baskets with fuchsias and tender perennials, then hang them in the greenhouse to develop. Use our step-by-step guide to planting a hanging basket.

Plant care

In May some plants, such as fuchsias, benefit from pinching, removing the very tip of a shoot to encourage branching. Check plants regularly as their demand for water increases, most will also benefit from weekly liquid feeds. If plants are becoming pot-bound, move into bigger containers. Alan Titchmarsh has more advice on watering plants.

Pest control

Watch out for pests. Treat immediately with conventional pesticides, or consider using biological agents for the control of whitefly, red spider mite and other pests. Most biological controls are very sensitive to pesticides, so do not use any sprays on plants if you are considering using them.

Vines

Pinch out the tips of shoots two leaves beyond a developing fruit truss to produce more growth.

Kitchen garden

Outdoor sowings

Crops to sow outside or under cloches during early May include dwarf French beans, beetroot, sprouting broccoli, Brussels sprouts, summer and savoy cabbage, cauliflower, ridge cucumbers, endive, kale, kohl rabi, lettuce, marrows, peas, radish, spinach, swede, sweet corn and turnips. Delay sowings if soil conditions are cold and wet.

French and runner beans

For an early crop of beans, sow French and runner beans in pots in the greenhouse or on a windowsill. Choose deep pots, if possible, sowing two seeds per pot, and thinning to leave the strongest seedling which is then planted outside in late May or June. Alternatively, sow directly outside under cloches in May or June for a slightly later crop. Our guide to growing beans will help you get a bumper crop this year.

Broad beans

Pull the soil up around the base of the stems with a hoe for extra support.

Support peas

Push twiggy supports into the soil along rows of tall peas to provide support as they grow.

Sweetcorn

Sow the seed in pots in a warm greenhouse, growing plants to the largest size possible before planting outside in June.

Rhubarb

Harvest stems forced under jars, by gripping them firmly at the base and then pulling them sharply away from the crown.

General care

Water new plants

Water newly planted fruit trees, roses and shrubs regularly to help their root systems establish.

Weeding

Hoe borders once a week to prevent weed seedlings establishing. Use our guide to help you recognise the most common annual weeds.

Plants for pots

Buy young plants for pots and containers, as well as for bedding displays. Most need to be potted up into 7.5cm (3in) pots and grown on in warm, bright conditions ready for planting out at the end of May. Be sure to acclimatise plants to cooler outdoor conditions before planting out.

Frost protection

Don't be lulled into a false sense of security by warmer days. While the weather continues to be unpredictable, it pays to take precautions. Keep a sheet of fleece handy, ready to use on cold nights if a ground frost is forecast. Throw it over emerging potato foliage, or fruit trees and bushes in flower. Sacking or sheets of bubble polythene can be spread over cold frames and newspaper spread over young plants on greenhouse staging at night will add a little protection. Learn how to protect your plants with our guide to coping with cold weather.

Plug plants

Seedlings and plug plant packages that you have delivered during April and May should always be opened immediately, as any delay can be detrimental to the plants, causing leaves to yellow and rot to set in. Make arrangements for a friend to collect and open any that arrive while you are away.

Slugs and snails

Control slugs and snails by trapping them under tiles or grapefruit skins. Collect the slugs and dispose of them. Only use pellets sparingly. Alternatively discover which plants are less susceptible to slugs and snails.

Vine weevil

Where vine weevils have been troublesome pests, perhaps in pots in the greenhouse, consider drenching compost with a biological control nematode that will kill the grubs. Mixed into a solution and watered around susceptible plants, the nematode travels through soil moisture on its search for weevil grubs. The nematode is not active when temperatures are below 12˚C (55˚F), so apply when conditions are warm. Discover how to spot signs of vine weevil.

Aquatic plants

Plant up new aquatic baskets with water lilies and other pond plants. If you have large, overcrowded plants, now is a good time to divide them.