MAY

GENERAL MAINTENANCE:

The Chelsea Flower Show kicks off the horticultural shows so get inspired with some great ideas for summer.

Spring bedding will soon need to be removed. Don’t be in haste to put summer bedding in until all danger of frost has passed. During May there is still a chance of a sudden frost. When frosts have completely passed, consider zonal geraniums and begonias. The are very good value for money. Regular dead heading will keep them in flower until the first frosts. They are also more drought tolerant.

Continue to water newly planted trees, shrubs and perennials. In warmer parts of the country containerized shrubs and succulents can be moved outdoors towards the end of the month.

As the weather starts getting warmer weeds growth seems to change gear so keep on top of your weeding.

Although the day temperatures are warmer keep an eye on the weather as night time temperatures can drop and there can be a chance of frost. Keep some horticultural fleece handy.

Climbers will also be putting on growth so start training and tying in.

Safeguard young emerging shoots of herbaceous perennials and dahlias from those greedy slugs and snails.

If you have summer bedding in the greenhouse start hardening them off by putting them outside in a cold frame and gradually lifting the lid more every day. Keep the frame closed at night. Also a good time to divide overcrowded daffodil bulbs.

PESTS & DISEASES:

Look out for bright red lily beetles and larvae. If you see the beetles carefully remove from the plants and crush them. Early control will help to keep populations down.

Warmer weather means pests and diseases increase activity. You may need to use chemical controls but bear in mind that they also harm good insects. Try and introduce biodiversity into the garden. Attract birds into the garden as they will eat the slugs and snails. Lady birds and hover fly larvae will feast on aphids and green fly. Roses attract aphids so keep an eye on them.

There are lots of plants that are emerging from the ground. Young shoots are a feast for slugs and snails. Use a biological control such as nematodes, pellets or wood pellets if you have to. Other options are surrounding your plants with sharp gravel.

LAWNS:

Mowing is now a regular task for established lawns. Feed and weed lawns with a high nitrogen fertilizer to encourage good growth. Steadily lower the setting on the lawn mower. Time is running out for seeded lawns. Finish this task before the weather gets too warm.

When newly seeded lawns have germinated and reached a height of about 2.5cm use a roller on them. It helps the grass to grow from the base and knits the grass blades closer.

PRUNING:

Chelsea chop herbaceous perennials around mid May. This helps to prolong the floral show in the garden.

Trim evergreen hedges. It encourages compact growth but before you start, check hedges for nesting birds. Do not trim if birds are nesting. Also trim evergreen shrubs to get rid of any frost damage or wayward stems.

Any early flowered shrubs should be pruned back after flowering to strong young side shoots. If you have shrubs that are very mature and over crowded it’s a good idea to cut out some of the older stems. This will encourage new growth from the base.

Spring flowering perennials can be cut back, divided and replanted. Give them a feed with some fertilizer after replanting.

Spreading, trailing perennials like Osteospermum and Aubrieta can be cut back hard. This will invigorate them into putting on fresh new growth.

Dead head primulas straight after the flowers die back. If you let them produce seed heads they will not come back next year.

Once your Rhododendrons have finished flowering, dead head the trusses encouraging stronger new growth and reducing stress on the plant.

Prune overcrowded and dead stems on early flowering clematis.

Cut down Penstemon to the ground if there are shoots appearing from the ground. If not but back stems to the lowest strong shoots.

BULBS:

Tulips will be in full bloom. Any spent spring flowering bulbs should have the heads pinched off. Do not cut down the stalks and leaves for at least six weeks, allowing the bulbs to build up their energy for next year. Feeding the bulbs with a little bit of fertilizer will help aid the development of next years flower buds. If you choose to lift bulbs make sure you heel them in into a shallow trench or put them into a pot filled with soil. Do not forget to keep watering them.

PLANTING:

Finish planting summer bulbs such as Gladioli, Galtonia, Polianthes tuberosa, Nectaroscordum, Oriental Lily and Begonias.

Once the danger of frost has passed, May is good for planting half hardy annuals, biennials such as foxgloves.

Start planting up your containers and baskets with summer bedding.