May

The flower garden:

If you’ve bought bedding plants from a garden centre you can harden them off now by introducing them gradually to outside conditions, in the daytime only at first.

As hostas start to produce new growth you can divide them. Lift out the whole clump with a fork and put them carefully on plastic sheeting or a wooden board. Divide tough-rooted specimens with a spade or knife, cutting through the roots. Loose roots can be pulled apart by hand. Try to get at least five or six shoots in any new clump. Plant the new plants at the same depth as the mother plant and water and feed well.

You can now take softwood cuttings from shrubs for propagating new plants. Take cuttings early in the day and choose non-flowering shoots. Cut up to 4 inches of stem from above a bud and pop it straight into a plastic bag. Store cuttings in the fridge if you can’t use them straight away. The cuttings should be trimmed below the leaf joint and have the lower leaves and shooting tip removed before potting. Use a propagator and rooting powder to get your new plant started but remember to give your plants occasional access to fresh air.

Trim lavender bushes.

Keep a good eye out for pests and diseases throughout the garden; problems spotted early are much easier dealt with.

Keep a particular eye on roses for black spot. If you have this serious disease you can use a fungicide like Rose clear. Because the disease develops resistance, it’s a good idea to rotate the treatments you use.

Fruit and veg:

It’s time to start harvesting rhubarb. Either cut or gently pull the stalks from the plant and remember to discard the leaves, which are poisonous.

Tender veg and salad crops like spinach, lettuce, carrots and many more can be sown directly into well-prepared seed beds. If you’re short of space, interplant fast-growing crops around slower maturing crops.

Vegetable seed you planted last month should be ready for thinning out.

Prepare well for carrot fly – a particularly tenacious pest – by using insect mesh. Rotating your crops each year can help if you use barrier methods of control.

Pheromone traps on fruit trees can be put up now. These can be bought for specific trees and moths. They may provide some protection, but their main purpose is to monitor when the insects are about and when you should spray with insecticide. Use them on apple and pear trees and keep them in place until August.

Strawberries can be protected from water damage, slug and snail attack and mould growth by protecting the fruits with straw. Lift the fruit and put the straw gently underneath.

You may be able to start earthing up potatoes planted earlier in the season. Do it when the stems are around 9 inches high. It helps produce bigger crops and also provides some protection from potato blight.

Other jobs:

You can still sow grass seed for filling bare patches in lawns.

Weeds will be loving the growing season too, keep on top of them to stop them spreading.