14 Aug 2022

In The Garden with Jo: May in the garden

In The Garden with Jo: May in the garden

May is the first month of summer, which is when most of our plants really start to shine, such as alliums which are now starting to do their thing.

Tulips and daffodils are still feeding their bulbs, so don’t be tempted to cut back the green leaves. Take note and record in your diary for September what tulips etc you like and want, for next spring.

Keep on top of weeding – weeds will compete for precious water, light and nutrients. Seeds planted earlier in the year should be potted on by now into a container with slow-release fertiliser.

Look out for signs of blackspot on roses. If discovered, remove infected leaves and destroy. Do not compost. Keep the ground surrounding your roses free of leaf debris and weeds. Good pruning, which allows for good air circulation and a healthy plant, helps to prevent this. See the recipe for blackspot spray at the bottom of this page.

Tie in climbing and rambling roses. Laying the stems horizontally will help to produce more flowers. This is also very true for trained fruit trees.

Plant summer hanging baskets, adding good-quality compost, slow-release fertiliser and water-retaining crystals to keep them in top condition. Protect them from late frost under cover. Depending where you are, until mid-May there's still a threat of frost.

Order your plants online.

Start feeding and watering container plants. That wind is very drying.

Harden off dahlias and tender exotics such as canna for planting as soon as the risk of frost has passed, which is usually in mid-May. Note: very dark flowers look terrific in a vase, but can be a bit lost in a garden, except if planted with a bright background.

Divide hostas as they come into growth. Bury shallow saucers of beer to protect fresh young growth between or beside clumps of hostas in the ground. Hostas also look terrific in pots.

Take cuttings of perennials, such as fuchsia, argyranthemum and pelargoniums (commonly known as geraniums). The new shoots of hardy perennials can also be used for cuttings.

Take softwood cuttings of shrubby herbs (such as sage and lemon verbena). Trim lavender plants, cutting off old flower heads and about 2.5 cm (1 inch) of the current year’s growth. You can use this for cuttings.

Prune out overcrowded and dead stems of early-flowering clematis (C. alpina, C. cirrhosa, C. macropetala, C. armandii, and their cultivars) after flowering. Prune spring-flowering shrubs after flowering. Cut back flowered shoots of choisya to promote a second flush of flowers in autumn.

Tie in sweet peas with plant support rings to encourage them to climb. Closely inspect plants for pests and diseases – early prevention is much easier than curing an infestation.

Pick off any larvae of rosemary, viburnum and lily beetle as soon as you spot them. Lift and divide overcrowded clumps of daffodils and other spring-flowering bulbs. There is still time to divide snowdrops and leucojum and either pot them up for a pal or spread them around your garden.

The Vegetable Garden

Continue earthing up potatoes. From planting you need to do this at least twice. Earlies should be ready mid-June. Thin out direct-sown vegetables such as

spinach, carrot and lettuce seedlings, then water the rows well. I have planted Carrot ‘Flyaway’ F1 Hybrid which is supposed to repel carrot root fly. Harden off outdoor tomatoes, courgettes and pumpkins for planting out.

There is still time to sow courgettes and pumpkins from seed if you do so now. Harvest rhubarb, picking only one-third of the total amount of stems. If you are not ready to use it, chop and freeze, as the leaves break down very quickly in your compost.

Barriers for Protection

Erect netting around soft fruit plants to prevent birds eating your crop. Red currants will be stripped otherwise. Protect carrots from carrot fly by covering with horticultural fleece or enviromesh. They are really hoppers and can only hop 60cm.

Pinch out the growing points of broad beans as soon as beans start to appear at the base of the plant to reduce the risk of black-fly attack.

Protect strawberries with straw (to control weeds and lift the berries off the ground) and netting (to keep birds off the fruit). Keep young fruit trees well watered while they are putting on rapid growth. Remove blossom and fruits from newly planted fruit trees to help them establish properly during their first year. The trees quit often are not strong enough to carry the weight of the fruit.


Feed your lawn with a high-nitrogen fertiliser to encourage healthy green growth. Never allow new lawns to dry out. A natural source of nitrogen is nettles, so you could make your own infusion and spray. Remember nettles are where butterflies lay their eggs, and they makes a delicious herbal tea and soup.

Continue sowing lawn seed and repairing bare patches wait until the lawn reaches 10cm in height and make sure the mower blades are on a high setting. The young roots need the green leaves to do their job of feeding them.

Remember strong roots make strong plants.

The Garden Pond

Feed pond fish, a little and often. I still have four left from two years ago. When the weather gets really warm, they will eat the larvae of midges and mosquitos.

Here is the recipe for Black Spot Spray

500ml water,

3 tsp. baking powder/bicarbonate powder

1 tsp. vegetable oil

A dash of eco soap

Mix all together into a spray bottle. If the roses are very dry, give them a good watering before applying spray.Cover leaves well with spray, will need to be repeated.

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