Garden Tasks

Look after faded spring plants

Bulbs

Now the majority of bulbs are coming to an end its time to make sure they reward you with a great show next year too. Start by doing nothing! By that I mean don’t be tempted to cut back scruffy stems and leaves – they’re working hard to gather energy for next years show. Throw some general fertiliser around them if you’re doing the rest of the border or give them a one-off liquid feed to bolster their bulbs. And if you’re feeling really committed to their welfare deadhead to stop them wasting energy making seeds.

Alpines

Many of the early alpines start to look a bit scrappy and bedraggled in May. Tidy them up with a trim to remove old flowers and cut them back to their allotted space. Many plants such as aubrietia can be propagated now with tip cutting from their new growth (in other words – your prunings). Or try layering them by covering a proportion of the exposed stems in a mix of garden compost and sand.

Shrubs

Spring flowering shrubs such as exocorda, spirea, ribes (flowering currant) and lilac can be pruned once their flowers fade. Keep ribes in check by removing one third of the flowering stems down to the ground, this can also be applied to large spireas. Exocorda can thinned with the 1/3 method or left to form a small tree. Lilacs require little pruning other than the removal of dead flower heads and diseased, damaged or badly placed stems.

Perennials

Early bloomers such as pulmonaria and doronicum start to look tired this month. Give them a new lease of life with a hard trim back. This will promote fresh new growth that’ll last till autumn.

Clematis

No garden is complete without the spring charms of Clematis Montana but it does seem determine to take over. Prune it as soon as it’s finished flowering by cutting it back to the size you want, it will take vicious pruning so don’t hold back, It will still produce plenty of new growth ready to flower next year.

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Hardy annuals

Early sowing will have made a good start so long as you’ve kept the soil moist through the dry spell over the last few weeks. Give them the best chance by removing any emerging weed seedlings. The biggest problem I’ve encountered this year is self-sown hardy annuals from 2006. I’ve opted for leaving the most determined ones such as the Californian poppy, nigella (love-in-a-mist) and small Shirley poppies.

Feed, feed, feed

Most plants are at their peek of growth at the moment. I’m sure you’ve noticed how the garden seems to literally grow overnight? If you’ve not done it already get some feed onto your borders. A general-purpose granular fertiliser with a 7:7:7 ratio of nitrogen, phosphate and potassium will give you plants a boost. Pick a dry day to avoid granules and dust sticking to the leaves and burning them. Bedding plants potted last month and newly purchased plants will also be running low on feed. Pep them up with a dose of tomato fertiliser.

What’s at stake?

Fast growing perennials and tubers such as dahlias need staking as they grow. Leave it till the end of the month and your plants will end up with that contorted, mauled look for the rest of the season. I use pea sticks (cut hazel stems) wherever I can. They provide great support and quickly get disguised. If you don’t have access to hazel try other woody prunings from the garden or go for ‘link stakes’. These plastic coated wire stakes can be formed into as larger ‘ring support’ as you need.

Peonies

These beautiful perennials have a nasty habit of collapsing under the weight of their rain filled flowers. Use pea sticks, canes and string or link stakes to stop them looking like beached jellyfish.

Summer bedding plants and pots

Get ahead of the game by planting up containers and hanging baskets now. They’ll grow on happily in a frost-free greenhouse and give you a much earlier display. Instead of endless feeding through the summer try using slow release fertiliser such as osmacote. You’ll find it at the garden centre – Miracle Gro also does their own version. It releases feed gradually for up to six months so it’ll see your plants out till the end of the season. Start toughening them up mid way through May ready for going out into the garden at the end of them month.

Greenhouse

Avoid pests getting a foothold this month with regular checks and treatments. The worst greenhouse culprits are red spider mite and white fly. Keep the spider mite at bay by damping down (watering the greenhouse floor) every day. This keeps the humidity up which they don’t like. If a problem does develop treat with either a bifenthrin based pesticide or try and environmentally friendly biological control. www.greengardener.co.uk sells treatments for both spider mite and whitefly. 

Shade your greenhouse as soon as possible to prevent sun scorch and excessive head. Try either mesh netting or ‘cool glass’, which you’ll find in powder form at the garden centre

Other jobs

Plant out spring sown sweet peas once you’ve hardened them off.

Sow spring bedding plants such as Canterbury bells, Cherianthus (wall flower), pansies and bellis (daisy). Started now they’ll be ready to bloom next spring.

Plant out Dahlias and Cannas

Keep a hoe handy. A quick scratch around every few days will keep weeds at bay until other plants cover the soil surface.