May’s a marvellous month in so many ways. The frosts have all but gone, the sun radiates its warmth, evenings allow us time to potter in the garden after work and bare white skin might even see the light of day! On a personal note, it’s the start of the cricket season and my birthday’s here. Life is rather good.
In the greenhouse, seedlings and baby plants are growing away strongly just itching to get outside, whilst tender plants and exotics are gradually being acclimatised for the summer ahead.
In particular it’s a busy time in the vegetable garden. Elsewhere, it’s mostly about tweaking this and that, getting everything into place for what should hopefully be a riot of colour, scent and plentiful harvests over the coming months.
Try and get as much done now as you can before attention turns to the routine tasks of weeding, mowing and watering later on. Oh, and maybe sit back once in a while to admire all that handiwork!
Plant up hanging baskets and containers
In all but the most northerly parts of the UK, it should be safe to plant out summer bedding by mid May. Use fresh compost, as well as water-retaining gels/crystals and a slow release fertiliser to keep everything ticking over through summer. Whether you like a colourful jumble of traditional favourites or a sleek, more contemporary look, pack plants in and away you go. A lovely job for a sunny weekend.
Plug gaps in beds and borders
With spring bedding coming to an end and bulbs going over, plunge pots of flowering bulbs such as late tulips, alliums or lilies into gaps or plant out spare bedding you have left over. I regularly use the likes of Nicotiana, Cosmos and Antirrhinums in this way. If you haven’t any yourself, pop along to your local nursery where there’ll be plenty of choice.
Last chance to sow hardy annuals this month – the cheapest and often most colourful way of filling gaps in beds and borders.
Give perennials the ‘Chelsea Chop’
This simple technique is used to stagger flowering over the summer, to delay flowering until later on, and to produce shorter, stockier plants less prone to toppling over. Either cut back randomly selected shoots on individual plants, or cut all the foliage back in one go. Likely subjects include Phlox, Sedums, Campanulas and Achilleas. Use prunings as softwood cuttings.
Get hoops and stakes in place before tall perennials become top heavy, and to avoid snapping stems. Use woody prunings if you haven’t any to hand, much as you’d use pea sticks. Put cane toppers on bamboo canes to avoid damage to eyes. The likes of Lupins, Delphiniums, Peonies and Oriental Poppies will soon be in flower and look all the better for some support.
Plant out Dahlias and Cannas
Work plenty of organic matter into planting holes as both are hungry and thirsty. Provide protection from slugs and snails, water regularly and stake dahlias from an early stage. Plant out chrysanthemums too.
Foxgloves, pansies and wallflowers are best sown in early summer. Biennials are plants which put on leaves in their first year, flowering the next. Sow in trays of seed compost, lightly top with horticultural grit and pop into a sheltered, semi-shaded spot. Prick out in 6-8 weeks.
Trees and shrubs
Garden lore has it that box should be pruned on Derby day (early June) but I like to lightly prune my hedges and topiary both now and then again in August. Use a clean and sharp pair of shears, avoid pruning in full sun to avoid leaf scorch, and mulch plants generously with garden compost thereafter. Delay pruning hedges where birds might be nesting.
Deadhead Rhododendrons, Azaleas and Camellias
Once their flowers begin to fade. Leggy or overgrown plants can be cut back now, cutting above an outward-facing bud. Treat those showing signs of chlorosis (yellowing leaves) to a feed of sequestered iron.
Spring flowering shrubs such as flowering currants and Forsythia should be pruned immediately after flowering (see last month). Pyracantha and Chaenomeles can also be pruned in May. Cut back hardy fuchsias, Ceratostigma, Hypericums, Caryopteris and Perovskia to emerging buds over a low framework.
Tend to climbers
Gently weave the twining stems of clematis and sweet peas as they grow, loosely tying to supports. Prune Clematis montana as flowers fade, simply cutting back to fill its allotted space and to encourage the production of sideshoots. Lightly prune overly-long Trachelospermum jasminoides shoots. Tie in new shoots of climbing and rambling roses as horizontally as possible as they grow.
Unwrap tender plants
Tree ferns, bananas, evergreen agapanthus, potted citrus trees and other exotics can all come out from under wraps this month. Remove protection, consider repotting if necessary, and gradually acclimatise to outdoor life again in either an unheated greenhouse or porch if you have the space. Start feeding and watering regularly, keeping fleece to hand for any cold nights.
Prune out reversion, remove suckers
Variegated shrubs often send out more vigorous, plain-leaved shoots as the plant tries to revert back to species. Prune these back as far as you can to maintain the plants appearance and keep it healthy.
Remove suckers from the base of fruit trees and ornamental subjects.
Take softwood cuttings
A host of shrubs can be propagated in this way – Fuchsia, Forsythia, Philadelphus, Spiraea, Weigela, Daphne and Hydrangea being just a few. Take 3-5” long cuttings first thing in the morning, dip into hormone rooting powder, pop into shallow pots of gritty compost and pop into a propagator. Keep adequately watered and pot up when roots begin to show at the bottom of the pot.
Minimise the threat of pests
Protect seedlings and leafy veg from slugs and snails, put collars around stems of brassicas, consider ‘companion planting’ (onions with carrots, dill with brassicas etc), net peas, fleece carrots, the list goes on….
Plant rows of French marigolds in the veggie plot – their scent masks that of everything else and attracts predators.
Freshly cut asparagus is a wonderful treat in early summer. Cut spears from now to early-mid June when they’re about 4-6” high. Keep ‘stands’ weed free, avoiding deep cultivations as they’ve fibrous and shallow roots. Make the most of it - it’s a delicious vegetable with a short cropping season.
Warm and wet weather sees weeds cropping up all the time. Dig out perennial weeds roots and all, whilst annual weeds in-between rows can be hoed off on a dry day. I grow most of my crops in raised beds and use an onion hoe for this – it’s lightweight and good for getting into tight spaces.
Earth up potatoes
If you haven’t already got the last of the potatoes in, the maincrops, do so asap. Earth up potatoes as they grow to encourage larger harvests and avoid those near to the surface turning green.
Sow little and often
Quickly maturing crops such as rocket, spinach, radish, spring onions and salad leaves are best sown in short rows every few weeks, or as ‘catch crops’ in-between rows of slower-growing veg to be cropped before they really get going. Also stagger sowings of peas, carrots, beetroot and oriental greens to avoid inevitable gluts.
Plant tomatoes in growbags and containers
Cordon tomatoes can be planted into growbags for growing outside as soon as the threat of frosts has passed. Plant deeply and tie loosely to canes from the word go. Pinch out sideshoots as and when they develop.
Plant bush tomatoes in containers or hanging baskets and sweet peppers and cucumbers in growbags under glass.
Sow tender veg indoors
Such as sweetcorn, courgettes and squashes for planting out later in the summer. Sow sweetcorn in old loo roll inners, squashes and other cucurbits with the seed on its tip end to prevent rotting.
Order sweet potato ‘slips’ from online stockists, praying all the while for a scorcher!
Plant out brassicas
If you’ve raised them under glass. Apply Growmore to the ground a week or two beforehand, giving them plenty of space when planting. Put collars in place to stop cabbage root fly (make your own out of cardboard) and net crops to keep cabbage white butterflies out.
Peas and beans can be direct-sown this month, the latter towards the end of the month if you’re in the north. Always choose an open, sunny position, treat to lashings of muck and water, and get supports in place early for climbing beans and peas.
When they start to pod, pinch out the growing tips of broad beans to deter black bean aphids. Spray with a soapy solution if they’ve already taken hold.
Keep cropping rhubarb
The rhubarb season’s fairly short (stop picking by mid-late June) so make the most of it! Never harvest more than half the plants stems in one go, keep well watered during dry spells and mulch generously once left to rest for the remainder of the year.
Dig out raspberry suckers
Raspberries send out suckers often some distance from their original planting rows, Chop out runners with a spade to maintain order in the fruit garden. Ensure all soft fruit is netted as fruits begin to form. Keep raspberries well watered, particularly when in flower.
Hang up pheromone traps
To avoid caterpillars of the codling moth tunnelling into fruits this summer, hang traps in apple trees this month. Males stick to pads inside the traps (available from garden centres), causing fewer females to mate.
Tend to strawberries
Keep well watered, pinch out runners, treat to a feed of sulphate of potash and net from birds. Mulch strawberry beds with chipped bark or, ideally, straw. It’ll conserve moisture, radiate heat and stop mud splashing onto the fruits in rain, in turn attracting disease.
Weed and feed
As per last month. Apply a nitrogen-rich lawn feed if you haven’t already done so. Dig out perennial weeds by hand or use a weedkiller. Alternatively, plump for a two-in-one feed and weedkiller.
Lower the mower’s blades
Grass should now be cut regularly, once a week if you can manage it. Lower the height of blades to something like 2 ½ cm. If drought is forecast, leave grass to grow that little bit longer.
Edge lawns regularly. For me the lawn’s only half done if the edges aren’t neat and tidy too!
Plant up margins
Now that ponds are teeming with life, have a look for gaps and plant them up. Decent garden centres will have fresh stocks of marginals and bog plants.
Keep the pond clear
Clean filters regularly, check pumps are in good working order, add oxygenators, remove decomposing foliage and fallen leaves, add barley straw and top up ponds with rain water rather than tap water. Consider adding a chemical algicide if all else fails. Be patient though, ponds always take a little time to settle during early summer. Aim to cover around 50% of the waters surface with plants such as water lilies.
Provide easy access for wildlife
It may seem obvious but make sure wildlife can gain easy access to the water from the pond’s edge. A few strategically placed stones here and there will make it easy for all the little beasties to come and go.
Keep sowing the fast growers such as dill, coriander, basil and chervil. Take cuttings from bay, sage and lavender. Divide mint, marjoram, thyme and lemon balm.
Split shop-bought herbs
A great little trick, and a particularly useful one if you’re not growing herbs from seed is to split shop-bought herbs. Pots of basil, parsley, coriander and the like can be knocked out of their pots, teased apart into several smaller plants and potted on. Harden off for a week or two as they’ll have been raised in a protective environment. Alternatively, split and plant straight out from early June.
Treat wooden furniture
Rub down wooden benches, chairs and tables with fine sandpaper. Brush down and apply a preservative to bring out the true colour of the wood and make it look its best for summer.
Treat arches, trellis, fences and decking with a wood stain or preservative.
Shade the greenhouse
As the sun gets higher in the sky and daytime temperatures rise, protect vulnerable seedlings from scorching and everything else from frying later in the summer. Draw blinds if you’re lucky enough to have them, put up shade screens on the south and west facing sides, or apply shade paint to the outside of the glass.
Leave doors and vents open at all times, closing only at night should temperatures be set to drop. Damp down floors regularly to increase humidity and deter pests.
Step up watering
If we’re lucky enough to have a dry spell, look to increase the irrigation of new plantings, emerging seedlings and containerised plants in particular. Consider putting up additional water butts if you have room.
Make a scarecrow
A bit of fun for the weekend and a job to engage little gardeners. Stand him or her up to look out over the vegetable garden, moving from time to time to baffle those birds!