Gardening in May: what to plant and tidy in your garden this month

From bulbs to vegetable plots, these are the essentials you need to take care of this month

Gardens are fresh and beautiful, full of young foliage and early summer flowers including alliums Credit: www.alamy.com

The late tulips are in bloom, lilac is in great billowing flower, and there is still lots of blossom around – hawthorn and apple are in full swing. 

Gardens are fresh and beautiful, full of young foliage and early summer flowers: alliums, foxgloves and irises. This is the month that finally sees us step unarguably into summer, and by the end of the month we should be guaranteed frost free all over the country. But watch out before then. A late frost can be particularly damaging, as it hits new tender growth. 

So this month is about juggling: plants must go out if they are to make the most of the warm months ahead of us, but they also are perhaps at their most vulnerable. Have cloches, horticultural fleece and the weather forecast always to hand, and don’t let a spell of warm weather let you get too laissez faire with your clout casting. 

Gardening jobs to do in May

Borders 

Growth is rapid this month and it is time to put supports in place so that all stays upright enough to show off the flowers to come. Buy perennial plant supports such as circular grid support frames or push shrubby pea sticks into the ground around floppy perennials such as peonies, oriental poppies, phlox and penstemon, and they will grow through it and be supported for the rest of the summer. 

Tie the base of tall flower spikes such as delphiniums to short canes pushed firmly into the ground, or use single stem ring supports. 

Push shrubby pea sticks into the ground around floppy perennials such as peonies Credit: BeeJay Images / Alamy Stock Photo

Veg plot 

This month’s main task is hardening off plants, ready to fill up the veg plot. By the end of the month all your tender plants, such as winter squash, pumpkins, cucumbers and aubergines, should be planted in their final positions for the summer, and if that is outdoors you need to be careful not to give them a shock. 

Start by putting them outdoors for a few hours in the day and bringing them in each night, then increase the outdoor time gradually, working up to having them outdoors in a sheltered spot, perhaps with a covering of horticultural fleece, before planting them out in final positions. 

Bulbs 

Daffodils have finished flowering now. This is the perfect time to lift, divide and replant them, which will revitalise them and increase the display through your garden. You can do this every three or four years – once the clumps start to become congested and flowering starts to decline. 

Water each clump an hour before and then use a fork to loosen and lift it, before using your hands to break it into smaller clumps of five or so bulbs. Replant clumps about 20cm apart at the same depth that they were at before, using fresh compost. Water well. 

Patio 

It is time to plant up your pots, hanging baskets and window boxes with bedding plants for really colourful summer displays. Garden centres will be full of pelargoniums, fuchsias, petunias, lobelias and many more. They will grow hugely over the next few weeks and months so give them space to grow, but do include some water retaining gel in your compost, as they will dry out easily. This can still be a month of cold nights, so keep them wrapped or indoors for now, especially if frosts are threatened. 

Greenhouse 

As you plant up your tomato plants, try to visualise just how large and greedy they will become before the summer is over. It is easy to think that the bamboo cane that is currently holding them upright will suffice, but it will soon have the plant leaning dangerously. You need tall and sturdy supports in place now. Also think about watering and feeding. Consider cutting a plastic bottle in half and ‘planting’ it neck down so that you can pour water into it and it will take it straight to the roots. Also make sure you have saucers for any tomato plants growing in pots, as the reservoir of water they hold can be helpful when tomatoes are at their thirstiest. 

As you plant up your tomato plants, try to visualise just how large and greedy they will become Credit: Westend61 GmbH / Alamy Stock Photo

Wildlife gardening 

The dawn chorus means that birds are pairing up, mating and raising chicks, all in quick succession. Stop feeding them peanuts, fat and bread over this time, as these can be harmful to young nestlings. Concentrate instead on high protein foods such as mealworms, black sunflower seeds, mixes for insectivorous birds, and seed mixtures that don’t contain loose peanuts. Soaked raisins, currants and chopped apple will also go down well, and it is also hugely helpful if you can provide a bird bath of clean water. 

Houseplants 

Cacti are adapted to growing in soils with low nutrients, but a bit of feeding can encourage them to flower. They should be fed around three times a year, once in early spring, once around now and a third time later in the summer. Choose a high potash, low nitrogen fertiliser: you could use tomato fertiliser diluted to a quarter usual recommended strength. Water in and then pour off any excess. They will also need lots of light to flower: they want full sunlight for as much of the day as possible. And you should be watering them regularly. Give a good trickle of water once a week, making sure that any excess is poured away. 

Lawn 

No Mow May is a campaign that encourages gardeners to put their mowers away throughout May in order to encourage those wild flowers (some might call them weeds) that are hidden in the lawn to come to flower. Lawns left uncut throughout May will provide early season foraging for pollinators that so need it, creating ribbons and patches of meadow throughout towns and cities. At the end of the month on the bank holiday you can take part in Plantlife’s ‘Every Flower Counts’ survey and receive your own nectar score, telling you how many bees your lawn can support, and helping them to learn about the health of the nation’s wild flowers.  

This article is kept updated with the latest information.