May is one of the most exciting months in the garden. It brings an abundance of new flowers, with fresh blooms opening almost every time you step outside. Bluebells (Hyacinthoides non-scripta) and the first flush of roses (Rosa) are among the most obvious signs of this time of year, while plants are rushing to flower and produce seeds.
The garden is now at its freshest and most lush, the air beginning to buzz with birds and insects. This makes May the perfect time to get outside and tackle those gardening tasks that make early summer so very special.
Summer wouldn't be complete without dazzling displays of flowers in containers and hanging baskets. So, from around the middle of May when the risk of frost has passed - or maybe a few weeks later if you live in the north of the country - start planting up outdoor containers and move all frost-tender bedding plants into the ground.
Check that all pots are clean before planting as the plants will be in them for about five months. Lay gravel in the bottom of the container for drainage - we recommend a depth of about 2.5 centimetres (cm) and fill it to about three quarters full with new potting compost.
Water the plants, then tip them out of their pots, planting them as close together as you can. It might seem a bit excessive, but it means the container fills out fast and you'll have a really stunning display right from the word go. Don't try to separate the roots when you plant them, and leave the root ball intact, as any disturbance will set the plants back.
Once you've got all your plants in place, fill around them with more potting compost so that the root balls are roughly level with the surface of the compost. Make sure there’s a gap of about 2.5cm between the rim of the container and the top of the compost to allow room for watering. Water the plants thoroughly. The potting compost will have enough nutrients in it to last about a month, after that feed the plants every week or two.
For more on which bedding plants to choose and how to plant up a hanging basket, head to our helpful how to guides.
May is when slugs and snails come out in force. They love tender, edible crops, so while you may ignore them in other areas of your garden, you'll need to protect your vegetable patch if you want to have plenty to harvest. Aphids (sap-sucking insects such as greenflies and blackflies) and other insects may also begin to appear now.
There are plenty of ways to deter and control these, and other, garden pests. For more advice on this, check out our article.
Now is the time to get clipping, so if you know there are no birds nesting, get your trimming tools out and begin clearing away dead foliage and flowers, and tidy up those hedges.
Shrubs that flower in the late spring or early summer, such as Mock Orange (Philadelphus), should be pruned as soon as their flowers have faded. The new growth made after pruning will bear the flowers the following spring.
Lightly trim topiary, box hedges and other formal hedging; this will keep them tidy through most of the summer, until they’re pruned properly later in the season. Give Leyland cypress hedges their first trim of the year. And clip fast-growing hedges, such as hawthorn (Crataegus monogyna), and remember to water and mulch newly planted hedges.
For more advice on trimming, check out our how to guide.
There are plenty of gardening tasks to get stuck into come May as planting and sowing are at their seasonal peak. And the more you add to your space, the more maintenance this brings, including watering, weeding, hoeing and thinning out.
Vegetables need watering doing almost daily when the weather’s dry, as vegetables are very shallow-rooted and a lot will have problems if they dry out. Aim to keep the watering consistent so the veggies grow steadily from start to finish, otherwise they may become woody and tasteless or else run to seed.
Sow all vegetables that will take the rest of the season to reach maturity, such as:
Once the risk of frost has passed, it’s time to sow those plants that are too tender to deal with the colder temperatures – just be sure to harden them off first. These include:
As the weather improves, it's time to keep a close eye on your greenhouse. Temperatures rise quickly inside them and so we recommend ventilating them during the day, as well as watering the plants growing inside them, more frequently.
Before the summer sun gets too hot, consider adding shading to your greenhouse glass with a shade kit. This includes a synthetic material that you hang like curtains, which is ideal for protecting your plants from the sun’s rays and helps control the intensity of the heat. It comes with all the fixings you’ll need, and is easy to install and remove. And, as it’s reusable, so you can hang season after season for years to come.
And to help cool your greenhouse further, consider investing in auto vents and louvre windows. Many greenhouses already feature adjustable air vents, yet auto vents automatically open and shut in response to the weather so you can afford to be less diligent. While louvre windows (pictured) consist of adjustable side panels that allow more air into the greenhouse.
May is the time to introduce new plants and fish to your pond. Add new floating plants and consider adding new water lilies. If your current water lilies are a bit overgrown, dividing them up and moving them around is more cost effective than replacing.
Keep new fish in a quarantine tank for three weeks before adding them to your pond. This will ensure that if they do carry any diseases, this will become evident before you put them in with your healthy fish. After this time is up, fill a plastic bag with water from the tank and then put your fish into it.
Put the sealed bag into the pond for about 30 minutes to allow the temperature of the bag to adjust to that of the surrounding water. After this time, slowly add pond water into the bag, ensuring that none of the bag water gets into the pond. Do this several times over 10 minutes to allow the fish to adjust to the pH of the pond. You can then remove the fish with a net and add them into the pond, remembering not to feed them for 24 hours and keep an eye on the pond to make sure everything’s okay.