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May Gardening

May is here and spring is starting to come to an end whilst summer is getting closer. This month is where plant growth seems to speed up and everything comes into bloom. There is lots to do in May to keep your garden looking tidy, to get it ready for the summer months. You should start to see a difference in the weather with more sunshine and the temperatures slowly rising, which means there are lots of opportunities for you to be out in the garden.

Essential jobs to do

  • Harden off summer bedding plants
  • Tidy up perennials
  • Tidy up foliage of spring bulbs
  • Plant hanging baskets and patio containers
  • Mulch and net strawberries
  • Feed raspberry plants
  • Plant courgettes and marrows
  • Sow seeds outdoors
  • Plant leeks, winter brassicas and other greenhouse crops
  • Trim and feed topiary
  • Keep on top of pests, slugs and snails

Last chance to

  • Plant summer bulbs
  • Sow half-hardy annuals

Harden off summer bedding plants

It is important to acclimatise plants raised indoors to the colder temperatures before they are planted outside. To harden them off, take the plants outside of the greenhouse during the day but bring them back inside at night for a week. After a week, start to leave them outside at night too but cover them with a fleece. After another week, the plants should be hardened off and can be planted out in the garden. Be aware of any late frosts, and avoid planting out until the risk has passed.

Tidy up perennials

Spring-flowering perennials such as Pulmonarias and Doronicums need cutting back. Add supports around any tall and floppy perennials before they become too tall and bushy. There are a wide range of ready-made supports you can use to do this.

Tidy up foliage of spring bulbs and mark

Once the foliage from spring bulbs such as tulips has died down and turned brown, clear it away. As the flowers begin to fade, snap off the dead heads before they make seed to help them concentrate their energy on producing next year’s blooms. It is a good idea to mark where bulbs are planted to avoid you accidentally chopping through them. You can mark where they are with short canes or sticks.

Plant hanging baskets and patio containers

Plant up hanging baskets and tubs using a container compost such as Gro-Sure Easy Containers. It is a good idea to put broken up piece of pot in the bottom of the container to improve drainage. Read our guide on How To Create A Container Garden for more information. Ensure that you protect the pots if a late frost is forecast.

Trim and feed topiary

Topiary are a great asset to have in the garden, bringing fun and decoration. It is a good idea to give them a trim because they will have probably grown and starting to look a bit untidy. Regular trimming is a lot easier as it keeps the shape. Once you have trimmed them don’t forget to give them a good feed.

Keep on tops of pests, slugs and snails

As the weather becomes warmer, pests can multiply quickly so it is important to keep on top of them. For slugs, Growing Success slug killer is a naturally-occurring pellet that is good to use to control slugs. They crawl under the soil to die, so there is no need to remove dead slugs from your garden or patio.

Plant summer bulbs

May is really your last chance to plant summer flowering bulbs such as dahlias and gladioli. The dazzling blooms keep colour in the garden in the late summer.

Sow half-hardy annuals

There is still time to sow hardy annual seeds, such as sunflowers and pot marigold plants, directly where you want them to flower. Ensure you remove all the weeds in the area where you are going to sow the seeds first, so that annual seedlings are not competing against the weeds.


Kitchen garden

Mulch and net strawberries

In May strawberries will flower and the fruits will start to form. It is important to mulch the strawberry plants to protect them from the mud, slugs and rotting. It also helps them to retain moisture in the soil. To mulch the strawberries you can use straw. It is also important to place a net over the strawberry plants to protect from birds.

Feed raspberry plants

May is a good time to feed your raspberry plants. This will encourage flowering and healthy leaf growth. Floricane types (summer fruiting) will enjoy tomato feed on a weekly basis, while primocane raspberries (autumn fruiting) will prefer a high nitrogen food, such as sulphate of ammonia, to encourage healthy canes and leaves.

Plant courgettes and marrows

Prepare the planting holes for courgettes and marrows by digging holes about 30cm deep and wide. Leave a 1m space between the holes. Dig in plenty of Gro-Sure Farmyard manure to improve the soil. If no frosts are predicted, you can plant out the marrow and courgette plants, but before you plant them out, make sure you harden the plants off. Once planted it is a good idea to cover with a fleece at the start to protect from wind, until they are established.

Sow seeds outdoors

Runner beans can now be sown outdoors. Prepare the trenches for the runner beans around a support so that they can grow up this support. Plant a few extra seeds around the support to allow for any eaten by pests. If there are too many seedlings, thin out the weakest ones.

Sweetcorn can also be sown directly in a warmish, sheltered site. Always plant the sweetcorn in blocks of at least 12 plants as sweetcorn is wind-pollinated.

Continue sowing beetroot, broad beans, winter cabbage, carrots, lettuce, peas, radishes, swedes and turnips. Protect cabbage and carrot sowings with fine mesh.

Plant leeks, winter brassicas and other greenhouse crops

Plant out leeks that were sown earlier. Prepare the leek bed a few days before planting out by raking in an organic fertiliser such as Fish Blood & Bone. Don’t firm the leeks into the soil but water well after planting.

You can also transplant winter brassicas that were sowed last month. Make sure the little plants are watered very thoroughly before moving them and keep well-watered especially in hot weather.

Peppers, cucumbers and aubergines should be large enough to plant into their final positions now too.


May is a good time to tackle any lawn weeds. If there are not too many then you can try to keep on top of them by removing them by hand. If there are quite a few then we advise using a lawn weed killer such as Resolva Lawn Weedkiller Extra. Try to mow your lawn once a week as now the warmer weather has arrived, the grass will start growing quicker.



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