May Gardening Calendar

Summer is fast approaching - spring bulbs are fading while lawns and flowerbeds are ramping up with the warmer temperatures and maintenance is becoming important

Flowers and shrubs

  • Watch out for late frosts - protect tender plants with horticultural fleece or cloches
  • In mild areas, plant out summer bedding at the end of the month. If you live in a particularly cold area, leave this until well into June or all risk of frost has passed
  • Finish outside sowings of hardy annual flowers, such as poached-egg plant, foxgloves, honesty and wallflowers and plant gladioli bulbs and dahlia tubers
  • Regularly hoe bare soil in flowerbeds or hand weed with a trowel so weeds don’t get too established - think about putting down bark chippings or weed suppressant to reduce weeds taking hold and self seeding
  • Divide primulas after they’ve finished flowering - to help them along you could plant them in a nursery bed until they are ready to go out again in the autumn
  • Bamboos and clumps of bulbs or rhizomes can also be divided now
  • Apply a liquid fertiliser to spring bulbs after they’ve flowered to encourage good flowering next year and help prevent daffodil blindness. Deadhead tulips and daffodils, then lift and divide over-crowded clumps of daffodils
  • Lift clumps of forget-me-not once the floral display wanes but before too many seeds are released as they can become invasive if left unchecked
  • Train and tie in new growth on climbing plants, such as sweet peas,clematis, wisteria and honeysuckle, to their supports. With clematis, lanky growth should be cut back hard to promote new shoots from the base
  • Tie climbing and rambling roses as near to horizontal as possible. This will restrict sap flow and create more side shoots along the length of the stem, which will produce more flowers
  • You may have already pinched out fuchsia tips in April but it’s time to do it once or twice again now to encourage side shoots and stop them getting too leggy
  • Lightly clip box hedging and topiary to neaten them up - it’ll only need doing another once or twice during this year’s growing season
  • Plant up hanging baskets and containers with summer flowering plants, such as dwarf sweet peas and petunias - liquid feed them every two to four weeks

Fruit and vegetables

  • Earth up potatoes by pulling soil up around their stems and promptly plant any still remaining
  • Grow rocket from seed for a peppery addition to summer salads - keep nipping off leaves to provide rich pickings for weeks
  • If the weather is good, sow beetroot, broad beans, carrot, lettuce, mangetout, onion, parsnips, peas, runner beans, spinach, swedes, turnips and watercress
  • Sow beans, marrows, courgettes and squashes, two per pot, and thin out the weakest seedling to leave the strongest plant
  • Sow sweet corn in deep pots
  • Pick rhubarb stems as they develop and generously water with liquid feed
  • Feed strawberries with a high potash feed, such as tomato fertiliser

In the greenhouse

  • Check plants every few days to see if they need watering - seedlings will need daily attention. Use rain, grey or recycled water whenever possible
  • Plant tomatoes in large pots or grow bags or trailing tomatoes in hanging baskets
  • Ventilate the greenhouse on warm days to keep temperatures consistent but close it at night - you might want to think about installing automatic vent openers
  • Prepare for hot weather by applying a shade paint to the outside of the glass or use blinds to prevent temperatures from soaring
  • Damp down the floor on hot days to increase humidity and reduce the risk of glasshouse red spider mite

Lawn and trees

  • Lay turf or sow grass seed - delay if the weather is bad and don’t walk over it or mow until it grows to about 7.5cm (3in) high
  • Make sure new lawns, from turf or seed, do not dry out and don’t walk on them for as long as possible to allow them to establish
  • Mow established lawns regularly and add clippings to your compost bin in thin layers so it aerates and doesn’t turn to sludge - try alternating grass with layers of kitchen waste (no meat to avoid rats) and torn up paper egg cartons
  • Apply a high nitrogen summer lawn fertiliser - with mosskiller if necessary - to encourage healthy growth
  • If you like the natural look, remember that lawn weed killers will kill wild flowers growing in the turfso they may not be the right choice for you
  • Ensure newly planted trees do not dry out. Water with rain, grey or recycled water whenever possible
  • Loosen tree ties that dig into the bark or could start digging in soon as the trunk growths

Plan ahead

  • If a hosepipe ban is looking likely, invest in a mulching mower that will finely shred grass clippings and blow them into the turf where they act like mulch and retain moisture
  • Order pug plants and seedlings by post
  • Plant out chrysanthemums for autumn flowers

Little green fingers

  • It’s the perfect month to sow useful herbs, such as parsley, chives, coriander, garlic, basil, dill, fennel, mint, thyme and sage. As they grow, teach your children the different smells and play a ‘guess the herb’ sniff test game
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