May jobs and tips for your garden
As bulbs fade and herbaceous borders grow in leaps and bounds, it is now clear that summer is approaching. Sowing and planting out bedding can begin, depending on regional weather variations, and you can take softwood cuttings. It's also time to get back into the lawn mowing regime, as the lawn will be loving the warmer temperatures this month brings. After taking time to relax after Easter it’s now time to carry on with the gardening. What’s more, May is the month that kicks up a gear as vegetable and flower plants can be planted outdoors into their final growing, weather conditions allowing of course. It is also good to be able to start taking care of lawns to get that appearance we love so much! Now that the soil should start to warm up, with weeds sprouting, it’s the perfect time for sowing seeds such as primrose, sweet william, cauliflower, spinach and radish. However, keep an eye on any weeds appearing as they will need taking in hand!
• Open greenhouse vents and doors on warm days.
• Water early and late to get the most out of your water, recycle water when possible.
• Check for nesting birds before clipping hedges.
• Keep on top of weeds to prevent them spreading.
• Clip evergreen hedges now.
• Should weather conditions still seem uncertain, take precautions to guard against frost especially at night by
placing garden fleece over emerging crops such as potatoes, covering cold frames with either polythene or
sacking, and young plants that are in the greenhouse can be covered with newspaper.
• Any plants being delivered this month must be opened immediately, if not, the leaves will go yellow with rot
setting in. Remember, if you are going to be away make arrangements for them to be delivered to a friend so
that they can still be opened up.
• Many plants are susceptible to attack by aphids and measures should be taken to bring this common pest
• Vine weevil can sometimes cause quite a problem so it may be an idea to use a biological nematode –
simply mix into a solution and water plants when larvae are active (soil temperature should approximately be
• To keep control of slugs and snails, trap them under tiles or even grapefruit skins remembering to collect
them up and disposing of them. There are also non-chemical traps available such as Slug Umbrellas and
Nemaslug Slug Killer – use pellets only sparingly. Keep this treatment up for the next few months to keep on
top of slugs and snails.
• Harvest rhubarb, picking only a third of the total amount of stems.
• Surround strawberries with straw to protect fruit, this will also help discourage mould. Net them to keep
birds off of the fruit.
• Hang pheromone traps in plum trees from May to August to monitor Plum fruit moth activity. Also hang
these traps in apple trees to reduce codling moth.
• Keep young fruit trees well-watered whilst they are putting on rapid growth.
• Remove blossom and fruits from newly planted fruit trees to allow them to establish properly during their
• Regularly check the centre of your gooseberry bushes for the green gooseberry sawfly caterpillars. They
will quickly skeletonise the leaves if not removed.
• Erect netting around your soft fruit plants to prevent birds eating your crop. Keep well-watered in dry spells
to ensure good setting and fruit development.
• For more growth on grape vines, pinch out the tips of shoots that are two leaves beyond a developing fruit
• Rhubarb stems that have been forced under jars can be harvested by gripping them firmly at the base, then
pulling them sharply away from the crown.
• Feed your lawn with a high nitrogen fertiliser to encourage healthy green growth.
• Water your lawn during hot weather, particularly newly seeded or turfed lawns. Do not allow new lawns to
• Sowing lawn seed and repairing bare patches can still be carried out in the early part of the month.
• Mower blades should be lowered this month to their regular summer cut height.
• Don't mow newly sown grass until it reaches 3 inches in height and make sure the mower blades are on a
• Provided the weather is mild and the grass is growing, applications of lawn fertilisers and weed killers can
be made to established lawns.
• Depending on growth, regular mowings with the blades set at maximum height may be necessary,
remembering to remove any dead foliage beforehand.
• This is the time to control fairy ring, also Yorkshire fog, couch weed, bindweed along with other weeds
being eradicated by teasing them out and cutting the roots.
• Beetroot and spinach can be thinned out at this time.
• Earth up potatoes by using a hoe to pull up the soil when they are approximately 23cm (9″) high and
promptly plant any still remaining.
• For extra support use a hoe to place soil up around the base of the stems of broad beans. Use 8ft (2.4m)
bamboo canes to make supports for your runner beans.
• If weather conditions allow, runner and French beans raised under glass can be planted out towards the
end of the month.
• Seeds could also be sown outdoors at this time under cloches. However, for an early crop sow two seeds
per deep pot in the greenhouse or on a windowsill, thinning out to leave the strongest seedling for planting
outside in late May or June.
• Marrow, courgette and sweet corn should be sown in the greenhouse and also outdoors at the end of the
month, into early June.
• There are also a number of other subjects which may be sown either outside or under cloches during early
May including broccoli, Brussels sprouts, cauliflower, kale, peas, lettuce, radish, spinach and swede.
• Baby vegetables are becoming very popular especially where space is limited. Many can be sown at this
time and, with the exception of sweet corn, can be grown in containers and growbags on the patio as well as
in the vegetable garden. However, should soil conditions be cold and wet delay sowing.
• May is still a perfect month for planting asparagus, seed potatoes and the new autumn maturing rhubarb
Livingstone. Livingstone is the first of the autumn harvesting varieties as it does not have summer dormancy,
which traditional varieties do. Rhubarbs are perennial plants once established and will benefit from some
well-rotted manure every winter and will reward you for several years.
• Harvest asparagus spears when they are no more than 18cm tall.
• Thin out direct-sown vegetables such as spinach, carrot and lettuce seedlings then water the rows well.
• Harden off outdoor tomatoes, courgettes and pumpkins for planting early next month.
• Plant out brassicas and leeks to their final positions.
• Protect crops from carrot fly by covering with horticultural fleece or enviromesh.
• Pinch out the growing points of broad beans as soon as beans start to appear at the base of the plant to
reduce the risk of blackfly attack.
• Applying an onion fertiliser will boost growth.
• Support your pea plants with twiggy sticks or pea netting.
• Be vigilant with weeding - weeds will compete for precious water, light and nutrients.
• Watch out for late frosts. Protect tender plants.
• Plant out summer bedding at the end of the month (except in cold areas).
• Lift and divide overcrowded clumps of daffodils and other spring-flowering bulbs.
• Thin out drifts of hardy annuals.
• Harden off half-hardy plants by leaving them outside during the day and bringing back under cover at night
for 7 to 10 days before planting outdoors.
• Harden off dahlias and tender exotics such as Canna for planting as soon as the risk of frost has passed.
• You can still divide herbaceous perennials now to improve their vigour and create new plants.
• Divide Hostas as they come into growth.
• Trim back spreading plants such as aubrieta, alyssum and candytuft after they have flowered to encourage
fresh new growth and more flowers.
• Don't be tempted to cut down or tie up the foliage of spring-flowering bulbs, let them die down naturally.
• To reduce the spread of forget-me-not, lift the plants now to prevent heavy self-seeding.
• Prune your Penstemons now - cut all the old shoots back to the base provided there is new growth at the
bottom of the plant. If there are no new shoots at the base, cut just above the lowest set of leaves.
• Take cuttings of tender perennials such as Fuchsia, Argyranthemum and Pelargoniums (geraniums). The
new shoots of hardy perennials can also be used for cuttings.
• Take softwood cuttings of shrubby herbs (such as sage and lemon verbena)
• Prune out overcrowded and dead stems of early-flowering clematis (C. alpina, C. cirrhosa, C. macropetala,
C. armandii and their cultivars) after flowering.
• Tie in climbing and rambling roses. Laying the stems horizontally will help to produce more flowers.
• Tie in your sweet peas with plant support rings to encourage them to climb.
• Prune spring-flowering shrubs after flowering.
• Cut back flowered shoots of Choisya to promote a second flush of flowers in autumn.
• Trim lavender plants now, cutting off any old flower heads and about 2.5cm (1 inch) of the current year's
• Feed and water container plants.
• Top-dress permanent pot plants to refresh the compost.
• Give your container plants a balanced liquid feed every two to four weeks to promote healthy growth.
• Start to closely inspect your plants for pests and diseases - early prevention is easier than curing an
• Pick off larvae of rosemary, viburnum and lily beetles as soon as they are seen.
• Look out for signs of blackspot on roses. If discovered, Blackspot can be treated with a systemic fungicide.
• Continue to weed beds and borders to prevent competition for water and nutrients.
• If soil conditions are not too wet, dahlia tubers can be planted direct into the garden soil from early May
onwards for late summer flowering. Gladioli can also be planted at this time directly outdoors for late
• Provided the risk of late frosts have passed, tender summer bedding plants can be planted outdoors
towards the end of the month, but if weather conditions are still wet and cold delay planting until early next
• Taller perennials or those subjects which may tend to fall over will require the support of frames.
• The sowing of hardy annual flowers should now be completed, however, later sowings will result in the
plants flowering later.
• You may find it worthwhile with some plants, such as fuchsias, to remove the very tip of a shoot which will
then encourage them to branch out.
• Nasturtium seed couldn’t be easier to sow, just push it into damp compost.
• It is always a good idea to regularly check your plants making sure they receive sufficient water and do not
dry out. Also commence weekly liquid feeds which will prove beneficial, and to re-pot any plants that show
signs of becoming root-bound.
• As pansy flowers wither remember to dead-head them to encourage further flowering.
• Now is also a good time to check for greenfly especially on spring bedding and bulbs such as daffodils and
• During early May chrysanthemums raised from cuttings can be planted out along with a tall cane for support
as the plants grow.
Hanging Baskets/ Containers:
• As long as your patio is sheltered or under cover, hanging baskets/containers can be planted up with
fuchsias and tender perennials.
• Why not incorporate a slow release fertiliser and water storing crystals to reduce feeding and help water
retention at the same time but remember not to place outside until end of May/early June so that containers
do not dry out watering can be stepped up on warm, breezy days.
• Dwarf dahlias can be potted up into containers ready to provide colour from mid-summer to early autumn.
• Want to know the secrets to handsome hanging baskets? Look no further! Firstly, when you plant up,
always use a good quality compost, and add some slow release fertiliser and water retaining crystals - they'll
make the baskets so much easier to care for come midsummer! You should also make sure you always
plant up around the sides of the baskets, this will give more impact, quicker! Finally, through the season,
keep taking off the dead flowers and you'll get more and more grow on!
• Harden off half-hardy bedding plants to acclimatise them to outdoor conditions.
• Continue pricking out and potting on seedlings and cuttings.
• Plant glasshouse tomatoes in beds or growing bags.
• Ventilate glasshouses on warm days.
• Use blinds or apply shade paint to avoid large fluctuations of temperature.
• Damp down your greenhouse on hot days to increase humidity and deter red spider mites.
• Hang fly traps throughout the greenhouse to monitor levels of whitefly, thrips and other pests.