When everything is sprouting and many plants are flowering, May is also a month that is peak season for pests and weeds. Measures need to be taken to ensure that these uninvited guests do not take over the beginning of the great flower show.
Soil
To ensure that your plants are not totally overgrown or suffocated by weeds you will have to do some regular hoeing. As well as removing the weeds, this also allows the soil to more efficiently absorb moisture in the air.
Vegetables
Outside
There should be plenty of vegetables to harvest in May including kohlrabi, lettuce, radishes and spinach.
White asparagus has its peak season from mid April to late June and May is a good time to pick. It does take time to develop and can be three years before you see any real crop.
Tomatoes grow very quickly at this time of year and will need to be supported by tying them to stakes. These can be grown outside if frost is no longer a threat.
Courgettes, French and runner beans and cucumbers can be grown outside but they may need covering if there is any late frost.
Green asparagus can also be planted in May – quite often this is done in raised beds as very fertile soil is needed. Don’t buy plants that are too old – one or two years are ideal.
Now is a goof time to grow swede in deeply dug soil and in rows 300mm apart. The seeds should be thinned to 150mm.
Successional batches of peas will be growing freely during the month and these must be staked as soon as they are a couple of inches in height.
Celeriac raised from seed in Late March may now be planted outdoors. Choose an open position ands plant 300mm apart in rows 450mm apart.
Chinese cabbage, chicory and sweet corn can be sown out of doors where the plants are to grow.
Various crops sown in drills out of doors will be in need of thinning during the month. Recommended thinning distances are as follows:
Globe artichoke - 150mm
Asparagus - 300mm
Carrots - 75-100mm
Kohlrabi - 225mm
Leeks - 100mm
Lettuces - 150-300mm
Onions - 150-225mm
Turnips - 100mm
As the early crops of potatoes start to shoot, draw more soil around them for protection as there will still be a chance of frost.
In the Greenhouse
Pot and harden off aubergines and capsicums – plants from the first sowings in late March should now be moved into 150mm pots with potting compost.
Seedlings from the second sowing in mid April should be potted singly in 75mm pots
Prick off and plant celery sown in mid April – give the seedlings plenty of space for they will be growing fast now.
Fruit and Berries
Outside
The young fruits on outdoor peaches and nectarines should now be about the size of marbles and these can be thinned and unwanted shoots removed.
Plum and sweet cherry trees can be pruned – as soon as a new shoot has made six leaves, pinch out the tip
Prune outdoor vines – reduce the number of laterals to one per spur.
Place clean straw around and between strawberry plants – this will protect them but also will provide a mulch and conserve soil moisture.
Mulch fruit trees by spreading a fairly thick layer or well rotted farmyard or stable manure around them. This will help keep weed growth down, provide nutrients and retain moisture in the soil.
In the Greenhouse
Ensure indoor vines are well ventilated.
Melons raised in mid April can be moved to frames and plant on a small mound of compost.
Plant tomatoes which will be safe now without any additional heat.
Use string or twine for them to grow up and remove any side shoots that grow in the leaf joints.
When the plants are flowering, spray them over at mid-day with water.
Flowers and Shrubs
Outside
You now have plenty to do in your flower garden. The old flower stalks of any bulbs that have finished flowering should be trimmed but the leaves should be left in place until they wilt.
Towards the end of the month, it’s a busy time for bedding plants – salvias, petunias, alyssum and begonias can all be planted to provide maximum colour for the summer borders.
Chrysanthemums can now be planted outside in well dug soil with well-rotted manure or compost.
Older peony roses will need some fertilizer – an all-purpose organic compost is best.
New peonies can also be planted in May but be aware they take a few years to develop.
Plant any annuals that are still on your windowsills or in the greenhouse. Overcast days are best for this as they need time to adjust to their new surroundings.
Annuals and perennials are all worth planting in May as well as water and swamp plants, cuttings and seedlings, hollyhocks , floxgloves, dahlias and gladioli.
Potted plants can go outside in May.
Make sure taller border plants such as delphiniums and hollyhocks are well supported
Now is a good time to take shrub cuttings – cut them just above a leaf joint so each cutting is 80-100mm long. Remove all but the top 2-3 leaves then immerse in a solution of copper fungicide and dip the cut ends in hormone rooting powder or liquid. Plant at about half their depth in a 100mm pot of cuttings compost. Cover with thin polythene and put in a shaded cold frame.
Roses will be sprouting furiously at this time of year and buds will start to appear. It’s a good time to apply the second dose of food in the form of a special rose fertilizer which should be worked into the soil. Remove any wild shoots in the earth close to the plant.
Rhododendron bushes and azaleas should be in full bloom at this time of year. They will need to be well watered and continue to deadhead them.
If you have a balcony, May is a good time to plant geraniums, fuchsias and African marigolds.
Plant up pots and fill hanging baskets for summer colour
Most bedding plants prefer the sun but there are some that thrive well in the shade – try mimulus, busy lizzies and lobelia or foliage plants such as Cineraria maritima.
In the greenhouse
Dahlia tubers can be potted up in 130mm pots and kept in the greenhouse until the first week of June.
Photo
Dahlia cuttings can also be taken either from new tubers bought this year or you’re your own stored tubers – use shoots about 80mm long and cut them with a sharp knife, leaving one or two on the tuber to carry on growing.
Sow some cinerarias if you want to have a few plants in flower by December.
Some winter and spring flowering greenhouse plants can be moved to a frame if you have one. Be careful of frost early in the month and cover with sacks.
Begonias, gloxinias and streptocarpuses from an early sowing in January/February should be ready for removal to their flowering pots.
Greenhouse primulas sown in late April will need to be pricked off into other trays and space about 40mm apart.
Lawns
Amidst all the blooming, don’t forget the lawn – it will need at least two trims in May because it grows quickly when fertilized.
Other Jobs
Now is a good time to plant herbs either in a herb garden or in amongst your vegetables. See our section on herbs for more information.
Control algae on ponds – ensure you have oxygenating plants and fish.
Trim ornamental hedges