Here are your gardening jobs for the month – with added links if I have more information on the subject. They are all still relevant to do now if you’ve fallen behind or if the weather’s been bad.
Sow salad crops, such as beetroot, Chinese cabbage, pak choi and radish. Leafy salads do better when sown in light shade, as hot, dry weather leads to bitter leaves.
Sow runner, French and broad beans, peas, squash, sweetcorn, and outdoor cucumbers directly into prepared beds. French beans are best sown in traditional rows, 45cm (18in) apart, at 15-22cm (6-9in) spacing.
Open doors and vents on greenhouses to increase ventilation. Damp down the floor to increase humidity. Give plants a liquid feed to encourage flowering and fruiting.
Plant out summer bedding and seed-raised plants. Make sure they are well watered in and keep moist during dry weather.
Gaps in herbaceous borders are best filled with hardy annual bedding, such as Calendula, Godetia, and Clarkia. Thin out earlier direct sowings in two or three stages at fortnightly intervals. Final spacing should be between 10-20cm (4-8in).
Divide Primula (primroses) after flowering, planting them in a nursery bed.
Hoe borders to prevent annual and perennial weeds from spreading and seeding themselves.
Lift clumps of forget me not once the display wanes, and before too many seeds are released.
Sweet peas need training and tying into their supports to encourage them to climb and make a good display.
Liquid feed container plants every two to four weeks.
Continue to protect lily, delphiniums, hostas, and other susceptible plants from slugs and snails.
Prune overcrowded, dead or diseased stems of Clematis montana once it has finished flowering. Untangling the stems can be fiddly, but it will take cutting back hard.
Sprinkle fertiliser around perennials, shrubs and roses.
Although most winter brassicas need to be sown earlier in the season, calabrese, turnips, and kohl rabi can be sown now for an autumn crop.
Celeriac and celery can be planted out. A well-prepared site with lots of organic matter dug in is essential.
Runner beans need well-prepared ground and suitable supports (even a frame made of New Zealand Flax flower stalks) for the shoots to twine around and grow upwards.
Don’t forget to give greenhouse plants more space as they put on new growth. This will help to prevent disease, and to contain early pest infestations.
Perennials such as hollyhock, delphiniums and lupins can be sown directly into drills outside. If space is limited, sow them into pots and place them in a cold frame or by the base of a sheltered wall in filtered sunlight.
Hellebore seed can be harvested once the seed heads have ripened. Sow immediately, while fresh – they need a winter’s cold season to break their dormancy. Seed-grown plants will differ from the parent.
Spreading and trailing plants, can become tatty – trim them back after flowering encourages fresh growth and new flowers.
Tackle bindweed when it appears in a border.
Stake tall perennials to prevent wind damage to flower spikes.
Inspect lilies for red lily beetle and crush them.
Tie in climbing and rambling roses as near to horizontal as possible. This will encourage side shoots to grow along the length of stem, for more flowers.
In wet areas, plant container trees and shrubs. In dry districts, wait until autumn.
Ward off carrot fly by covering plants with a fine woven plastic mesh like Enviromesh.
Net cherries against birds, keep protection in place for all soft fruit.
If you want to grow spring bedding for next year, wallflowers, pansies, and Bellis perennis need to be sown from now until next month to flower next spring. Polyanthus are best sown when temperatures are around 15°C (60°F). A sheltered cold frame provides the right environment. Winter bedding plants can also be sown, including ornamental cabbages, kales and winter pansies.
Cut back dead bulb foliage if not done already. It is important to wait until the foliage dies down naturally.
Pinch out the leading shoots on Chrysanthemum and Helianthus to encourage bushy plants.
Vine weevil larvae can be a serious pest of container plants and are active now. There are various biological controls available.
Thin out new shoots on trees and shrubs that were pruned in winter to stimulate growth. Remove crossing stems.
Rhododendrons can be lightly pruned after flowering. More severe pruning should wait until the following early spring.
Twining climbers (such as honeysuckle and Clematis) need regular tying in and twining around their supports.
Take softwood cuttings of many deciduous shrubs, including Fuchsia, Hydrangea macrophylla, Philadelphus and Spiraea.
Ensure newly planted trees and shrubs do not dry out. Water with rain, grey or recycled water. Loosen any tree ties that are digging into the bark.
Shorten newly planted raspberry canes once new shoots are produced.
Change the feed for pot-grown fruit to a high potassium liquid one, such as tomato fertiliser.
Water blueberries, cranberries and lingonberries regularly with rainwater. Only use tap water when butts run dry.
Peas need staking with pea sticks, netting or pruned garden twigs.
Keep tubs, hanging baskets and alpine troughs well watered. Use rainwater, or recycled grey water wherever possible.
Cut back clumps of spring-flowering perennials to encourage a fresh flush of foliage.
Cut back and deadhead Oriental poppies after flowering. Cutting them to ground level will stimulate new foliage and blooms. Mulch and feed.
Euphorbias look a lot better if spent flowers are removed, cutting the flowered stems back to ground level. This can be especially important with Euphorbia amygdaloides var. robbiae, as old stems are prone to powdery mildew.
Perennials that are showing new shoots from the crown can still be propagated via basal stem cuttings.
Take cuttings from garden pinks (Dianthus). They can be pulled off the parent plant while holding a suitable non-flowering shoot four pairs of leaves from the tip. Treat as softwood cuttings.
Pot on plants showing signs of being root-bound.
Remove early aphid infestations by hand. Aphids can transmit viruses, as can other sap-sucking insects.
Prune deciduous magnolias once the plant is in full leaf. If this is done in winter, when the tree is dormant, dieback can occur.
Clip evergreen hedges such as privet, box, and Lonicera nitida if needed. If they are not too woody, shredded clippings can be added to the compost heap. Prune out any frost damage from affected evergreen shrubs.
Prune flowering shrubs such as Deutzia, Kolkwitzia, Weigela and Philadelphus after they have finished flowering. If this job is left too late, the new growth put on after pruning may not have enough ripening time to flower well next year.
Prune wall-trained Pyracantha, removing any shoots coming out from the wall and shortening other new growth to about 8cm (3in). This encourages spur formation and increased flowering relative to green growth.
In ponds, continue to remove blanket and duckweed. Don’t introducing goldfish into wildlife ponds.
Some conservatory plants such as Cymbidium (orchids), Yucca, and citrus trees can be moved outdoors.
Regularly inspect plants, and the structures of the greenhouse and conservatory, for red spider mite, whitefly, thrips and other pests. Control with biological controls, and hang yellow sticky traps to help monitor numbers of flying pests.
Gaps between winter brassica plants can be used for radishes or lettuce.
Summer prune red and white currants and gooseberries.
Pinch out the top of broad beans once the lowest flowers have set to prevent aphid attack.
Peg down strawberry runners and remove cloches from outdoor strawberries once cropped.
Water tomatoes and peppers regularly to prevent blossom end rot – a symptom of calcium deficiency due to an erratic water supply.