It’s time to plant out summer bedding and seed- raised plants. Keep them moist during dry weather. Prepare cannas and dahlias for planting this month. Fill in the gaps of herbaceous borders (except anemones) with annual bedding. June is the best time to plant rhizomes after an overnight soaking, 5cm deep in a moist but free-draining soil or compost with organic matter added. Tubs can be planted up with summer bedding.
Sow fast-growing, late- flowering hardy annuals such as Calendula, Godetia and Clarkia. Perennials such as hollyhock, delphiniums and lupins can be sown directly into drills outside. Thin out direct sowings of hardy annuals. Wallflowers, pansies, Bellis perennis and winter bedding plants need to be sown between May and July in order to flower next year. If the temperatures are reliably warm (around 15°C ) you can sow Polyanthus primulas.
Trimming plants back after flowering encourages fresh growth and new flowers. In that case, cut back dead bulb foliage if not done already. It’s really important to wait until the foliage dies down naturally. Cut back clumps of spring- flowering perennials in order to encourage a fresh flush of foliage. Cut back to the ground level and deadhead Oriental poppies after flowering. It will stimulate new blooms. Mulching and feeding will help to support them.
Remove spent flowers from Euphorbias and cut the flowering stem back to the ground level.
Divide hostas as they come into growth and Primula (primroses) after flowering. Lift and divide overcrowded clumps of bulbs.
For a plants propagation, you can take cuttings from garden pinks (Dianthus) and treat them as softwood cuttings. You can still propagate perennials that are showing new shoots from the crown via basal stem cuttings.
Your garden needs some general maintenance this month… So, hoe borders to prevent annual and perennial weeds from spreading and seeding themselves.
Stake tall perennials to prevent wind damage to flower spikes.
Liquid feed containerised plants every two to four weeks.
Tubs, hanging baskets and alpine troughs must be well watered. Use collected rainwater or recycled grey water.
Pot on plants showing signs of being root- bound.
Pests and disease watch is truly important in the summertime. Vine weevil larvae can become active this month. Aphids can transmit viruses and hellebores can develop hellebore leaf spot on old leaves.
Aphids multiply rapidly in summer so you can remove early infestations by hand.
Continue to protect lily, delphiniums, hostas and other susceptible plants from slugs and snails.
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Primarily, look round for BOX TREE MOTH, because they can completely defoliate box plants. It’s relatively NEW insect to Britain.
Cut back tender shrubs such as Penstemon, Caryopteris, hardy fuchsias this month and prune deciduous magnolias once the plant is in full leaf. Prune out any remaining frost damage from affected evergreen shrubs and flowering shrubs such as Deutzia, Kolkwitzia, Weigela, Philadelphus after flowering. Rhododendrons and overcrowded, dead or diseased stems of Clematis Montana can be lightly pruned also. Young mimosa trees (Acacia dealbata) can be cut back once all risk of frost has passed and evergreens such as Viburnum tinus can also be trimmed in June.
Do not forget to clip evergreen hedges box (Buxus), Taxus Baccata (Yew) and Lonicera nitida if needed.
Thin out new shoots on trees and shrubs that were pruned in winter to stimulate growth.
Prune wall- trained pyracanthas by removing any shoots coming out from the wall and shortening other new growth to about 8cm.
It’s important to remove any reverted green shoots on hardy variegated evergreens such as Elaeagnus, to prevent reversion taking over.
Honeysuckle and Clematis need regular tying in and twining around their supports. You must tie in climbing and rambling roses as near to horizontal as possible if you want more side- shoots and flowers to be produced.
In wet areas, you can still plant containerised trees and shrubs. For their propagation, you can take softwood cuttings of deciduous shrubs, including Caryopteris, Forsythia, Kolkwitzia, lavender and rosemary, Fuchsia, Hydrangea macrophylla, Philadelphus and Spiraea.
Layering is a good way to propagate climbers and lax- stemmed shrubs.
Pay attention to your garden general maintenance needs this month. Prevent newly planted trees and shrubs from drying out. Water with rain, grey or recycled water wherever possible. Water around the crown of tree ferns, especially newly planted ones.
Loosen any tree ties that are digging into the bark, or could do so soon and sprinkle fertiliser around perennials, shrubs and roses.
Hybrid tea roses can be disbudded by removing all smaller buds from the cluster.
Dig out tree and shrub suckers.
Check roses for signs of blackspot, aphids and leaf-rolling sawfly damage.
Inspect V. tinus and V. opulus regularly and spray or pick of the grubs by hand, because they can start nibbling holes in the leaves this month.
Phytophthora root rots can cause dieback on mature trees and shrubs. Check for damage or cankers on deciduous trees.
Inspect sick looking box and holly trees for signs of blight.
Early caterpillars, aphids and other fly pests infestations can be removed by hand.
Mow regularly and continue cutting lawn edges with a half-moon edging iron to ensure they are neat and add grass clippings to the compost heap in thin layers.
Apply a high nitrogen summer lawn fertiliser ( if not done yet) to encourage a healthy-looking lawn. Ensure new lawns do not dry out during hot weather.
If moss is a problem, choose a combined fertiliser and moss killer when feeding the lawn.
You can start to stock new ponds with fish after new plantings have established. Start to stock and feed them only when water is warm.
Continue to remove blanket and duckweed.
Avoid introducing goldfish into the wildlife pond because they can disturb pond’s natural balance.
Use a pressure washer to remove algae from paths. Remove dirt and algae from walls, paving and patios.
Check and repair pergolas, arbours and arches if needed.
You can treat timber structures with wood preservative and stain in dry spells. Make sure you use appropriate products.
Go through your shed and remove any old, out-of-date garden chemicals.