Summer Gardening Calendar
A whole host of hardy border plants, such as pinks (Dianthus), delphiniums, lupins,, day , and oriental poppies, burst into flower this month, together with many of the hardy annuals sown earlier. New shrubs to flower include the early Dutch honeysuckle (Lonicera), potentillas, weigelas, hypericums, the climbing hydrangea, the potato-tree (Solanum crispum), jasmine nightshade (Solarium jasminoides), alternifolia, and B. globosa. One of the glories of June, however, is the , which make a tremendous show of colour – even those planted the previous autumn and spring making a fine display.
Complete plantingwith tender plants, including dahlias, cannas, and other bedding plants, as early as possible. Trim back brooms ( ), aubrieta, and heathers (Erica) as they finish flowering to keep them bushy. Check upright conifers to ensure that they have not produced competing shoots at the top. Remove dead from roses, annuals, and border plants as they fade. Keep a look out for suckers growing from the roots of budded or grafted plants, including roses and witch hazels ( ), and remove any as soon as you notice them. Conserve moisture by mulching the around plants when it is wet, covering it with a 50 mm (2 in) layer of , rotted manure, peat, or other suitable material. Divide and transplant any bearded irises that have become over-crowded as soon as they finish flowering. Loosely tie in to their supports the new, whippy shoots of to prevent them being blown about and damaged.
The butterfly bush (Buddleia davidii) blooms in July, together with hypericums, the daisy bush (Olearia x hastii), Jerusalem sage (Phlomis fruticosa), the climbing Schizofragma integrifolia, many of the later-flowering, large clematis cultivars, and the dainty yellow Clematis tangutica. Extra colour is provided in borders by white Chrysanthemum maximum, the pink, daisy-like cone flower (Echinacea), the blazing star (Liatris), and knotweeds (Polygonum). Border phloxes also burst upon the summer scene together with the brilliant purple Salvia nemorosa, dwarf dahlias, and all the summer bedding plants.
Continue dead-heading border plants and annuals to keep them tidy and flowering.
Keep tying in large dahlias (their brittle stems are easily damaged) as well as the later-flowering border plants. Hardy geraniums that have flopped over after flowering can be cut to the ground and will produce fresh foliage. Prune wisterias and weigelas when they, too, finish flowering. Order bulbs for autumn planting. Feed roses with fertiliser when the first flush of blooms had faded; this will improve the later display. Layer stems of clematis into pots of soil to increase your stock: two-year-old or older wood roots best. Keep bedding and other plants well watered in dry spells, giving the soil a thorough soaking each time with the aid of a hose pipe and sprinkler. Any heavy cutting of evergreen hedges is best done now so that the resultant new growth has time to harden before winter arrives.
The dainty Japanese anemones, golden rod (Solidago) ice plants, and tuberous dahlias take over the display in beds and borders as earlier plants pass out of bloom. The knot-weeds (Polygonum) show their advantages now and the charming dwarf Cyclamen neapolitanum adds to the display. It is also the month when the spectacular Campsis x tagliabuana opens its red trumpet flowers after a hot summer, and the bedding plants reach the peak of their display, as do some late cultivars and species of clematis.
Plant early-, such as crocuses, fritillarias, chionodoxas, the dwarf bulbous irises, , and narcissi for a display next spring. Also set out autumn crocus (Colchicum) bulbs as soon as they arrive. Continue to dead-head roses, buddleias, and border plants. Cutting off the spikes of Salvia nemorosa just above the top leaves on each stem will encourage a good second display. Shrubs and hardy plants ordered for autumn planting should begin to arrive this month. Cuttings of many hardy shrubs can be rooted in a frame, or outdoors under a bottomless box covered over at the top with clear polythene. Use side-shoots 100-150 mm (4-6 in) long, pulled off with a heel of older wood at the base. Keep them moist until rooted. Clear away hardy annuals that have finished flowering before they shed too many seeds. Lightly trim lavenders (Lavandula) with shears to keep them compact, but do not cut into the old wood. Give a final, light trim to any evergreen hedges that need it.