Aconitum (Monkshood) is a plant providing late colour in the herbaceous border at this time of the year. Aconitum provides height and colour very similar to their relatives, the delphiniums. Aconitum carmichaelii ‘Ardendsii’ has an unusual growth habit. In late summer the foliage starts to die back and turn yellow as if the plant was on the way out. Then the plant starts to flower producing blue hooded blooms on spikes that tower 4 feet or more above the border.
Aconites grow from tubers, which tend to become congested after two or three years, so they will need dividing and replanting. This is best done in the autumn, after flowering, planting back only the most vigorous and largest tubers. Aconites start growth very early in the year, new growth from the base of plants may be visible in January. Aconites grow best in cool, moist, fertile soil in partial shade but will tolerate most soils and full sun. Tall varieties will require staking.
Aconites are ideal for a woodland garden and for borders. They are good for cutting, but contact with the foliage can irritate the skin, all parts are highly toxic if ingested.
There are many varieties to choose from, some of them flowering early in the year. Aconitum cammarum ‘Bicolour’ produces blue and white flowers on arching branches in July and August. Aconitum ‘Spark’s Variety’ produces indigo blue flowers in August. Aconitum ‘Ivorine’ is a bushy perennial producing yellow flowers in late spring and early summer.
Persicaria are a group of evergreen, semi-evergreen or deciduous perennials that are grown for their flowers and autumn colour. Some varieties can be invasive spreading out to form a large clump.
They will grow in any moist soil in full sun or partial shade. There are small species suitable for a large rock-garden or at the front of a border.
Persicaria affinis (Polygonum affine) is a matt forming evergreen perennial with lance shaped dark green leaves which turn a bronze red colour in the autumn. From mid-summer to late autumn the plant produces short spikes covered in red flowers that fade to a pale pink and eventually brown to provide colour during the winter.
Persicaria (Tovara ‘Painter’s Palette’) is an upright herbaceous perennial with variegated leaves that contain V-shaped brown marks, yellow patches, deep pinkish red tinges and red midribs. In autumn it produces slender spikes up to 12 inches long with cup shaped green flowers that change to red.
Jobs for the week
Rambling and climbing roses are best pruned in late summer or early autumn. Ramblers flower on stems produced the previous year near the ground. Cut the old stems that have produced flowers down to ground level and retain the new young stems. Tie the young stems onto wires or other suitable support. Ramblers only produce one flush of flowers in summer. Rosa ‘Albertine’ is a rambling rose that produces a sweetly scented salmon-pink flower in mid-summer.
Climbing roses produce a main stem with lots of side shoots. Prune back the side shoots to about one-third. Climbing roses grow much taller than ramblers and can be fanned out along a wall to produce a burst of colour from summer to autumn. Rosa ‘New Dawn’ produces pale pink-flowers from summer to autumn. Rosa ‘Climbing Iceberg’ produces white flowers. After pruning give the base of the roses a mulch of well-rotted compost.
Flower buds are swelling nicely on camellias now. Water them regularly during this dry spell that we are enjoying. If the roots dry out the flower buds can fall off at any stage.
Move tender plants such as Heliotropium arborescens, Salvia patens and cosmos atrosanguineus to the greenhouse. Lift the entire plant using a fork, cut down all stems to about 3 to 4 inchesfrom the base, tidy up the rootball and replant in a pot filled with free-draining compost.
Keep the compost just moist during the winter.