Some plants have yet to reach their peak

Summer may be drawing to a close but late flowering perennials and shrubs should still look good, in fact some plants will be reaching their peak. If you’re wanting to extend the season even further consider choosing those with attractive seed-heads and berries which also provide food for wildlife. 

Here are a selection of my favourite plants and shrubs for September and October:

Ornamental grasses are brilliant as architectural features in the garden, now reaching their ultimate height with crisp leaves and swishing seed heads that glow in orange autumnal sun. Low maintenance once established, they are happy in a moist but well drained soil with good sunlight. 

• Miscanthus sinensis ‘Morning Light’ has a lot to offer. This subtly variegated variety has a large, yet compact shape. Flowers like pink feather dusters emerge in early autumn turning silvery beige as they set seed, they look truly stunning encapsulated by frost and also provide a source of late season food for foraging birds. 

Many members of the daisy (aster) family should still be looking great too.

• Rudbeckia fulgida var. sullivantii 'Goldsturm', a mid-height plant with rich yellow blooms works well with grasses and other warm coloured perennials in the mid-front of a border. Leave the seed heads for the birds and you may also receive a beautiful frosty display.
• Symphyotrichum ericoides ‘Pink Cloud’ is a delicate little aster ideal for the front of a flower bed with tiny pink blooms that go on and on, perfect for late season pollinators.

Penstemon deserve a mention here. These small perennials work well as gap fillers in beds or containers. We use several cultivars at Rosemoor, my favourite being ‘Hidcote Pink’. Pretty pink bell flowers are sent up from early-summer well into autumn, providing you regularly deadhead them. They can suffer in colder winters so take cuttings of non-flowering material in late summer to replace any losses.

Hydrangeas are great for late season colour and can tolerate semi-shady spots with moist soil. One of my favourites is Hydrangea paniculata ‘Silver dollar’ a lovely small-sized variety whose upright panicles of fresh creamy flowers fading to pink and then brown are elegant and long lasting. 

Rosa rugosa ‘Alba’ is a hefty reliable plant with simple white flowers that turn into handfuls of glistening red hips, also a good source of food for many birds. The rose foliage itself goes an attractive autumnal gold.

Top tips

Spring bulbs 

As autumn progresses with cooler temperatures and darker evenings you can begin to plan for spring. October is a good month to buy and plant most spring flowering bulbs such as daffodils, crocus (corms), Muscari and hyacinths. Tulips are better planted November to December when colder temperatures reduce the risk of diseases.

• In lawns you could try large groupings of Narcissus obvallaris, a good all-rounder that can tolerate damper soil conditions, its tidy foliage and pleasant blooms also suit beds, borders and pots. 
• Muscari look lovely in the ground or in containers alongside other larger bulbs. We use ‘Valerie Finnis’ a nice pale blue variety that also attracts pollinators.
• Lastly, for something different ,why not plant Scilla ‘Blue Giant’? This robust yet delicate bulb will produce a carpet of blue star flowers with pale centres at a height of 15cm.

Bulbs should generally be planted at a depth 3 times their own height. Discard any that are very soft or mouldy as these may spread disease to the soil. Squirrels are extremely fond of crocus corms so if you find this a problem cover containers or ground with chicken wire if possible.

Harvest

Collect seed from perennials and hardy annuals such as marigolds and nasturtiums to sow now or in early spring. Continue harvesting veg and autumn fruiting raspberries.

Plant

Late autumn can be a good time for planting herbaceous perennials, trees and spring bedding. The summer heat has mellowed and soil moisture increases so plants have a chance to get their roots down before the first frosts.

Protect

Lift tender perennials such as Dahlias towards the end of this period. Knock dirt off the tubers and store them upside down in a dry, well ventilated spot ready for potting on in the spring. 

Cut back

Use shears to shorten tall flowering shoots on bush and shrub roses to prevent wind rock. Continue to cut back and tidy herbaceous perennials as they go over.

Sally Newbrook

Horticulturist 

RHS Rosemoor