Both the aconitum and the rose-leaf sage can bring a touch of late colour to the garden as most other flowers have gone past their best. Between them, they can keep a border fresh for a few more weeks. They can be used individually and do not have to be close by each other but they work well as a combination too.

The blue flower is a form of aconitum or monkshood, while the pink-purple is a salvia called a rose-leaf sage.

The aconitum is a late-flowering species called Aconitum carmichaelii Arendsii. The normal aconitums or monkshoods flower in July and August and are well past their season now, except perhaps for a late flower or two, if the plant was cut back after its first flowering. By contrast, Aconitum carmichaelii only begins to flower in late August or September and will run on well into October. It is a rugged plant, a strong grower, which is native to parts of China and Russia. It makes tall, sturdy stems, much more robust than the summer monkshoods, taller and with a bigger spike of dark-blue inky flowers of the typical helmeted monkshood shape.

The dark blue colour is invaluable because it sets a perfect contrasting counterpoint to the glut of yellow autumn flowers, the perennial sunflowers, heliopsis, tickseeds, heleniums and rudbeckias. All of those are not only in the yellow colour range but they are daisy-type in flower shape and the aconitum makes a fine contrast of shape as well as colour. It is capable of growing to 1.5m or more, and making a big clump of rich green foliage. Arendsii is a dark blue selection. Others can be lighter in colour but are usually not available. Arendsii is a German-raised variety and can cope with a very hard winter.

The second plant is just as spectacular. The rose-leaf sage, Salvia involucrata, has leaves that are somewhat rose-like, bigger and hairier but similarly shaped. Its foliage is handsome before the plant begins to flower in August and into September. It flowers until the increasing cold nights put paid to it. Unlike the aconitum, this salvia is not fully hardy, native to Mexico. It is tough enough for an average winter but it can succumb to severe, prolonged cold. It is worth the risk. This is a superb border plant in autumn.

For some reason, the purple-red-pink colour seems neon-like in autumn. As the sunlight weakens, it appears darker and more intense. The flowers are relatively smaller on long loose shoots to 30cm long, and quite scattered over the bush but it works. It looks exotic and particularly so with the dark-blue aconitum. Of course, it is also good with the yellow flowers, with pink nerines and autumn-colouring foliage.

Both of these standout plants are large, capable of making a head-height bush. The salvia is actually a sub-shrub, not woody enough to be a shrub. They need space to reach their potential and this might be more possible in a country garden. They also have a naturalness about them that suits a rural garden too.

Both plants are reasonably easy to find in garden centres, although they are by no means standard stock items. The form of salvia usually offered is the variety Bethelii, which is very pretty but has shorter spikes than the basic species shown in the photograph. Both salvia and aconitum like good, fertile soil, not so rich that they will make mostly leaves, and not dry in summer, so that they do not luxuriate as they should.

Turnip-root celery

It has been a great year for all kinds of vegetables, and turnip-root celery, or celeriac, has done exceptionally well. While celeriac is the correct name, the common name turnip-rooted celery is more descriptive, because this is related to celery and it has a swollen storage root like a turnip. The difference is that the turnip’s root is swollen whereas the stem base of the celeriac is the swollen part.

It is used in a variety of ways in the kitchen, prized for its celery flavour. The roots can be used from now until they are lifted in early winter and stored. Try it in the meantime and if you want to grow it next year, the seeds are sown in spring under cover and the seedlings planted out after the danger of severe frost has passed, or covered if severe frost is expected.

Veg, fruit and herbs

Lift and store potatoes and carrots now for winter use, if you have not already done. Remove old vegetables as soon as they are finished and do not allow weeds to build up. Parsnips keep better when left in the ground. Prune raspberries, blackcurrants and gooseberries. Parsley can be covered in the open ground to protect it.

Trees, shrubs and roses

Root-balled evergreen trees can be planted now. All kinds of pot-grown trees and shrubs can be planted too. And prepare the area of ground for planting by controlling all grass and weeds. Rambler and once-flowering climbing roses can be pruned, if not already done, by taking out the old flowered shoots.

Flowers

Finish off planting spring bulbs as soon as possible. If bedding plants have declined, change over pots and hanging baskets to winter and spring colours. Divide early-flowering perennial flowers and plant new plants. Lift dahlias, begonias and gladiolus in frosty localities to prevent damage, or cover them with soil.

Lawn

If moss is a problem, sulphate of iron can be used to set it back. Test the application on part of the lawn first. Continue mowing as late as possible, as long as the ground is not squelchy. This will vary from lawn to lawn. An application of autumn lawn fertilizer, or high P and K and low N, will improve its winter appearance.

Greenhouse and house plants

Reduce watering of houseplants and stop feeding. The compost should be slightly dry on top, moist underneath, but never wet and never stand a pot in a saucer of water in winter. Pick the last tomatoes and ripen the bigger green ones indoors. Keep the greenhouse tidy and ventilated occasionally.