Gardening in October

Once dahlia foliage has been blackened by frosts, cut and compost the stems. In mild areas it’s possible to leave tubers in the ground over winter, protected by a layer of mulch, but it’s a gamble. In case winter is harsh, it’s best to lift dahlia tubers carefully using a garden fork, brushing soil off by hand, and leave them in a cool place to dry for a couple of weeks. Tubers should be stored in trays of dry sand over winter, leaving only old stalks exposed. Keep trays in a cool but frost-free place – a garage is ideal. Make sure to label the dahlia tubers so you can remember the variety when re-planting next spring.

After spent crops have been cleared, it’s time to deep clean greenhouses to get rid of any overwintering pests.

• Remove staging, pots and trays, and scrub glass (inside and out) with warm water containing a garden disinfectant, such as Jeyes Fluid. 
• Use a plastic plant label to remove algae between overlapping panes of glass, then give the structure a good blast with the hosepipe afterwards and allow to dry. The RCA 20 cordless pressure washer is also perfect for the job, especially if your greenhouse is away from a mains water supply.
• Next, fill a garden trug with warm water and disinfectant and wash plant pots and seed trays, removing traces of old compost which could harbour pathogens. You’ll be amazed at how many snails hideaway in pots! 
• Don’t forget to disinfect and wash greenhouse staging before reinstalling it.

The hardy banana (Musa basjoo) with its architectural foliage is popular in UK gardens, especially in exotic borders, and can survive light frosts – but plants need a helping hand to remain snug during extreme cold.

Cut off all but the uppermost leaves and wrap the plant stem with horticultural fleece, using twine to tie it in place (never protect with bubble wrap or stems won’t be able to breathe and will rot). Australian tree ferns (Dicksonia antarctica) need protection, too. Push straw gently into the fern’s crown, then circle the trunk with plastic or wire gauze, leaving about an inch between the gauze and trunk, and push straw into the gap to protect the trunk from freezing temperatures.

Sweet peas are one of the nation’s favourite cottage garden climbing plants and germinate well in spring, so why bother with an autumn sowing? Well, plants will be more vigorous, having developed extensive root systems, which leads to more flowers and bigger blooms. Autumn-sown sweet peas benefit from a longer flowering season, displaying better resistance to disease, especially mildew, which is notorious for cutting displays short.

• Fill deep pots or rootrainers with seed compost, sowing one seed in each, about 1cm (0.5in) deep. 
• Water lightly and keep at 14-16C (57-60F) until germination. 
• Grow seedlings on in an unheated greenhouse or cold frame over winter, pinching out the tips if the plants become leggy.

In September, we looked at sowing a lawn from seed. But October is a good time to lay new turf – as long as the weather is fair.

• As with seed, prepare the site, digging soil over, removing weeds and stones, and levelling the area. 
• Lay turf promptly after delivery, so it doesn’t deteriorate, starting at one side of the garden, kneeling on a wooden plank to avoid damaging the new turf. 
• Stagger the joints (as you would if building a brick wall), carefully pushing joints together and filling any gaps or dips with topsoil. 
• Gently tap the turf down with a rake then refrain from walking on it for a month. Water well, and continue watering regularly if the weather is dry.

Learn more about how to lay a lawn >

So many plant pots and window boxes lay barren once summer bedding is over, and that’s a shame, as plant containers can bring much-needed winter cheer. Fill plant pots with free-draining multipurpose compost and mix plants that thrive when temperatures plunge. Winter pansies (once sold as universal pansies) work wonders alongside heathers, miniature cyclamen and the bright pink buds of Skimmia japonica ‘Rubella’. Add trailing ivy to soften the edges of the container for a classic winter look.

With Halloween around the corner, it’s time to get prize pumpkins ready for harvesting so that they can be carved into your very own jack-o’-lantern. The biggest danger at this time of year, now the soil is damp and cool, is that fruits start to rot in their final stages. To reduce the risk, raise pumpkins up above the soil, resting crops on a piece of wood, a tile or pane of glass. Harvest before the frosts and leave fruits to bask in the sun – it’ll help the skin to harden.

Many gardeners grow citrus (often lemons) as a reminder of hot holidays in warmer climes. Unfortunately, we don’t have the climate of the Mediterranean, and while citrus thrives in outdoor plant pots during summer, winter cold can be a kiss of death for plants. Ideally, citrus need a minimum night temperature of 10°C (50°F), so move plants into a bright conservatory or porch and water sparingly with rainwater, but don’t let plants dry out altogether.

Don’t allow fallen leaves to rot or they’ll damage lawns – rake them up, or blow them into a corner and make leafmould, nature’s own soil conditioner! Beech, oak and hornbeam leaves work best.

• Place leaves in a bin liner
• Add a sprinkle of water
• Pierce holes in the bags, tie the tops and store out of sight
• Leave for a year and you’ll have a rich, crumbly mulch
• Leave for two years and it will have transformed into the perfect soil conditioner.

Learn more about how to manage fallen leaves >

We’ve all woken up after a stormy autumn night to find the garden fence flat on the ground. Now’s the time to replace tatty fence panels that won’t survive a gale, but give wooden fence posts a check, too.

• Gently push the fence post – excess movement indicates that it could be rotting below ground level. 
• Rickety posts should be replaced - on wet clay soil, consider installing concrete fence posts.  They should last a lifetime and can be disguised using shrubs and climbing plants
• If dry weather is forecast, paint weathered fence panels and sheds with wood preservative, to protect from winter wet.

Why are sweet peas great flowers to plant in October? After all, the season is winding down, and sweet peas germinate perfectly well in spring. And that is true, but October is the perfect time to plant sweet peas as it offers a host of benefits. Sweet peas sown now will grow slowly during winter, establishing good root systems during the colder months to give them a head start next year. They’ll be more vigorous with longer, stronger stems and bigger flowers which can appear earlier in the season on plants that can be less susceptible to mildew. That’s why exhibition growers sow seed in autumn, and gardeners would benefit from following their example.

It’s important to point out that we are talking about annual sweet peas, which only last for a year but are the best option for fragrance (as opposed to perennial sweet peas which are rarely good for scent). As long as good quality seed is used, few gardeners experience problems with germination; however, some swear by nicking the seed coating using a sharp knife (taking care to avoid the eye of the seed) which can help with speedy germination, or soaking seeds in a saucer of water prior to sowing. Fill deep plant pots or root trainers with a quality seed compost and sow the seed around 2cm deep, covering the seed with compost and watering before placing in an unheated greenhouse, cold frame or a cool porch. As plants grow, pinching out the tips helps to encourage bushier growth.

If you’re looking for the best scented sweet peas to sow now, here are a few tips. Sweet pea ‘Fragrant Boundary’ is a gorgeous mix of highly scented white, blue and pink blooms that are excellent for cutting. Another top choice for October sowing is ‘Painted Lady’, an heirloom variety that remains popular to this day due to its profusion of intensely fragrant pink-and-white flowers. No autumn sowing would be complete without ‘Matucana’ which is famed for its captivating fragrance, said to be the most intensely perfumed sweet pea available with bicolour purple and magenta blooms.

Broad beans can be sown in spring or autumn, and whichever option you choose crops will taste superior to beans that come from a supermarket freezer! If your soil is light and free-draining there are excellent varieties that can go in the ground now (but if you garden on heavy soil that’s prone to waterlogging, it’s best to wait until spring).

It’s important to choose a variety that’s hardy, making it suitable for autumn sowing. ‘Aquadulce Claudia’ is a tried-and-tested autumn favourite and holder of an RHS Award of Garden Merit for performance. Widely regarded as the hardiest broad bean, plants crop prolifically and pods are crammed with tender white beans which are most flavoursome when picked while young.

It’s also worth considering planting broad beans such as ‘Valencia’, which offers excellent tolerance to winter cold and is ideal for getting in the ground between October and November. Not only are its pods long but crops are excellently flavoured and freeze well.

• Choose an open, sunny site and, when the weather is fine, dig the soil over and remove weeds. 
• Sow seeds 5cm (2in) deep and only water if the soil is dry (unlikely at this time of year). 
• Keep an eye open for mice which can take a fancy to seedlings (it’s worth sowing a few spare plants in case some get devoured) and provide canes and string once plants are 60cm (2ft) tall. 
• You’ll benefit from harvests at least a month earlier than from spring sowings, and they’ll be over by June, freeing up space to sow other crops.

Japanese maples represent the very essence of autumn, putting on an unrivalled display of fiery leaf colours as the seasons turn. These Oriental marvels enjoy fertile, moist, well-drained soil and appreciate a sheltered spot. Get the conditions right and you’re in for a treat every year between October and November, making them the perfect garden plant.

Acer palmatum ‘Atropurpureum’ is a brilliant slow-grower that reliably puts on a show of fiery scarlet every autumn before its leaves fall. Although this small tree will grow happily in sun or part-shade, its hues are at their most intense when exposed to higher light levels, so position carefully for best effect.

Another plant to consider is Acer palmatum ‘Dissectum’, renowned for its elegant, deeply divided leaves that emerge sporting tones of green in spring but transform into a kaleidoscope of red, orange and yellow shades in autumn, one of the finest spectacles that a Japanese maple can deliver.

Acer palmatum ‘Osakazuki’ is not only a winner in small gardens, with classic Japanese maple leaves, but it has an enviable reputation for putting on one of the longest-lasting displays of intensely fiery oranges and scarlets, helping gardeners to savour the spectacle before its leaves finally drop.