Your autumn house plant jobs

More house plant advice:

• House plants for low light levels
• 7 ways to save money on house plants
• Top tips for growing house plants

Autumn house plant needs

Light

The autumn equinox in late September marks the point in the northern hemisphere when the nights become longer than the days. But it’s not just the amount of light that is changing, it’s also the angle at which the light might be entering a room. It might have been that a plant had been positioned to catch the morning light but now that light no longer reaches the plant. So it’s a good idea to check on your plants at different times of the day and, if plants need more light, reposition them in a brighter spot.

The intensity of the summer sun has waned now, so plants that were moved away from sunny, south-facing windows at the start of summer to avoid leaf scorch can now be moved closer to maximise the amount of light they receive.

I have a collection of tender succulents which spend the summer outdoors, but they need to be brought indoors before the temperature drops below 7°C – depending on how mild the autumn is and where you live this can be as early as the first week in September or as late as November. Sun-loving succulents need lots of light to thrive and a south-facing windowsill is the ideal spot for them from now until late spring.

House plants that spent the summer outdoors need to acclimatise to indoor conditions, so although plants might have specific spots where they live indoors it’s a good idea to position them near a bright window initially and gradually accustom them to the lower light levels indoors.

Heating

If we’re lucky enough to have a mild autumn, the central heating may not need to be switched on for a while, but once it is you’ll need to move any plants near radiators or fires away from these heat sources, otherwise the plants will shrivel up.

Draughts can be a problem for lots of plants because they cause temperature fluctuations and most plants like a steady even temperature. A draught could be a constant source of cold air coming in from a gap in a window or door, or it could be a blast of cold air when a window or door is opened then shut. When I was new to house plant growing, the first plant I bought was a lovely weeping fig which I placed by the door in the lounge. It was a small flat and the front door was nearby so every time that door was opened it let in a stream of cold air and within two weeks the plant looked a very sorry sight, having shed most of its leaves. Plants will sometimes recover and sprout new leaves if they’re moved somewhere more appropriate (mine unfortunately didn’t survive the experience), but it’s much better to try to avoid this kind of shock to your plants by placing plants away from draughts.

Humidity

Humidity levels indoors will drop during autumn as a result of the central heating kicking in and fires being lit as the nights become chilly. Many plants are from tropical areas where the humidity is relatively constant and high all year round, so low levels of humidity can cause some plants to develop dry, brown patches on their leaves, particularly at the tips. Those plants that need high humidity should be grouped together – this will create a micro-climate as the plants release moisture from their leaves during a process known as transpiration. Humid rooms such as the bathroom and kitchen are great places for these plants as they’ll love the steam created by baths, showers, washing up and cooking. You can then place plants that don’t need extra humidity, such as cacti and succulents, in less humid spots such as the lounge or dining room.

• Best plants for a bathroom
• How to raise humidity for house plants

Water

Plant growth will start to slow down at this time of year so ease off on watering, however, most plants will still need some moisture. You may only need to water every two to three weeks but it’s best to check rather than following a rigid regime as some plants will dry out quicker than others. Employ the ‘finger dip’ technique where you push your finger into the compost to the second knuckle, which is about 5cm or 2in deep. If your finger comes out dry then water, if not wait a few days and check again. You’ll probably find plants in brighter, warmer rooms may need to be watered more frequently. Succulents and cacti can be watered sparingly every five to six weeks.

Early autumn is when I start to bring Cyclamen persicum back into growth so that I can have flowers for winter. This is a wonderful plant for indoor winter flowers – in the right conditions it’ll bloom for three to four months. I kept the plants I grew last year cool and dry over the summer so that they could have a rest, but early autumn is when I start to encourage them back into life. I like to repot them into fresh compost, then I’ll water the pots from below by placing them in a sink filled with a couple of centimetres of water. Once the surface of the compost is moist I’ll remove the pots from the water and allow them to drain before putting them in a cool but brightly lit spot. It shouldn’t be long before I start to see new leaves emerging from the compost.

Food

Most plants are preparing for their winter rest so there’s no need to feed them during autumn. The exceptions are plants that are flowering – continue to feed these once a month with a high-potash fertiliser, and for orchids use a specialist orchid feed.

Pest and disease problems

If some of your house plants have spent the summer months outdoors it’s important to bring them inside before it gets cold. Even if the days are warm, at this time of year the nights can be quite chilly, something your tropical house plants won’t like at all. Keep an eye on the weather forecast, and if the temperature is likely to drop below 15 degrees then bring them indoors. But before you do, it’s worth giving each plant a thorough once-over to make sure they aren’t harbouring any pests such as vine weevil, which can be a particular problem for succulents such as aeoniums.

Tip plants from their pots to inspect the root balls. If you see any creamy-white grubs or signs of root damage it’s worth removing as much of the compost from the root ball as possible – you can wash it off using a hose – then repot into fresh compost. Don’t move any plants into bigger pots though – the plants won’t be actively growing so the extra compost will just absorb water and may cause the roots to rot. Instead wash the old pot thoroughly in hot soapy water and repot into that.

Wipe down the leaves and stems with a damp cloth to remove any dust and dirt that may have collected while they’ve been outdoors and to remove any possible pests such as scale insects. For plants that have furry or hairy leaves dust these with a fine brush.

General care

Cut back any yellowing leaves – it’s not uncommon at this time of year for plants to shed some leaves – and snip away any old flower stems. Remove any plant debris that may be sitting on top of the compost as this can encourage fungal diseases to take hold.

Growing Greener

Many of the house plants available in garden centres, in supermarkets and online have been grown abroad and transported to the UK. These plants come with a high carbon footprint as a result, but it is possible to reduce the impact your green-fingered hobby has on the environment by buying house plants that have been grown here in the UK.

• The Little Botanical grows many of the houseplants it sells itself (look for the ‘grown by us’ symbol on their website), using renewable energy sources, recycling plastic waste and harvesting rainwater
• The Glasshouse is a social enterprise that works with female prisoners who nurture houseplants while training in horticulture, and the plants they produce are for sale online
• Surreal Succulents is based in Cornwall and produces a mind-boggling selection of colourful and interesting succulents
• Dibleys is an award-winning grower specialising in streptocarpus and African violets

Seasonal stars

Aspidistra elatior

Known as the cast iron plant because of its reputation for being able to put up with low light, pollution and neglect, this elegant house plant was a particular favourite with the Victorians where it was the botanical accessory for every parlour. Its lovely glossy green foliage might not be as showy as some house plants – there are variegated cultivars if you want something fancier – but it’s tough as old boots and sometimes you just want a reliable fuss-free plant, and this is it. It’s the go-to house plant for tricky corners, and it can be moved outdoors in summer where it makes a lovely addition to a lush, tropical-themed planting scheme. It doesn’t like full sun and avoid excess moisture around the roots, aiming for evenly moist compost when you water. It can tolerate temperatures down to 7°C and doesn’t need extra humidity.

Spathiphyllum wallisii

This popular plant has masses of handsome glossy, dark green leaves with white flowers (these are actually modified leaves known botanically as bracts) that look a bit like white flags, hence its common name, the peace lily. It’s also said to be one of the best plants for purifying the air of toxins. Native to South America it loves a warm spot away from cold draughts with bright but indirect light – a sign of too much light is yellowing leaves. Avoid over-watering – the most common reason for peace lilies dying – by checking the compost first. Keep those wonderful leaves looking sparkly by removing dust with a damp cloth. If you have pets you might want to avoid this plant as it can be toxic to cats and dogs.

Phlebodium aureum ‘Blue Star’

I’ve always struggled with indoor ferns as they seem to need more humidity than I can give them and they invariably turn dry and crispy. So I’d all but given up on them until I came across Phlebodium aureum at my local garden centre. It was a really tiny specimen meant for a terrarium, but I thought I’d give it a try. It’s a polypody type of fern with long, wavy-edged fronds that are a gorgeous blue-green colour. It’s native to tropical rainforests so it does like humidity but it seems happy enough on the windowsill in my bathroom.

It doesn’t like direct sunlight and its ideal temperature range is 16–247°C. It doesn’t need much in the way of feed – apply a liquid house plant fertiliser once or twice during the growing season. Handily it’ll indicate when it needs watering as the leaves start to sag. Water thoroughly and these will quickly bounce back.

Opuntia microdasys

The bunny ears cactus, from the deserts of Mexico and Arizona, is an iconic-looking plant with flattened pads stacked on top of each other that are covered in a mass of hair-like prickles known as glochids. While cacti can put up with irregular watering and are great plants if you’re away a lot they do still need some water. They won’t like sitting in waterlogged compost so it’s important to grow them in a free-draining compost mix (using a specialist cacti compost is a good idea). In autumn and winter they may only need to be watered every four to six weeks. Cacti can be tricky customers when it comes to repotting because of the spines, and those with fine hairs like Opuntia can cause skin irritation. Depending on the size of the cactus you can use large tweezers, silicon tongs or rolled up newspaper to hold the cactus. I prefer to water from below as this avoids the possibility of getting water on the plant which can cause rot.

Thrifty tip

Try growing cacti from seed. Several seed suppliers in the UK sell cacti seeds including Chiltern Seeds and Suttons, or you could join the British Cacti and Succulent Society – membership includes some packets of seeds and access to their annual seed list.