From crispy leaves to soggy succulents, our Houseplant Doctor gives expert answers to your top houseplant questions.
How often should I water my houseplant?
There is no fixed rule because how often you need to water your houseplant depends on a host of environmental factors (light, temperature, time of year) and the individual species. Bear in mind that overwatering is often more fatal than underwatering as most plants have natural strategies to cope with short periods of drought but are less able to survive flooding. If you find watering a chore there are plenty of dry loving plants which cope well with neglect. For more information on watering see our Houseplant Watering Guide.
Why have the leaves of my houseplant gone yellow?
Observe whether it is the leaves at the top or bottom which are showing signs of yellowing.
The lower leaves of your plant may occasionally go yellow and drop and this is quite a normal part of the plant growth process. However, if a lot of the leaves are affected then environmental factors are to blame. Often, lower leaf yellowing is a sign of incorrect watering, most frequently overwatering. Tip your plant out of its pot and check the root ball. If necessary, dry it out thoroughly by standing it on a bed of newspaper.
When the upper leaves of a houseplant go yellow this can be an indication of nutrient deficiency caused by watering with hard water or by lack of nitrogen in the compost. Nutrient deficiencies are often indicated by a distinct pattern of discolouration known as ‘interveinal chlorosis.’ This means that the leaf veins remain dark green whilst the tissue between the veins yellows or becomes pale. Treat your houseplant to a liquid feed and see if the problem improves.
If the leaves have gone yellow on the side which is away from the window, then lack of light could be the issue. Turn your plants regularly or find them a brighter spot.
How do I choose the right plant?
Firstly, decide on where you are going to put your houseplant. If you have a bright room which is south or west facing, then your choice is unrestricted. But if you want a plant for a north-facing room which doesn’t get direct sunlight, you will need to be more careful and choose plants which can cope with lower light levels. For more information see our Houseplant Lighting Guide.
Secondly, make a realistic assessment of your level of gardening experience and how much time you have. There are a vast number of easy to maintain plants, see our Top Ten Easiest Houseplants. Once you have decided on the environment and level of maintenance then you can get creative about decorating with plants.
Should I water my plant from above or below?
There are some houseplants which are much happier with bottom watering. This includes dry loving species which are prone to root and stem rots such as cacti and succulents. Other plants do not like water on their leaves or crowns including Saintpaulia (African Violet), Gloxinia (Sinninga speciosa) and Cyclamen.
With these plants you should always seat the pot in a saucer. After filling the saucer with water leave the plant for about half an hour to absorb the water. Don’t leave them to sit in water for long periods and allow the plant to drain fully after watering.
The majority of other houseplants are fine with watering from above.
Which houseplant can I put in a dark room?
Plants can’t survive without light but Aspidistra elatior (Cast Iron Plant) is especially tolerant of low light levels as its natural habitat is the deep, dry shade of the forest floor. Low light levels will slow down plant growth so you can compensate for this by treating your plant to a lighter spot for at least some of the growing season.
What are the easiest houseplants to grow?
The three top bombproof houseplants are Aspidistra elatior (Cast Iron Plant), Sansevieria (Mother in Law’s Tongue) and Zamioculcas zamiifolia (ZZ plant). All of these will tolerate a substantial amount of neglect and you can read more about them and other low maintenance plants in my Top 10 Easiest Houseplants.
7. How do I know if a plant needs repotting?
It’s important not to repot your houseplant unnecessarily as it could result in plants becoming overwatered. Generally, houseplants enjoy being quite snug in their pots. Be especially careful with dry loving species such as cacti and succulents and plants which have naturally shallow root systems. If your plant is growing happily, leave it alone!
When repotting is needed, it will become difficult to water your plant. The root ball will be so congested that water and liquid fertiliser fails to penetrate. Roots will also poke out of the drainage holes which might make it difficult for you to release the plant from its pot. Growth is slowed down or halted.
Tip your plant out of its pot and examine the root ball. The plant is pot bound if the root ball is very dense, with roots circling round and round the pot so that there is little compost visible in the bottom third.
Do any potting up early in the growing season when your plant is in active growth and will have time to expand into its new pot long before winter dormancy. Bear in mind that potting up will cause your plant to grow larger. If this isn’t wanted, then lightly trim the bottom of the roots instead. When you do pot up don’t reach for an extra-large pot. Choose a container which is only 1-2cm in diameter larger than the existing pot. Moderate your watering regime afterwards as until the plant roots have expanded into their new pot they will be surrounded by a layer of wet compost. Be sure to use the correct compost for your plant type; most houseplants enjoy a free-draining medium.
Why has my houseplant grown tall and spindly?
This is most likely a problem with lack of light. Other tell-tale signs are uneven growth, with the plant stretching towards the light and small pale leaves. It is a common problem in the winter when your home remains warm due to central heating which encourages active growth at a time when there isn’t enough light to support it.
Where possible, move your plant into a lighter position. In the winter, you can encourage your plant to go into a resting phase by watering it less and keeping it in a cool spot.
Why have are the leaves of my houseplant gone brown at the edges?
If just the edges or tips of the leaves have gone brown, this is normally a problem with dry air or draughts. Move your plants away from radiators and mist them regularly or stand them on a bed of pebbles in a tray full of water.
Also check for any watering issues. See Overwatering or Underwatering below.
Why is my houseplant suddenly dropping leaves?
This quite often happens when you bring a new houseplant home or when you move a plant from one room to another. Ficus benjamina are especially prone to leaf drop.
It indicates a sudden change of conditions, the most common being variations in watering, light and temperature.
Overwatering or Underwatering
Firstly, check the potting compost and if necessary, tip the root ball out of its pot to have a good look at it. Feel the compost and assess the moisture level. If the root ball is soggy then you have overwatered, it. Quickly remedy this by standing the bare root ball on some newspapers. Keep refreshing the damp newspaper until the root ball has sufficiently dried out. Unfortunately, overwatering can cause irreversible damage. In future, avoid leaving your plant to sit in water. Take care to ease off watering during the winter months when the plant is not actively growing.
If the root ball is very dry it may be that you have underwatered it. Try to maintain a consistent level of water during the growing season whilst allowing the top few centimetres of compost to dry out between waterings.
Changes in Light
Too little light can cause the lower leaves to drop and is a common cause of leaf drop in Ficus benjamina. Try to provide as much light for your plant as possible, particularly during the winter. For more answers to houseplant questions on lighting, see our Houseplant Lighting Guide.
Changes in Temperature
A change in position, room, seasons or temperature can cause leaf drop. This frequently happens with new plants which have transferred from a warm and humid greenhouse environment to a cool, dry home. Other stressors include turning on the heating in winter, placing plants near radiators or in drafts.
Try to find a position for your houseplants where the environment is consistent. Newly bought plants may take a while to acclimatise and should gradually recover by themselves providing their other needs are met.
Why has my succulent/cacti gone rotten at the base and keeled over?
This is normally caused by overwatering. Unfortunately, it indicates that the roots have rotten and the damage is irreversible. However, with succulents you may be able to trim the stem back to healthy material and repot it to grow new roots.
Another frequent cause of this problem with succulents is vine weevil grubs – particularly if you have left your plants to stand outside in the summer months and then brought them back under cover for the winter. These grubs eat all the roots leaving a hollow stem and the whole rosette becomes detached from the soil. When you remove the rosette, you should be able to spot C shaped, creamy bugs about 10mm long with brown heads. As above, trim off all the dead and damaged parts and a few of the leaves so you have enough of a stem to re-anchor the plant and pot it up into a new container. The rosette will grow new roots. If vine weevil is a frequent problem, avoid the use of pesticides and treat your plants with biological nematodes which parasitise the vine weevil grubs.
Houseplant Doctor : Answers to Top Houseplant Questions