One of the most interesting parts of working with plants is the diverse range of questions we get asked on a daily basis. We always say in horticulture that there are no silly questions but we definitely have questions that we get asked more than others. We put them all together below in the hope that it will make life easier for a few of you.
Q. How much should I water?
A. The amount of water you give your plants is the same if it is a fern or a cactus. You should always water until water comes through the pot. This way you know the roots are watered all the way to the bottom of the pot. The duration between waterings is what differs. A cactus will need to dry completely between watering whereas a fern should be watered when just the top of the soil has dried. You can find a helpful watering care sheet here
Q. How much light do indoor plants need?
A. Light for an indoor plant is not deemed as direct sun. Most indoor plants originate from low on the forest floor where light has been diffused by the tree canopy overhead. The easiest way to determine if an area in your home is suited to an indoor plant, it is best to look at it from the plants perspective. Is there a view of the sky from this position? If there is then this spot is perfect as long as there are no direct rays hitting this spot. In Winter some indoor plants like Ficus may appreciate a couple of hours of morning sun but this should be avoided through the hotter months. Never put your indoor plants outside in the sun. They may burn as they aren't used to such exposure.
Q. What are those annoying little black bugs buzzing around my indoor plants?
A. Fungal gnats. These pesky bugs love to live and breed in constantly moist soil. They need to be treated in 2 ways,
Firstly, as they enjoy soil that is constantly moist it pays to push your plants a little harder and allow them to get really close to dry between watering. Self watering pots should have their reservoir emptied and treated as a regular pot while you have an outbreak.
Secondly, they will need to be treated with a pesticide. The best we have found is Neem granules. This product works in 2 ways. It creates a barrier on top of the soil which the adults don't like to crawl through as it had sharp edges. It also secretes neem into the soil which works as an organic appetite suppressant and also disrupts the insects ability to grow and reproduce.
Q. Should I plant directly into the pot?
A. This question depends on a range of factors. If it is a small pot with a drainage hole and saucer and can be easily carried to the sink then it is perfectly appropriate to plant directly. If your pot has no drainage holes then it is best to not plant directly. These are what we call cover pots and are designed to sit the plastic pot inside to disguise it. The plastic pot should always be removed to water the plant and not returned to the cover pot until it has finished draining completely. In the case of larger indoor plants it is generally easier to leave them in their plastic pots so that they can be removed and carried to the sink to thoroughly water. In the case that you have a very large indoor plants such as a Fiddle leaf fig then nestling a plastic saucer in the bottom of the pot can make the task of watering without it escaping everywhere a little less daunting.
Q. Should I repot?
A. Containerised plants rely on a fresh, open potting mix for optimum growth. Over time nutrients are used up and the make up of the soil changes as it breaks down. Vigorous plants will fill out a pot within a couple of years and tell-tale signs are roots coming out of the drainage holes or a pot which is firm when you squeeze it. Another common sign is that plants are drying out a lot faster than they previously were. Therefore, there are 2 main times when repotting is needed. When the soil has lost its structure or when a plant has reached its potential in that pot size. When repotting you should only go up one pot size at a time so that the plant can easily fill out the fresh potting mix within a season. Over potted plants can find it difficult to establish as their roots are surrounded by a dense, wet barrier of potting mix. If a plant is sick or looking poorly then repotting can benefit but keep in mind that repotting is a stressful exercise for a plant so it can also have the opposite effect and set the plant back further. It is best to repot when plants are in active growth so that they will establish themselves quickly after repotting.
Q. Should I be fertilising my indoor plants?
A. Fertilising encourages healthier plants and healthier plants are much more likely to grow bigger, thicker and greener leaves as well as flower more freely and be better equipped to fight off pests and diseases. Fertiliser comes in 2 main forms:
Slow release or complete fertiliser. This is most usually sold as beads or pellets and contains all the macro nutrients required for plant growth (Nitrogen, Phosphorus and Potassium aka NPK) as well as micro nutrients such as Calcium and Magnesium. This form of fertiliser is made available to the plants as needed using either heat or water to release nutrients.
Liquid Fertiliser. Liquid fertiliser is water soluble and watered directly into the root zone where the plant can access these nutrients and put them to immediate use. Liquid fertiliser is best applied as plants are actively growing so it is best to ease off for the winter months. Seaweed based products such as Seasol aren't considered fertilisers and shouldn't be used in place of a fertliser. The best way to tell if a product is a fertiliser is to check on the side of the packaging for a NPK breakdown.
Q. I always kill my indoor plants, What am I doing wrong?
A. Even experienced horticulturalists kill plants. It shouldn't put you off. Plants can die from a range of reasons but are generally always attributed to water and light or a pest.
Watering is one area where beginners tend to get confused. A care sheet for watering is available to read here. We often hear "I was afraid of over watering so i just gave it a little drink" but over watering is caused by plants not being allowed to sufficiently dry again between waterings not by the act of actually watering thoroughly. When plants aren't watered deeply the feeder roots at the bottom of the pot can desiccate which can effect the plants ability to take up water and nutrients as well as making them more prone to fungus and disease.
Lighting for indoor plants is deemed as bright but not direct sun. The best way to assess if a position is suitable for a plant is to look at it from the plants perspective. If you can see the sky from this position then it is suitable for an indoor plant.
It pays to get familiar with common pests that can attack your plants as it is important to respond to them quickly. A cheat sheet on common pests and their kryptonite can be found here
Q. Should I mist my plants?
A. The question that has divided the facebook groups since Zuckerburg made his first billion. Many of our plants we grow indoors come from tropical origins and it is true that they are adapted to areas of higher humidity. The real question is, is misting plants the most efficient way to raise humidity? When a plant is misted the ambient humidity around that plant will be elevated but only for a short amount of time until the water beads off or evaporates. Using a humidifier creates a constantly elevated humid environment but can mean that plants have water constantly sitting on their leaves which can lead to diseases and fungal issues without adequate ventilation. The safest way to elevate humidity is with a humidity tray which is a saucer slightly wider than the pot filled with pebbles for the plant to sit on. The saucer is filled with water which will evaporate around the plant. This elevated humidity while keeping the leaves dry.
Q. Should I give my plants an outdoor holiday?
A. Plants grow acclimatised to their conditions so moving them at any time comes with some risks. If plants are moved from indoor to outdoor they should always be moved into full shade before being gradually introduced to any sun. Most indoor foliage plants will prefer to never have direct sun but others such as Ficus can be introduced to quite a lot of sun over time. If your plant is sun hardened however it will have to adjust to the lower light conditions once reintroduced to the indoors. Plants should only be moved outdoors during the warmer months. If they are moved out in winter they will be shocked or it may just be well outside their natural cold resistance regardless. The benefits of giving your houseplants a bit of fresh air and rain are there but also keep in mind that your indoor plants are perfectly suited to a full time indoor lifestyle.
Q. I have a lot of indoor plants, Is that a problem?
A. No, You are a perfectly well adjusted human being reaping the rewards of all the benefits of keeping indoor plants. Indoor plants improve your air quality and keep us connected to nature. On top of that they have proven benefits to our mental health. Continue to go about your plant collecting with the smug knowledge that you are obsessed with one of the oldest and healthiest hobbies one can pursue.
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