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Indoor Plants

Indoor plants can look beautiful all year round providing you choose the right varieties and help them get used to their new environment.

Acclimatisation involves helping plants adapt to changes in things like temperature, light and air quality.  It happens to all plants when they are moved from one place to another, e.g. from a greenhouse or nursery to the interior of a building or a shaded area around the house.  Since plants cannot move themselves from an unfavourable position, they must adapt to the conditions where they are.

Why Acclimatise?

When plants are provided with suitable light, high nutrition, adequate water, suitable temperatures and humidity conditions they respond accordingly and grow beautifully. When they are suddenly moved into the low-light, low-humidity conditions found indoors, most are subject to stress. This can result in leaf drop, reduced growth and even death.

Light intensity and water stress have the most obvious effect in the acclimatisation process. Leaves from light loving plants, when grown in the shade, tend to be smaller and thinner than those grown in the sun. They also have a more reflective surface, and are closer together on the stem.

When placed in a shady spot, changes occur in the leaves over the next 4 to 8 weeks. Food reserves may be depleted and leaves may drop off.  With time, the leaves become acclimatised and become a healthy darker green.

How to Acclimatise

The first step is to talk to your nurseryman about the history of the plant you wish to buy.  How long has it been sitting in the nursery? Has it been receiving a lot of light? Remove any slow release fertiliser which may be on the surface of the plant. Thoroughly leach the soil by flushing with good clean water.  Place the plant in 50% shade in a protected area, either under a large tree in the backyard or on a shaded veranda under other leafy plants.

How to Care for the Acclimatising Plant

  1. Never expose the plant to low temperatures, direct sunlight or wind during this period. Bring the plant indoors at night or on windy days and then take it back outside to its protected area when conditions have improved.
  2. Throughout the acclimatising period keep the soil moist but never wet, and keep a close eye on any potential pest or disease problems.
  3. Light pruning and shaping can be done during this period but don’t overdo it, as the plant may suffer another setback in growth.
  4. If the plant shows signs of stress (burnt leaf tips, wilting or leaf drop), move the plant to a more protected position for a few days. You may need to find a new, more sheltered, position for the acclimatisation period.
  5. When the plant shows signs of recovery, give it a half-strength liquid feed.

Acclimatising Period

The length of time required for a plant to be acclimatised varies according to species, its previous treatment, and the magnitude of the change. Up to 8 weeks may be necessary for some plants.

Philodendron and Aglaonema require very little time, but sun grown Ficus benjamina and Brassaia require 40% to 80% shade for approximately 5 weeks. Ficus nitida requires 10 weeks at 50% shade. The larger the plant, the longer the process; to acclimatise properly a plant must have a fully developed root system.

Indoor Palms

Most palms, except the drier inland species, require moist soil conditions with good drainage. The soil should not be allowed to dry out totally. Palms, especially those from rainforests, can handle the occasional short waterlogged period. Avoid areas that are regularly waterlogged.

The soil is best if slightly acid   Ph 6.0 to 6.5, though palms can handle a wide range of soils from clay to sand.

Being hungry feeders, compost enriched soil or fertilisers may be needed. High nitrogen fertilisers with an NPK (Nitrogen/Phosphorus/Potassium) ratio of 10 3 6 are regarded as the best. This should be applied in spring, summer and early autumn at a rate of about 3 to 5 kg per square metre.

If older fronds become yellow, this indicates a nitrogen deficiency which can be corrected with fertilisers such as Sulphate of Ammonia.

Dead fronds are frequently removed to keep palms looking tidy.  If fronds are cut back while still green though, this can set the plants back and slow growth.

Because their trunks are so flexible and bend in the wind, tall palms are less likely to blow over in a strong wind than a similar size woody tree.

HINT:  If a palm in a pot is next to a wall, turn the pot weekly so the foliage up against the wall can get a spell in the light.

Ferns as Indoor Plants

Many indoor plants suffer through a lack of light. Ferns are often the solution in this situation. Most (but not all) ferns tolerate very poorly lit situations. They generally are ideal as indoor plants both creating the aesthetic affect required and being able to deal with the indoor environment for a reasonable period of time without deteriorating. Remember though, that ferns and all other plants do not naturally occur inside buildings! Any indoor plant will sooner or later need a spell outside to rejuvenate itself.

Herbs as Indoor Plants

Many herbs are ideal as indoor plants. Remember though, that conditions are not always ideal inside.

  1. Temperature can get too high, especially if the house is heated or if the plants are near cooking appliances.
  2. Air - lack of ventilation (gas and air conditioning a problem); heaters cause a lower humidity than out of doors  
  3. Light can be too low. In temperate climates   direct sun in winter for at least 3 to 4 hours per day is needed for most (not all) herbs grown indoors. In warmer climates direct sun even in winter may burn or overheat herb plants grown indoors.

The ideal temperature for most herbs should be around 10 - 23°C. Most types of herbs will grow happily in rooms that are a little too cool for human comfort. Most plants are tolerant slightly above or below the ideal temperature range when exposed for short periods. The main cause of death is temperature fluctuation. A sudden drop of even 8°C can damage the plant or kill it. Try to minimize winter night temperature falls by checking the plant is out of draughts and removed from cold areas. Also high temperatures such as hot spots created by sunshine will scorch leaves and dry out the plant.

Periodically plants grown indoors should be taken outside and given adequate light to build up carbohydrate levels essential for the plant's growth. This should be done in a temperate season, where temperatures are not going to be at extremes.

Grow Healthy Indoor Plants

ACS offer an extensive range of plant and horticulture courses. Learn about successfully growing plants indoors with our specialist course, or learn horticultural techniques to apply to your garden.

Study with the help and support of our specialist Horticulture tutors; they have a wealth of knowledge and experience. If you have any questions about studying with ACS or want to know more about any of our courses, get in touch with our Horticulture tutors today. They will be pleased to help you.

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