How to grow houseplants

Check to see if you can provide the growing requirements of plants that interest you

• Read the plant label, or use your phone to research the growing needs of the plant, to see if it will be happy in the conditions you can provide before buying.
• Where it's not possible to provide for its needs, it is much better to select another plant you like that will grow well in your home, rather than risk disappointment

Look for strong robust plants 

• Plants should be balanced in shape and have no dieback
• Leaves should be healthy and have no discolouration
• Compost should be clean, weed and algae free
• Avoid plants with browning foliage or leaf spots 
• Buy from reputable garden centre where they would generally have been stored and cared for correctly
• Avoid buying wilting plants whose soil has become too dry 
• Especially avoid buying those wilting while in moist, or wet compost, as this can indicate root damage from overwatering, or root disease

Check for the presence of pests, in particular:

Fungus gnats (sciarid flies)

Fungus gnats (sciarid flies)

Glasshouse red spider mite

Glasshouse red spider mite

Mealybug (Glasshouse)

Mealybug (Glasshouse)

Scale insects

Scale insects

Avoid plants with common fungal diseases:

Grey mould

Grey mould

Leaf damage on houseplants

Leaf damage on houseplants

Getting the most out of flowering plants

• A plant with plenty of unopened buds, will be in flower for longer
• Place the plant away from a bowl of fruit. Ripe fruit produces ethylene gas that can shorten the life of the flowers
• Placing plants in cooler, not cold temperatures (15C (60F) when in flower, can help the flowers last longer
• Flowers are often aborted if the
  Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.

  compost becomes too dry
• Remove flowers as they fade, to prolong new flower production

Transporting the plant home

• Cover the plant for the journey home, to protect against exposure to cold, especially in winter

Where to place your houseplant

What light does my houseplant need?

• Research your plant to see how much light is optimal for good growth
• In winter, houseplants will benefit from full sunlight when daylight is weak
• In summer strong sunlight can scorch susceptible plants through glass
• Bright shade i.e. bright light which does not cast a sharply defined shadow, is generally OK in summer
• Flowering houseplants often need more light than foliage plants

How do I improve humidity for my houseplant?

• Place the plant on a saucer over a tray of moist gravel or hydroleca
• Group plants together to benefit from local humidity created by the combined moisture given off by their leaves
• Spraying can be helpful if done frequently

What is best temperature for my houseplant?                          

• Some plants deal with heat and cold better than others. Research their minimum temperature tolerance before positioning
• Excessive heat can cause those plants preferring cooler conditions to dehydrate and wilt
• Temperatures that are too low can cause plants liking a warmer spot to collapse and rot
• Don’t leave plants behind drawn curtains in winter as the space there can become very cold
• Close proximity to radiators can cause leaves to dehydrate and become brown around the margins
• Too much warmth along with low daylight levels in winter can force the plant to make weak unhealthy growth

Draughts

• Place away from cold draughts which can shock a plant and cause it to collapse. 

Potting media

• Check if the plant prefers acid or alkaline soil conditions
• Acid-loving plants (e.g. azalea) need ericaceous compost or foliage will become yellow (chlorosis)
• Top-heavy plants are best potted into loam-based compost which is heavier and provides more stability
• Plants requiring extra drainage will benefit from the addition of perlite, grit or sharp sand to the potting compost

Choosing the pot size

• Choose a pot size 5-10 cm (2-4 in) larger in diameter than the current pot, or enough space for growth for two to three years

When to repot

• Compost degrades in time and compacts, reducing the volume of air reaching the roots which can promote disease
• Pot on every two to three years 
• Plants are best potted on in spring, to establish during the subsequent growing season
• Algae appearing on the surface of the compost, can indicate the compost has become sour and that the plant requires repotting

When to water

• Water when the surface of the compost becomes dry
• drier pots feel lighter than wet ones
• don’t water routinely, check that the pot needs water first
• pots dry out faster in winter when the atmospheric humidity is lowered by central heating
• plants in a cool room will need watering less often than plants in a warm room

How to water

• Bring water to room temperature before use, particularly in winter. Cold water can kill
• chlorine in tap water can be toxic to plants so allow the water to stand in an open container for a minimum of 24 hours for the chlorine to dissipate
• Water the pot thoroughly so that water escapes from the drainage hole

Importance of drainage

• Containers should always have a drainage hole to allow the water to escape 
• Plants’ roots need air to breathe.
• If your plants are allowed to sit in water for long periods, the airspaces in the soil can be replaced with water and cause the roots to drown
• Once your plants have been watered, allow them to drain thoroughly and then empty any water-filled saucers 

Does water quality matter?

• Hard tap water is alkaline which ericaceous (acid loving) plants don’t like
• Ericaceous plants are best watered with rainwater
• It often contains fluoride which can be toxic to plants, the effects accumulating over time
• Chlorine in tapwater is also toxic to some plants. 
• Tap water should be allowed to stand in an open bowl for 24 hours to allow the chlorine to dissipate
• Domestic water softeners contain salts that are highly toxic to plants and so should never be used to water them

Holiday care

• In winter, houseplants can be left for a week or two without water as long as the room temperature is cool, but does not fall below the minimum tolerated
• In summer, with higher temperatures plants are more active and dry out faster.
• Water loss can be controlled by;
  • Grouping the plants together and covering with a polythene sheet
  • Placing the plants onto a tray containing wet capillary matting for the plants to absorb water from
  • Insert one end of a wick made from a strip of capillary matting into the base of a container and the other end into a large container of water.  Your plant will draw on the water as it needs it

When to feed

• Plants are best fed during the growing season March to October
• Feeding during the winter should be limited to once a month as the light levels are too low for your plant to use the fertilser to make good growth

How to feed your houseplants

• A liquid fertiliser can be applied once or twice a month, or a quarter strength can be applied at every watering during the growing season
• Alternatively, you can apply a granular fertiliser to the soil surface one or twice a season
• Don’t apply fertiliser to dry soil as this can burn the roots of your plant

What to use

• Ericaceous plants need an acidic plant fertiliser
• Organic fertilisers can be a little too smelly to use indoors
• Slow release granules save labour, releasing a small amount of feed at each watering
• High nitrogen fertiliser (N) are suitable for foliage plants 
• Flowering plants should have fertiliser higher in phosphorous (P) and potassium (K)

Fertiliser labels explained

Fertiliser labels explained

Plant nutrition: feeding plants

Plant nutrition: feeding plants

When your plants aren’t given the conditions they need to grow properly, they can become weakened and stressed.

Some non-disease problems to avoid

• brown leaf edges - possible under-watering 
• Plant collapse, or yellowing leaves which drop - possible overwatering
• Soils that have become overly dry - may cause wilting foliage drop and dieback and check the plant’s growth
• Plants which are unstable in their containers - weak root system
• Yellowing leaves with green veins - nutrient deficiency, chlorosis
• Plant drying out very quickly, and making little growth - possibly pot bound, repot into larger container

Common Pests

Glasshouse red spider mite

Glasshouse red spider mite

Mealybug (Glasshouse)

Mealybug (Glasshouse)

Scale insects

Scale insects

Fungus gnats (sciarid flies)

Fungus gnats (sciarid flies)

Common diseases

Grey mould (Botrytis cinerea)

• improve ventilation to reduce humidity remove any  dead plant material

Grey mould

Grey mould

• improve ventilation 
• spraying with broad spectrum fungicide may have incidental control 
• avoid wet foliage persisting on plants after dark in cool/cold temperatures