How to grow avocados

What are avocados?

Avocados (Persea americana) are tender evergreen trees from Mexico and Central America. They are often grown as houseplants in the UK, raised from the large seed in the centre of the fruit.

Growing from seed is an easy and interesting project for all ages. The resulting plant will grow into a slender tree with large, glossy leaves all year round.

There are hundreds of avocado cultivars, but few are readily available in the UK. The fruits sold in UK supermarkets are mainly knobbly-skinned 'Hass' and smoother, green-skinned cultivars, probably 'Fuerte' or 'Ettinger'. Other cultivars may sometimes be available – it's worth looking out for them, so you can experiment with germinating

Germination is the process by which a seed develops into a new plant. It starts with the seed coat absorbing water, expanding and splitting, which allows oxygen and water into the seed so its food reserves can be broken down and used by the embryo for growth. The first root (called the radicle) pushes into the soil to anchor the new plant in place and start absorbing water and nutrients. The first shoot (called the plumule) then grows upwards, out of the soil, towards the light. different types.

Avocado plants won’t generally flower or fruit when grown as houseplants. After a few years, they tend to go into decline, so are usually considered short-term plants. Still, it’s easy to grow replacements.

If you want avocado plants to produce fruit, you'll usually need more humidity

The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting. and light than in most homes. You also need a lot of space and patience, as the trees can grow to several metres tall before they are mature enough to flower, which can take ten years or more. A large, warm, humid greenhouse or conservatory may be suitable.

Houseplants: to support human health

Buying avocado plants

Avocado saplings are sometimes available online. These are usually tender 'Hass' avocados, so need the same growing conditions as above. You may possibly find grafted plants on a dwarfing rootstock, which means the plants may stay more compact. Grafted plants may be more likely to fruit. For more about the benefits of grafting

This involves joining the roots of one plant to the stem of another related plant, so they fuse together to form one plant. There are various methods, all requiring great skill. Grafting is mainly carried out by commercial growers to combine one plant’s qualities of flowering or fruiting (the upper section or scion) with the vigour or resilience of the other (the roots or rootstock). Fruit trees are often grafted, along with a few ornamental shrubs and trees, and in recent years grafted vegetable plants (mainly tomatoes, but also chillies, cucumbers, aubergines, etc) have become available. , see our guide to grafting.

There are some hardier avocado cultivars, such as 'Wilma', but these are not generally available in the UK.

See our guide to buying plants by mail order.

Given good light, humidity

The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting. and plenty of water, avocado plants should thrive indoors for several years.

Positioning

Avocado plants are best grown in containers in a warm, bright spot indoors. They can also be grown in a heated greenhouse.

You can move an established plant outdoors for the summer, into a warm, sheltered spot in dappled shade, especially in milder areas of the UK.

In winter, keep plants indoors at 13–18°C (55–65°F). Larger plants may survive lower temperatures, possibly in an enclosed porch, cool conservatory or greenhouse, but must generally be kept frost-free.

Watering and humidity

Water as needed in spring and summer, especially in hot, sunny spells. Reduce watering in winter. See our guide to watering.

Make sure the compost

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. is neither excessively wet nor completely dry. The leaves may curl up if the plant is overwatered, and may go brown and drop if underwatered.

Avocados like humid air. To increase humidity around the plant, mist the foliage regularly, or stand the container in a tray of damp gravel. Make sure the water level is just below the base of the container, so the compost doesn't become waterlogged

Describes soil or potting compost that is saturated with water. The water displaces air from the spaces between soil particles and plant roots can literally drown, unless they are adapted to growing in waterlogged conditions. Waterlogging is common on poorly drained soil or when heavy soil is compacted. .

Collecting, storing and reusing water

Feeding

To encourage strong growth, apply a general-purpose houseplant feed during spring and summer, following the frequency and dose rate recommended on the packet. For the rest of the year, feed every six to eight weeks.

Container maintenance

How to feed plants

Re-potting

Young plants grow rapidly and should be re-potted regularly. Move into a new container that is just slightly larger, as soon as you see roots emerging from the drainage holes. Avoid overpotting into too large a container.

Use soil-based, free-draining compost, such as peat-free John Innes No 3, with added sharp sand

Sharp sand is washed, gritty sand used in potting compost mixes, This is sold for gardening and is not the same as builders sharp sand. .

Established plants

Established plants have been in their current location for two or three years and so have well-developed root systems able to support strong growth with healthy foliage and flowers. should be re-potted annually in spring, into a slightly larger container.

For more on looking after plants indoors, see our guide to houseplants.

Peat-free compost choices

Overwintering

Avocado plants can be moved outdoors in summer, but should be brought indoors before temperatures drop, and kept at 13–18°C (55–65°F) over winter.

Large plants may possibly survive lower temperatures, so it may be worth experimenting if yours has outgrown its space indoors. It may survive in a cool greenhouse or sunny sheltered porch, especially if wrapped in biodegradable fleece, but it is a risk. In very mild parts of the UK or warm city gardens, established plants may even survive outside in a very sheltered, frost-free spot.

See our guide to overwintering tender plants in conservatories and our guide to wrapping tender plants.

Caring for older plants

Avocados generally grow well as houseplants for a few years, but eventually start to decline, becoming spindly with yellowing leaves. This is often due to insufficient humidity and light, so they may fare better in a humid, heated greenhouse or conservatory.

Alternatively, once a plant starts to look past its best, you could simply replace it with a new one raised from seed.

With young plants, once they reached 15cm (6in) tall, cut back the main stem by half to encourage branching. Make your cut just above a leaf.

As the plants grow further, pinch out

Removal of a plant’s growing tip (usually with finger and thumb) to encourage it to produce side-shoots, forming a bushier, well-shaped plant that will bear more flowers and/or fruits. the shoot tips regularly to encourage branching. This will help to create bushy, well-shaped plants.

If an older plant gets too tall and spindly, you can prune it back hard and it should recover well. Still, it is often easier to replace older plants once they start to show signs of deterioration.

It's easy to grow avocado plants from the large seed inside shop-bought fruits. You can either start them off in water or sow straight into damp, peat-free seed compost

Seed compost is a free-draining compost formulated for germinating seed. It often contains a mix of fine materials including sterilised loam, coir, coarse sand or grit. It contains low levels of nutrients, as high levels could damage seedlings. . You can do this at any time of year. Seeds may be slow to germinate, but the resulting seedlings

A seedling is a young plant grown from seed. should grow rapidly.

In water

• Find a wide-necked jar or tumbler and fill with water
• Pierce the avocado seed with four cocktail sticks, about halfway up. Rest the sticks on the rim of the jar, so the seed is suspended vertically inside, with the rounded end just in the water
• Keep at 20–25°C (68–77°F). Change the water regularly, and keep it topped up so the base of the seed is kept continually moist
• The seed will split and a root, then a shoot, will form. This can take eight weeks or more. Once the plant has several leaves and a lots of fibrous roots, remove it from the jar and plant it
• Fill a pot with peat-free John Innes No 2 potting compost
  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. . Plant carefully, spreading out the roots and positioning the seed so it sits vertically, halfway exposed at the surface. Water regularly

In compost

• Soak the seed in hot water, at 40–52°C (104–125°F), for 30 minutes
• Cut a thin slice from the pointed end
• Position the seed upright in a pot of moist, sandy peat-free seed compost, with the cut end upwards, sitting slightly above the surface
• Water to moisten the compost, then place on a sunny windowsill, at 20–25°C (68–77°F)
• Keep the compost slightly damp. Germination
  Germination is the process by which a seed develops into a new plant. It starts with the seed coat absorbing water, expanding and splitting, which allows oxygen and water into the seed so its food reserves can be broken down and used by the embryo for growth. The first root (called the radicle) pushes into the soil to anchor the new plant in place and start absorbing water and nutrients. The first shoot (called the plumule) then grows upwards, out of the soil, towards the light. should take four to eight weeks

Aftercare

• When the main stem has reached 15cm (6in) tall, cut it back by half to encourage branching. Make your cut just above a leaf
• Once it has grown another 15cm (6in), pinch out
  Removal of a plant’s growing tip (usually with finger and thumb) to encourage it to produce side-shoots, forming a bushier, well-shaped plant that will bear more flowers and/or fruits. the two newest sets of leaves so the shoots branch again

After two or three years, avocado plants often begin to show signs of leaf discoloration and deterioration. This may be due to the dry atmosphere and low light levels in our homes.

Re-potting into a slightly larger container with fresh compost

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. may revive them temporarily. They may also fare better in a conservatory or warm greenhouse, or in a warm, sheltered spot in the garden over the summer. Still, it is generally best to regard these as short-term foliage plants, to be replaced every few years.

Fruiting

Avocado plants won't usually flower or fruit when grown as houseplants – they need more humid conditions, as well as lots of space, and patience. Trees can take ten years or more to reach fruiting size and may need to be several metres tall. A large, warm, humid greenhouse or conservatory may be suitable, but even then it can be difficult to get them to fruit successfully in the UK.

Pests and diseases

Several pests and diseases can affect avocado plants, so check them regularly. The earlier you spot any problems, the easier they are to remedy. Look out for:

• aphids
• fungal leaf spots
• glasshouse whitefly
• mealybugs
• red spider mites
• root rots (Phytophthora)
• thrips

Managing pests and diseases without chemicals

Preventing pest and disease problems