Malus (Crab Apple Trees) Growing Guide

Planting

Crab Apples need a sunny site and a neutral soil to grow, flower and crop well, a pH of 6.5-7.5 is ideal.

Plant your trees as soon as possible after receipt, allowing sufficient space for them to grow. If allowed to develop naturally most varieties will reach a final size of 5-6m (15-20ft) in height by 3-5m (10-16ft) in spread, though there are exceptions. Weeping varieties like ‘Sun Rival’ or ‘Royal Beauty’ seldom exceed 2.5m (8ft) in height and spread, while dwarf varieties suitable for the patio such as ‘Laura’ may stay below 2m tall by 1.5m across (7ft by 5ft) or even less if summer-pruned. Please consult our individual variety descriptions if unsure. Crab apples may also be trained as fans or espaliers if planted along a wall or fence in which case space as above, or as cordons when they may be planted 60cm (2ft) apart.

Should weather conditions be adverse (i.e. if the ground is frozen or too wet to plant), then the trees should be temporarily heeled in until conditions improve. Dig a hole or shallow trench, lay the trees at an oblique angle and cover the roots loosely with sufficient soil or compost so that no roots are exposed to the air.

Improve the soil structure by thorough digging before planting, ideally to a depth of about 45cm (18in) - two spades deep. Mix in plenty of well-rotted manure or compost.

Soak the root system in water for 1-2 hours. Dig a hole comfortably large enough to take the root system (so the roots can be evenly spread out), ensuring the top of the root system is level with the surrounding soil or up to 2.5cm (1in) deeper. Apply rootgrow™ mycorrhizal fungi directly to the roots before planting - this will help the tree to establish quickly. Tread firmly and water-in thoroughly. Stake the tree and secure with tree ties to prevent rocking whilst the roots establish.

TO GROW IN A POT - Crab apples can be grown in pots. Initially pot your tree up into a container that is approximately 30-40cm (12-15in) in diameter using a good quality free draining loam-based compost such as John Innes No. 3. The pH. should be relatively high (between 6.5 and 7.5).

Watering

Keep the soil around the tree moist throughout the first growing season. In later years only water during prolonged dry spells, drenching thoroughly no more than once a week.

IF GROWING IN A POT - Your tree will need daily watering during the growing season, in extremely hot dry weather maybe even twice a day. Aim to keep the compost moist at all times, but do NOT leave it standing in water or you risk drowning the roots.

Weeding & Mulching

Keep the area around the tree free of weeds, particularly during the first year. An annual mulch of well rotted compost will greatly improve moisture retention and soil structure, and help suppress unwanted weeds.

Pruning

FOR A STANDARD - Virtually no pruning will be needed throughout its life. Should any shaping be necessary the ideal time to prune is in July or August.

FOR A CORDON - Trim back all side shoots to 10cm (4in) spurs and the leader by half. In later years in late July trim back all new side growths to 10cm (4in) spurs and shorten the leader by a third. Then in winter just remove any late growth made from these spurs after the summer pruning.

FOR AN ESPALIER – The aim is to train the side branches in pairs out to left and right in a series of horizontal tiers approximately 45cm (18in) apart. It is usually easier to set up horizontal wires or bamboo canes at the correct 45cm (18in) spacing on the wall or fence before planting the tree, together with a vertical bamboo cane to keep the main stem straight. The structural pruning to form the tiered espalier shape is done in winter, each arm is then summer-pruned as a cordon.

Structural pruning (for an espalier):

At time of planting if there are two suitable side-shoots at around 45-50cm above soil level these can form the lowest tier, carefully tie them out to the lowest wire or cane, one to each side. Do this carefully to avoid breaking them. If they seem particularly stiff don’t bend them right down to the horizontal in one go, this can be done in a series of steps over a month or two if necessary. If there are no suitable side-shoots, cut the main stem back to a bud 50-60cm above soil level then continue from (2) below. Tie the main stem (leader) of the tree to the vertical cane. Trim back any other side shoots to spurs about 10cm (4in) long.
To create the second (and subsequent) tiers. If the leader already stretches more than 50cm (20in) above the first tier, prune it to a bud at about 50cm (20in) above the first tier. You now need 3 shoots to grow from just below this cut: the central one will be the new leader, the other two will form the next tier of your espalier. During their first summer start to train them outwards at an angle of approximately 45° away from the vertical. This will prepare them to be tied down to the horizontal wires the next winter. If the main shoot reaches less than 50cm (20in) above the previous tier allow it to grow on for a year then cut it back the following winter to a bud 50cm (20in) above the previous tier. In this way an extra tier will be added every year or two, depending how vigorously your tree is growing.

Maintenance pruning (for an espalier):

Each summer trim back all new side-shoots that have grown from the arms and the main stem to 10cm (4in) fruiting spurs. Leave untouched the 3 shoots growing at the top of the tree to form the next tier and the outermost new shoot on each arm which is extending the spread of the espalier. These new shoots will be growing outwards and upwards, wait till winter to tie them down to the horizontal wires or canes, at which time trim them back to about 30cm (12in) long extensions.

FOR A FAN - Plant your tree about 45cm (18in) away from a wall or fence and cut it back to about 60cm (2ft) high. Then in summer tie out 8-10 strong shoots (leaders) in a fan. Each year thereafter in late July trim back all new side shoots to 10cm (4in) spurs and shorten each leader by a third.

FOR A PATIO TREE - Trim annually in late June or July to keep it neatly shaped.

Feeding

Most garden soils contain sufficient nutrients for a tree to grow healthily, though a balanced general purpose top-dressing (such as Fruit Feed) in early spring can be beneficial.

IF GROWING IN A POT - Your tree will need regular feeding during spring and early summer. For application rates follow the instructions on the packaging. To keep the tree growing healthily it will also need fresh compost to root into each year. In the early years this is best done by potting the tree on into progressively larger pots. Once the final pot size has been reached (we would recommend a pot that is 45-50cm [18-20in] in diameter), remove the tree from the pot in late winter each year, cut or chop away about a third of the rootball from the bottom, part fill the pot with fresh compost and re-pot.

Pests & Diseases

Crab apples are susceptible to a number of pests and diseases, common examples are aphids (greenfly), mildew and scab. In a typical garden setting however these are not normally severe enough to need any treatment and many varieties have good natural disease resistance, again check the individual variety descriptions if in doubt. Any chemicals should be used strictly as per the manufacturers instructions.

Further Information

For further information refer to RHS Growing Fruit by Harry Baker.

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