Trees

Pruning apple and other fruit trees is especially important in a tree’s first five years, as it allows one to create a structure best suited to the space allocated. Best undertaken just before a tree emerges from hibernation, pruning involves three types of cuts, namely heading, thinning and notching, which can produce highly varied training systems both free standing and high density.

Why Should I Prune?

Pruning is not a particularly time consuming process, as it’s only necessary a few times a year. It allows one to maximise value, promoting plant health and reducing size. It’s essential for many fruiting plants, such as raspberries, gooseberries, and many fruit trees, which often only produce on new wood, with old unproductive wood unable to fruit.

How Does Pruning Affect Plants?

To understand how pruning affects plants, you first have to understand how plants function.

Plants harness the sun’s energy to produce sugars through the process of photosynthesis, which primarily occurs in leaves. They absorb water and nutrients through roots, which flow up by capillary action. As sugars and water move around plants, so can many other substances, such as hormones, which control plant processes.

The most important hormones are auxins and cytokinins, which act to give plants their structure. Auxins are produced in plants’ leaves and flow downwards, while cytokinins are produced in the roots and flow upwards. Auxins act to simulate root and shoot growth and cytokinins the production of lateral buds, which are initiated in a shoot’s tip. Auxins also act to inhibit cytokinin through a process of apical dominance.

When you prune a plant, the auxin-cytokinin pathway is interrupted. Without auxin flowing downwards, apical dominance is broken and dormant buds emerge at the shoot tip. Hence, pruning encourages branching. It also temporarily upsets a tree’s balance between top and bottom, causing cytokinin to become dominant.

Types Of Cuts

The most common cuts practiced are known as heading and thinning. Heading removes part of a shoot or limb, while thinning removes an entire shoot or limb. As pruning causes branching, heading cuts alters a tree’s natural habit, causing unnatural branching. As thinning cuts completely remove a limb, a tree’s habit is unchanged, albeit with missing branches. Heading isn’t necessarily bad, and is commonly used with fruiting plants, but it’s important to note by heading trees you are altering its natural habit.

Training vs Pruning

It’s important to practice pruning and never let a tree get out of hand, as remedial pruning is more challenging and detrimental to the tree’s health than bi-annual maintenance. In the early years of your tree’s life, it’s best to practice formative pruning or training to establish an ideal form. For example, with hedging plants you may cut down to 15-30cm to encourage branching at ground level, giving you a thick screen from bottom to top. Training can take a long time, up to 4-5 years, but gives you the best value for the rest of a tree’s life.

Pruning is more about function and size. It can be used to encourage fruiting, by removing old unproductive wood, or simply maintaining an ideal size. In early years, you may reduce vigour, removing weak or crowded growth. In later years, you may try to promote vigour, removing old unproductive wood, and remove shading branches, maximising sunlight penetration.

Establishing a Framework

Note: most trees will arrive 2 years old and have already been pruned at the nursery. Some steps below may be unnecessary.

The point in the trunk from which the first branch emerges is known as the head. Trees can be low or high-headed depending on what height the first branch is maintained. Low headed trees are structurally stable, easy to harvest and necessarily produce earlier (because less branches are removed). While high headed trees are disadvantaged, they are grown for their ornamental value.

The major branches that emerge close to the head are known as the scaffold branches (and branches growing off the scaffold branches secondary scaffolds). Selecting the best primary scaffold branches is key to establishing productive fruit trees, as because any tree has limited resources it’s best to concentrate on a few scaffolds. Any young tree will have dozens of shoots to choose from but only select the strongest, removing weak growth and those too close together. Optimal scaffolds have wide crotches, characterised by gaps between the trunk and scaffold, which ensures they are mechanistically strong, grow horizontally and have a reduced risk of disease. Wide crotches can be established by weighing down branches.

Training Systems

Left unpruned, trees grow into structurally stable forms able to withstand strong winds and bear fruit load. However, they grow too tall, with shading of the interiors. What is required is known as codominance, whereby the main stem is relegated in importance, and more energy is transferred into the scaffolds on which the bulk of the fruit is produced. Multiple, training systems were developed to establish codominance.

The open centre system involves severing the main trunk up to a 1m of newly planted trees. Early severation reduces the dominance of the main stem and leads to branching. From these branches 3-5 are selected, growing in different directions. The system is ideal for growing and harvesting fruit, but isn’t mechanically strong as the heavy scaffolds are so close together.

The delayed open system involves first selecting a few scaffolds and then severing the main trunk, higher up. A problem with this method is that adequate branching (to be selected as scaffolds) is not guaranteed.

The modified leader system is an intermediary between the two extremes. Here, the main trunk is left to develop until it reaches 2-3m and growth is restricted. Scaffolds are selected as normal, however laterals higher up the trunk are selected to compete with the central leader, reducing apical dominance. The central leader and the laterals are periodically pruned, maintaining the tree at one size.

High Density Training Systems

Better suited to the average garden are high density training systems such as fan, cordon, espalier and stepover, although the latter two are only suitable for apples. Most high density systems require rigid horizontal wires run at intervals, bamboo canes, weights and twine or ties to keep branches in place.

Fan and espalier require more vigorous rootstocks such as the M26/MM106. Stepovers require very dwarfing rootstocks, specifically the M27. With cordons the M27 is again recommended, but the M26 will suffice. It’s important you choose spur fruiting trees as shortening any tip bearers cause a drastic loss in fruit output. Where possible, choose maiden trees; they are not only easier to shape, but also cheaper.

Espalier training involves repeatedly severing a young tree’s main trunk to establish tiers of branching on one horizontal axis. A first cut is made about 40cm above the ground, above a few strong buds. Once the buds have grown, two opposing branches are then tied to galvanised wire, and weighed down, ensuring they grow horizontally. Another branch is then selected to be the new central leader. This one is then headed around 30cm from the first tier, and the process repeated. Up to 4 tiers can be established this way.

With fan training, the first cut is again made about 40cm from the ground, but this time the resultant branches are trained at 45 degree angles, attached to bamboo canes. From each of these two branches, four shoots are chosen, two growing upwards, one on the lower side and another to further extend the arm, and these are again attached to bamboo canes in turn. No central leader is tied in.

Cordons are very simple to set up and are often grown at 45 degree angles. Every year, the leader needs to be shortened by about a third, and branches shortened to three or four buds.

With stepovers, you are carefully bending the central leader until it grows horizontally, tying it to a low-lying wire. The key is to tie at multiple points as to distribute pressure.

When Should I Prune?

Pruning during the growing season allows quick recovery. Just before the end of dormancy is ideal, although pruning in this period may remove flower buds. It’s common to wait till after flowering, but you can continue tidying to midsummer. Avoid pruning late summer and early autumn as it will make plants vulnerable to frost injury.

Avoid pruning during times of drought. Leaves produce a plant’s food, and severe damage to a plant’s production capability can result in death.

Maintenance Pruning

Remove the 3 D’s: dead, dying and diseased wood. These will only worsen your plant’s health.

Remove water shoots and suckers. Water shoots are vigorous shoots that grow from the top of a branch upwards. They will not fruit, but cause crowding and waste energy. Suckers emerge from a tree’s roots, and will compete with the central stem for resources. With grafted trees, suckers will be a completely different variety entirely.

Notching is another cut, similar to heading, but more precise. It involves making a notch into the bark, above a bud, interrupting the flow of auxins, causing the bud to grow into branch. It can be used to force secondary and tertiary scaffolds in the optimal locations.

Additional Tips

Consider how large the secondary scaffolds will end up. If two secondary scaffolds are close when young, they’ll definitely cross when old. Remove one.

Consider biomechanics. A tree adapts to its exposure. Leaving it lopsided, or without too many branches, can cause a plant to sway in the wind, and potentially topple.

Consider shading. Often branches are left on the south side to shade the trunk during peak heat.

Consider rootstock. If you want to experiment choose a vigorous rootstock. Extreme dwarfing rootstocks do not grow fast enough to establish an elaborate structure and are best left as a bush.

Additional Resources

Skillscult is an invaluable resource for pruning, and expands upon all the concepts in this post.

If crabapple trees had an alternative name it should be the utility tree, as you get unmatched value from a single tree. Lately, it’s been common to straightjacket trees as either ornamental or fruiting, but crabapples excel at both, producing wonderful floriferous displays and versatile fruit, great for cooking and attracting wildlife.

What are crabapples and how do they differ from apples?

Crabapples grow throughout the Northern Hemisphere, including in North America. Most species’ fruits are less than 2 inches in diameter, but there are some exceptions to this such as Malus sieversii, the progenitor of the modern apple whose fruits are as large as 7cm.

Sieversii grows on the slopes of the Tien Shan mountain range on Kazakhstan-China border, but once grew widely, stretching all the way to Almaty – the ex-capital of Kazakhstan that derives its name from “fatherland of the apple”. In these wild apple forests, the fruits are eaten by bears, which act to disperse and fertilise the tree’s seeds.

Here, fruits can be as small as 2.5cm, which shows the powerful selection effect humans exerted. Many are sour and are unsuitable as eating apples and there is a wide variety of flavours including hazelnut, liquorice, sweet honey and berries.

Sieversii spread wherever humans travelled, and were a great portable snack, and useful feed for horses. Eventually, it was crossed with Malus sylvestris, the European crabapple, which is native to the UK, and is commonly grown in hedgerows.

Sieversii and sylvestris and to a lesser extent some other crabapple species gave us the apple, Malus domestica. Therefore, it is correct to say all other Malus species that are not domestica are crabapples, even if crabapples and apples are closely related and can crossbreed.

Even today, growers are attempting to introduce genes from sieversii and other crabapples into domestica as they naturally resistant to disease.

Why buy crabapple trees?

Unlike other trees, crabapples produce multiple bursts of colour in a year with nearly every flower turning into a sizeable fruit, which often completely cover the crown. One particularly heavy fruiting variety, ‘Golden Hornet’ literally lights up with a mass of warm golden-yellow fruits.

Often the colour of the bud is different than the emerging flower, and as the buds open at different times, every bloom is multi-tone. With ‘Sun Rival’, the bud is pink-red and the flowers white.

The warm tones crabapples produces when it’s leaves begin to colour up are not given justice, with different varieties turning yellow, orange-red and maroon. ‘Prairie Fire’ spectacular autumn shades is arguably match the best maples and sweet gums.

Unlike the other blossom tree, the ornamental cherry, whose evanescence blossom symbolises the transient nature of beauty, crabapple blossom lasts for weeks, as they flower on both one-year wood and spurs. With the variety ‘Profusion’, flowering lasts for a whole month.

The extended flowering time makes crabapples ideal for attracting pollinators to your garden as well as pollinating your apples. Indeed crabapples are in a class of their own when it comes to apple pollination, and are commonly used by commercial growers in orchards.

They suffer from none of the genetic incompatibility issues apple do (some are too closely related) and can pollinate apples spread across multiple flowering groups. If you are to choose a crabapple for apple pollination, it’s best to choose one with blossom that matches the colour of apple blossom, which is white with a hint of pink. This is because bees tend to move between trees with the same colour blossom.

‘Evereste’ remains the cultivar of choice for apple pollination, not just because of the colour of its blossom, but because it is resistant to apple scab, powdery mildew and importantly, fire blight. It also sits in flowering group 3 and will therefore pollinate most apple varieties.

Much like the rowan’s berries, some crabapple fruits hang on all the way until Christmas. Try ‘Evereste’, which was not named after the mountain, but is a play on the words, “forever resting on the tree”. ‘Comtesse de Paris’ is a great alternative, with its small citrus-like fruits. These fruits can help attract birds into your garden in the colder months, providing a welcome source of nutrients.

Crabapples over 4cm tend to fall off soon after ripening. With more flesh, these fruits are best turned into culinary delights. ‘Jelly King’ doesn’t follow convention with huge, pectin-rich fruits that persist longer than most large fruited varieties. ‘Laura’ makes a great alternative and is nice and compact. Both exhibit good disease resistance.

Crabapples can be used as part of your cider blend to raise the acidity and sugar content. This is useful as most cider apples will need to be paired with an additional tree, as any blend without requisite acidity will spoil.

Now, nearly all crabapples are too tart to be eaten raw, although eating quality will improve in time, as sugar converts to starch. One notable exception, ‘John Downie’ is good to eat when fully ripe, but doesn’t compare to the best dessert apples.

One advantage of crabapples is there small stature, which is well suited to urban planting. With most varieties reaching 5-6m tall, they are much more easily manageable than many popular landscape trees such as Acer, Birch and Willow.

Like apples, they are compatible with dwarfing rootstocks and some varieties can be planted in containers. ‘Sun Rival’ is a lovely weeping specimen with white blossom and bright red fruits that is great as a centrepiece in a small garden.

The Best Crabapple Varieties

The Dark Crabapples

‘Royalty’, ‘Toringo Scarlett’, ‘Toringo Aros’ and ‘Crimson Cascade’ are all examples of crabapples with dark leaves and red, purple, pink flowers and red berries. Both ‘Royalty’ and ‘Toringo Scarlett’ have a spreading habit, and ‘Royalty’ is slightly larger. ‘Toringo Scarlett’ is small in stature and slender, making it ideal for small gardens. While its berries are almost black, it’s flowers are pink with white veins. ‘Crimson Cascade’ makes a nice alternative to the other weeping crabapple ‘Sun Rival’.

The Light Crabapples

The angelic cousins of the dark crabapples, these trees reflect light and are best used as centrepieces. Compact and naturally dwarfing, ‘Admiration’ produces possibly the best flowering display of any crabapple with its dense blooms of white. ‘Red Obelisk’ is an excellent alternative, with slightly darker leaves and deep pink buds.

‘Golden Hornet’, ‘Butterball’, ‘John Downie’ and ‘Comtesse de Paris’ all produce white flowers, followed by yellow/orange fruits. ‘Butterball’ can probably be considered an advance over ‘Golden Hornet’, as its fruits don’t rot on trees. Not previously mentioned, ‘Red Sentinel’ remains a classic with its ruby-red jewel-like fruits that hang on well into winter.

Crabapple FAQ

Are crabapples related to apples?

Crabapples are all species within the genus Malus that are not apples (M. domestica). Apples are produced from multiple crabapple species and exist thanks to human cultivation.

Can you eat crab apples off the tree?

Yes, but they’ll be tart. Crabapples are best cooked or used as part of a cider blend.

Where do crabapple trees grow?

Crabapples are found throughout the temperate regions of the Northern Hemisphere, and are therefore well suited to the UK’s climate.

How big do crabapple trees get?

Most crabapples will reach an ultimate height of between five to eight metres, but there are of course naturally dwarfing varieties and giantitic 12m varieties.

A tree’s habit affects a tree’s spread with upright trees taking up less space than a spreading tree at the same height.

Like apples, crabapples can be grafted onto rootstocks, which help reduce vigour.

You can always prune a tree to reduce its size. In orchards, growers may head a crabapple to reduce its size.

How do you identify a crabapple tree?

Most crabapples have five lobed blossom just like apples, but while apple blossom is white with hints of pink, crabapple blossom can be red, pink and pure white. Crabapple fruits are smaller than apples, being less than 2 inches in diameter, and can be yellow, red, green, purple, and pink.

The native Malus sylvestris has is lopsided, rounded crown and a wide, dense canopy. Bark is grey, and with age, often twisted and covered in lichen.

Are crab apples poisonous to dogs?

Crabapples and apples can be fed to dogs, but need to be cored as the seeds contain cyanide.

Do crabapple trees have deep roots?

Crabapples are not known to have invasive root systems. As with all trees, a tree’s root system grows horizontally as opposed to vertically as most nutrients are found in the uppermost layers of soil.

Can you grow crabapple trees in pots?

Crabapple trees can be grown in pots. Pots act to restrict growth, reducing a tree’s eventual size. With trees in pots, it’s necessary to water regularly and replenish its nutrients periodically.

Do crabapple trees need a pollinator?

Nearly all fruiting plants need to be pollinated to produce fruit. Usually this is done by insects, which transfer pollen from one flower to another. With self-fertile varieties, pollen from the same tree can be used, but with self-sterile varieties pollen from another variety is necessary. Crabapples are relatively common, and are compatible with apples, so pollination is almost guaranteed.

Can you transplant a crabapple tree?

You can transplant any tree, but chance of success diminishes with maturity.

When can you trim crabapple trees?

Crabapples can be pruned late autumn and early spring. Remove dead, dying and deceased wood and suckers and water sprouts.

Why are crab apples called crab apples?

Ostensibly, from the Swedish skrabba, meaning fruit of the wild apple tree. Alternatively, from the noun crabbed, meaning crooked or wayward gait of a crab. Crabapples are often slightly lopped sided and their fruit disagreeable when eaten fresh.

What are some good crab apple trees for small gardens?

Crowned best in show at the National Plant Awards, ‘Toringo Aros’ is one the smallest crabapples thanks to its slender habit and short stature, but also one of the most impactful with its gorgeous burgundy leaves, pretty pink blossom and dark maroon fruits.

A worthy alternative, ‘Red Obelisk’ creates an unmatched spring spectacle with its heavily-blossomed upright branches racing towards the sky.

One of the few weeping crabapples commercially available, ‘Sun Rival’ makes an excellent choice for a centerpiece with white flowers and bright red fruit.

What is the best crab apple tree for jelly?

Try ‘Jelly King’.

What is the best crabapple tree for wildlife?

All crabapples make an excellent choice for a wildlife tree. Most and produced from a mix of species.

What season do crab apple flower and fruit?

Crabapples flower in April and May and fruit from August to October.

Small crabapples tend to hang onto the tree for longer, while larger ones fall off soon after ripening. ‘Evereste’ fruits last until Christmas.

Crabapples make excellent pollinators due to the spread of bloom. ‘Profusion’ flowers for a whole month.

Can crabapples be grown as part of a hedge?

Malus sylvestris is commonly grown as part of a mixed hedge, owing to its dense, twiggy nature and due to the fact it supports over 90 species of bird and insect.

How do I prevent crabapple tree fungus?

As fungus thrives in warm, damp and dark conditions, it’s important to remove plants that shade, crowd or grow into your tree. Trim in early spring to allow light to enter the interior and improve air circulation. Ensure sprinklers do not wet leaves and ensure you pick up dead leaves as potential sources of vectors.

If you are still considering a crabapple tree, ‘Golden Hornet’, ‘Liset’, M. floribunda and Adirondack all exhibit high resistance.

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Jorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!

His ideal afternoon would involve a long walk, before settling down for scones.

Jorge is a journeyman gardener with experience in growing crops.

See all of Jorge’s posts.