Rowan tree: characteristics, care & pruning

Rowans, or mountain ashes, are elegant trees that occur naturally in the UK and have great ornamental value for home gardens. Find out everything you need to know about the rowan tree, from its properties to how to plant one in your own garden.

The rowan tree (Sorbus aucuparia), also known as mountain ash, is a native tree species with brightly coloured fruits that can be found throughout Britain, but tends to grow more in the northern and western regions. Read on to learn how to plant, propagate and care for rowan trees.

Rowan tree: origin and description

Rowan belongs to the rose family known as Rosaceae and is closely related to the service tree (Sorbus domestica), the checker tree (Sorbus torminalis) and the common whitebeam (Sorbus aria). There are many different rowan varieties and crosses with related species. Rowan trees are native mainly to Central Europe, but can be found almost all over the rest of the continent. The single- to multi-stemmed trees or large shrubs are mostly found growing along sparse forest edges, in wild hedges, in fields and on pastures. In Norse mythology and culture, rowans were dedicated to Thor, represented fertility and marked sacred places and courts.

Rowan trees grow into small to medium-sized trees or shrubs and usually live between 80 and 150 years. They reach an average height of 6 to 12 metres and the crown can be 4 to 6 metres in diameter. Rowan trees are vigorous growers and typically gain about 40 cm in height per year. The bark of young rowan tree shoots is chocolate brown with light spots.

Rowan tree flowers, fruits & leaves

Rowan tree leaves are what is known as imparipinnate, meaning they are shaped like a feather. They comprise five to eight pairs of opposite leaflets plus one terminal leaf. Each leaflet has serrated edges and is grey and fuzzy underneath. The foliage often turns a gorgeous red or yellow in autumn. In winter, hairy, almost velvet-like buds appear at the end of the otherwise bare shoots.

Rowan trees flower between May and June. Numerous, white, five-petalled individual flowers grow together in 15 cm wide panicles. Bees love rowan tree flowers, as they provide both nectar and pollen for these little pollinators. Rowanberries are up to 1.5 cm in diameter and resemble small apples with a tiny core. Rowanberry seeds are also similar to apple seeds, being brown and tear-shaped. Rowanberries are round to ovoid and usually orange-red in colour when ripe. There are also rowan varieties with light pink, yellow, orange or violet red berries. While the fruits of the wild form and some varieties are inedible raw, others can be eaten from the bush directly and enjoyed as wild fruits. You can read more about this topic in our article on rowanberries.

Do birds eat rowanberries? The brightly coloured rowan tree berries are an important and popular food source for many birds including song thrushes (Turdus philomelos). As rowan trees do not immediately drop their fruit when ripe, they continue to serve as bird food for a long time during the cold, winter months. When the fruits eventually drop from the trees, small mammals will also help themselves to these vitamin-rich berries.

Common confusions

There are a few trees that rowans are often confused with. At first glance, the shape of rowan tree leaves resembles that of the leaves of common ash (Fraxinus excelsior). But this is where the similarity between these trees starts and ends. Common ash does not produce typical flowers or fruits, but is wind-pollinated and produces winged seeds similar to those of maples (Acer).

The fruits of hawthorn (Crataegus) are reminiscent of rowanberries. Unlike rowanberries, however, hawthorn fruits are not set in large panicles, but in smaller clusters, and are more distributed throughout the tree. Hawthorns also differ in that they have simple, lobed to toothed leaves and the thorny shoots. Just like rowanberries, hawthorn fruits, called haws, are also edible. They taste bland and mealy, but are perfectly safe to eat raw.

Unfortunately, rowanberries can also resemble the toxic fruits of the guelder rose (Viburnum opulus). However, this native shrub has distinctly shaped, lobed leaves and, unlike rowanberries, the fruits are bright red and shiny rather than dull and orange-red.

Planting rowan trees

You can either grow mountain ashes as wild hedges or plant them individually as trees. Rowans grow rapidly when young. They have a graceful, filigree growth habit and pretty flowers and fruits, making them popular additions to home gardens.

Rowan trees prefer acidic to calcareous, dry to fresh, humus-rich, loose and loamy soil. They like sunny to semi-shady locations, whereby the more shade a rowan tree gets, the fewer flowers it produces. Rowan trees need well-drained soil, as waterlogging could lead to root rot over time.

The best time for planting most trees is between October and the end of November, when they go into winter dormancy and have lost most of their leaves. Solitary trees need a planting distance of 3 to 4 metres, depending on the variety. Place hedge plants closer together, to about 1 metre apart. To do this, first dig a planting hole that is about 1.5 times the size of the root ball. If the soil is clayey, sandy or low in humus, mix some high-quality planting soil into the excavated soil, such as our Plantura Organic All Purpose Compost. Our soil is rich in compost and provides a great foundation for humus build-up. It is also a peat-free and therefore environmentally-friendly option.

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When planting your rowan tree or shrub, do not place the root ball too deep. Once the tree and root ball are in place, fill the planting hole with the excavated soil and press down on the soil to compact it around the plant a little. For larger rowans, drive two stakes into the ground at right angles to the direction of the wind. Then, using ties, secure the tree to the stakes. Lastly, use soil to form a watering ring and water your rowan vigorously.

Rowan tree care

Rowans are quite easy to care for. Nonetheless, there are some important care measures to bear in mind when looking after rowan trees and hedges.

Watering and fertilising

Young rowans especially need watering for the first few months to years. Their root systems are mostly shallow and only reach to a depth of about 2 metres. So, prolonged drought can be problematic, especially for young plants.

It is hardly ever necessary to fertilise well-rooted rowan trees or shrubs in regular garden soil. If in poor soil or in the first few years after planting, consider fertilising your rowan to stimulate growth. To do this, apply mature compost in spring or work in an organic, slow-release fertiliser, such as our Plantura All Purpose Plant Food. The soil organisms in this granular fertiliser ensure that the nutrients are released to the plant slowly over the course of several months. Only then are the nutrients available to the plant roots and there is no danger of nutrients being washed out.

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Pruning rowan trees

Solitary rowan trees do not need pruning, but it helps to remove dead wood, diseased or injured shoots in early spring. Rowan hedges, on the other hand, need pruning annually to maintain their shape and to stimulate branching. You must prune rowan hedges if you want to keep them small. To do this, regularly remove larger branches or shorten shoots. In the case of multi-stemmed rowan hedges, saw the shoots off about 10 to 20 cm above the ground. But make sure there are a few eyes remaining, as this is where the rowan tree will sprout anew. Seal large cuts with wound resin to prevent disease. You may need to smooth the edge of wounds with a sharp knife before applying the wound resin.

Rowan diseases and pests

Rowan tree diseases and pests mainly afflict the sensitive, young and not yet well-established trees. Young trees are particularly susceptible to fire blight (Erwinia amylovora), apple canker (Nectria galligena) and coral spot (Nectria cinnabarina). The latter mainly attacks the deadwood of rowan trees, so maintenance pruning is the best solution.

Green weevils (Phyllobius) are a species of weevil that attack rowan leaves. The caterpillars of leopard moths (Zeuzera pyrina) and pear slugs (Caliroa cerasi) can also feed on rowans. However, in most cases they are neither dangerous to rowan trees nor worth controlling. Additionally, the larvae of apple fruit moths (Argyrestia conjugella) and sawflies (Hoplocama alpina) can get in the fruit. Young rowan trees near forests are also at risk of their shoots, leaves and bark being nibbled off by woodland critters.

Are rowan trees hardy?

Rowan trees are winter hardy and can tolerate temperatures below -30 °C. Occasionally, late frosts in spring can cause rowan tree flowers to freeze, but usually most of the flowers survive, so it is hardly worthwhile to protect the tree.

Propagating rowan trees

Rowans can be propagated via cuttings, eye grafting or sowing seeds. You can collect seeds for sowing once the fruits ripen in late autumn. With the ripe fruits in hand, separate the seeds from the pulp and sow them in pots or in a garden bed to a depth of about 1 cm. Rowan seeds require cold stratification in order to germinate. Cold temperatures in winter break down the germination-inhibiting substances in the seeds over a period of weeks. But you can also replicate this process by putting your rowan seeds in the fridge. As the ground temperature rises in spring, the seedlings will begin to germinate. After a few weeks, move the rowan saplings elsewhere if necessary for further cultivation. Rowan trees will also propagate naturally in suitable locations due to birds dispersing the seeds. This makes it quite easy to simply dig up a rowan sapling and plant it in your own garden. It typically takes about five to six years for a rowan tree to flower for the first time.

If you do not have any rowan seeds, you can propagate by taking cuttings or eye grafting. In early summer, look for a green, not yet woody rowan shoot to take a cutting from. Once cut, place the young shoots in moist, sand-enriched growing soil, and leave them to root for a few weeks in a spot with high humidity. Propagation via cuttings does not work for some varieties, in which case eye grafting may be an option. To do this, you will need to take a budded branch from a rowan tree and graft it onto a suitable rootstock.