Sorbus (Rowan Trees & Whitebeam)

Planting

Sorbus grow best in a sunny site with well-drained soil, a pH of 6.0-7.5 is ideal.  If your drainage is poor, improve it - wet or boggy conditions can kill them. If this is not possible mound up the soil and plant on top to keep the roots out of the worst of the winter wet.  The ‘mountain ashes’ prefer deeper loamy soils, they are unlikely to thrive in shallow chalky soils. Whitebeams in contrast are much better adapted to shallow chalky soils.

Plant your trees as soon as possible after receipt, allowing sufficient space for them to grow. If allowed to develop naturally most Sorbus will reach a final size between 5 and 8m (15-25ft) in height by 3-5m (10-16ft) in spread, though there are exceptions. Compact bushier varieties like ‘Beissneri’ or ‘vilmorinii’ seldom exceed 4m (13ft) in height and spread. Please consult our individual variety descriptions if unsure.

Should weather conditions be adverse (i.e. if the ground is frozen or too wet to plant), then heel-in the trees temporarily 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.
 

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.
 

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 OR HALF STANDARD - Virtually no pruning will be needed throughout the life of the tree. Should any shaping be necessary the ideal time to prune is in July or August.  Sorbus resent regular restrictive pruning.

FOR A MULTISTEM OR LARGE BUSH - Cut back the main stem when planting to around 75cm (30in) tall to encourage plenty of new shoots from low down.  Thereafter no further pruning should be needed throughout its life. Should any shaping be necessary the ideal time to prune is in July or August.
 

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.
 

Pests & Diseases

Sorbus 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.

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