Scots pine

Identification and origin

Pinus sylvestris belongs to the Pinaceae family. Its natural range is the largest of the whole genus: it covers northern Eurasia from Scotland to the Russian Far East, and from the Arctic Circle down to the steppes, with populations from Spain and the Pyrenees to the Caucasus, Turkey, and Mongolia. It is absent from peninsular Italy. It is the only pine native to Great Britain, where it now survives in the wild only in Scotland. It has naturalized in the northeastern and north-central United States. Its wood is one of Europe’s major timbers.

In cultivation the tree usually reaches 30–60 ft tall and 30–40 ft wide; in the wild it can exceed 98.5 ft. Young trees are conical or columnar. With age it often sheds its lower branches and forms an open, rounded, irregular crown on top of a long bare trunk. It grows fast.

The bark is its best identifying feature: on the upper trunk and branches it is thin, orange to reddish brown, and flakes off; toward the base it darkens and cracks into plates or ridges. The needles, held in pairs, are 2–4 in long depending on the tree’s vigor. Stiff and often twisted, they range from bluish green to gray-green. In the typical form they turn dull or yellowish green in winter.

Each tree carries both sexes. In spring, small yellowish-green to red male cones cluster at the base of new shoots, while reddish-purple female cones appear at their tips. Mature cones, gray to light brown, are about 2–2 in long. They hang in groups of two to four, pointing back along the twig, and release winged seeds in spring.

There are many cultivars. ‘Beuvronensis’, which arose from a witch’s broom, forms a dense dome that barely reaches 12 in – 2 ft in twenty-five years, then 3–4 ft; it is valued in rock gardens and as bonsai. ‘Watereri’, slow but not truly dwarf, has glaucous needles and eventually becomes a small tree. ‘Aurea’, ‘Gold Coin’, and ‘Gold Medal’ turn golden in winter; ‘Fastigiata’ is narrowly columnar, and ‘Hillside Creeper’ stays low and spreading.

Light

Scots pine needs full sun: give it at least six hours of direct sun a day. In shade its needles grow longer and branches that lack light die back. It accepts any aspect, sheltered or exposed, and even coastal sites.

Watering

Once established in the ground, it handles drought well and tolerates both dry and moist soils, provided they drain well. Water a young tree during dry spells.

In a container, the root ball dries out much faster. Water as soon as the surface of the mix starts to dry, without waiting for it to dry deeper down, and let the water drain freely. Pines hate a permanently soggy mix, but they must never dry out completely. Avoid keeping the foliage wet for long, because moisture on the needles encourages several diseases.

Potting mix

In the ground it prefers acidic, moist, well-drained soil, but it adapts to clay, loam, or sand, and to poor, dry, or even alkaline soils. It copes well with urban conditions and transplants easily. In a container, use a very free-draining mix based on coarse mineral materials that lets air reach the roots.

Temperature

It is one of the hardiest trees there is: it suits USDA zones 2a to 7b and withstands cold below -4 °F. Its weakness is heat: it prefers cool summers and suffers in the combined heat and humidity of subtropical climates. A container tree must spend the winter outdoors, because it needs a cold rest period. Still, protect its roots from freezing winds when the root ball is frozen.

Repotting

Repot a young container pine in spring, as the buds begin to swell, or in late summer. An established tree only needs repotting every three to five years. Its roots live in partnership with a beneficial fungus, visible as white threads: never wash the roots, and keep a little of the old mix to preserve it.

Pruning

In the ground it needs no pruning. To keep a compact shape, shorten the young candle-like shoots in late spring, but never remove them all: Scots pine makes only one flush of growth a year. Prune in dry weather with disinfected tools, and cut out diseased shoots as soon as they appear.

Propagation

The species is grown from seed. The seeds need exposure to frost to germinate: sow them outdoors in early spring. Cultivars are grafted in late winter.

Common problems

Yellowing of the oldest needles in early autumn is normal: the tree is renewing its foliage. Yellowing all over, on the other hand, can come from compacted mix that lacks air, overwatering, too little light, or disease. Look at the symptoms before acting.

• Diplodia tip blight: stunted current-year shoots with short brown needles, resin flow, and tiny black fruiting bodies. Spores spread by rain and wind from spring to autumn. Remove affected shoots and fallen debris; excess nitrogen makes the disease worse.
• Pine wilt: carried by beetles, this microscopic worm invades the water-conducting wood. Needles turn grayish green, then brown, and stay on the tree; it dies within weeks or months. Scots pine is very susceptible, especially after ten years of age. There is no cure: the tree must be removed.
• Brown spot needle blight: small yellow to brown spots, needle tips that die while the base stays green, then needle drop in autumn, mostly on lower branches and young trees.
• Lophodermium needle cast: yellow spots that turn brown with a yellow halo; affected needles brown completely and drop in spring. Like brown spot, it needs wet needles: improve air flow, keep water off the foliage, and rake up fallen needles.
• Pests: sawfly larvae, gray-green with black heads, that eat the old needles in spring (pick them off by hand), aphids, adelgids, scale, and pine shoot moths.
• Root rot: honey fungus can attack the roots.

Toxicity

No toxicity has been reported: Scots pine does not appear among the plants listed as toxic to dogs and cats by veterinary references. Another pine, ponderosa pine, is even listed as non-toxic to dogs, cats, and horses, but it is known to cause abortions in cattle. Keep livestock from browsing its needles.