If you can avoid the serious problems that sometimes afflict the Austrian pine (Pinus nigra), it can be the perfect conifer for a city landscape. It is able to withstand many challenging environmental conditions of an urban environment, such as pollution and salt sprays in the air. It is also quite an attractive pine in the landscape.
I. Appearance and Characteristics
Pinus nigra, the Austrian pine or black pine, is a moderately variable species of pine, occurring across Southern Europe from the Iberian Peninsula to the eastern Mediterranean, on the Anatolian peninsula of Turkey, Corsica and Cyprus, as well as Crimea and in the high mountains of Northwest Africa.
Pinus nigra is a large coniferous evergreen tree, growing to 20–55 metres (66–180 feet) high at maturity and spreading to 6 to 12 m (20 to 39 ft) wide. The bark is gray to yellow-brown, and is widely split by flaking fissures into scaly plates, becoming increasingly fissured with age. The leaves (‘needles’) are thinner and more flexible in western populations.
The ovulate and pollen cones appear from May to June. The mature seed cones are 5–10 centimeters (2–4 inches) (rarely to 11 cm) long, with rounded scales; they ripen from green to pale gray-buff or yellow-buff in September to November, about 18 months after pollination. The seeds are dark gray, 6–8 millimeters (1⁄4–5⁄16 in) long, with a yellow-buff wing 20–25 mm (3⁄4–1 in) long; they are wind-dispersed when the cones open from December to April. maturity is reached at 15–40 years; large seed crops are produced at 2–5 year intervals.
Pinus nigra is moderately fast growing, at about 30–70 cm (12–28 in) per year. It usually has a rounded conic form that becomes irregular with age. The tree can be long-lived, with some trees over 500 years old.
II. How to Grow and Care
Sunlight
This tree grows best in a location that receives full sun, especially when it’s outside of its native zone. Cool, dark areas, particularly on lower branches, can develope fungal issues without the full sun.
Temperature and Humidity
This tree is well suited for USDA zones 4 to 7, hardy down to minus 25 degrees Fahrenheit. This is a species that prefers cool to cold temperate climates; in warmer, more humid climates it will be susceptible to more disease and pest problems.
Watering
For newly planted seedlings or new plants, water once every morning and evening during hot spells in the summer. Do not water midday, as this can cause root burn or strangle. Water plants according to your individual climate and rainfall in other seasons. For mature plants, only water when they are dry, keeping in mind that these plants are drought resistant. For indoor potted plants, spray water on the surfaces of the leaves once every morning and evening when it is dry. Be careful not to provide excess water – this hinders air circulation in a pot, leading to the rotting of roots and the withering of branches and leaves.
Soil
Austrian pine can grow in a variety of different soil types, including bare mineral soil, sandy soil, volcanic ash, calcareous soil, limestone soil, and everything from dusty soil to red soil. Since it is resistant to drought, it will even grow in barren landscapes. However, it grows best in loose, fertile, well-drained, and slightly acidic soil. In the case of too much alkalinity, needles of potted plants will turn yellow and fall, so it is best to use natural mountain soil in pots and containers.
Fertilizing
Feeding is not required for this tree. A 2- to 3-inch layer of mulch under the canopy will help provide slow-release nutrients and keep the soil moist and cool.
Planting Instructions
Austrian pine is best planted in early spring. Ideally, use healthy and vigorous seedlings with soil balls, as this can greatly improve the survival rate. In the case of many lateral roots, the deep main root can be cut. Otherwise, the root system should be protected to avoid damage.
plant in a high, dry, well-drained, and well-ventilated place, with loose soil. In low-lying places with accumulated water, or places with sticky soil, try building a platform or changing the soil before planting. The planting pit should be treated with a basal fertilizer before planting. Newly planted large seedlings should be supported to prevent them being blown down by the wind. Before planting, excess branches should be pruned off. Protect the plant’s shape from damage as much as possible, as this will help to restore growth at a later stage.
Ideally, plant indoor potted plants in the spring, and repot every two or three years in the late fall or early spring. Repotting too frequently will lead to the death of the plant. If the plant is growing weakly, find out the cause of this and change the flowerpot soil, or replant in a larger pot.
Cut back on water before repotting, so as to keep the soil slightly dry. Remove the soil ball from the pot, keeping it whole, and then prune away any old roots from the bottom and sides. Remove some of the old soil from the middle of the soil ball, replace with new soil, apply a small amount of basal fertilizer, and then cover the plant with new soil. Ensure a suitable pot size – a deep pot will easily accumulate water, leading to root rot.
Pruning
For an indoor potted plant, any dead, diseased or damaged branches should be removed. You can then adjust the tree’s shape by pruning branches, pinching buds, and trimming leaves, giving you a better ornamental effect. Prune the plant before all of its needles fall off, so as to obtain a compact shape, richer lateral and side branches, and a better form overall. Pruning should be done during the dormancy period, so as to prevent excess loss of sap and damage to the plant’s vigor.
For a plant in a garden, dense lateral branches should be pruned so as to improve the survival rate. Remove excess lateral branches during the vigorous growth period based on needs, focusing on encouraging the trunk to grow tall and straight. Cut off any diseased or dead branches right away, so as to prevent the spread of pathogens.
Propagation
Pinus nigra, like most species in the genus, is difficult to propagate by vegetative means, so it is usually propagated by seed.
Austrian pines are propagated by seeds found inside the cones. However, the seeds are slow to germinate and develop into saplings and can take as many as five years to grow in pots before they are suitable for landscape planting. Further, some of the named cultivars do not produce viable seeds, so this method works best for the native species. If you want to try seed propagation, here’s a method that works for most pines:
- In the fall, collect some large cones that are fully brown and still closed. Lay the cone out indoors in an open box to dry.
- As the cones dry, the scales will open and the seeds inside can be shaken to release them. If the cones are reluctant to dry, you can put them in a warm spot (100 to 110 degrees) until the scales open.
- Mix the seeds with moist sand, place them in a clear plastic bag, and refrigerate them for three to seven weeks. This cold stratification improves your chances for successful germination.
- Sow the seeds in small pots, just barely covering the seeds, and set them in a bright location at a temperature of about 60 degrees. This may require placing them in a basement or garage under grow lights. The seeds should sprout within 30 to 60 days; continue to grow them in their small pots until spring.
- In spring, transplant the seedlings into larger pots filled with peat-based potting mix. and move them outdoors. The seedlings should be at least 2 inches tall before transplanting.
- Continue to grow the seedlings outdoors in their larger pots until they are large enough to transplant into the landscape. Depending on the variety, this can take several years. Potted trees should be moved to a sheltered location for winter.
Potting and Repotting
Dwarf cultivars of this slow-growing specimen can be grown in large pots, at least twice as wide and deep as the tree’s nursery container. A heavy clay pot is best, as it will resist tipping. Make sure the container has good drainage holes, and use a good-quality peat-based potting mix. Adding perlite or vermiculite will help the soil’s porosity.
Plant the tree at the same height it was in its nursery container, tamping the soil firmly around the root ball to eliminate air pockets. Slowly water until the potting mix is fully saturated. A potted pine tree will need more frequent watering than an in-ground tree, And because nutrients leach out of the soil faster, a potted pine tree will appreciate a yearly small dose of slow-release fertilizer. Avoid heavy fertilizing, though, as this can make the tree grow too fast.
Pine trees generally grow well with confined roots, so repotting won’t be a frequent task. When the tree finally does become root-bound, the best repotting strategy is to carefully remove it from the pot, trim back about one-third of its root mass, then repot in the same container using fresh potting mix.
Overwintering
Once they are mature, Austrian pines in the landscape will usually not require protection against winter cold if they are being grown within their established hardiness range. Young trees will benefit from a thick layer of dry mulch placed over the root zone for winter. If the fall has been dry, water thoroughly in the fall to prevent desiccation over the winter months.
Potted Austrian pines must be moved to a sheltered location for the winter, such as a garage or shed. Another option is the bury the container in the ground up to the rim for the winter months. Left above ground and unprotected, a potted tree’s roots may die.
Pests and Diseases
Common Pests and Plant Diseases
The Austrian pine is prey to many fungal diseases, such as lophodermium needle cast, diplodia (sphaeropsis) tip blight, as well as various wood rots and decays. Remove affected branches as you spot them. Spraying with fungicide may slow the spread, but once infected, it is hard to save a tree.
Insect pests include the European pine sawfly, weevils, and Zimmerman pine moth. The tree is also frequently damaged by yellow-bellied sapsuckers feeding on the many insects that infest it. Spraying with horticultural oil may lessen insect damage, though this is difficult with a large established tree.
The many problems with Austrian pine are so pronounced that the use of the tree is discouraged in many regions.
Common Problems
Aside from its susceptibility to pests and fungal diseases, Austrian pine can be susceptible to wind damage, especially in the winter if heavy snows weigh down the branches. Prune away dead branches as you spot them. With young trees, shake off heavy snow from the branches to reduce weight.
III. Uses and Benefits
- Ornamental uses
In the US and Canada, the European black pine is planted as a street tree, and as an ornamental tree in gardens and parks. Its value as a street tree is largely due to its resistance to salt spray (from road de-icing salt) and various industrial pollutants (including ozone), and its intermediate drought tolerance. In the UK the tree is planted as an ornamental tree in parks and gardens. It is planted with great success as far north as Edmonton, Alberta, Canada.
In both the US and UK most of the specimens planted are from Austrian sources, the P. nigra subsp. nigra and P. nigra subsp. nigra var. nigra seed selections. In the late 1950s and early 1960s, when demand for natural trees was extremely high, its rapid growth, deep green color and low cost made it briefly a popular Christmas tree, but the extreme length of the needles (making it very difficult to decorate) soon led to its fall from favor, and it has long since been abandoned in the US for that purpose.
P. nigra is planted for windbreaks and shelterbelts in the US, recommended for windbreaks in the Northern Great Plains on medium to deep moist or upland soils.
- Lumber
The timber of European black pine is similar to that of Scots pine (P. sylvestris) and red pine (P. resinosa), being moderately hard and straight-grained. It does however tend to be rougher, softer, and not as strong, due to its faster growth. It is used for general construction, fuel, and in paper manufacture.
In the United Kingdom, Pinus nigra is important both as a timber tree and in plantations (primarily Corsican pine subsp.). Recently however, serious problems have occurred with red band needle blight disease, caused by the fungus Dothistroma septosporum, resulting in a major recent decline in forestry planting there. In the United States it is of low importance as a timber species.
In regard to Austrian pine, the fungus Dothistroma septosporum is widespread and rapidly spreading out of control throughout the United States. It is out of control and not recommended for landscaping, especially in groups or rows.
- Ethnobotanical and ethnomedicinal use
In Turkey, this pine (subsp. pallasiana) was and is used in various ways, both topically and internally, as well as for construction and for livestock. Among its uses are curing acne, common cold, osteomyelitis, and viral infections; acting as an oral antiseptic; treating cracked hands and feet in the winter; and sealing wooden roofs.
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