Stone pine (Pinus pinea) is an evergreen tree whose rounded, umbrella-like canopy provides plenty of shade. It thrives in full sun and is drought-tolerant. Its pine cones produce the popular and delicious pine nuts, a valuable food crop that can be harvested, dried and eaten.
I. Appearance and Characteristics
The stone pine, botanical name Pinus pinea, also known as the Italian stone pine, Mediterranean stone pine, umbrella pine and parasol pine, is a tree from the pine family (Pinaceae). The tree is native to the Mediterranean region, occurring in Southern Europe and the Levant. The species was introduced into North Africa millennia ago, and is also naturalized in the Canary Islands, South Africa and New South Wales.
Stone pines have been used and cultivated for their edible pine nuts since prehistoric times. They are widespread in horticultural cultivation as ornamental trees, planted in gardens and parks around the world. This plant has gained the Royal Horticultural Society’s Award of Garden Merit.
Pinus pinea is a diagnostic species of the vegetation class Pinetea halepensis.
The stone pine is a coniferous evergreen tree that can exceed 25 metres (80 feet) in height, but 12–20 m (40–65 ft) is more typical. In youth, it is a bushy globe, in mid-age an umbrella canopy on a thick trunk, and, in maturity, a broad and flat crown over 8 m (26 ft) in width. The bark is thick, red-brown and deeply fissured into broad vertical plates.
The flexible mid-green leaves are needle-like, in bundles of two, and are 10–20 cm (4–8 in) long (exceptionally up to 30 cm or 12 in). Young trees up to 5–10 years old bear juvenile leaves, which are very different, single (not paired), 2–4 cm (3⁄4–1+1⁄2 in) long, glaucous blue-green; the adult leaves appear mixed with juvenile leaves from the fourth or fifth year on, replacing it fully by around the tenth year. Juvenile leaves are also produced in regrowth following injury, such as a broken shoot, on older trees.
The cones are broad, ovoid, 8–15 cm (3–6 in) long, and take 36 months to mature, longer than any other pine. The seeds (pine nuts, piñones, pinhões, pinoli, or pignons) are large, 2 cm (3⁄4 in) long, and pale brown with a powdery black coating that rubs off easily, and have a rudimentary 4–8 mm (5⁄32–5⁄16 in) wing that falls off very easily. The wing is ineffective for wind dispersal, and the seeds are animal-dispersed, originally mainly by the Iberian magpie, but in recent history largely by humans.
II. Types of Stone Pine
The stone pine most commonly available is the straight species. Stone pine is the primary source of edible pine nuts in Europe. Twenty species of pine trees produce seeds for consumption, including these three:
- Colorado pinyon (P. edulis): A pine native to North America that can get up to 45 feet tall with a short trunk
- Mexican pinyon (P. cembroides): A compact tree also native to North America, growing 20 to 30 feet tall
- Korean pine, Chinese nut pine (P. koraiensis): A hardy pine with a pyramidal shape, growing 30 to 40 feet tall
III. How to Grow and Care
Sunlight
Italian stone pine thrives in full sun conditions, requiring direct, unfiltered sunlight for the majority of the day to grow optimally. While italian stone pine exhibits a robust tolerance to varying light levels, prolonged exposure to less than ideal light, such as partial shade, may lead to suboptimal growth and health, including reduced vigor and density. Italian stone pine is endowed with needles that effectively capture light, which is an adaptive trait for light absorption, albeit no significant color change or leaf adjustment occurs in response to light variations. Ideally suited for outdoor cultivation, italian stone pine performs best when planted in open areas where sunlight is abundant to meet its light preferences for healthy development.
Temperature and Humidity
As a native of the Mediterranean, stone pine prefers a mildly warm environment without notable temperature swings and relatively dry conditions. It does not do well in very humid environments, where it can be susceptible to fungal problems and rot. Nor does it like environments where there is a vast difference between winter and summer temperatures.
Watering
This is a drought-tolerant tree once established, but in the first growing seasons make sure to give it adequate watering to help root establishment. This species is native to dry Mediterranean regions, so the best environment will mimic those conditions.
Soil
Stone pine prefers well-drained soil that is not too moist. It tolerates a wide range of soil pH levels, though, like most pines, it thrives in slightly acidic soil conditions.
Fertilizing
For italian stone pine, utilize balanced nutrition fertilizers, applying them in early spring and late autumn to support growth phases. The target is promoting root strength, needle health, and robust structure. Precision is key, with recommended quantities specified by the product, ensuring not to over-fertilize and risk root burn. Seasonal variations matter—less is more during dormant winter months. Practical tip: always water italian stone pine after fertilizing to aid nutrient absorption and mitigate fertilizer concentration.
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
While starting stone pine from seeds is the method most commonly used to propagate the tree, it is also possible to propagate from cuttings. Here’s how:
- Using sharp shears, cut a piece of new growth (softwood) that’s about 6 inches in length. The best time to take a cutting is in the late spring or early summer.
- Use disinfected shears to remove any branches or needles from the bottom of the cutting. You will not want any needles touching the soil.
- Use a small knife to make grooves along the length of the cutting.
- Dip the grooved end into rooting hormone and place it in a pot filled with potting soil.
- Keep the soil moist but don’t overwater.
- After a few months tug gently on the new plants to check for root development. Once roots have sprouted, it is OK to transplant the tree into the ground. It can also live in a pot for a few years, as long as the container is deep enough.
How to Grow From Seed
The most common method of propagation is from seed, but seeds will not be viable unless the tree is relatively mature. The tree must be several years into cone production before the seeds can be propagated. Seed propagation is a somewhat involved process, per these steps:
- Harvest the seeds, which can be done by collecting cones and placing them in a warm sunny location until they are fully open. The seeds may fall out on their own, but it is more likely that you will need to break the cone apart to release the seeds. The edible portions of the seeds are contained within shells that you will have to remove.
- Soak seeds in water overnight.
- Place soaked seeds in a plastic bag filled with damp sphagnum moss and place them in a refrigerator for 60 to 90 days of chilling to trigger germination.
- Fill some small pots with seed-starter mix (or a mixture of sand, peat moss, and vermiculite), and plant the seeds about 1/4 inch deep.
- Spray the surface with water and place the pots in a sunny window. Check daily and keep the soil surface moist with spraying.
- As the seeds sprout, thin out the weaker seedlings.
- Grow the plants in their pots for a full year until branches begin to form. They are then ready for transplanting into a garden location.
Potting and Repotting
Thanks to their slow rate of growth, stone pine trees can be grown in containers for many years indoors. A terra-cotta container is best because it lets excess moisture evaporate, and it is heavy enough so the tree won’t topple over.
A potting mix of two parts compost (redwood compost works well) along with one part pumice or perlite should work well as the growing medium for your tree indoors. Keep the soil moist but not too wet. A good guide is that when the top 2 or 3 inches of the soil is dry, it is time to give it a drink. Keep your potted pine in an area where it gets bright light, but avoid the strong midday sun. Also, keep it away from heat sources such as a fireplace, radiator, or air vents.
Stone pine roots tend to grow at a rapid rate, even though the tree itself grows slowly, so you may want to shake the tree out of its container every six months to see if it has become rootbound. If so, it’s time to repot.
Overwintering
If you live in an area with big seasonal temperature swings and are growing your stone pines in pots, you can keep them outdoors from late spring to early fall and bring them back inside well before nighttime temperatures get chilly. Before bringing them back inside, you can give them a good soaking and then use ice cubes to keep them moist during the colder months.
When mulching stone pines outdoors, leave a space of a few inches between the trunk and the mulch. If they touch, this can cause problems like fungal diseases and make it harder for the tree to get oxygen.
Pests and Diseases
Common Pests & Plant Diseases
Few serious disease problems are found with this species. You may see episodes of pine needle cast—a fungal disease that causes the needles to turn brownish-red and fall off. Such an issue can be treated with a fungicide containing neem oil or copper salts.
Sometimes though, the issue could be caused by bark beetles. These pests cut tunnels in the inner bark layer, beneath the outer bark. They are hard to treat with pesticides, so the recommended control is to remove and destroy affected branches. A major infestation may require the removal of the entire tree.
Other possible pests include Western conifer seed bugs (Leptoglossus occidentalis), which rarely harm the tree permanently, though they will reduce seed production.
Common Problems
Stone pine trees are quite durable once established, but they can be temperamental in the early years and are hard to restore if problems arise. Watch for these issues if you plant a stone pine.
Needles Browning
If you notice your pine needles turning brown but have ruled out a fungus or beetle issue, then the cause is likely root rot due to overwatering or poor soil drainage. If the tree is young, you may be able to trim away the damaged roots, correct the drainage issue, and still have a successfully growing tree.
Snapping Branches
This tree cannot typically handle high winds. If you live in an area that experiences high winds regularly, this tree is best avoided, as its somewhat delicate branches will easily snap off during big gusts. These trees are also easily damaged by ice.
III. Uses and Benefits
- Ornamental uses
The tree is among the current symbols of Rome. It was first planted in Rome during the Roman Republic, where many historic Roman roads, such as the Via Appia, were (and still are) embellished with lines of stone pines. Stone pines were planted on the hills of the Bosphorus strait in Istanbul for ornamental purposes during the Ottoman period. In Italy, the stone pine has been an aesthetic landscape element since the Italian Renaissance garden period. In the 1700s, P. pinea began being introduced as an ornamental tree to other Mediterranean climate regions of the world, and is now often found in gardens and parks in South Africa, California, and Australia. It has naturalized beyond cities in South Africa to the extent that it is listed as an invasive species there. It is also planted in western Europe up to southern Scotland, and on the East Coast of the United States up to New Jersey.
In the United Kingdom it has won the Royal Horticultural Society’s Award of Garden Merit.
Small specimens are used for bonsai, and also grown in large pots and planters. The year-old seedlings are seasonally available as table-top Christmas trees 20–30 cm (8–12 in) tall.
- Culinary uses
Pinus pinea has been cultivated extensively for at least 6,000 years for its edible pine nuts, which have been traded since early historic times. The tree has been cultivated throughout the Mediterranean region for so long that it has naturalized, and is often considered native beyond its natural range.
- Other uses
Other products of economic value include resin, bark for tannin extraction, and empty pine cone shells for fuel. Pinus pinea is also currently widely cultivated around the Mediterranean for environmental protection such as consolidation of coastal dunes, soil conservation and protection of coastal agricultural crops.
