The swiss stone pine or Pinus cembra is an exceptional evergreen landscape tree. It is a useful specimen tree from the Pinaceae family. Pinus cembra is a five-needle haploxylon (one fibrovascular bundle per leaf). They can easily be identified by the white stomatal lines on their needles. The swiss stone pine has a sought after pyramidal structure with strong branch unions. Its upright form makes it useful for softening the transition from building walls to the lower planes of the landscape. The needles add a calming blueish-green color to any landscape, especially in the winter. Newer stems exhibit a rust colored pubescence on their surface. Pinus cembra can even be grown in popular edible landscapes because the pine nuts are edible and relatively sizable for consumption (similar to P. pinea). The nuts can be found in 2.5-3” purple-green cones that ripen to a purple-brown in the early fall.

Note: swiss stone pine foliage contains terpene, which is what turpentine is derived from. According to Natural Medicinal Herbs, Higher levels of this chemical are found in trees growing in warmer climates, which can affect taste. The chemical also inhibits the germination of other seed.

Pinus cembra is native to mountainous regions in eastern Europe and parts of Asia. Commercially sold seed is harvested in those regions (ex. slovakia). They are a slow growing tree, so they are best planted in adaptable landscapes. They can tolerate small amounts of shade, but prefer full sun. They are well adapted to hardiness zones 4-7. They are not adapted to tolerate summer heat beyond AHS Heat zone 7 in their native habitat. They are known to be much larger in their native habitat (nearly 100 feet), but these pines usually reach heights of only 30 to 40 feet, with spreads of only 15 to 20 feet when cultivated. They are most often found at heights nearing 12’ with a 6’ spread in most residential plantings. Swiss stone pines tolerate a large quantity of soils, but according to the Missouri Botanical Garden, they prefer sandy loams. When planted in a suitable environment, they are relatively low maintenance trees. They may need watered in times of drought and high heat. They should be inspected for the pests (ie. sawfly and scale) and diseases (ie. blight and rot) that generally affect the Pinus species, however, P. cembra is relatively resistant to most problems (ie. blister rust).

They are a slow growing species (generally one whorl of branches are produced annually), and like most slow growing trees, they can be expensive, especially when purchasing larger forms. If the time is available, seed production can be a great way to diffuse the cost of buying containerized trees like swiss stone pine. The straight species, Pinus cembra, is primarily propagated by seed. The seed-based propagation method is especially applicable for smaller production nurseries and/or amateur growers because the seed is somewhat sizable and easier to handle than most pines. Propagation methods like in-vitro rooting or tissue culture are not yet applicable for this species because the rooting of micro plants tends to result in failure. Swiss stone pine, however, does have a variety of cultivars like ‘Herman’ and ‘Chalet’ that are best propagated through grafting because the seed will not grow true to the parents’ phenotype. This can result because the tee is wind pollinated and monoecious (having separate flowers on the same plant for each sex). The straight species, however, remains useful as an exceptional evergreen specimen in any landscape. The desire to produce a cultivar which is identical to the parent (or not) shall define your propagation method.

• Note: In the wild, these pines depend on animals to steal and spread their cones, so containing the area around the tree is recommended. You can use animal netting or chicken fence to provide protection against curious animals that may wish to open the cones before you do.
• Collect ripened cones in the early fall. The ripened cones of swiss stone pines do not remain attached to the branches like the cones of P. parviflora, so ripened cones can easily be collected off the ground.
• The collected pine cones should be placed in an area with low humidity. They should be contained in a bowl to catch debris.
  • Note: Hands can become sappy when collecting cones. I find that lava soap works well to remove the sticky sap.
• When they begin to break open, the partially opened umbos (cone scales) can be pulled back to reveal the seed inside.
  • Note 1: When manually assisting seed removal, special care is required to not drop or scatter the seed on the floor. Working over a collection container is recommended.
  • Note 2:Viable seed is roughly 1,314 in quantity per pound or 345.1997 milligrams per seed.
• To begin imbibition, seeds should be soaked in room temperature water (mildly warm prefered) A large mixing bowl is suitable. Don’t let them dry out after this step.
  • Note: This step may also serve as a test for viability. Extremely light seeds that do not sink below the water surface, or are visibly undersized/underdeveloped when adding to the water should be discarded, as they are most likely not viable.
• Seal the seeds in bags of moist peat moss with no free moisture. The sealed container or Ziploc bag of seed should be in a dark environment
• To continue, 60 days of warm stratification should be enacted. Warm stratification involves temps of (65-75 F) which is slightly above room temperature. The collection of peat moss and seed should be monitored for mold, which can destroy the seed.
  • Note: Pinus cembra seed is not quiescent, so the stratification process may not be skipped. The warm and cold treatments are part of a simulated seasonal dormancy.
• 120 Days of cold stratification is the next step. Cold stratification is the same as warm stratification, but requires temperatures at (35-40 F).
• Sow seed in pots (bury roughly ⅜” below the soil surface and tamp lightly) with a standard seed starting soil mix.
• Keep the soil warm (slightly above room temperature) and moist.
• Slowly acclimate the new seedlings to the adverse weather conditions of the outside. (Ex. slowly reduce temperature regulations)
• Plant in a suitable environment (as described in “planting”) and watch your Pinus cembra saplings(s) grow.
• *Pre planting moist pots with Pinus cembra seed and housing in a cold frame for two years is a more labor intensive and less recommended method which is also exercised.

• http://www.pinetum.org/classi.htm
• https://www.monrovia.com/plant-catalog/plants/1974/silver-whispers-swiss-stone-pine/
• http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a355
• http://www.naturalmedicinalherbs.net/herbs/p/pinus-cembra=swiss-stone-pine.php
• https://pfaf.org/user/Plant.aspx?LatinName=Pinus+cembra
• https://davesgarden.com/guides/pf/go/128228/
• http://hort.uconn.edu/detail.php?pid=321
• https://sheffields.com/seeds/Pinus/cembra
• http://www.mortonarb.org/trees-plants/tree-plant-descriptions/swiss-stone-pine