Swiss Stone Pine, Pinus Cembra
Being (quite possibly) the cold hardiest of trees, and a nut pine, and one of the few truly cold hardy nut pines that maintains a Christmas tree shape throughout much of its life, you might say that this is the most likely candidate species for the food forest owned by Santa Claus.
- Cold hardiness zones: 1 – 9 (can withstand cold down to -60° F, or -51° C). One of the most cold-hardy trees known.i It ought to be noted, however, that in climates and soils unlike its native lands, Swiss stone pine is listed as only being cold hardy down to zone 3. It may be that other conditions (the ideal soil, moisture, sunlight, etc) equip the tree with what it needs to thrive in zones 1 and 2.
- Soil PH: 5.0 to 7.4ii
- Watering needs: Medium. It can tolerate short periods of wet soil (though not lasting periods), and is drought tolerant.
- Blooming Season: mid to late springiii
- Harvest season: Fall of the following year. Cones take just over a year to grow from flower to ripe cones.
- Fruiting age: 10 – 12 yearsiv
- Average mature yield: ≈ 8 – 23 lbs, or 3.6 – 10.5 kg (based on 80,000 – 210,000 nuts per year)v
- Pollination for nuts: More than one Swiss stone pine tree is needed to produce nuts.
- Size at maturity: 30 – 100 feet tall, 15 – 25 feet wide (9 – 30 by 4.5 – 7.6 meters). * It should be noted that in traditional cultivation, Swiss Stone pine tends to only grow to about 30 – 40 feet tall, but in the wilds of its native climate, it can grow to 100 feet, or 30 meters.vi Thus in climates similar to its native area, it might occupy the canopy layer. In other climates, however, it is likely to occupy an understory layer.
- Sun needs: Full sunlight, though it can tolerate light shade.vii
- Preferred habitat: Cold, high mountaintops, with wind, snow, and little competition. (It’s native lands include the Alps of central Europe, Austria, Czech Republic, France, Germany, Italy, Poland, Romania, Switzerland, Ukraine)
- Growth rate: Slow (6 – 12 inches, or 15 – 30 cm per year, sometimes even slower). Some sources suggest that closer to 2 inches per year may be common. Depending on how ideal the conditions are, the early years may be some of the slowest. In general, trees tend to grow faster the older they get.viii Such growth obviously slows as they approach their full, maximum height. See notes below.
- Natural reproductive rate (and methods): Low, mostly by seed.
- Propagation method: Seed. Pine seeds can be stratified easily outdoors by filling a lidded bucket (poked with holes in the top and bottom) with sand mixed with pine seeds in the fall, filling the bucket with water (which will drain out the bottom holes), and then burying the bucket to ground level. This mimics the seeds being buried by animals and forgotten. Then, in the spring, when it’s warm enough to plant, pull out the bucket and carefully sift through the sand, gently removing the seedlings from the sand. If the propagation was successful, long roots will be extending from the seeds (sometimes 4 – 12 inch roots, or 10 – 30 cm). Carefully plant these in their permanent location with the root poking down and the seed just below the surface. A light mulch layer can help retain moisture and provide additional protection to the seedling.
- Average life span: 500 – 1000 yearsix
- Plant family: Pinaceae
Because of its incredible cold hardiness, Swiss stone pine (also simply called Swiss pine) often lives in areas where few other plants can survive. Don’t mistake this for overall hardiness, however. When grown in warmer climates, where other species thrive, Swiss pine’s slow growth makes it hard for it to compete with other species for the sunlight it needs. This doesn’t imply that it is a high maintenance tree—it’s not. In fact it’s a low maintenance tree.x You’ll just want to plant it in a location it can get the sun it needs to grow at its preferred pace.
In addition to being cold and dry tolerant, Swiss pine is rather wind tolerant, making it a potentially good windbreak.xi
Pine needles are a good bandaid for acidifying soil. They can lower the PH of soil temporarily, giving an acid-loving species a chance to start working on becoming established. The only way this can be of long-lasting help, however, is to continue to lay down new pine needs every six months or so. Even well-established mature acid-loving plants can die if the soil doesn’t remain at that lower PH.
One response to this maintenance problem is to plant pine trees around acid-loving species. Most pine species shed about 1/3 of their needles per year, mostly between late summer and early winter.xii Since Swiss pines grow so slowly (sometimes it can take 30 years to get 5 feet tall),xiii smaller, acid-loving plants (ones that won’t grow high enough to shade out the pine) may be grown near their base to reap the benefits of this needle drop. Such smaller species may live out their entire lives of 5, 20, or even 40 years before the Swiss pine overshadows their need for sun. And in that time, said smaller plants may have expanded far outward, so that succeeding generations continue to reap the needle-drop benefits without the worry of their “canopy” shading them out. Just keep in mind that even with smaller species living out their lives, having children, and expanding outward, those future generations may grow far out of the pine’s needle-drop-reach. Perhaps natural selection and slow adaptation will create a small but balanced ecosystem, so the acid-lovers never grow too far out of reach, and the pine-tree grows at its comfortable, slow pace.
vhttps://pfaf.org/user/Plant.aspx?LatinName=Pinus+cembra+sibirica, the weight listed is a rough estimate based on the assumption that 1 Swiss stone pine nut weighs .05 grams (about half the weight of a commercial pine nut). Commercial pine nut weight reference: https://recipeland.com/ingredients/pine-nuts-8054