Anyone with any experience growing Pinus longaeva from seed? I recently purchased 100 seeds from Sheffield's and I wanted to give it a try -- I'm planning on using a standard grow tray/seedling medium and a small grow light in an unheated garage in Zone 7b starting in September. I know I'm pushing the USDA zone the tree will tolerate (especially at sea level), and longaeva appears to be finicky and difficult to keep alive even under ideal circumstances. Any experience out there? Tips?
You'll need extreme drainage (coarse sand / grit, more than soil), and if at all possible, sow the seed directly where it is to grow; the seedlings have very long, slender, fragile roots which are very prone to fungal disease in wet conditions, and don't transplant easily.
Hmm.. that presents a problem on two fronts. 1) I was going to use the seed starter soil that comes with the typical seed tray, and 2) If I need to sow them where they'll eventually grow, I can't use a seed starter tray at all! Two follow-up questions, and thank you for your input in advance! 1) Do you recommend sowing them directly into larger (i.e. trade gallon) pots? 2) Is there a commercially available pre-mixed coarse soil you would recommend? (i.e. a "Succulent & Cactus" fast draining mix, a sphagnum-heavy mix, or a pumice/lava/pine bark bonsai mix?)
Larger pots will be better, but still not ideal - the point about those long roots is they grow as deep as possible, as fast as possible, to get to deep water sources (the only water they get in nature, apart from a little spring snow melt). So they'll still reach the bottom of the pot a few days after germinating, and then have nowhere to go other than round and round in circles, which isn't good. Yep, either a cactus/succulent or a bonsai mix is best. Avoid anything with peat in the mix; for any organic matter, coconut coir or pine bark is better. Peat (in my experience) has a nasty way of wadding down into a soggy anoxic mess - fine for bog plants, but very, very bad for anything that needs good drainage.
Thank you, although this poses something of a problem. The germination rate of longaeva appears to be quite low outside of the native range -- I've seen videos on YouTube where individuals report <10% surviving past the first few weeks. This would represent a huge number of large pots and expensive bonsai mix that are essentially growing nothing. Any way around this? Use 3-5 gallon pots and sow a dozen seeds in each one, perhaps? P.S. This seems to be in contrast to information from the US Forest Service, which states: "The Great Basin bristlecone pine's root system is mostly composed of highly branched, shallow roots [91].." More here: Pinus longaeva
The germination rate (% of seeds germinating) is different to the survival rate (% surviving past the first few weeks); the hope with the highly draining mix is to improve the post-germination survival. The info at the link is referring to mature trees, not seedlings. Those highly branched, shallow roots is most of the total, but does not include the deep 'sinker' roots for access to deep groundwater; these are what developes first in seedlings, to get them through those first few critical years until they are mature enough to spread a wide shallow root system to capture the brief spring snow melt for their year's water supply. I fear it does also need to be admitted: the survival rate in the wild is also exceedingly low! To maintain a steady population, it only needs one survivor to reach adulthood per tree per lifespan. In an average year, you might have 100++ cones per mature tree, each cone with ~100 seeds, every year for a thousand years. That's one survivor out of every ten million seeds....
Ok, so an update -- took your advice and planted these in larger 3" pots using bonsai mix/perlite, and growing with ultraviolet lights (considering they grow at 10k feet above sea level natively). Lo and behold, every single seed germinated. I now have two problems: 1) They all seem to be "helmet heads"; not a single one is growing without the seed coat attached. I know this is abnormal for peppers, but can't find whether or not it's normal for conifers. 2) I have 3-4 growing out of each pot, as I didn't expect all of them (literally) to germinate. What do I do? Wait for one to outcompete the others naturally, or try to separate them?
1) - that's normal for pine seedlings; as the cotyledons expand over the next few days (to a week or so, rarely two weeks), they'll push the seed coat off the top, then the cotyledons will expand further and form like the spokes of a wheel. Expect something similar to this in a few days: File:Clear shot of germinating pine (18432822239).jpg - Wikimedia Commons
I'd be inclined to separate at least some of them right away, while the roots are still short and unbranched (and thus, not entangled with each other). If you're quick with the moves and keep the exposed roots moist, I don't see why it shouldn't succeed.
Ok, so an update and a question! Here they are at a little over 1 year; about 75% of them are still alive and doing well. My question: I'm thinking ahead to repotting these soon (they're currently in 5" deep liner pots). But usually when I repot my maples, I depend on a good amount of soil remaining with the root ball, which makes repotting easy. These, however, are in pure gravel/perlite; since there is nothing compactible, they will be immediately be bare-rooted when i turn the pots sideways. Any advice on re-potting them in that state without damaging the root structure?
They're looking very good! As long as it is cool (around 5°C plus/minus a little) when you transplant, you should be able to do it without too much trouble. Have holes in the new pots ready for them, and fill gently in after putting the roots into the new holes.
Those look amazing. You might consider an experiment: a bit of boiled kelp gelatin, cooled on a cookie sheet, but not yet set, added to each pot to temporarily bind the potting medium for transplant. Drizzle it around the edges of a couple liner pots, just enough to make the outsides clump when it sets. A good soaking shouldn't kill them in a new bigger pot, as long as the 2:1 ratio of coarse sand to perlite holds true. My friend uses it on her cacti, for those with troublesome root systems. But don't try it if you feel uncomfortable risking it.
That's an interesting idea, and I might consider it.. although I had decided to leave them in the liner pots for one more year so that they become almost-but-not-quite root bound, and they develop enough to "hang on" to a significant portion of the bonsai mix when I repot them.
