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In yet more exciting news about actual practical plants, a European research and development group for alternative sources of natural rubber have hit a benchmark recently as one of their partner companies prototyped natural-rubber tyres, made from two plants that can be grown in temperate climates - Guayule in warm-temperate regions and Russian Dandelion in cold-temperate areas such as here in Scotland.
|Tyres from weeds by Dutch firm Apollo Vredestein :)|
On more practical temperate plants, from what I've tried here so far, germinating tree and large shrub seeds still seems to be very hit-and-miss. After I had only two strawberry tree seeds germinate out of about a couple dozen tiny seeds sown (they were so small that trying to count them looked pointless), the first one to germinate didn't grow more than its initial pair of leaves, then later shrivelled up and died from what looks like a fungal infection.
|Two Arbutus Unedo seedlings, 1 month after sowing. Re-potting the right-hand one after its original container got knocked over was likely another factor in its demise, though its growth was already stunted by then.|
|My only surviving Arbutus Unedo seedling up close, soon to be re-potted. Fortunately they are self-fertile, so I just hope this one is as fruitful as it is disease-resistant.|
|After sowing a tray of 24 mulberry seeds, 12 germinated within a week while a 13th one seems to be lagging behind weakly.|
While disposing of monkey puzzle seeds that had failed to germinate, I noticed one thing that might have been a factor in me only getting 1/4, as there was what looked like a thick tap-root trying to grow straight down from one of the failed seeds, which of course didn't get far before it turned a right angle on the bottom of its pot, since I was quite stingy with some peaty potting mix when I sowed them.
|Monkey Puzzle taproot (trimmed slightly).|
So, more than half of the various dormant seeds that I have tried to cold-stratify in a fridge have been afflicted by mould, though all the jars used were washed with boiling water before they were soaked. My best guess is that either the seeds already had such fungi and bacteria on them when they were dropped in to absorb water, or that airborne spores entered the jars when they were opened to put seeds in and later drain water out before chilling.
Since creating an even more scrupulously sterile atmosphere for the seeds would involve a disproportionate increase in effort, this lead me to wonder whether some natural fungicide could be put in containers used for cold stratification, so I'll be testing that with my next few batches of seeds that I keep for sowing next spring. From this study, clove or cinnamon essential oils sound like promising candidates.