I've had excellent germination on seeds sent to me by a fellow sweet potato enthusiast in Sweden, some seeds sent to me from a warmer local and from my own (albeit limited) seeds grown out from short season sweet potatoes here.
Germinating Sweet Potato Seeds:
They seem to germinate easily after scarifying by clipping carefully with a nail clipper away from the root and soaking. You can continually soak until you see roots or soak until seed coat starts to swell and crack. At this point, they could be direct sown into deep containers - they have quickly growing and long ranging roots - or you could monitor them in the baggie method somewhere warm. Took 1-2 days for most seeds with swollen seed coats to germinate fully. The rest took up to a week.
Seedlings start off slowly raising out of the soil, shedding their seed coats and setting out roots. The cotyledons (seed leaves), that look like butterfly wings and betray their morning glory relations, grow quickly in vigorous seedlings.
What I've learned about growing seedlings so far:
1. Make sure you bury the germinating seeds so that the seed coat properly softens and is easily discarded by the unfolding seed leaves. Soaking slightly longer may also help with this process. The seedling should be pulling itself out of the soil.
2. Slow and struggling seeds have not improved much several weeks in. I have about three seedlings that had damaged seed leaves at emergence and now have undersized true leaves. These will be discarded shortly.
3. Seedlings benefit from warmth.
Cotyledon shape varied slightly in shape and colour. The Purple Selfed emerged unsurprisingly as purple though the true leaves are so far light in colour. Most seedlings have emerged with yellow to bronze to purple baby leaves that have greened up afterwards.
I started one set quite early in order to set out robust seedling (because of an issue last year) and started another set recently. Plan to grow on inside and then in the lean to greenhouse before setting out to see what treasures they may grown beneath!
All about growing, selecting and using edible plants in the Ottawa valley.