The first rule of growing sweet potatoes is that they are not potatoes. That's right, Ipomoea batatas (sweet potatoes) is not even in the same Genus as Solanum tuberosum (potatoes). So, put away most of what you know about the nightshade tuber and embrace the morning glory tuber.
To start, they like heat. And despite what you may have heard, at least in our part of the world - Ottawa, Canada, they can withstand and even thrive in drought (I have two significant droughts in 2012 and 2016 with bumper sweet potato harvests and no irrigation in sandy drought prone soil to attest to that contrasted with poorer harvests in wetter, cooler years). So you won't want to plant out until after last frost in warm soil, even better if you pre-warm it with clear or black plastic mulch. You'll be planting directly into that.
You won't be cutting them up. You won't be cellaring them in cold, moist conditions. And you will ideally not wait until vines have been blackened by frost to harvest.
So how do you start them?
Using a process called slipping. Typically sweet potato sprouts will develop from one end more than the other though there are variations. Therefore you won't want to cut them up.* Some people skewer them and suspend them in glass jars full of water which will work but a more efficient technique, for me, has been placing them half way into a tray of moist starter mix. If they have little sprouts developing, I place those ends upright. Place them in a warm, sunny spot or under lights. Growth will start slowly with the leaves unfurling and them inching upward but suddenly they'll explode into vines.
Once they are about 4-8 inches or so, you can break the slips off the sweet potato. They may have roots on them or they may not. Either way, then you can plant these in a new tray of moist starter mix to grow on until planting. I've also seen people break the new unfurled sprouts off and grow these on. I've not tried it but it would probably work well too if you stay on top of the watering. The slips will keep coming for awhile so don't discard the tray of tubers right away.
Often sweet potatoes in storage will develop sprouts which will stay dormant for quite some time but grow as soon as the conditions are right. The longest I've tried starting a pre-sprouted tuber is 18 months. (Incidentally sweet potatoes, properly cured and stored, will store a long time.)
All sweet potato slips will be similar if not identical to their parent. Despite the fact that each should be clones, occasionally there are sports - mutations - that make the child plant slightly different from its parent tuber.
I usually don't plant out before the very end of May or beginning of June meaning that I'm slipping sometime in April normally unless I have some project up my sleeve meaning I need to start earlier. Harvest in Ottawa is sometime near the end of September or beginning of October, before first frost as the soil begins to cool. They will be damaged by temperatures less than 10C.
Make sure you harden off your rooted slips before planting out and enjoy!
2016 Sweet Potato Harvest
* Advanced observation - broken tubers often sprout more vigorously, earlier. I do not know what this means but I stand by the don't cut them up advice for now. This is probably a function of a stressed plant part desperately trying to survive.
A tray full of seedlings awaiting selection and planting out. Some growers may seed into cells but I find this dry out more easily with my setup so I scatter and transplant instead. Feel free to do better than I.
You can already see variation at this stage with different amounts of speckle, variation on waviness and serration of leaf margin as well.
But the variation begins much earlier. As this was my first year growing this seed, I did no early selection but once I know a plant, I will often select at the cotyledon (baby leaf) stage if I can. You'll notice a couple variation on the left. The bottom has spotting are lady, the one in the middle is crinkled. On the right, at the first true leaf stage, you'll see speckled in the middle, pure green on the right and just above a slightly speckled leaf.
A spur of the moment cross late in the year seems to have worked! 2016 was a drought year and my plants all looked more than a little thirsty. In the tomato rows, Santorini Paste and OSU blue were the tomatoes that were the least parched looking so I decided to try my hand at crossing them. I had never attempted to cross a tomato before mostly because I had never felt any interest. After all there are so many tomatoes already that I couldn't see how I could add to the already bloated inventory. However, drought tolerance is an interest of mine so I went out one morning to find a very immature looking flower of OSU blue (as per instructions) and removed the boy parts. The fragile looking thing was bagged and pollen from Santorini added the next day with the bag being immediately replaced. All other flowers in the cluster were removed. Honestly I didn't expect anything to happen but low and behold a fruit grew!
It didn't even fully ripen when I picked it and saved the seeds. Doubt crept in again. But the seeds grew not only adequately but vigorously. Now to wait and see what sort of plants and fruit the babies will reveal.
This year's seedlings of a cross between San Michele blush savoy cabbage and Red Rock Mammoth. These are f3s. There was quite a bit of segregation happening in the f2s grown out last year so I'm looking forward to seeing what levels of savoy and purple this generation will have.
Trenching cabbage stems for overwintering in 2016.
Last year, I cut off the cabbage heads (as they won't overwinter here), took backup cutting (which were decimated by aphids) and trenched the stems. This was by digging up the stems, making a furrow, planting them horizontally, covering with soil, straw, more soil and then the whole bit with row cover. They wintered beautifully this way.
Compare this with a uncovered row of a different project, seed from the Toad's Garden, where the heads were removed but the stems were left planted. Most died back (which is typical of older plants) but a few survived. The now two cabbage projects will be separately tunnelled for seed collection as I have a third Brassica oleracea project on the go as well.
Stay tuned for The seedlings of spring and flowering food.
Spring has sprung in the gardens and forest! Lots of perennials popping back up. If you were wondering what they look like, here's part one.
Hablitzia tamnoides is one of the earliest perennials to start to grow. We have ours planted in the forest garden at the base of the fruit trees. They take advantage of the light before trees leaf out.
A couple pictures of the chef's garden which has larger rows for easy harvest compared to the blobs and swirls of the forest garden underplanting. Left is Welsh Onion and right is Patience Dock.
Tuber and bare root sales
If this has you wondering if it might be time to order tubers. I'll be doing a survey and posting numbers shortly.
All about growing, selecting and using edible plants in the Ottawa valley.