On Growing, Harvesting, and Curing Sweet Potatoes
We love sweet potatoes for many reasons:
#1. They are easy to grow and pest free – provided that you can protect them from mice (they eat the tubers) and deer (they eat the vines)
#2. They are delicious (if properly cured – I’ll tell you how)
#3. They are versatile and can be used in all kind of dishes, from simply baked or steamed; in soups or savory puddings; in pancake and muffins; mixed with meat in casserole (for example this recipe with lamb or beef); turned into pie or cakes.
#4. They keep for a long time at cool room temp (provided they are properly cured after harvest). No need for a fridge or a root cellar.
#5. They are easy to propagate (but you need to plan for it).
#6. The tender shoots are a delicious summer green – particularly when quickly sauteed with onion, ginger, and finished with a splash of coconut milk.
I already wrote about how to propagate sweet potatoes. This year, I went one step further: I filled a tray with light weed-free soil,nestled my “seed stock” sweet potatoes in there (at harvest time, I picked a few tubers to save for propagation, and labeled them so we would not eat them by accident), placed the tray on a heat mat, and created a clear tent with hoops & a large clear (clean) trash bag held by small clips. They loved it, and produced lots of slips – lots more than I can use for myself.
Of course you can buy slips, and sometimes plants. But is it easy to produce them and I am in total control of the timing. No back-order or anything like that! It also provides several extra weeks of growth (compared to mail-order slips) which translates in a bigger harvest at the end of the season.
Wait for planting till there is absolutely no threat of possible frost. For me that means mid-May. I do look at the long-range forecast in early May, and sometime (especially if I have extra slips), take a chance in early May – with row covers at the ready. Sweet potatoes are tropical plants from the lowlands and they cannot manage cold. They will take all the heat you can give them. If you receive slips when the weather is not yet warm enough, pot them in 6″ or 8″ tall pots, they will start developing roots and can wait happily for a few weeks.
I used to plant my sweet potatoes in the ground, until 8 years ago, when the tubers (while still growing) were eaten by mice. The above ground plants did not show any sign of damages, so I did not know the extent of crop loss until I went to harvest. We lost 90% of our crop that year! Ever since I plant the sweet potato slips (or plants) in sturdy 15-gal containers, or 1/2 barrels (about 25-gal) in full sun. I use a mix of garden soil, composted horse manure, and rehydrated coconut coir (I used to use peat) and one slip per pot. They look lonely in their big tub, but do not be tempted to plant more than 1 per container. It really will not increase your yield. It just takes a few weeks for the plants to take off, and then they grow and grow and grow. We water well and often.
Throughout the summer, I pick vine tips for eating. Just the tips, so they are tender, and cook quickly.
By August, the sweet potatoes vines have created a dense cover, which – by mid-October is threatening to take over the bee yard (in spite of the deer eating all the vines that grow on the other side, through the fence). Good thing that it is then time to harvest before frost damages the plants!!!! The first frost is generally in late October/early November for us, and I let the sweet potatoes grow as long as the weather permits; since they are perennial, the longer the growing period, the heavier the harvest.
Finally comes a day in mid October when the nights are consistently under 50F. It’s time to harvest. It’s easier as a 2 person job. We first cut off the vines at the soil line and drag them to the compost pile. And then we dig the sweet potato out with our hands first, and finally tip out the very heavy containers to get all the tubers. Sometime, they are all the way at the bottom of the pot. There is a video of the the actual harvesting in 2019 on our Facebook page.
Our typical harvest is about 10 lbs of tubers for every slip. Sizes vary, in part depending on the cultivar planted: Beauregard, for example, tends to produce huge tubers – some have weighted over 5 lb EACH; that’s not a problem for texture or taste (a huge sweet potato is just as tasty as a small potato), but it is a lot of sweet potato at once! Better to use those for a large dinner party, roasted or steamed.
As we dig, I select a few good looking healthy tubers from each cultivar I grow and set aside them, labeled with their name. Those are my “seed stock” for the following years – the tubers from which I will produce slips. The sweet potatoes are sorted immediately by size, and washed with a water spray. Any damaged one is set aside to be eaten very soon. The rest (including the seed stock) goes into the curing chamber.
Sweet potatoes should be cured to develop flavor (starch turning into sugars), and to harden their skin. Both phenomena allow the tubers to stay in good shape, edible, AND delicious, at cool room temperatures (60F/ 15C) for months. We often eat sweet potatoes from the fall harvest until late spring or early summer the following year.
Curing – in that case – simply means to keep the sweet potatoes above 85F (29C) with a high humidity in a dark space… but with air circulating. For about a week. We set up wire shelves in a shower stall, with a space heater, and a fan. The shower is blocked off with a sheet of light plywood. Depending on the year, we either set a bucket of water with a cloth hanging out of the water to wick moisture out to humidify the air (the simplest), or I use the shower head once or twice a day to thoroughly wet the sweet potatoes (removing both fan and the heater before watering, and putting them back afterwards – which is more thorough and more work).
Once cured, I simply store them between sheets of newspaper in crates. I check the remaining stock a few times in the winter and remove the few that go bad.
Then comes March; the cycle starts again, with forcing my seed stock to produce slips.