I first learned about the sweet potato plant less than 10 years ago! Weird, huh? Seems like the whole world is eating them in a zillion ways, but here it was definitely not popular until the last few years. You couldn't buy sweet potatoes in any store, except some specialty gourmet shops with imported produce.
At some point a friend of mine shared he worked on a sweet potato farm in the USA while on a student working holiday over there. And he wanted to try and grow them here. So we started researching requirements, weather conditions, soils, watering, feeding, everything we could about that relative of the morning glory flower :)
Two main motivators were the fact it does not get attacked by potato beetles nor does it suffer from the whole slew of fungal problem the Solanaceae family is so susceptible to.
The one main obstacle was our much shorter growing season and the fact sweet potatoes basically won't grow at all in cold soil and cold nights.
So the regular protocol of starting them indoors a couple of weeks before the last frost date and then planting them out definetely wouldn't have worked. We regularly have frosts in April, including late April and the soil is not really warm before mid May, when we plant our beans and corn.
Mind you, that happens maybe 8 years ago. So this is what we devised.
- We will start them much much earlier, indoors.
- We will pot the slips (the new growth stems that come out of the sweet potato) in good soil and grow them indoors on a sunny window for at least 4 weeks.
- We will acclimate the plants by bringing out the pots and keep them outdoors after risk of frost have passed, for at least 2 weeks.
- By that time the plants will be much larger and with better roots than regular bare root slips that are usually used.
- We will prepare a bed by removing the straw mulch so the sun can warm the soil but then return the mulch before planting the slips.
- After that, easy - water once a week, harvest, enjoy.
So here are a few photos of the indoor part of the process.
First we put a couple of sweet potatoes in a deep pot with clean water and keep them in the warmest place in the house until stems start growing.
After the stems themselves have individual roots, we pull the stem off the sweet potato, gently. Take a look at the photo, see how the left stem still does not have own roots, while the right one already has roots.
Next photo shows the separated stem with its own roots. The sweet potato is returned in the pot of water. The stem is planted in a 500 ml pot, but sometimes we use 1 liter, for exceptionally large slips. Water well, keep mosist but not too soggy,
Here are our potted slips on a sunny windows. They are in varying age, that's why we put younger in front to catch more light.
Harvest time
So now we're moving forward in time, up to 3 years ago when we dared grow our first sweet potato crop. Previous attempts were a joint effort and in a garden in a much warmer part of the country.
Still we decided to try and subject the poor plants to a May of 5-8C nighttime temps!
And I'm glad we did, because even on the first year, when we still hadn't figured out all the details and planted only 4 slips, we got a few kilos of amazing sweet potatoes.
Problem was we delayed our harvest too much. You see, regular potatoes you dig out when the above ground portion dries out. Turned out, that's too late for sweet potatoes and most of them were full of holes made by slugs. Still, we salvaged about 30-40% of them to eat.
Next year we got better, smarter, better planing, another variety = better yield and almost none eaten.
And finally, last year, because of the 'Rona we couldn't start many slips in time, but still managed to grow a few plants. Here they are mixed with sunchokes, which we start to harvest about that same time, early October.
So I encourage you to try and grow some sweet potatoes even though you might think you're in a cold spot. If they can grow here, zone 6A, they would be growing in much of the northern hemisphere. Just make sure you start them early on! Let me know if you have any tricks or maybe favorite recipes with sweet potatoes!