Not like the poisonous leaves of the potato, sweet potatoes can be grown for their sweet and juicy, spinach like, leaves and shoots. They can be grown from an existing shop bought organic sweet potato. These perennials like sunny, but not dry conditions and won’t survive a typical UK winter outside. Fertile soil will give you lots of leafy growth.
Despite their similarity in producing tubers that can be eaten and used for propagation, sweet potatoes (Latin name Ipomoea batatas) are very different to our normal potatoes (Latin name Solanum tuberosum). Potato plants, of the nightshade (or Solanaceae) family, have poisonous leaves. Even a tuber that gone green from exposure to sunlight can be poisonous. The leaves of the sweet potato, however, are edible, tasty and useful as a cut and come again leafy green. Blanched or lightly fried they are sweet and juicy and a little spinach like. Raw they can be a little bitter. Sweet potatoes themselves can be used like potatoes and are, of course, sweeter. I think they taste like a cross between a pumpkin and a potato with the texture of potatoes.
How to start growing
If you buy sweet potato plants to grow the tubers, you buy them as sweet potato ‘slips’. These are small shoots removed from a growing tuber. They’re not particularly cheap, but you are more likely to get varieties that will grow well in your climate. You can grow plenty of your own sweet potato slips from a shop bought sweet potato. The only proviso is that you need to buy an organic potato. Sweet potatoes are often treated to stop them from sprouting. Another issue you may face is that the variety you grow slips from may be from growing conditions that you do not have yourself. Because I was never expecting to be able to grow sweet potatoes, I was only growing for the leaves, this wasn’t an issue.
You fill the jam jar with water and wait. It is sometimes recommended that you change the water every couple of days, but I didn’t. In very hot weather, if the water evaporates quickly, the water will need to be topped up. They can sprout rather quickly.
That last photo was exactly a month after the tubers were first set up to sprout. There were no pictures in the intervening 2 weeks because we went away. That is why I transferred it to a pint glass – in order to be able to be able to leave it with plenty of water.
As you can see, within 4 weeks there were already some shoots and leaves that could be eaten. If there are any shoot without roots (slips) you can put the stems into water, and they will root. We ate them as a taste test instead.
They were planted in some fertile compost in pots. As I had plenty of slips, I planted them in several different pots and in the edge of a big pot with a tree (a serviceberry) already in it. Fertile soil can lead to lots of leafy growth and less tuber production, but this is what I was aiming for. They need to be kept somewhere sunny, but also need regular watering in hot weather. My pots were also going to be a bit small for particularly good tuber production.
Unfortunately, I started these far too late in the year (July), which meant that they didn’t have a very long growing season. I didn’t mind as I wasn’t aiming for sweet potatoes, only for the leaves and shoots to eat. The cold weather killed all but one pot that over wintered in the porch. It has just begun to grow its shoots again now in late March. This means I should have something to eat from it in the next few weeks.
So, like potatoes, sweet potatoes are perennial. However, if you leave potato tubers in the ground (and you always inevitably will, as it’s easy to miss the tiny ones that break away during harvest) you will get the plants reappearing each year. Unless your winter is very mild, any sweet potato tubers left in the ground won’t survive the winter. You either need to overwinter shoots in a pot inside or grow new sweet potato slips the next year.
There didn’t seem to be many problems with slugs or snails, but there was a bit of an issue with two tone spider mite. This unfortunately meant removing the affected leaves. I was sad to lose a couple of meals. Spider mite is fine if you catch it early. If you notice too late, you’ll basically have to remove all the leaves that you can see are even slightly affected. A water spray with a few drops of rosemary oil may have helped. They tend to run rampant in hot, dry weather. Just so you know, spider mite are not species specific. They affected both the sweet potatoes and physalis nearby. Make sure you know where you’ve planted the sweet potatoes as the not edible bindweed can look similar. Sweet potatoes are unfortunately not as invasive or persistent. The flowers apparently look similar too, but my plants never got that far.
Use in the lock down
It’s helpful to be able to grow nutritious green shoots from a tuber you can buy in the supermarket, if your nearest garden centre is no longer open for plants and seeds. It doesn’t require any specialist equipment and you could have some greens to eat after a month. It’s entertaining for kids stuck at home to watch them sprout and it’s a useful educational tool for them to see both shoots and roots. It could be expanded to a lesson on cloning if you’re that way inclined (are you feeling rather sorry for my 4 year old?). If you leave some of the leaves and give it a long enough growing season you could then be eating the tubers in autumn.
I’m rather excited to see how the overwintered plants will grow. Hopefully, if I put them in a much bigger pot, or in the ground in a nice sunny spot they will grow potatoes this year. I won’t be too concerned if the tubers fail though, as I’m more interested in leaves for quick food in these difficult times, I don’t know whether this variety grows tubers well in this country (grows leaves well) and my little one refuses to eat sweet potatoes anyway.
Before lockdown I started a new sweet potato in a jar for slips, but so far there hasn’t been anything. I’ll have to wait till the next time we emerge from the house to buy food to secure another one. I wonder if I can find another fun purple one?