Growing sweet potatoes

(Originally posted in 2018)

I have just harvested my sweet potatoes in the last week or so and the crop was very successful (particularly pleasing as this was my first attempt at growing them). I hadn’t even thought about growing these until the beginning of this year, they are not something I have a particular taste for but my other half is quite partial. This gave me the motivation to grow them; knowing that they would be eaten and enjoyed being a kind of reward for the time and effort growing them. I say effort – based on this experience I would say they are generally quite easy with a few basics being considered. Most of what I read before starting, talked about people in the UK largely growing them in polytunnels or a greenhouse, I have these but the space is spoken for. With that, the only choice was outside and my expectations were lowered a little with this in mind, as it happens outside was fine but I didn’t know that at the time.

As this was my first attempt I went for the easy option and bought 5 small rooted plugs from Mr Fothergills. If you are more adventurous you can try creating your own ‘slips’ either from one you have grown previously or buying an organically grown sweet potato from a super market (from what I have read). Being the first run, a solid start was always going to be important and this was the best way of trying to assure that. The rooted 3cm plugs arrived at the very beginning of May and I got these planted up straight away into some 3inch square pots using regular garden compost. They lived in the greenhouse for a short time in these pots until they started to show some signs of growth and the late cold snap had passed – frost is an absolute no for these!

Potted on arrival

When it came time to planting them out I decided to dedicate one entire raised bed to them (1.3 x 3.5m) – I did have a single row of onions at each end. My soil is quite sandy (I may have mentioned this in previous posts) which is a mix of good and bad, on the plus its difficult to get the soil too water logged, but on the bad it has less nutrients and retaining them is more difficult. To help with this I made a good sized planting hole for each young plant – at least a foot cubed even though they were only in 3inch pots. I mixed into each hole about 60% garden compost and 40% of the soil that was dug out. This was for two main purposes, primarily to aid in some moisture retention and secondly the extra nutrients that the compost contains.

I mention moisture and this is one of the two things about growing sweet potatoes that I found out. They are originally from tropical regions of south America, so obviously they like the heat. The other thing I was advised was that they don’t like to get too dry – this doesn’t mean water logged though; so just be aware depending on the conditions.

The first few weeks of being outside I had the plants under clotches, a little extra safety net in case of a drop in temperature overnight that wasn’t forecast. It also helped to get the soil temperature up a bit higher early on giving a boost to the early growth. This seemed to work as it didn’t take long before the first shoots from the vine forced me to remove the clotches. I wasn’t really prepared for how much top growth there would be but received a handy tip online – create some form of frame for the vines to be threaded through and grow up. I used some 4 foot wire fencing with 2 inch gaps – plenty of room to thread through this way and I believe this helped. It kept more of the vines exposed to sunlight than if they had been left to roam free, it also kept them off the nearest other raised bed. The fence went round 3 sides of the bed leaving the side with the most sun open so as not to deprive light from the centre.

Most of the rest through to harvest was fairly straight forward – I keep them watered and weed free as much as possible. The top growth soon filled out the bed and before the end of the growing season it had reached the top of the 4 foot fence as well. I am told you can eat the young leaves from the vine (not unlike you might with spinach) but I didn’t try this, I wanted all the energy going into developing the tubers uninterrupted. The plants got a feed of liquid seaweed a couple of times during the season just as a small boost, I can’t really say if it helped or not to be honest though. What I’m sure did help was the blisteringly hot spell we had this year – 6+ weeks in my area with just warm sunshine often into 30 degrees. It did mean keeping the watering up was important but that went for the whole garden as well. What I did get as an early indicator during the summer was a few flowers on the vines, not double figures but it was better than none and made me a little more confident that things were going well.

We had the slightest hint of frost a few weeks ago and a small number of leaves on the vines were caught by this. The next weekend I decided it was time to have a look and lift a test root to see how things were going. Important lesson learnt here! Be careful when lifting these tubers, they are a bit fragile so snap and mark easily. I didn’t realise this so went to the first root with the same manor I would regular potatoes – not a disaster but certainly realised quickly this was not they way for the others when it was their turn. That said, even with the slightly brutal approach I was left with a really good harvest off a single root.

1st harvest

The final four roots I lifted last weekend (7th October) with a great deal more care. Using my small hand trowel, digging out around each plant and tuber which paid off with a much tidier harvest. Before the digging I should add I removed all the top growth, from the four remaining plants I filled 3 barrows with this which gives an idea just how much growth it had put on.

Main harvest

The last and an important stage is to cure the tubers – you can’t just eat them after digging like a potato. It is the curing process that develops the sweet flavour. I have read a few bits on this and the advice is a bit varied but not drastically, curing time it seems is usually one to two weeks. Temperature was slightly more varied with temps anything from 15 to 30 degrees, I have opted to try for the best temperature I can achieve at the moment. They are curing in my polytunnel inside some of the propagators which should get a good temperature during the day and preserve some of it into the evenings. I don’t know if this will work out but I am hopeful and will report back later on twitter once some have made it to the most important test – eating!

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