I got serious about sweet potatoes this year.
I have been growing them successfully for a couple of years now, but my
production has been inconsistent. I have grown some dandy, perfect, awesome
looking sweet potatoes. I’ve also grown some massive, gnarly, wrinkled, and
crazy looking ones that tasted fine but looked terrifying. I was okay about
eating the bizarre looking ones, but with running the CSA this year I want to
make sure that they are as pretty as well as delicious.
So I followed the suggestions in Ken Allan’s book about growing sweet
potatoes. Ken Allan is a local author/gardener who specializes in sweet
potatoes. He’s the “local sweet potato guy.” I’ve always wanted to be one of
those “experts” in a field … that “’fill-in-the-blank” guy. Totally immersed in
and knowledgeable on every aspect of a subject. I think people around here see
me as that “renewable energy guy” thanks to the numerous Green Energy Fairs
that I have organized. And that’s good. But with interests in energy and food
and sustainability and personal resilience I’m afraid I’m more of a generalist.
Which helps with the workshops that we offer here at Sunflower Farm. We talk
about energy in general, and renewable energy, and growing food and storing
food, and economics and a variety of other issues that our participants are
But this summer I am trying upgrade my sweet potato growing skills.
I think one of my problems that I’ve experienced in the past has been an
issue with water. In previous summers I’ve been so busy dealing with drought
conditions in the rest of my one-acre of vegetable gardens, that I have a
tendency to overlook the sweet potatoes. They “look” like they handle droughts,
but I think a lack of water has seriously affected the cosmetic appeal of the
I also think that I may not have been getting enough heat to them.
Sweet potatoes are a tropical tuber and they love heat. Here in Ontario we’ve
been getting hot summers but I sense at the beginning and end of the season I
may be missing the boat as the days cool off and the nights really get cool.
So this year I decided to grow them under plastic. I went with clear plastic
as Ken Allan recommends. He suggests that black plastic does help, but it
absorbs a lot of the heat that you really want to pass through and get deep
into the soil where the roots are forming sweet potatoes. So I bought a 50’
roll of 6 mil plastic that is 8 feet wide. I cut it in two 4-foot wide strips.
This spring I learned what happens when you put a big sheet of plastic on your
lawn. It really amplifies the heat. It toasts your grass in less than two
hours. (Read about that here.)
So I’m assuming this same principle will apply to warm the soil deep down to
the sweet potatoes’ roots where the tubers will form. And after the lawn fiasco
obviously I’m expecting to incinerate my precious sweet potato plants.
I had hilled up the soil in advance with the hope this will ensure that the
sweet potatoes are forming in an environment conducive to growth. I figure if
they’re growing in tough, untilled soil, they’re more likely to go gnarly. Here
the sandy soil is light and fluffy, which is what I’d want if I were a sweet
Then I watered the soil like crazy. Once the plastic goes on it’s going to
be tougher to get moisture in there, so I really wanted to make sure the area
was well watered. I’m a big believer that you need to keep soil moist so that
its capillary action will allow water to move over a large area when it’s
I also decided to put down a length of drip irrigation hose under the
plastic. This way when we hit a drought I can get water in there. The plastic
is going to help prevent excessive evaporation, and I have a flat area on top
of the plastic to allow water to accumulate and go down through the plastic to
the roots. But with my sandy soil I’m paranoid so I went with the backup
plan of drip irrigation.
I secured the plastic along the edges with soil. Then I went down the row
and cut holes every 12 inches, just big enough to fit a sweet potato cutting. I
put my fingers down the hole to spread the soil apart. Then once I
inserted the cutting I tucked the soil around the root ball as best I could.
Then I put a couple of handfuls of sand around the plant. I did this to help
direct water to the roots and to help hold the plastic down and stop it from
flopping around in high wind. I used sand that I had dug from a deep hole on my
property hoping that it will have fewer weed seeds in it, so it’s one less
place for me to have to worry about weeding.
I also had a whack of straw that I had scrounged from a barn, so I put a
deep layer of mulch on each side of the plastic. Again, this should help reduce
weed growth. And as it breaks down it will help build up the sandy soil.
So our sweet potatoes were a pretty big production this year. And I’m
anxious to see if and how much it improves the yield. Although it was more work
upfront, it will be significantly less work as the season progresses. Less
weeding. And most importantly - less watering. And hopefully more sweet
potatoes, and more cosmetically attractive ones. I have customers now. I need
to provide the best quality product that I can.
So far so good. As you can see in these photos the plants are doing well! I
planted them about 3 weeks ago. I’ll keep you updated and take some photos in
fall at harvest time.
For a previous post about growing sweet potatoes, be sure to click here.
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