A few years ago I got it in my head to grow sweet potatoes. I did some research and ended up planting an area about 10X10 with a dozen or so sweet potato slips. I purchased the slips through some online garden catalog. A couple weeks before planting we covered the entire bed with clear plastic and buried the edges. When the slips finally arrived, we planted them by cutting X marks in the plastic. Most of the plants survived and we had lots of vines. After the first frost I dug them out. There were lots of fingerling size tubers, but few of any size. There was one large sweet potato, a few medium size and lots of small ones.
My conclusion was that it was too dry under the plastic. The one large potato was at the edge of the bed where the ground sloped away receiving more water. I did cure the sweet potatoes and we enjoyed them.
The next summer, 2013, I was ready to try again, but didn’t have much time. I ordered the slips and planted them alongside a barn wall facing south thinking it would maximize the heat with the sun reflecting off the wall. The vines grew well, but no tubers formed at all so it was a total failure.
I am fairly persistent when I get something in my head so I wanted to try again. In the spring of 2014 as I was doing research I found a book called “Sweet Potatoes for the Home Garden With Special Techniques for Northern Growers”. It is written by Ken Allan who lives in Kingston, Ontario. I had to order it directly from him as it was not available in any bookstore I could find.
I learned some new techniques from the book and decided to plant 100 sweet potato slips. This time I ordered from a sweet potato farm that would send me the slips when I wanted them. The farm that I bought from was George’s Plant Farm. The slips arrived when I wanted them and they looked great.
We made raised rows and covered them with clear plastic burying the edges in the soil. We made sure the soil under the plastic had been thoroughly soaked to prevent lack of moisture under the plastic. When the slips arrived we planted them by making X marks in the plastic and then adding dirt on top to seal the hole made for the slip. Here is a picture after a couple weeks of growing.
We had two 25′ rows and two 15′ rows planted in sandy soil that was amended with compost. We also planted some into rows in heavier clay / loam soil for an experiment. All the slips grew well. I did minimal weeding. I was a bit worried because the summer seemed to be on the cool side. It was also very wet and it seemed like the rows in the clay were sitting in excess water. The two 15′ rows were the only rows that were watered, the rest were on their own for moisture due to their location.
By Sept 13th we had a killing frost and here is what the same raised row looked like.
Here is what it looked like when we started pulling back the plastic. We didn’t do a very good job of covering the edges of the plastic with dirt which allowed some weeds to grow under the plastic. If the plastic was sealed well, then very little vegetation should grow under the plastic.
Here is a close up of the tubers under one plant.
Here is the harvest from the two 25′ rows. Unfortunately I didn’t get around to weighing the box and determining a per plant yield.
In summary the yields didn’t seem to vary between the sandy soil beds and heavy soil beds. The beds that were watered did not do better than the others. All beds had some potatoes that were split from growing too fast. Ideally the potatoes would be nice and smooth. We also had some potatoes that were damaged by rodents chewing the tops of the potatoes.
After harvesting it is important to cure the sweet potatoes. The curing process ensures that the potatoes will keep for a long period of time. We are still eating sweet potatoes that were grown last year. They are in excellent condition. I will post about curing sweet potatoes some other time.
Now, we are upon the 2015 growing season. I want to plant 200 sweet potato slips this year. I’ll keep you posted on how it goes!