A friend of mine in Arkansas who is knowledgeable about these sorts of things once told me that if he were going to be stranded on a tropical island and could only bring one thing it would be a sweet potato. They are nutritious and easy to grow when it's warm. Myself, I'd rather skip the stranded part and just eat sweet potatoes.
Sweet potatoes are not hard to grow in the garden, but I rarely see them attempted. They're not only nutritious, but their vigorous growth habit works well to smother summer weeds in your garden.
To grow sweet potatoes you plant transplants (called slips) once the soil has warmed and nights are consistently above 50°F. Other than water, they require little care and thrive in poor soil. (Alkaline soil, such as in Chalfant, will need to be amended to lower the pH.) Sweet potatoes' growth rate is based on the heat accumulated in the plant over the season. In our climate, it will take about 100 to 120 days to raise a crop. You will probably be setting slips outside in June and harvesting after the kids have started school again.
Harvest sweet potatoes gently and allow them to cure for about 1 week to improve their storage life and flavor. To cure a sweet potato, ideally it should be stored at 85°F and 85% humidity. (We might have a hard time with the humidity here!) A greenhouse, sunroom or sunny bathroom works well for this, but keep them out of the sun. Once cured, they will store well at 55°F.
The only challenging part of growing sweet potatoes is obtaining slips. There are dozens of mail-order sources for slips; however, almost all source their slips from growers in the Southeast. California doesn't allow importation of sweet potatoes from this region to keep out pests and diseases. This leaves us three options to obtain slips:
- Order from a mail-order nursery that's not shipping from the Southeast. I am aware of only one: Sand Hill Preservation in Iowa.
- Obtain slips inside California. There are some growers around Merced that do this, but we have a hard time getting to Merced from here. Any garden centers you encounter that have slips for sale would be fine, too.
- Grow your own slips.
It is not hard to grow your own slips, but there are as many ways to grow them as there are sweet potato growers. With heat and moisture, sweet potatoes form shoots and grow roots easily.
Some gardeners use moist, heated sand beds. Sweet potatoes are placed in these beds and when the tops emerge, the slips are harvested. This is a good way to grow a lot of slips.
An easy way to just grow a few slips is to suspend a sweet potato above a mason jar partially filled with water using toothpicks just like you would start an avocado from seed. I've also seen people lay sweet potatoes down in a glass baking dish filled with about 1” of water. Either way, keep the bottom ½ wet and warm. Once the sprouts emerge, break them off the sweet potato root, and set them in a clean jar filled with about 1-1/2 inches of water to form roots. This whole process takes about 20-30 days depending on temperature.
In order to ensure this sprouting process works, you should buy Organic sweet potatoes so that they haven't been treated with any type of shoot inhibitor.
It's important to have warm soil to plant sweet potatoes outside. If the soil still needs to warm up but your slips are ready, you can plant them in containers filled with potting mix while you wait.
You shouldn't have too many problems with this plant, but even if you have a few, its rapid growth rate usually makes up for any damage. As an added bonus, they are a fantastic part of a crop rotation in the garden as they are unrelated to most other things we eat, including Irish potatoes.
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