Looking for a crop that can grow despite the brutal heat your particular patch of Southern Oregon soil gets? Look no further than sweet potatoes. With the ability to survive even the warmest locations we have in the Rogue Valley, sweet potatoes are a favorite crop of many local gardeners.
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| Istockphoto |
There are a half dozen or so varieties of sweet potatoes, in different shapes and colors from white to orange or purple. They are not related to common potatoes, but are actually the roots of certain vines within the morning glory family. Some varieties can spread vines up to 20 feet, so choose carefully what you plant; there are some high-yielding bush varieties that are better for smaller gardens.
How to Sprout
You can purchase some organically grown tubers in mid-winter and keep them in a pantry or cupboard till they sprout. Once the sprouts come, the potato can be put in a jar with the sprouts up so that they grow until planting time. A good way to give the potatoes a further head start is to cut them off the potato once they are 4 to 6 inches long and root them in paper cups or pony packs full of wet potting soil. In this rooted form they are now called “slips.” You can also buy slips in nurseries or at farmers’ markets.
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When to Plant
This is a hot-weather crop, so wait till after the last frost danger (mid-May in the Rogue Valley) before planting. Harvest will come at the end of August or September. It is interesting to dig up a couple of potatoes after 12 weeks, 14 weeks, and so on until the first frost to really learn how they develop and taste at these various stages.
Notes on Planting and Care
Loose sandy soil is best, but they will also grow in heavy clay. However, the more you amend your soil with sand or organic material, the looser it will remain. Soil amendment gives two advantages in this case: it promotes fuller growth of the sweet potato, and it makes digging and cleaning easier at harvest. This is generally true of any root or tuber crop you want to grow.
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| Tess's Japanese Kitchen |
Sweet potatoes are one of the most forgiving crops, being drought tolerant, and will stay alive even if they are allowed to dry out and wilt and then are watered again. Optimally they should receive 1 inch of water per week. Direct sun is great, although a little afternoon shade is OK.
The Process
1. Till your soil deeply (10 inches) and make mounded rows.
2. Since sweet potatoes are heat-loving plants, cover the rows with thin black plastic about 3 inches wide.
3. Pierce the plastic by driving a dibble or stick through the plastic and 6 inches deep into the freshly tilled earth, making holes a foot apart.
4. Fill each hole with water, slide a slip into each hole, and fill in the hole and around the base of the slip on top of the plastic with loose soil.
5. You can tear a bit larger hole in the plastic around each plant to make sure watering is effective.
6. Water each slip as a final step.
The black plastic will help prevent weeds, and your plants should develop a mat of vines covering the entire row of plastic sheeting. The earliest harvest is normally 90 days, but you may want to sample the developing sweet potatoes at various intervals the first time around as suggested above, to learn about these plants and your preferences in size and development when it comes to eating.
To keep neat rows you may trim the ends of the vines at the outer edge of the plastic if you wish. The first frost will shut down the plants, creating a logical time for actual harvest in September or October. To harvest, start at least 18” out from the plant center and begin digging deeply straight down with a shovel. Lift the earth gently and watch for the sweet potatoes, often hanging in clusters.
Clean the potatoes off and allow them to dry outside for a few hours. They can be stored in a cool, dark place for cooking later in the fall and winter!
