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Complete Book of Potatoes

by Chani West-Foyle, Marketing Associate on March 29, 2011

in Food, Gardening

We gave away advance copies of The Complete Book of Potatoes a little while ago, and now the book is in our warehouses and ready to be purchased by the eager potato growers of the world! Potato planting season is on, and I thought this would be a good time to post some excerpts from the book on special techniques for growing potatoes.

Growing Potatoes in Mulch

Mulching is a practice which can be applied to many different vegetable crops. Advantages of mulching include reduced weed growth, more uniform moisture conditions, and moderation of soil temperature. There are many types of mulching, both with organic as well as with inorganic materials. In all cases there is no substitute for proper soil preparation and fertilizer application (see chapter 3).

Straw Mulch

An example of organic mulch for potatoes is straw. In the spring dig a furrow about 4 in. (10 cm) deep and 12 in. (30 cm) wide. Place the seed tubers in the center of the trench and cover the trench with 6 in. (15 cm) of clean straw. The straw should be weed-free to reduce the chances of weeds establishing in the mulch and because mice are attracted to weed seeds. When mice run out of seeds they will start munching on the potatoes. Rodents find straw mulch a comfortable place to reside so be aware of that at harvest time.

As the potato plants emerge, add another 4–6 in. (10–15 cm) of straw. The straw acts to keep the sunlight off the tubers and also keeps the soil moist. By late summer, you can begin harvesting clean, soil-free “new potatoes.” Simply pull back the straw, take what you need, and carefully replace the mulch. After the vines die back, the main potato crop is ready for harvest (Healy 2009). Straw can also be used to simply cover the soil after the potatoes have emerged to conserve moisture.

Plastic Mulch

Potatoes can be grown successfully on raised plastic mulch beds similar to the way other vegetables are grown. The finished raised beds should be 3–5 in. (7.5–13 cm) high and 36 in. (90 cm) wide. Since the plastic is usually 4 ft. (1.2 m) wide this leaves 6 in. (15 cm) of plastic on both sides of the bed which can be secured by burying it along the edges.

There are several types of plastic mulch, including black, clear, and red. Black plastic provides excellent weed control and therefore is the material of choice for potatoes. Clear plastic will warm soil more than black plastic but provides a great environment for weeds. Since plastic mulches warm up the soil, this method can be used to speed up the growth of the potato crop early in the season and thus advance the harvest by seven to ten days.

If the use of plastic mulch is combined with planting green sprouted (chitted) potatoes (see chapter 4), then the harvest can be advanced even more. After the beds have been properly prepared and fertilized, spread and secure the plastic at the edges with a small amount of soil. Plant two rows of potatoes in the bed, with the rows 18–22 in. (45–55 cm) apart and the potatoes 10 in. (25 cm) apart within each row. You can use a bulb setter to punch a hole in the plastic. Plant the potatoes 4–5 in. (10–13 cm) deep and cover them with soil to the level of the plastic.

Particular attention must be paid to the watering of plants growing in plastic mulch as rainfall and surface irrigation will be shed off the plastic layer. An easy way to do this is by means of drip irrigation tubes under the plastic. The equipment is usually available at local garden centers. Another way is careful watering by hand.

Growing Potatoes in Containers

Container gardening is increasing in popularity. It is a good solution for those who only have a small yard or no yard at all. There is an almost endless list of containers which can be used to grow potatoes.

The container should be large enough to accommodate a large potato plant — about 5 gallons (20 liters). Make sure that the container has one or more drainage holes in the bottom. Potatoes growing in containers must be monitored very carefully for water stress. Try to avoid constant direct sunshine on the container, especially on hot afternoons.

Various types of containers and suitable growing mixes can be purchased at local garden centers. Appropriate fertilizer for container gardening should also be available at the local garden center.

Some container gardeners grow potatoes in bushel baskets. Potatoes can also be grown inside old tires. As the plants grow you can add more tires and more soil. Some gardeners even grow potatoes on their compost pile!

Potato-Tomato Grafting

Grafting is a common practice in many horticultural crops. Potatoes and tomatoes can be grafted together because they are closely related. This involves grafting the top of a tomato plant (scion) onto the stem of a potato plant (rootstock), thus (at least theoretically) enabling the combination to produce both tomatoes and potatoes. This is not a new procedure. Nearly a century ago Luther Burbank (1914) described “The tomato and an interesting experiment — a plant which bore potatoes below and tomatoes above.”

Some companies which sell potato-tomato grafting kits display misleading drawings which show an abundance of both tomatoes and potatoes on the same plant. The grafting process itself is relatively simple, and the resulting plants can bear a good crop of tomatoes, but the tubers tend to be small and immature even when the plant is past maturity and the foliage starts turning yellow. The reason for the low yield of potatoes from such graft hybrids is twofold: (1) in the competition for photosynthetic product the tomatoes usually win out and (2) tomato vines do not provide the tuberization stimulus to the stolons in the way that potato vines do. Nevertheless, for some home gardeners it may be fun to do some experimenting with this technique and thus demonstrate the close relationship between potatoes and tomatoes.

Occasionally the potato rootstock may produce one or more sideshoots. These should be removed. If they are inadvertently left on the plant then care should be taken to only eat fruit produced by the tomato portion of grafted plants. Potato fruits, regardless of whether they are produced on “normal” (ungrafted) or sideshoots of potato rootstock contain glycoalkaloids (see chapter 10) and should not be eaten.

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