Over the years, I have heard many stories on the best way to plant potatoes. I am sure that most of these methods worked, some by pure luck but some were the proper way to plant potatoes. This column will provide you with an outline of what conditions a potato needs to thrive and produce a large crop, a few steadfast rules and a few proven suggestions on how to plant your seed potatoes. Follow the guidelines in this column and you will be well on your way to a bountiful crop of potatoes this season.
Potatoes will grow in almost any soil type but do grow better if the soil has pH range of 4.8 to 5.5 (neutral pH 7.0), a little on the acidic side. Most of us have soil that is closer to neutral or more basic. So to help out your potatoes, add oak leaves, sawdust or pine needles to compost in the soil in your potato patch in order to make the soil a little more acidic. Also if you plan to grow potatoes in certain areas of your garden (remember the suggestions of rotating your crops annually) do not add lime or manure to the area of your garden that you plan to grow potatoes in this year and next year. Both manure and lime can raise the pH of your soil causing it to be less acidic. Lime also can promote the growth of potato scab on your crop of potatoes. The best place to plant potatoes is in the place where you had peas or beans, because they fix nitrogen into the soil and the potato plants will use the nitrogen. Try your very best this year, not to put your potatoes where you had plants from the same family growing last year (the nightshade family – potatoes, tomatoes, peppers and eggplant). The looser your soil is, the better your potatoes will grow. It stands to reason that if you have heavy clay soils it will be harder for the tuber’s shoots to penetrate the soil thus producing a smaller yield. If you have heavy soil, work the soil thoroughly by hand or with a tiller before planting potatoes.
Many gardeners think that a potato plant produces the new potatoes right off of the seed potato that you plant. In reality that seed potato actually sends up a shoot that becomes the green plant above ground and as that plant grows, it produces runners, and new potatoes develop on these runners below the new plant, but above where the seed potato was planted. The seed potato that you planted dissolves in the soil, as it provides food for the developing plant. Realizing this, it now makes sense why I recommend planting in a deep hole or trench.
Since you purchased your seed potatoes, you have been storing them in a dry, warm (60 degrees) and dark area, usually the basement. Being in this environment provides the optimum conditions for the potatoes to develop shoots. You can plant potatoes as soon as the soil in your garden has warmed up to 60 degrees, even if the threat of frost is still some time away. The only time I suggest holding off on planting potatoes, early in the season, is if we have had unusually wet spring conditions and the soil is waterlogged. Let the soil dry out before planting so the seed potatoes won’t rot before developing into new plants. A few days before you are going to be planting your seed potatoes, take them out of the box or bag they are stored in and look them over, as they should have developed many small shoots by now.
The smaller potatoes, up to 2.5 inches in diameter should be planted as is, regardless of how many shoots have developed. Larger seed potatoes can be cut into smaller pieces making sure each piece that you cut has a minimum of three eyes developing into shoots on each piece. On some of the potatoes you cut, you may only get two pieces or you may get four, it depends on the number of eyes that are producing shoots and how these developing eyes are positioned across the outside of the seed potato. Just use your best judgement here and if you find that a larger potato is too hard to cut between the shoots then just leave it whole. Any potatoes that have eyes that haven’t swelled or developed shoots by now or have signs of rot, throw away, because they probably will not develop into a potato plant. If none of your seed potatoes have produced sprouts after a few weeks of storage in a warm dark place then you may have a poor producing seed.
Try storing them in a warmer dry place (70 degrees) for a few days and then check them again. If they have started to sprout great, if not you may have to scramble to find some replacement seed potatoes. Once you have finished cutting your seed potatoes, lay them out on a tray or layer of newspaper in a dark, warm place for a few days to give the cut areas a chance to “seal off”, preventing rot from occurring and disease from entering the cut wounds when they are planted. Some gardeners swear by adding sulphur powder to their seed potatoes because it is a natural protector against disease. You can find sulphur in powder form at a feed store, garden supply store or some drugstores. A little goes a long way so a small container is fine. The best way to apply the sulphur is to apply it right after the cuts are made while they are still damp so the powder will stick. Put a few tablespoons of powder in a paper or plastic bag and then add a few seed potatoes at a time, shake gently (IMPORTANT: do not damage the new shoots) until coated in sulphur and then remove with a rubber gloved hand. Add more sulphur to the bag as needed and continue until all of your seed potatoes are coated. Excess powder from the bag can be put in the composter. Wash hands thoroughly once you are done and either wash or dispose of gloves in the garbage along with the bag.
When you are ready to plant, you must provide deep holes or trenches 10 to 12 inches deep for your seed potatoes. This provides an area for the new plant to form and produce new potatoes and as you gradually fill in the hole the soil stays loose and allows for more tuber shoot penetration and a larger yield of new potatoes. You can dig individual holes for each hill or rows of trenches (some gardeners have a tiller attachment for this) across your planting area. Which ever is easiest for you. Space your holes (or potatoes in the trench) 12 to 14 inches apart if you want to produce high yield with large potatoes. If you want to produce smaller sized potatoes (potatoes called creamers in the grocery store) space the holes or seed potatoes about 6-8 inches apart. Try a combination of spacing to get both sizes. Once your hole or trench is dug, place 1 seed potato in the hole with the shoots facing up. It is important that the shoots face up, as this is the new plant forming. You only need one seed potato per hole, as long as, it has a minimum of three developing shoots. Contrary to popular belief, planting more seed potatoes in each hole does not produce more potatoes, what it does produce, are multiple plants that compete for space, water and nutrients in each hole actually reducing your crop yield. Potatoes require a lot of nutrients while they are growing so give your new plants a boost, by sprinkling a 1⁄4 cup of bone meal in the bottom of each planting hole. Bone meal is high in phosphorus, which is needed for the production of roots and tubers. Bone meal can actually touch the seed potatoes but if you cannot find bone meal use a high phosphorus granular fertilizer (high middle number) mixed thoroughly into the bottom of the hole and then cover the fertilizer with an inch of fresh soil before placing the seed potato in. Once you have placed your seed potatoes in the ground cover with a few inches of soil, continue covering the plants in each hole (or the trench) with a few inches of soil as the new plant emerges. Covering with soil will also protect the plants from frost early in the season. Once the plants have grown the full height of the trench or hole let them grow up to be about 10-12 inches tall and then hill a mound of soil all around the plant almost covering it again. Let it grow another 8-10 inches and then hill again with a hoe. . I like to sprinkle more bone meal (or high phosphorus fertilizer) on the top of the soil around the plants each time that I hill the potatoes to ensure proper nutrients. Never add a fertilizer high in nitrogen to your potato patch as it will produce plants as large as you but no potatoes will develop. Remember that all of this hilling is providing the environment for new potatoes to develop in. The larger the hills and the looser the soil the better the crop will be. One word of warning though, never hill potatoes that have started to bloom. Once a potato plant has started to bloom, the tender shoots that produce new potatoes are developing. Hoeing around the plants to form a hill could sever these tender shoots killing all of your new potatoes and destroying all of your hard work. As important as a good nutrient level in the soil, is a good moisture level. Potatoes need a steady supply of moisture in order to develop into good sound vegetables. If we have those hot dry spells you will have to supplement the moisture level of the soil with watering. Good constant moisture levels, moist but not waterlogged soil, prevents the potatoes from developing hollow spots in their insides. Good moisture combined with good nutrition will produce the best potatoes around. Keep up the hard work until the blossoms die on the plants and then you can harvest your potatoes and enjoy the fruits of your labour.
Tip: If you are planting multiple varieties of potatoes with multiple ‘days to maturity’ I always plant the earliest potatoes near the front of the patch and put the latest maturing ones in the back. I plant a progression then I can easily access the early potatoes with out damaging the plats of the later varieties. Mark your rows of hills or trenches so you can tell where each variety is planted. A garden sketch is also a good idea to help you keep track a few weeks down the road once the plants emerge.