Are You Considering Growing Purple Potatoes?
Purple potatoes are now on the grocery store shelves and offer great antioxidant qualities. Consider growing one of these four varieties of purple potatoes this season. The Peruvian Purple Potato is an heirloom direct from the Andes. Adirondack Blue, Purple Majesty and All Blue potato varieties are easy to grow as well and add a splash of color to the table. To determine which purple potato is best for your garden schedule we have compared these potato types below, including when to grow, how well they store, their width and height in your garden, what nutrients they require and a bit about cooking and disease.
There are over 3,500 of different potato varieties, most which you will not find outside of in the high antiplano region of Peru and Bolivia where potatoes originate. If you ever spend time in these countries you will find they come in all shapes and sizes – red, green, blue, purple, yellow, big, small; served many different ways. I even had a black potato once when I was travelling in Bolivia. Once I got over the look, it was delicious!
Most of these potatoes are adapted to their micro-climates were they originated. For growers that live at 11,000 feet, you are in luck. For most of us we have to settle for what is commercially available. There are hundreds of cultivars available for purchase. If you want to try growing purple potatoes, here’s a few to investigate.
Growing Potatoes in the Garden
Soils for Potatoes
Potato Pots and Potato Bags
Many have had a lot of luck growing purple potatoes in potato pots or potato bags. These above-ground containers keep the voles, mice and other subterranean critters from eating your potato shoots. Another advance is that you can place the pots wherever you want, and move them as needed. Many fold-up and provide easy storage when the harvest is done.
They come in 7, 10 and 15 gallon containers, many with roll-up windows at the bottom, so you can check on the progress of the potato root development. Fun, but not really necessary except to check on when it’s time to harvest. When you do harvest, you will need to pull the entire plant from the pot anyways.
The disadvantage of potato pots is that you have to add your own soil, which is an additional expense. A high quality potting mix, with additional wormcastings (also known as vermiculture) and mychorrizal innoculum is recommended.
Mychorrizal Innoculum Pellets
Mychorrizal inoculum, a fungi that helps plants update nutrients, is a must for any gardener that wants consistently higher yields. Select a commercial variety that has multiple strains of inoculum for the best results. Potatoes require the endo-mychorrizal fungi type, so be sure to look for that on the packaging.
Compost Tea Making
In addition, consider brewing your own compost tea. It’s an all-around organic product that provides many benefits, including increased root growth, larger harvests, and reduced pathogens. This inoculum can be applied to leaf surfaces to prevent leaf mold. It’s best to make your own out of wormcastings or compost, but there are a variety of commercially available, shelf stable products that you can buy if you are not up for the task.
For direct planting, a cover crop, planted the season before is also a great way to prepare the soil for potatoes. Cover crops improve the soil organic matter, nutrient availability, microbial activity, and water holding capacity when incorporated into the soil. If you use manure, apply and incorporate into the soil 3-4 weeks prior to planting.
Do not fertilize with fresh manure, as this can cause scab on the surface of the potato. Be careful with manure, since it can be really high in salts, which will inhibit growth.
Location for Potatoes
The Purple Majesty potato needs full sun; that is 6 or more hours of direct sunlight a day. The Adirondack Blue, All Blue, and Peruvian Purple only require partial sun; 3-6 hours of sun daily in the morning and early afternoon.
Seasonal Rotation of Potatoes
Potatoes should be rotated in the garden, and not grown in the same spot until there has been a 3-4 year absence of potatoes. If you have serious problems with grubs or the Colorado potato beetle, keep a distance of roughly 650 feet from the previous potato harvest (or tomato/peppers/eggplants, since they are all in the nightshade family).
Avoid planting in a new areas that has had a plant grown the previous season that has high nutrient needs, such as corn, tomatoes, broccoli, cauliflower, cabbage or lettuce. If you have no other option, then you will need to add an extra large dose of organic fertilizer, since potatoes are “heavy feeders”.
Potato Bed or Potato Pot Preparation
Potatoes can be sown directly into the soil, but also do well in containers.
About a week or two before planting to promote sprouting, expose the seed potatoes to direct light and warmth. A window sill that has direct sunlight is a great location. Cut the potatoes into 1-2″ squares a day or two before planting and include 1-2 eyes in each square and allow to dry.
If you are growing in potato pots and there is any soil remaining (there may not be), then consider removing 50% of the soil and adding fresh nutrients, mycorrhizal inoculum, and new soil each.
Otherwise, the same rules apply for potato preparation.
You’ll need about 5 to 8 pounds of potatoes to plant a 100-foot row. Plant the purple potatoes in rows spaced about 3 feet apart, in trenches that are 6-8 inches deep. Plant each piece of potato cut side down, with the eyes pointing up every 12-15 inches. Only cover the potatoes with 4 inches of soil. As the plants start to grow continue to fill in the trench. Leave only a small portion of the growing vines exposed encourages additional root development. Keep tubers covered to prevent development of Solanine. The soil can be mounded around the plants as they continue to grow.
Having the right mix of potting soil will make a huge difference in your purple potato harvest. The potting mix should be a blend of organic ingredients, focused on the high nutrient needs of potatoes. Organic fertilizers are superior to the synthetic in that they provide much wider array of essential nutrients for the potato.
How To Know When to Harvest Potatoes
To see if the potatoes are ready, place a spade in the soil just beyond where the outer leaf is growing and dig down gently. Slowly pry up a small test area of the potato plant to see how mature the potatoes are. If the skins are thin and rub off easily, the potatoes are not ready and should be left in the ground for a few more days. If the skins are thick and firmly attached to the flesh they are ready for harvest.
Potatoes can tolerate light frost. However just prior to when the first hard frost is expected, it’s time to really harvest and put them in storage.
After the potatoes have been harvested, brush the soil off but do not wash until they are on the menu for the night’s meal.
After harvesting, potatoes must be cured. Let them sit in temperatures of 45 to 60 degrees Fahrenheit for about two weeks. This will give the skins time to harden and minor injuries to seal.
Potatoes should be kept in a cool, dark place. Temperatures should always be above freezing, and generally about 39 °F, since below this temperature potato starch turns into sugar and gives the potato a sweet taste. Potatoes should not kept in a refrigerator since it is too cold.
Potatoes should be kept dry (not washed before storing) and not in a sealed bag, since dampness promotes early spoilage. Best to store them open air or in a perforated bag.
If the potatoes’ skin turns green it is a result of a build-up of Solanine, a chemical that produces a bitter taste, and can be harmful if eaten in large quantities. Solanine is produced as a result of the potatoes being exposed to too much light. Cut the green area from the potato skin before cooking and eating.
If the potato sprouts it means it is ready to grow. Do not eat the sprouts and simply cut away before cooking. Storing in a dark, cool place will reduce sprouting.
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