What are Seed PotatoesThe term "seed potato" can be a little misleading. Although potatoes do set seed, they do not grow true to seed. To get the variety of potato you want, you need to grow them vegetatively, meaning we re-plant a part of the actual potato. These pieces of potato are referred to as seed potatoes.
Selecting Seed PotatoesBecause potatoes are propagated vegetatively, any diseases from the prior year will be carried over. That's why it is so important to use disease free seed potatoes and that means certified seed potatoes, rather than supermarket potatoes. Certified seed potatoes are certified by some government authority to be disease free.
However, even certified potatoes can contract disease once planted, especially diseases that are not apparent in the seed stage, like ring rot or fusarium wilt, but at least you have a bit of an edge, with some disease tolerance.
Any potatoes that have soft spot, cracks or bruises or signs of rotting should be discarded. Start with the healthiest, strongest seed potatoes, to avoid problems and guarantee an good harvest.
So what exactly do you plant?You do not need to plant a whole, intact potato. Seed potatoes can be cut into pieces, as long as the pieces have at least 1 eye each. An "eye" is a bud that grows into a new plant. [See photo.] If you've ever kept your potatoes in the cabinet too long, you've probably seen them sprout.
You can plant whole potatoes or pieces with multiple eyes, but in general:
- More eyes per piece = more, but smaller potatoes
- One or 2 eyes per piece = less, but larger potatoes
Preparing Seed PotatoesIf you decide you want to cut your seed potatoes into pieces, cut them about 2 days before you plan to plant. This allows the pieces to callus or seal and prevents rotting and soil born diseases, while the pieces sprout and take root.
To further protect your seed potatoes, you can dust them with powdered sulfur, right after cutting them. Place the potatoes in a bag, add the sulfur and shake. Then lay the pieces out and let them dry for 3 -- 4 days.
To Chit or Not to Chit PotatoesChitting - and I have no idea where that name came from - is the term for pre-sprouting your seed potatoes, before planting. It may also be referred to as "greening". Many gardeners feel this give them a head start, but you do not have to chit your potatoes, to get a good crop. The two circumstances, when chitting is advised are:
- If your seed potatoes are already sprouting.
- If you have an early variety and want an early crop.
How to ChitAlthough potatoes will sprout in the dark, you will get long, pale shoots that easily break. Instead, place them in a cool (room temperature) spot with bright light. This way, the sprouts will grow stocky, sturdy and dark green.
A traditional method for chitting is to place your seed potatoes upright in an egg carton, with the bud end facing up, but you can just lay them out on a tray or screen, as long as they are not pile one on top of another.
It will take about 2–4 weeks for the chits to develop, so don't start until about 1 month before your planting date. (Potatoes will store for several months without sprouting, if kept dark and at about 40 F / 4 C) .
You can plant as soon as the sprouts or ½ in. – 1 in. long. If you have to postpone planting because of weather or some other reason, move them to a cooler spot, to slow down their growth. Don't want too long, or your seed potatoes will dehydrate and begin to shrivel.
Handle the seed potatoes carefully, so the sprouts do not break off or become damaged. You can plant the whole potato or cut into pieces with at least 1 eye each, as discussed above, but do this after chitting, not before. Plant with the sprouts facing up and cover lightly with soil.
How Much Should I Plan on Planting?On average, 1 lb. of seed potatoes should yield about 10 lb. of potatoes. One lb. is about 5 – 8 tubers, which should plant about a 10 ft. row.
For more on advice on planting and growing potatoes, readGrowing Potatoes in the Home Garden
Guidelines for Seed Potato Selection, Handling and Planting (North Dakota State Univ.)
Planting Seed Potatoes