Whether its according to the phase of the moon, or by George Washington’s birthday, mid -February is time to plant Irish potatoes. The Almanac indicates February 10-17 as moon-favorabile dates for planting potatoes, and those who garden according to the weather say about 4 weeks before average last freeze, both put it about now for potato planting time!
Potatoes grow and produce best between 60 and 75 degrees during the day and 45 to 55 degrees at night, which doesn’t happen for very long each spring. Potatoes must set and size their tubers before the soil temperature hits 85 degrees at which point tuber initiation stops.
Potatoes are heavy feeders so add all the needed fertilizer before planting. Sidedressing after they are up and growing does not benefit the plants and can reduce tuber size. Do not add lime unless your soil pH is below 5.0.
Always purchase certified seed potatoes from a nursery supplier or garden/feed store. Never use grocery store tubers as these may not sprout and can possibly carry diseases which would reduce yield.
Potato tubers have ‘eyes’ which are really compressed shoots. Each piece that should have at least 2 or 3 eyes. Large seed potatoes can be cut into 3 ounce pieces with several eyes on a piece. After cutting, treat them with dusting sulfur to help reduce disease problems. You can put the cut pieces in a bag with the sulfur and shake to coat the pieces. Cure the cut pieces for 4 to 7 days before planting so the cuts can heal.
Potatoes need good drainage, so if your soil tends to stay wet, create raised beds or rows to prevent rotting. If you have well-drained soil, you can plant without raised beds. Make a planting furrow about 3 inches deep and space the seed pieces 8 to 12 inches apart. Cover and gently firm the soil.
Several weeks later, once the shoots are about 5 or 6 inches tall, shovel about 3 to 4 inches of soil (or organic matter) to the base of the plants, leaving a couple of inches of shoot exposed. Repeat this procedure as the plants grow until the original seed piece is about 6 to 8 inches beneath the surface of added soil.
If you only have a small area to plant, here is a method for growing potatoes above ground. After preparing the soil, take your seed pieces and press them into the soil and cover them with 6 inches of organic matter like compost, shredded leaves, etc. After the shoots come up and the organic matter has settled, add more organic matter to the row to cover more of the stem. Continue this process until you have the original seed pieces buried about 8 to 12 inches.
The reason for adding soil or organic matter is because the tubers do not develop below the original seed piece, but from the shoots that grows up from the eyes. By gradually and continually increasing the depth of the seed piece, the tubers will develop in the mulch or added soil.
Use a sprinkler (if it does not rain) to keep the added organic matter or soil moist to encourage tuber development. Do not allow the planting to become excessively wet or dry.
If you grow potatoes the traditional way by dirting with soil, mulch with organic matter right after planting to keep the soil cool and reduce weeds.
Here is another variation on growing potatoes – a good patio project for the kids. A local nurseryman said he was able to harvest 3 to 4 pound of potatoes from 5 gallon nursery pots filled with potting soil. The seed piece should be near the bottom of the pot. A water soluble fertilizer can be used to supply the needed nutrients.
Potatoes can be harvested at any time they reach usable size, although it takes about 3 to 4 months to reach full size. At that time the foliage should be begin to yellow and die. If the foliage begins to yellow and die prematurely, it’s probably be due to disease, most likely the same disease which caused the Irish potato famine in the mid-1800’s.