FIMBY: Potatoes from the garden -- easy harvest once they're planted

This is another in our “Food in My Back Yard” series, dedicated to edible gardening.

March and potatoes go hand in hand, and not just because of St. Patrick's Day. Late winter is an excellent time to start seed potatoes and have a fresh crop by, say, Father's Day. 

Sacramento's last average frost day is March 18, two weeks from today. From now through April is ideal for planting potatoes, though they also do well here if planted in August to mid-September. However, seed potatoes are plentiful now in nurseries and hardware stores, which gives the gardener the best selection.

Potatoes are one of the easiest vegetables to grow in a home garden. And the easiest way to grow them, I believe, is in cloth grow bags.

A couple of reasons:

First, the grow bags can be be set up anywhere, even on a patio. Potatoes need at least 6 hours of full sun, so find the right spot before actually planting.

Second, potatoes like soil that is loose and nutrient-rich, which makes potting soil mixed with compost just about perfect. Clay soil needs lots of cultivating to accommodate the plants.

The third reason? Potatoes shouldn't be grown where tomatoes, peppers or eggplant grew before -- and vice versa. Those summer vegetables are all part of the Solanaceae plant family. As the UC master gardeners note: "Rotating crops in the garden not only enhances soil fertility, but it can be effective against insect and disease pests that develop on a narrow range of vegetable plants."

With the grow bag, the soil is isolated, and you know exactly what grew there. It's easily reused the next year (with nutrients replenished) for something like carrots (which also like loose soil) or beans.

Finally, it's easy to harvest potatoes from a grow bag: Reach in and grab a few, or dump out the whole bag onto a tarp. This guarantees you get all of them. It's easy to miss one or two when harvesting from in-ground gardens, and then these potatoes sprout next year, probably where you don't want them. (Ask me how I know this!)

Potato growing is mostly front-loaded when it comes to tasks, so allow some prep time for the following:

-- Choose potatoes you like to eat and which grow well in our area. (Note: Russets take a long time to grow, and generally don't like hot weather.) If you can find a nursery selling individual seed potatoes, go for it: You can see which ones look plumpest, with good eyes on them. But many seed potatoes come in packages, which might be mesh but are not always. If they're in plastic, try feeling through the plastic for the size and shape.

Well, why not just plant potatoes from the grocery store? Reason: Those are usually treated to prevent sprouting -- or at least sprouting before you can buy them. Organically grown potatoes, however, will work for planting. 

-- Up to a week before planting, place the potatoes in a warm spot to encourage initial sprouting. I lined up mine on a sunny window sill that is near a heater vent. This year I chose Red Norland and Yukon Gold seed potatoes, some of which already had tiny sprouts.

-- One to three days before planting, cut any large seed potatoes into pieces with at least 2 eyes each. Little potatoes (egg size or smaller) don't need to be cut. Return the pieces to the sprouting site so the cut parts can harden over.

Now to plant!  Fill the grow bag about one-third full with a mix of potting soil and rich compost, watering it well if it's very dry. (This  should be done ahead of time, too.)  Nestle the potatoes or pieces into the top of the soil. Three to four potatoes can be planted in a 15-gallon grow bag -- make sure to space them out. A 5-gallon bag is the smallest one to use for potatoes, and that at best would be for one plant.

Cover the potatoes with more soil and compost, 2 to 4 inches worth, and dampen the soil surface.You're done. For now.

During the growing period, make sure the soil doesn't dry out but should not be soggy -- good drainage prevents root rot. When stalks and leaves start emerging, add more potting soil and compost to the grow bag, up to the lower leaves of the plant's top 2 to 3 inches. Keep doing this as the plants grow, making sure any growing tubers are not exposed to sunlight. (That turns them green.)

When flowers emerge on the plants, you'll know that havest is coming. But wait until the stalks yellow and wilt to harvest.

Newly harvested potatoes can be eaten at once. But if you plan to store the potatoes, first harden them off: Brush off the dirt and place them in a well-ventilated container in complete darkness for 10 to 14 days. Store potatoes long-term in darkness at temperatures about 50 degrees.