Sunroots

Flower & Garden Magazine, Feb-March, 1995 by William D. Adams

Jerusalem Artichokes Are steadily becoming more popular despite a name that is not adequately descriptive - the plant is neither an artichoke, nor is it from Jerusalem. In fact, it's a perennial sunflower that has been grown for centuries by Native Americans. Today garden writers seem to agree that "sunroot" (Helianthus tuberosus) is a better name, although "sunchoke" lingers as a transitional term.

The plant can be somewhat weedy, growing up to 10 feet tall and, if given the room, spreading almost as wide. During the shorter days of fall, it produces single, yellow sunflowers and edible tubers. Older varieties had tubers with lots of hard-to-clean knobs, while newer varieties are smoother and more cylindrical.

PLANTING

Organic matter is the key to good soil preparation. Add 4 to 6 inches of compost, peat moss or finely ground bark to the soil if you are preparing a new planting area. These soil amendments will help sandy soils to hold water and nutrients longer and clay soils to drain better. While you're tilling the soil, work in 2 pounds of a complete fertilizer, such as 12-24-12, per 100 square feet of bed area and lime if recommended by a soil test.

The tubers are best planted whole, 12 to 18 inches apart and 4 to 6 inches deep. Sunroots have a reputation for being invasive so some people use a root barrier 6 to 12 inches deep around the bed perimeter. Metal edging or old roofing, heavy tar paper or special root barrier cloths will do the job. It is perhaps best to treat the sunroot planting area as you would a perennial bed. Chances are you will overlook a few tubers as you harvest, and these tubers will sprout the following year.

Gardeners in the South can plant almost anytime; even when planted in June, the tubers should have time to mature before fall. Obviously, since you can store them in the ground, they can also be planted in the fall. Northern gardeners can plant in the spring a few weeks before or after the average last frost date (depending on the availability of tubers) or in the fall. Obtaining tubers for planting when you want them may be a challenge - some sources offer them only in spring, others in spring or fall. You can even plant grocery store-bought sunroots, although you won't know which variety you're planting.

Sunroots aren't especially demanding, but they appreciate a layer of mulch to conserve moisture. If growth seems a bit stunted, try foliar feeding with a hose-attached fertilizer sprayer. Pests are comparatively few so spraying shouldn't be necessary.

HARVEST TIME

For Northern gardeners a hard frost in October or November is a signal to cut down the stalks and prepare for the beginning of harvest. The tubers develop a sweet, nutty taste after they have cured a few weeks in the ground. If harvested immediately after cutting back, they have a dirty or "green" taste, even when thoroughly washed. This "green" flavor may be due to the carbohydrate inulin (not insulin), touted as a benefit to diabetics and which begins to break down into sugars during the curing process.

Don't dig up these tubers and leave them out to cure like you would Irish potatoes; they will quickly become rubbery and will not revive. Extend the harvest through winter by spreading a thick layer of mulch over the bed. Even in cold climates heavy mulching can make it possible to harvest as needed until spring. Harvested tubers can also be stored in plastic bags in the refrigerator, but they won't maintain their quality as long.

In the South, where a hard frost may not occur until January, cut back the plants in October or November (a 90- to 125-day growing season is required). Allow the tubers to cure a few weeks, then harvest as needed. If the plants are cut back too soon, before the weather is sufficiently cool, the tubers may begin to sprout again before they can be harvested. Gardeners in the tropics and subtropics may need to dig, wash and store tubers in plastic bags in the refrigerator.

Sunroots can be used almost any way you would use potatoes, plus they can be pickled or used raw in salads. The new varieties are easy to clean - just scrub them with an abrasive rag. Peel them if you must, but because the tubers are small and brittle you may end up with more peel than vegetable. Sunroots also oxidize and turn brown rapidly, so toss them in a little lemon juice unless they are to be cooked or processed immediately.

Sunroot Varieties 'French Mammoth White' White, Chunky, productive. 'Fuseau' Long yam shape with few knobs, comparatively early. 'Red Fuseau' Similar to 'Fuseau,' with red skin 'Golden Nugget' Golden yellow skin, smaller. 'Smooth Garnet' Smooth skin, few knobs, chunky shape. 'Stampede' Early-maturing variety with roundish white tubers. 'Sunray' Lots of flowers, dwarf by comparison.