Yacon

Roughly two months before you intend to plant out (which is itself after your last frost), bury the corms in moist potting soil to wake them up. Once shoots appear, separate the sprouted corms and move each into a 6- or 8-inch pot to grow on until the weather settles. Yacon needs about 180 days in the ground to size its storage roots, and it will not tolerate frost at either end of that run, so the head start indoors is what buys a full-season crop in a short-season yard.

Set the potted plants out in spring after freezing nights have ended, 30 to 40 inches apart with 3 to 4 feet between row centers. Give it loamy, nutrient-rich soil in full sun; raised beds with plastic mulch keep weed pressure down. Yacon runs best between 64 and 80 degrees and is damaged at 32, so it gains nothing from going out early. The wide spacing matters because a single plant throws a root cluster nearly a foot across.

No fertilizer recommendation exists specifically for yacon, so follow potato: about 200 lb/acre of nitrogen, with phosphate and potash applied only as your soil test calls for. Ammonium sulfate or a controlled-release fertilizer both work. Nitrogen does double duty in this crop, raising both total yield and the fructooligosaccharide content that is the whole point of the sweet storage roots.

Do not let yacon run dry through the heat of the season. Steady rain or irrigation, paired with cool nights, is what drives corm and storage-root formation. Yacon will take temperatures as high as 105 degrees so long as water is available, but the swelling of the storage roots is the step that moisture stress shuts down first, and that is the harvest.

Walk the plants for slugs, caterpillars, beetles and leafhoppers, and check for Fusarium, Sclerotinia and Alternaria on foliage. If roots come up stunted or knotty, suspect nematodes. Handle what you find culturally: hand-pick, clear debris, and rotate. Yacon defends itself unusually well. Its monoterpenes, diterpenes and sesquiterpenes are genuinely pest-suppressive and the trichomes on leaves and stems are a second barrier, so damage rarely reaches a threshold worth treating.

Wait for the first killing frost to shrivel and blacken the top growth — roughly 180 days (6-7 months) from planting. Then lift the whole cluster with a fork, starting a foot out from the stems and working around the plant so you bring up the root ball intact. The storage roots are brittle and snap easily, so lever from well outside the crown rather than pulling against it. Leave the crown and its rhizomes attached until you separate the storage roots for eating. Frost-killed tops are the plant's own signal that it has finished moving sugars down into the storage roots; dug earlier, the roots are noticeably flatter in flavor. UF/IFAS puts maturity at 6-7 months from planting.

After the first killing frost but before the ground freezes, lift the crown, cut the stems back to 3 to 6 inches and brush the soil off by hand — do not wash it. Leave a few of the small storage roots attached to the rhizome; that improves storage life. Let the surface dry for a day or two in a cool airy spot, then pack the crown in slightly moist sand or mulch and hold it near 40 to 50 degrees in the dark. Divide and replant in spring once frost danger has passed. The crown rhizomes, not the edible storage roots, are what regrow the plant, and they are frost-tender. Unlike dahlia or canna tubers, yacon rhizomes shrivel rather than keep if you dry-cure them hard, so the aim is a barely-damp medium and a cold dark hold, not desiccation.

Lay the cleaned storage roots out in direct sun for about six days before eating. They will wrinkle as they lose water and turn markedly sweeter. Once sweetened, hold them cold and dark. Sunning hydrolyzes the fructooligosaccharides into free fructose and glucose. Measured over six days, FOS fell from 50-62 percent of dry matter to 29-44 percent while free sugars climbed from 29-34 to 45-51 percent, and the roots shed about 40 percent of their water.