A tall Andean perennial grown as an annual for its crisp, sweet, low-calorie tubers that taste like a cross between apple and watermelon.
Smallanthus sonchifolius · also called Peruvian ground apple, strawberry jicama
Start crowns indoors 4–6 weeks before last frost; transplant out after all frost risk has passed.
Yacon stores its carbohydrates as fructooligosaccharides (inulin-type sugars that pass through digestion largely unabsorbed), making it unusually low in available calories. It produces abundantly with minimal inputs once established.
A little history. Native to the Andean foothills of South America, yacon produces two distinct underground structures: edible storage tubers and smaller, knobby propagating rhizomes (the crowns used to start new plants). These are botanically separate organs.
Press crown pieces just below the surface, cut side down; keep the top inch moist but not waterlogged until shoots emerge. Seedlings emerge in 10–21 days in warm soil.
Deep soak once or twice a week during active growth; reduce once tops begin to yellow in fall. Water when the top 2 inches of soil feel dry or leaves show midday wilting that does not recover by evening. Aim for about 1–1.5 inches per week including rain.
Side-dress (scatter fertilizer along the row and water in) once at planting and again when plants reach 3 ft tall. What to use: balanced compost or a low-nitrogen organic blend; excess nitrogen drives leaf growth at the expense of tubers.
Pinch (remove by hand) the growing tip once plants reach 3 ft to encourage branching and redirect energy toward tuber development; remove any flower heads that form to keep the plant vegetative.
It's ready when dig after the first light frost kills the tops, or when foliage yellows naturally; tubers should be firm, tan to reddish-brown, and 4–10 inches long. Cut tops to 6 inches, then loosen soil 12–18 inches out from the crown with a fork; lift the entire clump, separate the edible tubers from the smaller propagating crowns, and handle gently to avoid bruising.
Cure tubers uncovered in full sun for 3–5 days to convert starches and concentrate sweetness; then store at 50–60 °F (10–16 °C) in a cool, dry place for up to 4 months. Do not refrigerate below 45 °F (7 °C).
In frost-free climates, crowns can remain in the ground year-round; in cold climates, store propagating crowns in barely moist sand or peat at 45–50 °F (7–10 °C) indoors and replant after last frost.
Nasturtium
Aphids often settle on nasturtium's soft stems before they find yacon's new shoots, so a ring of it at the bed edge can pull the first wave away. Pull and bin heavily infested nasturtium rather than letting it become a nursery.
French Marigold
French marigold has been shown to reduce root-knot nematodes, which gall yacon tubers, but only when grown as a thick solid stand for a full season and then turned into the soil. A few flowers along the edge will not do it.
Comfrey
Comfrey feeds from a deep taproot while yacon fills the top 12-18 inches, so they rarely fight over water, and cut comfrey leaves make a useful mulch. Site it at the bed edge, since it is permanent and hard to dig out once established.
Sweet Corn
Andean growers have long set yacon among maize at field edges, and gardeners keep the pairing going. No mechanism has been demonstrated; both are tall and hungry, so give each at least 36 inches and expect the shorter one to stretch.
Potato
Both crops host root-knot nematodes, and growing them together or in sequence can build the population that leaves knobby galls on yacon tubers. Digging potatoes mid-season also churns soil right where yacon crowns are working.
Tomato
Yacon reaches 6-9 feet with broad leaves and will shade and out-drink a tomato planted beside it. The two also share root-knot nematodes, so keeping them in separate beds spares the tomatoes and slows nematode build-up.
Give the lettuce family 2 years away from this spot before any of its relatives return.
The pea and bean family, the cabbage family or the tomato family thrive in this ground next season.
Digging yacon leaves the bed loose and deeply worked, with little fertility used up. Keep other daisy-family crops (lettuce, endive, sunflower) out of that ground for two years. Legumes, the cabbage family, or nightshades all follow well here.
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