Jicama is a root vegetable, native to Mexico and Central America. It has the texture and crunch of a water chestnut, a mildly sweet taste and is quite juicy - not dry.
The Jicama tubers can be eaten either raw or cooked. Above ground portions of the plant, which includes the foliage, flowers, seeds and stems should only be eaten by followers of Dr. Kevorkian - they are highly toxic - even deadly in some cases.
Jicama also known as the Mexican yam, or Sweet turnip grows as tubers on a sprawling vine which reaches 10 to 15 feet in length. A trellis is advisable. Jicama also has as a very long growing season which is perhaps why it is virtually unknown in Anglo-North America. It requires 8 - 9 months of hot weather to produce a good crop. That doesn't mean they can't be grown in cooler regions - but they have to either started indoors very early or grown in hydroponic set ups or greenhouses.
Jicama can also be grown under polyethylene tunnels which heat up the air and soil around the plants.
A location with full sun and adequately drained soils is needed. Place transplants in the ground after hardening off only when the soil temperature has reached a persistent minimum of 50-55 F or higher.
Plants should be spaced at least a foot apart to allow space for tuber development and above ground spread. Presumably you will be trellising it.
The soil for Jicama should be moist, but well-drained soil, clay soils will simply not suffice. Soil should also be high in phosphorus and potassium and low in nitrogen, as nitrogen encourages foliage growth at the expense of the tubers.
6-24-24, or 8-24-24 fertilizers are preferable. If you don't know what these numbers mean See Understanding Fertilizer Labels. Compost or Peat moss mixed in the soil for drainage is also advisable.
I can not stress enough , DO NOT eat any parts of the plant other than the tuber - that's a big NO-NO. The above ground parts of this plant are Poison. The fact that the above ground portions of the plant is poisonous is probably why insects won't go near it, those little buggers know better. The only ones that do sometimes bother Jicama are a few weevils indigenous to southern regions.
Harvest and Storage
Try to time your harvest to just before the arrival of Jack frost and his entourage of frigid harbingers. Dig the subterranean tubers p in the same fashion you would harvest potatoes. The plants will not produce as bountifully as spuds - figure on a maximum of 5 baseball size jicamas per plant.
However, If you notice the vine starting to wither and die back, go ahead and harvest.
If you notice any parts of the tubers sticking out of the ground and being exposed to the sun, cover them with soil. Exposure to sunlight during its active growth stage will concentrate the plants toxicity into the tubers and make them inedible.
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Thank You and Happy Gardening.