Water Chestnut (Chinese)

Plant the corms in spring, then flood for one day and let it drain

Set the corms 4 to 5 inches deep in the soil and 30 inches apart, in rows spaced about the same. Flood the plot and keep it submerged for a single day, then let the water drain away naturally rather than holding it. Waterchestnut needs a growing period of 220 frost-free days to carry corms to edible size, so planting has to open as early as the season safely allows. The one-day flood and slow drain settles the soil around the corms and establishes the young plants before the bed goes back under water.

⚠ Buy Eleocharis dulcis specifically. European water chestnut, Trapa natans, shares the common name but is a different plant entirely - an invasive that is spreading through Northeast and Mid-Atlantic waterways - and Penn State Extension notes it has nothing to do with the edible variety.

Re-flood at 12 inches tall and hold 4 to 6 inches over the soil

Once the plants stand about 12 inches high, flood the bed again and keep 4 to 6 inches of water over the soil surface for the rest of the season. Grow this only where you can raise and lower the level on your own schedule - a tub, a lined pond, or a bed with ditches and dikes. This is a flooded crop, and the standing water carries it through the summer while the rhizomes spread and set corms. Open swamp or marsh will not do, because the whole system depends on controlling the water level rather than accepting whatever the site gives you.

Drain the bed about 30 days before you dig

Cut the water off and let the bed dry down roughly 30 days ahead of harvest, so the ground is firm enough to work when you come to lift the corms. Treat 30 days as the guideline the extension source gives; how long your bed actually needs will depend on your soil and drainage. The corms sit in mud at the bottom of a flooded bed and have to be scooped off the bottom with forks. Until the water is off and the ground has dried enough to work, there is no way to reach them.

Check for daughter plants 6 to 8 weeks after planting

About 6 to 8 weeks in, look for secondary plants coming up in a ring around each parent. Under favorable conditions they appear on their own and the bed begins to close in. Those daughter plants are the crop building the rhizome network, and the corms form along it rather than in a clump under the parent. A bed that has not started throwing secondaries by this point is not on track to yield.

Dig the corms in late fall, once the bed has dried down

After a full summer of growth the corms reach edible size in late fall. Scoop them off the bottom with a fork, and work the whole spread of the bed rather than just under the original planting spots. The corms only size up at the very end of the season, so there is nothing worth lifting before late fall. They form along the rhizomes that ran out from each parent, which is why the harvest covers the entire bed.