School High Tunnels

Maximizing garden-based learning and agricultural literacy in schools

October 9, 2012
by Katie Bigness
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High Tunnel Harvest Time

The fall harvest season in our high tunnel brings some interesting new crops that are easy to grow, and fun to harvest: peanuts and sweet potatoes.  Here are some details on how they fit into a school high tunnel program.

A peanut plant, showing leaves and stems.

Both peanuts and sweet potatoes (called yams in the Southern US), are widely grown in the southern states, and grow well in warm conditions.  As such, they are well suited to growing in a high tunnel during the summer.  We purchased peanut seed (variety Jumbo Virginia) from Gurney’s Seed and Nursery Co., and sweet potato rooted cuttings (variety Beauregard) from Johnny’s Seed Co.  and planted them around May 15 in our high tunnel at Cornell University.

The soil fertility requirement for peanuts is modest.  The plant is a member of the legume family, so fixes its own nitrogen.  The soil should be of neutral pH, with adequate calcium content.  The latter is needed for fruit formation (see below).

A peanut branch, showing the fruits borne at the end of long, stalk-like pegs. The pegs and fruits are buried in the ground.

 

We spaced the seeds of peanut a foot apart in our 3-foot beds, placing the seed about an inch deep.  Each plant grew about 8 in. tall, and spread sideways on horizontal branches.  In mid-summer, inconspicuous yellow flowers were produced on these branches, and after these faded, a thin peg was produced that poked into the soil.  This thin probe enlarged at the tip to form the familiar peanut fruit.  These fruits are hidden from view until the plants are dug up at harvest.  Plants are then hung up or spread on newspaper to dry, after which the peanuts can be detached and shelled.  Although peanuts can be eaten raw, they are normally roasted first.

The sweet potato is an important root crop grown in warm climates in this country and in the Tropics.  The plant grows vigorously on long, spreading shoots that lie on the ground.  We spaced our cuttings a foot apart in the middle of the 3-foot bed.  The vines covered the bed by mid-summer, and by end of September started to show purpling and yellowing of the oldest leaves.  The soil at the base of the plant then started to rise, and careful digging revealed the enlarged red-skinned roots.  These are the “yams” that are a familiar feature of Thanksgiving dinner and other fall dishes.

Sweet potato leaves at end of September, growing in a high tunnel.

 

These two crops fit well into a school high tunnel program.  The plants are started in May, and will grow with little care except for regular watering all through the summer.  They are then ready for harvest in the middle of the fall term, when the students can do the harvesting, and use the peanuts and yam tubers for snacks and fun dishes.  From a cultural standpoint, the two crops are important food sources for many people, and form the basis for commerce and nutrition in tropical countries.  Students will have fun investigating where and how peanuts and sweet potatoes are grown and used.

 

The base of a sweet potato plant, showing the horizontal stems and the edible roots. Soil has been washed away to show the roots.