How to Grow Sweetheart Melons in a Polytunnel

Plant Sweetheart (Chanterais) melon seeds in a polytunnel in mid-spring when temperatures reach 60 to 65 degrees Fahrenheit. These seeds require warm air and soil temperatures so don't plant them before the last frost, even in a polytunnel.

Use any bright, quick-draining site in the polytunnel. Melons do well with the diffuse light inside the structure and don't require light supplements. Set out planting sites at 2 to 3 feet in the row, with 6 feet between multiple rows. Dig into the top 6 inches of soil in the individual planting sites and add 3 inches of organic compost for moisture retention and nutrition. Mix 5-10-10 fertilizer into the top 3 to 4 inches of soil for optimal rooting.

Plant Sweetheart melon seeds 1/4-inch deep in your amended soil. Use 2 inches of water for each seed to settle the planting then put the new plants on a schedule of 2 inches of water every week. Use 1 inch of organic mulch to maintain soil moisture throughout the season.

Give melons ammonium nitrate fertilizer per the manufacturer's directions when the vines develop. Fertilize each plant again at the first sign of fruit development. Don't over-fertilize the melons as this may lead to vegetative growth rather than fruit growth. Always water the plants immediately after feeding them.

Leave windows and doors open, during the summer, to take advantage of natural summertime warmth and sunshine. Close doors and windows when temperatures drop, during fall, to protect the vines when frost arrives.

Harvest Sweetheart melons when their maturity dates approach. Watch for the rinds to change from gray/green to yellow/buff. Don't leave the melons on the vine, after they reach maturity, to avoid fruit rot.