Marrows are a traditional vine crop in the UK, but have been mostly overlooked by gardeners in the U.S. These squash relatives can grow up to 3 feet long, but are best when they are picked between 8 and 12 inches in length. Marrows can take between 10 and 14 weeks before the first harvest, but they will continue producing until frost kills them off, if you continue to pick them when they ripen.
Dig the soil in your marrow plot 12 inches deep and remove all the roots and rocks you find. Mix in a 4-inch layer of well-rotted compost.
Plant the marrow seeds 2 feet apart, planting two seeds next to each other in each spot. Marrow vines grow large, so don't space them any closer together.
Plant the seeds 1 inch deep, cover them with soil and tamp the soil down on top.
Water the ground thoroughly until it is saturated. Keep the ground moist while growing your marrows, giving 1 inch of water per week.
Thin each pair to just one plant when they have two sets of true leaves. Nip off the weaker plant with your fingernails right at the soil line.
Place mulch over the soil around the seedlings to help keep in the moisture and to prevent weeds from sprouting.
Fertilize with liquid fertilizer when the plants have produced fruits. Continue fertilizing once a week until the frost kills the plants.
Pick your marrows when they are 8 inches long. Continue picking every few days to keep the plant producing for the rest of the season.