Growing Winter Melon: Watering, Feeding and Managing a Vine That Runs Twenty Feet

What you are actually managing

Winter melon is not a fussy plant, but it is a large one, and almost every problem with it comes from treating it like a normal vegetable in a normal bed. The vine runs fifteen to twenty feet (4.5 to 6 m), roots wherever a node touches damp soil, and carries fruit that individually weigh as much as a small child. Care is mostly about giving it enough of what it needs early, then getting out of its way and keeping the fruit dry.

The single most useful decision is restricting each plant to one or two fruit. A vine allowed to set five will size all of them poorly, ripen them late, and give you nothing that stores. Two well-fed fruit on one plant beat five mediocre ones every time, and the restriction is what makes the rest of the care work.

Watering: deep, infrequent, and never on the fruit

A plant this size moves a lot of water, and in the six weeks while fruit are sizing it will use more than anything else in the plot. But it roots deeply, so the right pattern is a long soak once or twice a week rather than a daily sprinkle. Shallow frequent watering keeps the roots near the surface and makes the plant collapse the first time you go away for a weekend.

Aim for one to two inches (2.5 to 5 cm) of water a week during fruit sizing, delivered at the crown and along the rooted nodes. Water the soil, early in the day, never the leaves. Wet foliage overnight is the reliable way to bring powdery mildew and downy mildew forward by a fortnight.

1. Check at a spade's depth Push a trowel in six inches (15 cm) beside the crown. If it comes out dry at that depth, water. Surface dryness means nothing on a mulched bed.
2. Soak, then leave it Give each plant five to ten gallons (20 to 40 liters) in one go, then leave it for several days. That drives roots down where the moisture is steady.
3. Mulch once the soil is warm Straw or compost three inches (8 cm) thick over the root area holds moisture and keeps the fruit out of splash. Do not mulch cold ground, and keep it clear of the stem itself.
4. Ease off as the fruit finishes In the last two to three weeks before harvest, cut watering back sharply. Heavy watering late thins the skin, dilutes the flesh and shortens storage life considerably.

Wilting leaves at midday in strong heat are normal on a plant carrying this much foliage and do not mean it needs water. Judge by whether the leaves have recovered by early evening. If they have not, water deeply that night.

Feeding: nitrogen early, then stop

The feeding pattern matters more than the fertilizer you choose. Winter melon needs nitrogen to build the enormous frame of leaf that will eventually fill a twenty pound (9 kg) fruit, and then it needs that nitrogen to stop. A plant still being pushed with nitrogen while fruit are sizing makes more vine, sets fruit poorly, and produces soft-skinned fruit that will not keep.

The switch happens at first flowering. From that point on, potassium and phosphorus are what you want, and nitrogen becomes a liability.

A vine that is all lush leaf with flowers that drop without setting has been overfed with nitrogen. There is no quick fix. Stop feeding, water less, and the plant will usually correct itself in two to three weeks.

Managing the vine and protecting the fruit

Because this crop lies on the ground, the fruit spends two months in contact with soil, and that contact is where every avoidable loss happens. A twenty pound (9 kg) fruit that rots on its underside is discovered at harvest, when it is far too late to do anything about it.

There is a second, subtler point that decides whether the crop keeps at all. Winter melon develops a white waxy bloom on its skin as it matures, and that bloom is what allows the fruit to sit in a cool room for months without shriveling. It rubs off with a careless hand, a dragged tarpaulin, or wiping the fruit clean. Once it is gone from a patch of skin, that patch is where the fruit will fail. Handle the growing fruit as little as possible and never polish it.

1. Get a board under each fruit early Once a fruit is the size of a grapefruit, slide a tile, a plank or a thick straw pad underneath. Do it before the fruit is heavy enough to be awkward to lift.
2. Root the runners as they go Press soil over a node every four or five feet (1.2 to 1.5 m) along the main runner. Each buried node roots and feeds the vine, which matters enormously if a borer takes the crown.
3. Direct the vines, do not cut them Guide runners back over themselves or along a path edge rather than shortening them. Leaf area is what fills the fruit and you want all of it you can get.
4. Do not turn or wipe the fruit Unlike pumpkins, a maturing winter melon should be left alone. Turning it scuffs the bloom on the underside and wiping it removes it entirely.

Weather, wind and the things that go wrong

Heat is what this crop wants. Days in the 80s Fahrenheit (27 to 32C) and nights above 65F (18C) are ideal, and growth slows noticeably whenever nights fall below 60F (15C). Wind is the other consideration: a big flat canopy catches it, and vines flipped over repeatedly tear at the rooted nodes. A hedge, a fence or a row of tall plants on the windward side pays for itself.

Notes worth keeping

Winter melon is grown once a year and each plant gives you one or two data points, so memory is a poor guide and a few written lines are unusually valuable. Keep them per plant, not per bed.

1. How many fruit you let each plant carry Record the number you kept and what each one weighed at harvest. Two seasons of that tells you exactly what your ground will support.
2. The date you stopped nitrogen Note when you made the switch and whether flowers set well afterwards. Late switching is the commonest cause of a leafy plant with no fruit.
3. The date the vines began to run This is your best single marker of how the season is going. Compared against last year it tells you early in the season whether you are ahead or behind.
4. Where each fruit sat on the ground Note whether a fruit was on a board or on bare soil, and whether it kept. One season of that note usually ends underside rot for good.