Gadenin日本語Get the appWhat the plant is doing after planting out
The first three or four weeks outdoors are slow and can look like failure. The plant is building roots and the top growth barely moves. Then, once the soil is properly warm, luffa switches into the fastest growth of anything in the garden and can add a foot (30 cm) of vine a day in high summer. Your job through that switch is simply to remove obstacles: no dryness, no competition, no check from cold.
Keep the root zone weed free and mulched. A thick mulch of straw or compost laid once the soil has warmed holds moisture, keeps the surface roots cool and stops the soil splashing up onto low leaves, which is where mildew and leaf spot usually start.
Do not cultivate deeply around an established plant. Luffa roots run wide and shallow, and a hoe run through them in midsummer costs you a fortnight of growth at the worst possible time.
Watering a very large vine
A mature luffa moves a remarkable amount of water. In peak summer a single plant in open ground wants the equivalent of one to two inches (25 to 50 mm) of rain a week, delivered in one or two deep soakings rather than daily sprinkling. Shallow watering keeps the roots at the surface where they bake. Water at the base, in the morning, and keep it off the leaves.
Read the plant rather than the calendar. Big luffa leaves wilt in the middle of a hot afternoon even when the soil is perfectly moist, so the meaningful check is early morning: leaves still drooping at dawn mean the plant is genuinely short. Push a finger into the soil under the mulch, and water when the top two inches (5 cm) are dry. Fruit that swell during a dry spell and then get a sudden flood are the fruit that split.
| Stage | Water | Feed | What you are aiming for |
|---|---|---|---|
| Establishment | Keep evenly moist, little and often | None beyond the compost worked in at planting | Roots taking hold; visible new leaves |
| Rapid vine growth | Deep soak once or twice a week | Balanced feed every two to three weeks | Leaf area and length of vine |
| Flowering begins | Deep and consistent | Cut nitrogen, switch to a low nitrogen high potassium feed | Female flowers rather than more leaves |
| Fruit sizing | Heaviest demand of the season, never let it dry out | Potassium rich feed every two weeks | Fruit filling evenly, no splits |
| Fruit drying down | Reduce steadily | Stop feeding | Skin hardening and moisture leaving the fruit |
Feeding without growing a monster
Luffa is hungry, but it responds to nitrogen by making vine. A plant fed generously on a high nitrogen feed all season produces a magnificent green curtain, a great many male flowers and very little fruit. Work plenty of compost into the ground before planting, feed a balanced liquid feed every two or three weeks while the vine is running, and then change over at the first sign of flowering to something low in nitrogen and high in potassium.
If your plant is all leaf and no fruit in midsummer, the diagnosis is almost always feeding rather than anything exotic. Stop the nitrogen entirely, keep watering, and it will usually come into female flower within a fortnight.
Pollination, and why you may need to do it yourself
Luffa carries separate male and female flowers on the same plant. The males come first, sometimes for two or three weeks before any female appears, which alarms new growers every year. A female flower is unmistakable once you see one: a miniature gourd sits behind the petals. The males are borne in clusters on a long stalk; the females sit singly, close to the stem.
The flowers open in the morning and are receptive for a single day. If your fruit are yellowing at the tip and dropping off at an inch or two long, they were not pollinated. Bees do most of the work in most gardens, but in wet weather, in a poorly visited town garden, or in the first weeks when very few females are open, hand pollination turns an empty vine into a full one.
- Pick a male in the morning Choose a freshly opened male flower shortly after it opens. Snap it off with an inch (2 cm) of stalk and peel the petals back to expose the pollen bearing center.
- Dab the female directly Touch the male center onto the stigma in the middle of an open female flower and roll it gently around, transferring visible pollen. One male will comfortably do two or three females.
- Mark what you pollinated Loop a piece of colored twine on the stem behind each pollinated female. On a crop where days from pollination to a ripe sponge is the number you need, an unmarked fruit is a fruit you cannot date.
- Repeat every morning through the setting window Fruit that sets in the hottest weeks is the fruit with enough time to ripen. Late set fruit will still be green when frost arrives, so concentrate your effort early and stop bothering once the season is too short.
Thinning, tidying and what to record
A vigorous plant will set more fruit than it can ripen. If you are growing for sponges, count the fruit that set in the main flush and remove late ones, along with any that are misshapen or lying against the structure. Fifteen to twenty well spaced fruit on a strong vine will all ripen; forty will produce forty spongy half finished gourds. Take off any leaf that has gone yellow at the base of the plant to keep air moving.
Keep a note of the date the first male flower opened, the date the first female opened, and the date of each pollination you performed. Add the date you switched feeds. Together those tell you next year whether your gap between males and females is normal for your site, and exactly how late in the summer a fruit can set and still finish.