Gadenin日本語Get the appTwo crops, one decision
Every luffa fruit is on a one way journey from vegetable to sponge, and the point of no return arrives early. In the first week or so after pollination the fruit is tender all the way through and cooks like a courgette. From then on fiber begins forming from the inside out, and by the time the fruit is a foot (30 cm) long there are strands running through the flesh that no amount of cooking will soften.
So decide fruit by fruit as the season runs. Take the first few small ones to eat if you want them, but leave the fruit that set in the hottest weeks alone, because those are the ones with enough time in front of them to dry down on the vine. Each fruit you eat is a sponge you will not have, and each sponge you wait for is roughly four months of the plant's attention.
Do not try to salvage an over sized fruit for the kitchen. Once the fiber network has formed the fruit is inedible and stringy no matter how it is prepared. Leave it and let it become a sponge instead.
Picking young fruit to eat
For eating, pick at four to six inches (10 to 15 cm) long, when the skin is smooth, deep green and easily marked with a thumbnail, and the fruit snaps rather than bends. That is usually five to eight days from pollination in warm weather. Cut with snips leaving half an inch (1 cm) of stalk rather than pulling, since pulling tears the lateral.
Young fruit does not keep. Use it within three or four days, stored in the salad drawer of a fridge wrapped loosely in paper. In peak season a single plant will hand you something every day or two, and picking regularly at this stage encourages more female flowers, which is a genuine reason to eat a share of the crop even if sponges are the goal.
Judging a sponge on the vine
A sponge is ready when the fruit has essentially dried on the plant. Green fruit is heavy with water; a finished one is startlingly light for its size, and that change in weight is the single most reliable test you have. Pick one up without detaching it and compare it with a green one on the same vine. The skin goes from green to yellow to a dull tan or brown, becomes loose over the fiber, and often cracks or flakes at the blossom end.
Shake it gently. A ripe fruit rattles, because the seeds have dried and come free inside the fiber. If the stem attaching it to the vine has gone brown and dry, the fruit has finished drawing anything from the plant and can come off whenever you like.
| Signal | Not ready | Ready |
|---|---|---|
| Skin color | Green, or green going yellow | Tan to brown, often blotchy |
| Weight in the hand | Heavy, dense, full of water | Surprisingly light for its size |
| Skin over the fiber | Tight and firmly attached | Loose, papery, cracking or flaking |
| Sound when shaken | Silent | Seeds rattling clearly inside |
| The stem | Green and pliable | Brown, dry and shriveled |
| Squeeze test | Firm and solid | Gives slightly and springs back |
Peeling and cleaning the sponge
There are two routes, and they suit different endings to the season. If frost is close and your fruit are still green or only just turning, cut them and peel them green: the skin comes away in wet strips and the inside must be washed hard. If the fruit have dried on the vine, dry peeling is far easier and far less messy. Either way, get the seeds and the sap out completely, because sugars left in the fiber attract mold and turn a good sponge gray within weeks.
- Dry peeling Press the fruit between both hands until the brittle skin cracks along its length. Snap off the blossom end and shake the loose seeds out into a bowl, then peel the skin away in sheets. A tan, rattling fruit peels in under a minute.
- Green peeling Soak the fruit in water for a day or two to loosen the skin, then peel it off in strips. Wear gloves: the sap is slimy and stains hands and clothing brown. Squeeze the fruit repeatedly under running water like a sponge until the water runs clear and no slippery feel remains.
- Wash out the sap Whichever route you took, wash in warm soapy water, squeezing hard and rinsing several times. Any remaining stickiness means sugars are still in the fiber. This is the step people cut short, and it is the reason a sponge later goes moldy.
- Lighten it if you want to A soak of twenty to thirty minutes in one part household bleach to ten parts water turns a beige sponge pale cream and kills off spores. Rinse thoroughly afterwards. Skipping this leaves a perfectly usable sponge that is simply darker.
- Dry it hard Hang the cleaned sponge in full sun with plenty of air until it is bone dry right through, which usually takes two to four days. Squeeze the middle to check. A sponge stored even slightly damp will spot with mold in storage, and no cleaning brings it back.
Seed, storage and what to record
Keep the seed that fell out of your best fruit. Spread it on paper for a week until completely dry, then store cool and dark in a paper envelope, where it stays viable for four to six years. Only seed from fully ripened tan fruit is mature; seed shaken from a fruit peeled green will not grow. Finished sponges keep indefinitely in a dry, airy place, and should never be stored in sealed plastic.
Record the date of the first ripe sponge and how many days it took from the pollination date you marked on that fruit. Note how many fruit ripened fully against how many were still green when frost ended the season. That ratio, more than anything else, tells you whether to sow earlier next year or simply grow fewer plants and pollinate a narrower window.