When luffas are ripe their skins turn brown and dry and stems turn yellow. Check your plants frequently and harvest only ripe gourds. Full-sized fruit that are still green produce soft, fine-textured sponges that don’t last. After the first killing frost remove any nearly ripe gourds to a warm well-ventilated place to allow them to dry. Gourds left wet for long will readily discolor.
If the luffa has just ripened, gently squeeze and pop its skin. Break the blossom end cap and pull the vascular bundle (that’s the sponge!) up the side of the gourd like a zipper. The sponge will pop out, wet and white. Quickly rinse it in water to prevent oxidation.
If gourds are too dry to pop the sponge out, ret them (thoroughly soak in water) for several days until the skin sloughs off leaving only the spongy fiber. After retting, shape and dry the sponge. Remove seeds either before or after retting. We found it easy to do before retting: cut open the larger end of the gourd and either shake or rinse out the seeds. If you wish to whiten the sponges, bleach by soaking either in a 10% bleach solution or in hydrogen peroxide. Rinse luffas thoroughly in clean water and dry before use.
Ornamental gourds avg, 500 seeds/oz; Luffa avg 280 seeds/oz; Hardshell gourds avg 120–200 seeds/oz. Gourds come in two major categories (Luffa is a third). The small ones are Cucurbita pepo var. ovifera, known as ornamental gourds for their variety of shapes, colors and surfaces. These vigorous viners will usually mature in our climate if direct-seeded. The larger ones are Lagenaria siceraria or hardshell gourds, named from the Greek lagenos, ‘a flask,’ and sicera, ‘an intoxicating drink.’ Lagenaria, though lacking the color range of their smaller cousins, fascinate with their magical shapes.