Luffa is a warm-season gourd vine with two uses: pick the fruit young and cook it like squash, or let it mature and dry into a biodegradable sponge. It grows much like cucumber, but the vines are far longer and need a tall trellis. Fruit lying on the ground tends to rot.1, 2
When to plant luffa in Florida
Region
Months on the UF/IFAS calendar
North Florida
Apriltransplant with care · Maytransplant with care · Junetransplant with care · Julytransplant with care
Central Florida
Marchtransplant with care · Apriltransplant with care · Maytransplant with care · Junetransplant with care · Julytransplant with care
young fruit for eating needs about two to three months of hot weather (EDIS HS1285)
Gardening Solutions says to sow from March through July in full sun. EDIS HS1285 describes two Florida production seasons, early March to late July and late July to late November. Move seedlings out once they have two or three true leaves. Direct seeding is quicker but must wait until frost is past; transplants extend the season and give an earlier harvest. Seedlings in cold, wet ground can damp off. Luffa also grows in 2- to 5-gallon containers. The first three varieties listed are smooth luffas; the rest are angled types.
neutral to slightly alkaline (Gardening Solutions); HS1285 suggests the cucumber target of 6.0 to 6.5 until luffa-specific advice exists
Water
Needs consistently moist but well-drained soil; standing water slows growth and raises the risk of root disease.
Fertilizer
UF/IFAS has not set fertilizer rates for luffa yet. Follow the cucumber recommendations; Gardening Solutions suggests a balanced slow-release fertilizer when needed, guided by a soil test.
Vines are long (HS1285 gives stems up to 23 feet and vines up to 30 feet; Gardening Solutions says up to 30 feet), so put up a vertical trellis about 6 feet tall or more. Trellising raises yield and gives straighter fruit. A well-grown plant can bear about six or seven fruits. Pollinators visit the yellow flowers.
For eating, pick fruit while young and under about 6 inches long; it can be eaten raw or cooked like squash. Left on the vine it turns fibrous and bitter. For sponges, wait until the fruit is fully mature and its green or brown skin is pulling away from the fibers. Then slit it lengthwise, peel it (a soak helps), shake out the seeds, rinse, and dry in the sun. Dry seeds and store them somewhere cool, dark and dry for next season.
Neither source names luffa. FAO's cucumber entry says squash, zucchini and melons suit media beds because of their large roots and need a lot of nitrogen and potassium (p. 173); this rating rests on that cucurbit-group statement. FAO gives no guidance on vines this long.
What this lesson doesn't cover yet
No seed depth was found in UF/IFAS sources.
HS1285 gives two different maximum lengths (stems up to 23 feet, vines up to 30 feet); both are reported.
Your county extension office and its Florida Master Gardeners can fill these in for your garden.