Germination temperature
Warm: 25-30 °C (77-86 °F).
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Water lemon is a vigorous tropical passion vine with fragrant purple-and-white flowers and edible yellow fruit. Its seed germinates best after the pulp is fermented off and the coat is lightly scarified, at a steady 25-30 °C.
Warm: 25-30 °C (77-86 °F).
About 1 cm (0.4 in), pointed end down.
Usually 2-3 weeks; some seeds take longer.
Covered seed; bright indirect light once seedlings appear.
Ferment off the pulp, scarify lightly, soak 24 hours.
Sow in pots; plant out beside a support when well rooted.
If you have fruit, scoop the seeds and pulp into a clean glass jar, cover it and stir daily for 5-7 days until the jelly coat (aril) separates. Rinse the seeds in a sieve and air-dry them for 24 hours. In a seed trial, fermentation plus scarification gave the best germination for this species, 75%.
Recommended. Rub the seeds between two sheets of medium sandpaper (100-150 grit) for 3-5 minutes until the coat shows scratches; do not grind through to the inside.
Not needed. This is a tropical species and cold treatment does not help.
Soak the scarified seeds in clean water for 24 hours just before sowing.
Keep the pots at 25-30 °C (77-86 °F). In most of India this is easy from spring to the monsoon; in cooler climates use a heated propagator or a warm windowsill.
About 1 cm (0.4 in) deep, with the pointed end of the seed facing down, because the root emerges from the tip.
A good-quality, free-draining seed compost in small pots or deep cells, one or two seeds per pot.
Evenly moist but not saturated. Wet, cold compost makes the seed rot before it germinates.
No light is needed until emergence. Then give bright, indirect light and move seedlings gradually into sun.
Scarified passion fruit seed usually germinates in 10-20 days. Water lemon can be uneven; keep pots warm and moist for two to three months before giving up.
When seedlings have a few true leaves, move each one into a larger pot. Give a thin cane early: the vine climbs by tendrils from the start.
Plant out in warm weather, or at the start of the rains in the tropics, in full sun beside a strong trellis, fence or pergola. The vine can reach about 10 m (33 ft).
Water regularly; this species needs plenty of water. Young passion vines may take up to a year to grow large enough to flower.
Cause: pulp left on the seed, an unscarified hard coat, or a cold pot. Fix: ferment and rinse the seed, scarify it lightly, soak 24 hours and keep at 25-30 °C.
Cause: saturated, cold compost. Fix: use a free-draining mix, water only to keep it moist and keep it warm.
Cause: the species is self-incompatible; a single plant often sets no fruit. Shade and too much nitrogen also cut flowering. Fix: grow at least two seedlings, give full sun, and hand-pollinate with a soft brush between plants if bees are scarce.
Cause: fusarium wilt or collar and root rot on wet ground. Fix: plant on well-drained soil, avoid overwatering and do not let water stand around the stem.
Cause: caterpillars, aphids or mites. Fix: check new growth regularly and remove pests early; aphids also spread passion fruit woodiness virus.
Water lemon is a liana of the wet tropics; in India it has naturalised in Assam and the Andaman and Nicobar Islands. It suits humid, frost-free lowland gardens. In frost-prone climates keep it in a large container under glass.
It tolerates partial shade but fruits better in full sun. Keep watering steady while fruit develops; irregular watering causes fruit drop and shrivelling.
Mix organic matter into the planting site. Avoid heavy nitrogen, which produces leaves at the expense of flowers, and reduce feeding once the vine is mature.
Thin crowded growth so light and air reach the stems; this reduces leaf diseases. Clean tools between cuts.
Scarify and soak water lemon seed, then sow it 1 cm deep in a warm pot.
Yes. Water lemon bears yellow, lemon-shaped fruit with juicy, edible pulp, besides its ornamental flowers.
The species is self-incompatible: in a Florida trial a single clone set no fruit. Grow two or more seedlings and hand-pollinate if few bees visit.
Usually two to three weeks at 25-30 °C after fermentation, scarification and soaking; some seeds take longer, so keep the pots for a couple of months.
No. It is a tropical vine without frost tolerance. Grow it in a container under glass and keep it frost-free.