Plants
Onion Plant
Crinum spp.
Origin: Aquarium crinums come from Africa and Southeast Asia. The African onion plant (calamistratum) is from the rivers of West Africa (Cameroon), and the Thai onion plant (thaianum) from the rivers of Thailand. They grow in flowing water, rooting by a bulb in the substrate.
Also known as: Crinum, Crinum calamistratum, Crinum thaianum
Fact sheet
- Height
- 80 cm
- Temperature
- 22–28 °C
- pH
- 6–8
- Lighting
- Medium
- CO₂
- Not needed
- Growth rate
- Slow
- Placement
- Background
Overview
Crinums are large bulbous plants with long strap-like leaves that form striking specimen rosettes for big aquariums. The best known are the African onion plant with narrow dark green strongly crinkled leaves and the Thai onion plant with long green strap-like leaves. They are hardy, long-lived, undemanding plants that need no CO2 or bright light. The key rule is not to bury the whole bulb (it will rot) and not to disturb an established plant. Crinums resist herbivorous fish thanks to their tough leaves.
Appearance
A large bulb from which a rosette of long strap-like leaves rises. The African onion plant has narrow (1–2 cm), dark green, strongly crinkled leaves; the Thai one has long (up to 1.5 m) green ribbons. Height is 40–120 cm depending on the species. It can flower underwater and above water with large white lily-like blooms.
Care
Undemanding: moderate light, 22–28 °C, pH 6.0–8.0, a wide hardness range. CO2 is not required. Plant the bulb so the upper third stays above the substrate. They dislike being moved — an established crinum is best left alone. Nutrient-rich substrate is needed.
Fertilizing
A bulbous plant with heavy root feeding: it appreciates nutrient-rich substrate and root tabs. Liquid fertilisers and iron support leaf colour. A nutrient reserve is stored in the bulb.
Breeding
It propagates by daughter bulbs (offsets) that form at the mother bulb; they are separated once rooted and leafed out. Seed propagation is possible when flowering.
Fun facts
The tough leaves of crinums are left alone even by herbivorous cichlids, making them valuable for cichlid tanks. An established crinum dislikes transplanting and may stall its growth for a long time after being moved. Crinums are relatives of garden lilies and can flower underwater.