Crinum lily plants are poisonous. In fact, while they’re called spider lilies, they’re also called poison bulb! Right about now, I’m guessing you’re wondering why you’d want to grow a poisonous plant. The answer’s simple: it’s because they’re stunning.
These plants reach heights of four to six feet tall, with long, slender blade-like leaves. Their flowers are usually white, but may have red or purple highlights. They thrive in subtropical temperatures. In fact, they’ve become naturalized in much of the southwestern United States.
If you’re in a warm climate, you’ve probably seen these before. Popular plants that they are, they’ve become widespread. So let’s talk about crinum lilies and how to care for them safely!
A dwarf species with a umbel of one or two (rarely three), comparatively large and fleshy flowers that are strongly scented. The peduncles are underground and therefore the fruit are usually partially buried. The segments are white, with a pink flush, usually keeled with deep pink.
C. bulbispermum orange river lily (Eng.), oranjerivierlelie (Afr.)
Frequently confused with C. macowanii in nurseries, the leaves are greyish green and not the brighter green or less glaucous (pale bluish green) colour characteristic of the latter species. One of the largest of the South African species, the bulb is very large and the sheathing leaves usually form a thick false stem up to 400 mm long, glaucous green.
C. campanulatum vleilelie (Afr.)
One of the true aquatic species that needs to be placed under water to flower. Flowers are few, up to seven. The perianth is funnel-shaped, segments are white to uniform light pink, becoming deep red in the fading flower. Endemic to a small area in the Eastern Cape.
C. graminicola graslelie (Afr.)
Closely related to C. stulmannii and differs mainly in that its fruit develops faster and is usually beaked. The peduncle is usually relatively short and spreading. Flowers are usually a uniform deep pink color but many plants have flowers that are white with a prominent, deep pink keel. This species is unusually slow to mature, a minimum of eight years should be expected and it flowers irregularly.
C. lugardiae veld lily (Eng.); veldlelie (Afr., Du Plessis & Duncan 1989)
Despite its recorded common name, the species is more often recorded in areas adjacent to vleis or areas subjected to brief seasonal flooding. It is an easily grown species (though slow-growing), but adapts well and flowers regularly in a garden. C. lugardiae is smaller, but similar in appearance to C. macowani and they are sometimes confused. Distribution is from Gauteng to Namibia.
C. macowanii Sabie crinum, Cape coast lily (Eng.) umNduze (Zulu)
Particularly suitable for use as a landscape or garden plant. It is probably the easiest species to cultivate owing to the large number of seeds produced and plants can flower within three years in optimum conditions. When flowering between October and December, the large inflorescences with up to 25 large white flowers present a spectacular display (Archer & Condy 1999b).
C. moorei Natal lily (Eng., Du Plessis & Duncan 1989), boslelie (Afr.)
A tall plant with its almost evergreen leaves emerging from a thin pseudostem, is horticulturally most suitable for any garden. This is the only one of the South African species which grows and matures new leaves each season, therefore the leaf tips are neat and not truncated as in the other species. Five to ten flowers are born on a long, erect peduncle. The perianth segments are white or pale pink and form a very wide open funnel, adding to its attraction. In addition, the species prefers shade. In most highveld gardens leaves die off after March and emerge early in July.
A smaller plant often found in large numbers in vleis. The vlei on the Sandhof Farm in Namibia is a small natural wonder when a million plants are in flower simultaneously. It has a scattered distribution from KwaZulu-Natal and Mozambique, to Namibia. The leaves are light green and gracefully arch outwards ‘like young mealies’. Flowers 5 to 11, white to pink, sometimes with a darker pink keel.
C. stuhlmannii candy-striped crinum (Hesse 2001)
Until recently known as C. delagoense or C. forbesii (Archer & Archer 1996; Lehmiller 1997). The species occurs from KwaZulu-Natal to East Africa along the coastal region and along the low-altitude Zambezi and Limpopo Valleys. The species is similar to C. graminicola but with a long erect peduncle and with numerous (up to 30) flowers. The perianth segment usually has a prominent deep pink keel which gave origin to the above-mentioned common name.
Crinum Lily Care
Light & Temperature
Spider lily loves the sun. But it’ll accept partial shade, particularly if it’s during the hottest part of the day. It can develop leaf scorch if the intensity of the sun is particularly brutal.
Most people will find that 6-8 hours of sunlight is perfect for optimal growth. If you’re in a particularly hot climate, consider 4-6 hours of direct sun and a couple hours of partial shade.
In cooler climates, this plant should be brought indoors before cooler weather arrives. Once the temperature dips below the 40’s at night, you run the risk of the leaves becoming cold-damaged. These plants are not frost-hardy at all, and the first frost often causes dieback of foliage.
These plants love moist soil! They perform best in locations that get consistent watering. Pond borders and poolside placements are common. But don’t limit them to those areas. If you water regularly, you can place these throughout your yard.
While the crinum lily can tolerate infrequent watering, they won’t grow as fast. Short periods of drought are okay, as long as they don’t last more than a few days to a week at most. These may need more water during the hottest times of year.
At the same time, don’t overwater. If there are puddles or the ground is muddy, wait for the water to drain away and the soil to partially dry. Excess water can cause the bulb to develop rot issues.
Your ideal soil for your spider lily plant should be moist but well-draining. It should be rich with organic matter and fertile. While this plant can grow in poor soils as well, it will be vigorous with this mix! I like to use a sandy soil base and amend it with lots of compost.
I recommend adding shredded leaf mulch or wood chip mulch around the base of plants. Not only will this continue to improve the soil quality, but it’ll prevent evaporation.
White, starburst-like flowers of crinum asiaticum. Source: Tim Waters
For my crinums, I like to use a slow-release, balanced granular fertilizer. Spread this in early spring, early summer, and early fall around the base of plants. Work it lightly into the soil. This should be plenty of food for your plants.
If you’d prefer a liquid, opt for a half-strength liquid fertilizer. From spring through the summer, fertilize monthly. Only fertilize it once early in the fall, and skip the winter entirely.
Seeds are slow to get started and may be unreliable, but it is an option. Plant shallowly, no deeper than 1/8″ beneath the soil’s surface. Once they have germinated, remove the weaker ones and keep the strong ones. Allow them to develop some foliage and to begin to form a bulb before transplanting into small pots.
Plant your seedling plants outdoors in the spring after all chance of frost has gone. It’s important to harden off your plants to the outdoor conditions before transplanting.
Division is often the simpler option. Loosen the soil around your plant’s base and determine how large the bulb is. Remove it and all attached offshoot bulbs. Be careful not to damage the bulbs! It should be easy to separate the plants by gently untangling roots and separating them.
Once separated, replant in the garden bed, leaving at least two to three feet between the plants. They will grow to fill in the space. You can also place smaller offshoot bulbs into pots. They prefer to become rootbound in the pot, so use a pot which is just slightly larger than the bulb itself.
When planting offshoot bulbs or replanting your older ones, bury all but the top of the neck under the soil. Leave the neck poking up over the soil’s surface. It’s from that neck that your plant will form.
The leaves can reach up to 4 feet in length and nearly 5″ wide at the base. Source: Jungle Garden
Generally speaking, your poison bulb plant won’t need much in the way of pruning. But when you do trim it, take precautions. All portions of the plant are poisonous, so wear gloves. Sterilize your pruning tools before and after working with this plant.
Trimming off dead leaves or spent flowers is most of what you’ll need to do. Remember, 20 or more flowers can form on one scape, so be sure all the flowers on the scape are spent. Then, cut the scape back close to the plant’s base. Another scape will develop from the same location when it next flowers.
If you live in zone 8 or 9, you may need to prepare your plants for overwintering. This ensures that any frost won’t hurt the plant. Trim back the leaves to the ground as the weather gets cool. If you’d like, you can cover over the plant with a couple inches of mulch to protect the bulb from chilly conditions.
Those who get frosts and freezes throughout the winter should be ready to move indoors. Crinum lilies are not tolerant of freezing weather! Carefully uproot your bulb and place it in a pot just a bit larger than the bulb itself. Fill in around it with soil. Keep it indoors in the brightest area you can find through the chilly months.
Plants in hot, full-sun conditions can experience leaf scorch. While not common, it does happen when the temperature peaks mid-to-late summer. If you have a large plant, a few scorched leaves won’t cause you any harm. But if it’s young, this may be a problem. Try to place your plants where there’s afternoon shade if you’re in a hot climate.
If over-watered, you may find the bulbs start to rot. They’re tolerant of excess water to a point, but eventually will succumb. Ensure your soil is well-draining to prevent this problem by adding sand or perlite.
If the tips of the leaves are starting to go brown, this is usually a sign of too little water. Be sure the moisture in your soil is consistent. Mulching around your plants can help keep the soil moist for longer periods of time.
Because of its poisonous alkaloids, its only real pest is the specifically adapted black-and-yellow-striped amaryllis caterpillar (Brithys pancratii) and occasionally snails and slugs, which may render especially the thin-leaved species an unsightly mess in a short time. However, the bulbs of large plants are seldom entirely destroyed by the caterpillars and new leaves grow out quickly. A broad-spectrum insecticide containing a modern pyrethrin can be used. In a garden, the amaryllis caterpillar often necessitates regular spraying in summer.
Virus-infected plants, especially from large or retail nurseries can be a problem and should be checked carefully for any symptoms. Unfortunately it is not easy to distinguish between viruses and some fungal diseases and any suspect plants should be destroyed to stop the virus from spreading by root disturbance or insects. Basal stem rot occasionally infects the plants but can be treated with fungicides.
Anthracnose leaf spots are not uncommon on these plants. Your best bet to combat these is to use a copper-based fungicide. Sulfur-based fungicides will also work, but to a lesser extent.
Powdery mildew occurs when the weather is warm and humid. It won’t severely injure your plant, but it’s unsightly and annoying and can spread. Neem oil acts as both a preventative and a curative for this issue.
Botrytis cinerea is uncommon but may occur. This is also most prevalent when it’s warm and humid outside. Provide good airflow around your plant and avoid watering from above. If necessary, treat outbreaks with an organic fungicide. Just be careful to vary your methods when fighting botrytis. It’s been known to become resistant to fungicides after repeated use.