Sago palm

Identification and origin

Cycas revoluta belongs to the family Cycadaceae, a very ancient group dating back some 200 million years. It is native to southern Japan, notably the island of Kyushu and the Ryukyu Islands, as well as southeastern China and Taiwan, where it grows in thickets on hillsides. Although it is often called a palm, it is not one: it is a gymnosperm, botanically closer to conifers. It does not flower but produces cones.

It forms a symmetrical rosette of evergreen leaves atop a thick, dark brown, shaggy trunk. The pinnate leaves are glossy dark green and 3–7 ft long depending on the plant’s age. Each carries many narrow, leathery, rigid leaflets 3–6 in long, ending in a sharp point; their edges roll under, hence the epithet revoluta, “rolled back.” The lowest leaflets are often reduced to spines.

Growth is extremely slow: a young plant reaches 2–3 ft over several years and can take fifty years or more to approach 10 ft. In a container it stays smaller. Young plants produce leaves in several flushes a year, mature plants in just one. The plant is dioecious: the male produces an upright, yellowish, pineapple-shaped cone 12 in – 2 ft long; the female forms a rounded, golden, feathery head that holds bright orange seeds if a male has pollinated it. Indoors, cones are rare. Its slow growth also makes it a popular bonsai subject.

Light

Sago palm wants bright light. Indoors, give it four to six hours of filtered sun a day, for example through a sheer curtain at an east-, west-, or south-facing window. Harsh sun can damage the leaves. Outdoors it grows in full sun or part shade, and part shade often suits it best; in shade its leaves grow larger.

Watering

Watering is the trickiest part. Sago palm does not tolerate overwatering or poor drainage, yet it should not dry out completely either. Water when the surface of the mix is nearly dry, then moisten the whole root ball and empty the saucer. During active growth, from early spring to early fall, its needs are steady. The rest of the year, water sparingly. Once established in the ground, it is drought tolerant.

Potting mix

In a container, use a loam-based mix lightened with sand and a little leaf mold or grit: drainage must be excellent. In the garden it likes sandy or loamy soil rich in humus, acidic to neutral. A terracotta pot, which dries out faster, is a good choice.

From early spring to early fall, fertilize once a month. Its needs are similar to those of palms, so a palm fertilizer containing manganese works well. Overly alkaline soil locks up this nutrient.

Temperature

Sago palm likes warmth. Indoors, winter nights should not fall below 55 °F.

Outdoors it tolerates brief cold spells, but frost damages the foliage; the plant does not survive below about 16 °F. The crown is more cold-resistant than the leaves, and scorched foliage is often replaced by a new flush of healthy growth. In the ground it is grown in USDA zones 9a to 12b; elsewhere it is kept in a pot so it can be sheltered in winter.

Repotting

Sago palm grows so slowly that it needs repotting only occasionally, roughly every third year. It likes being a little pot-bound. Move it to the next pot size up, using a loam-based mix. Wear gloves: the leaflets are sharp and the plant is toxic.

Pruning

No pruning is needed. Simply cut dead or damaged leaves off flush with the trunk. A spotted leaf will not recover: wait until a new flush of healthy leaves has emerged before removing it.

Propagation

Sago palm is propagated by offsets or by seed. As it ages, it produces offsets, or pups, at its base, which can be separated and potted in a very free-draining mix. This is the most practical method, but it takes patience: growth remains very slow.

Seed is only possible from a female plant pollinated by a male, which almost never happens indoors. The seeds are the most toxic part of the plant: handle them with gloves and keep them out of reach of children and pets.

Common problems

• Scale: cycad aulacaspis scale (Aulacaspis yasumatsui), white and waxy, causes yellowish blotches followed by drying leaves and can kill the plant; it even colonizes the roots. Wash the leaves with a strong spray of water, remove the worst-affected ones, and treat with horticultural oil, covering leaf undersides thoroughly. The roots of a small potted plant can be dipped in a 2% horticultural oil solution. Other scales can appear as well.
• Mealybugs: cottony clusters, honeydew, and sooty mold, especially in shady, cool spots.
• Spider mites: common in dry air.
• Small, distorted new leaves that turn yellow, then brown: manganese deficiency, often caused by alkaline soil, but also by roots damaged by rot, too much or too little water, or recent transplanting.
• Root rot: too much water or poor drainage.
• Evenly browned leaves, mostly on top: cold injury.

The same symptom can have several causes: always check watering, drainage, light, and pests before drawing conclusions.

Toxicity

Sago palm is highly toxic to dogs, cats, horses, and people. All parts contain cycasin, a neurotoxin, and the seeds have the highest concentration. In animals, ingestion causes vomiting, black stools, jaundice, increased thirst, bloody gastroenteritis, bruising, clotting problems, and liver damage that can progress to liver failure and death. Pets are often attracted to the plant. In people, symptoms include vomiting, diarrhea, weakness, seizures, and liver failure. The plant also irritates skin: wear gloves. Keep it out of reach of children and pets, and if any part is eaten, contact a veterinarian or a poison control center right away.