Gymnocalycium pflanzii
| Light | Bright, indirect light with some shade from harsh summer sun |
|---|---|
| Water | Moderate in growth; allow to dry between waterings, keep dry in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9b–11 |
| Propagation | Seed (primary); offsets on clustering forms |
| Toxicity | Non-toxic to cats and dogs |
Gymnocalycium pflanzii is a large, flattened-globular cactus native to Bolivia, Paraguay and northern Argentina, and one of the more robust members of the genus Gymnocalycium. It forms a broad, low body with wide, rounded ribs and stout spines, producing funnel-shaped flowers with whitish to pale-pink petals set off by a deeper pink to reddish throat. It is a variable species that has absorbed several once-separate names, so the same broad species may be met in collections under labels such as zegarrae, now usually treated as a subspecies of it.
Description
Gymnocalycium pflanzii is among the larger, chunkier species of its genus. The body is a flattened globe that can broaden to 15 cm or more across, dull to glossy green and sometimes flushing bronze or purplish in strong light. It is divided into broad, low ribs — usually about ten to twelve — which are crossed by shallow grooves that break them into rounded, chin-like tubercles below each areole — the "gymno" (naked-budded) genus is named for its smooth, scaleless flower buds.
The spines are stout and somewhat curved, borne on large woolly areoles and usually held close to the body; colour ranges from pale amber to grey-brown, often darker at the base. Flowers open from the crown in spring and summer, funnel-shaped and a few centimetres across, with whitish to soft-pink petals and a characteristic carmine to purplish-pink throat. They are followed by rounded fruits carrying the small dark seeds typical of the genus. Older plants may slowly offset to form small clusters.
Distribution and habitat
The species has a wide range across the dry interior of central South America, spanning parts of Bolivia, western Paraguay and northern Argentina. It grows in warm, seasonally dry scrub and thorn forest, typically rooted in gritty or stony ground among low shrubs and grasses that filter the strongest sun. Across this broad territory the plants vary considerably in size, spination and flower colour, which is the main reason so many local forms were historically described as separate species.
Cultivation
Gymnocalycium pflanzii is a forgiving, good-natured plant and a sound choice for a grower moving beyond the very easiest cacti. Grow it in a very free-draining, mostly mineral mix and give it bright light with a little shade from the fiercest afternoon sun in summer; too much shade dulls the body and softens its shape, while gentle sun-stress can bring out attractive bronze tones. Water thoroughly through the warm months once the soil has dried out, then reduce sharply and keep the plant dry and cool over winter. This winter rest both prevents rot and encourages a good flush of flowers in spring. See Watering and Repotting for general technique.
Like most Gymnocalycium, it tolerates a little more shade and moisture than desert globulars such as Astrophytum, but overwatering in cold or dull conditions is still the main way plants are lost.
Propagation
Seed is the usual and most reliable method, and the one that best captures the species' natural variation. Sow onto a warm, mineral surface kept humid until the seedlings establish; the genus generally germinates well. Clustering plants can also be propagated by removing rooted offsets once they are large enough to handle. See Propagation — seed and Propagation — offsets for full walkthroughs.
Common problems
- Rot — almost always from overwatering or a slow-draining mix, especially in a cold, wet winter; the body softens and discolours from the base.
- Corky scarring — this genus is prone to developing tan, corky patches low on the body with age or from cold, wet exposure; usually cosmetic rather than fatal.
- Pests — mealybugs (white fluff in the areoles and among the roots) and red spider mites (fine webbing, a bronzed, stippled skin) are the common offenders. See Pests and diseases.
See also
- Gymnocalycium — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Propagation — offsets · Repotting · Pests and diseases