Mature size & growth rate

How big does Bishop's Cap Cactus (Astrophytum myriostigma) get?

Also called Bishop's cap cactus, Bishop's miter cactus, Bishop's hat, Star cactus, Monk's hood cactus.

More about bishop's cap cactus

Size at a glance

Indoor / contained size: Slow-growing: usually 10-20 cm (4-8 in) tall and 8-15 cm (3-6 in) wide as a potted houseplant. Very old or wild specimens can eventually reach 30-100 cm tall. Plants may take around six years to first flower.
Growth rate: Slow grower
Habit: Solitary, spineless globular cactus that becomes shortly columnar with age. The chalky grey-green body is covered in tiny white woolly scales (trichomes) and typically carries five prominent ribs forming a clean star shape - the bishop's-miter silhouette that gives it its name. Ribs may increase to 6-10 over many years. Glossy yellow, sweet-scented funnel-shaped flowers appear from the crown intermittently through the warm months on mature plants.
Time to mature size: many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years

About Bishop's Cap Cactus

Astrophytum myriostigma · also called Bishop's cap cactus, Bishop's miter cactus · houseplant

Bishop's cap (Astrophytum myriostigma) is a slow-growing, spineless Mexican desert cactus prized for its chalky white-flecked, star-shaped ribbed body and yellow summer flowers. Give it bright light and sharp-draining cactus mix, water only when bone dry, and keep it warm and frost-free. Not individually ASPCA-listed; treat as low-risk but verify with a vet.

Mature size: Slow-growing: usually 10-20 cm (4-8 in) tall and 8-15 cm (3-6 in) wide as a potted houseplant. Very old or wild specimens can eventually reach 30-100 cm tall. Plants may take around six years to first flower.

Indoor size vs how big it gets in the wild

Bishop's Cap Cactus grows into a room-scaled plant of roughly slow-growing: usually 10-20 cm (4-8 in) tall and 8-15 cm (3-6 in) wide as a potted houseplant. very old or wild specimens can eventually reach 30-100 cm tall. plants may take around six years to first flower. — bigger than a tabletop plant, but not a tree. Indoors and in a pot, expect slow-growing: usually 10-20 cm (4-8 in) tall and 8-15 cm (3-6 in) wide as a potted houseplant. very old or wild specimens can eventually reach 30-100 cm tall. plants may take around six years to first flower.. A pot, your light levels and a little pruning are what set the final size in a home, far more than the plant's theoretical potential.

It builds steadily in both height and spread to a medium, manageable size, filling a pot and a corner over a few years.

Growth rate and years to mature

Bishop's Cap Cactus is a slow grower. Realistically, expect many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years. Its feeding profile backs this up: feed lightly only during the spring-summer growing season. a diluted (half-strength) low-nitrogen cactus fertiliser once a month, or a single balanced spring feed, is plenty. do not fertilise in autumn or winter while the plant is dormant. over-feeding causes soft, distorted growth.

Want this turned into the right next pot at the right moment? The pot size calculator and the bishop's cap cactus repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast bishop's cap cactus grows.

How to keep bishop's cap cactus smaller

You are not stuck with the maximum size. For bishop's cap cactus specifically, these are the levers, in order of impact:

Prune the tallest or longest growth back to a node to hold bishop's cap cactus at the size you want.
Keep it slightly pot-bound and feed sparingly to cap the overall size.
Remove the largest or oldest leaves to keep the footprint in check.

How to grow bishop's cap cactus bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for bishop's cap cactus the accelerators are:

It already has good light; a yearly pot-up plus spring-summer feeding drives the fastest growth.
Pot up a size every year or two while it is establishing.
Feed and water consistently through the growing season for steady, faster size gain.

Light is almost always the ceiling. The bishop's cap cactus light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When bishop's cap cactus outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for bishop's cap cactus:

It crowds the shelf or corner it lives in and starts leaning for light.
Roots circling the pot base or escaping the drainage holes.
It needs a noticeably bigger pot every year — a sign to pot up, divide, or prune.

If it is the pot rather than the room, it is a repotting job, not a goodbye — see the bishop's cap cactus repotting guide. If you want more of this plant instead of a bigger one, the bishop's cap cactus propagation guide turns prunings into new plants.

Bishop's Cap Cactus size — frequently asked questions

How big does bishop's cap cactus get?

Bishop's Cap Cactus reaches slow-growing: usually 10-20 cm (4-8 in) tall and 8-15 cm (3-6 in) wide as a potted houseplant. very old or wild specimens can eventually reach 30-100 cm tall. plants may take around six years to first flower. when grown indoors. It builds steadily in both height and spread to a medium, manageable size, filling a pot and a corner over a few years.

Is bishop's cap cactus slow or fast growing?

Bishop's Cap Cactus is a slow grower. Expect many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years. Bishop's Cap Cactus grows into a room-scaled plant of roughly slow-growing: usually 10-20 cm (4-8 in) tall and 8-15 cm (3-6 in) wide as a potted houseplant. very old or wild specimens can eventually reach 30-100 cm tall. plants may take around six years to first flower. — bigger than a tabletop plant, but not a tree.

How long does bishop's cap cactus take to reach full size?

Roughly many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years. Light, pot size and feeding move that timeline more than anything else.

How do I keep bishop's cap cactus smaller?

Prune the tallest or longest growth back to a node to hold bishop's cap cactus at the size you want. Keep it slightly pot-bound and feed sparingly to cap the overall size. Remove the largest or oldest leaves to keep the footprint in check.

How can I make bishop's cap cactus grow bigger or faster?

It already has good light; a yearly pot-up plus spring-summer feeding drives the fastest growth. Pot up a size every year or two while it is establishing. Feed and water consistently through the growing season for steady, faster size gain.