Actual size and flowering may vary slightly based on season.
Monk's Hood Cactus
Monk's Hood Cactus is the largest of the star cacti, a ribbed green column banded with white flecks and armed with stout amber spines. It starts as a ball and slowly becomes a tall column, often with ribs that twist as it ages. Once it is about 6 inches tall, it opens large, scented, lemon-yellow flowers in summer. It handles Valley heat well with some afternoon shade.
Best for: a cactus accent in a rock garden or bed, a tall pot plant, and a mixed cactus planting that needs height.
It grows slowly from a ball into a column 1 to 4 feet tall and 6 to 12 inches wide. That height sets it apart in a bed of round cacti.
Large lemon-yellow flowers with a light scent open at the top in summer. Plants usually need to reach about 6 inches tall before they bloom.
Bands of white flecks run across the ribs, and stout amber spines turn gray with age. It stands out against dark rock and gravel.
Soil that stays wet in winter rots it, so keep it dry from fall into spring. New plants can sunburn, so give them light shade the first summer.
- Plant to plant12 in apart
Wait about a week after planting before the first water. In summer, water when the soil has dried out, about weekly in a pot. Keep it completely dry in winter.
It takes Phoenix heat well in full sun to light shade. Some afternoon shade in summer keeps it from scorching.
It can be damaged below about 20°F. On frost nights, cover it with frost cloth or a sheet that reaches the ground, not plastic, and take it off in the morning.
Plant it with the side that faced the sun still facing south. A newly planted cactus can sunburn in its first summer, so light shade cloth helps until fall.
Drainage test first. Dig the hole and fill it with water. If water is still sitting in the hole a day later, you likely hit caliche, clay or hard soil, so fix the drainage before planting. If it drains very fast, the soil is sandy. Standing water around roots is a common reason new plants fail.
Weed cloth. Cut it away from the planting hole and where the roots will spread. Remove any plastic sheeting completely, since it keeps water and air out of the soil.
Rock or decomposed granite with no soil underneath. Bring in soil close in texture to your native soil, mix it with the soil below, and build up enough depth for roots before planting.
If you can break through. Use a breaker bar, pick, or jackhammer. Dig through the caliche and break out the solid chunks. Backfill with the soil you dug out, with no compost or manure in the hole. Confirm drainage before planting.
If you cannot break through. Dig narrow holes through the hard layer beside the root ball, not under it, and refill them with the same soil, not gravel. If it still will not drain, plant on a low mound of the same soil.
Root ball. Check the outside edges for any roots circling around. Loosen or cut those so they grow outward. Do not break up the center of the root ball.
Depth. The top of the root ball should sit at or just slightly above the surrounding soil level. Planting too deep can lead to rot and kill the plant.
Drip emitters. At planting, put the emitters on the root ball, on different sides of the plant. After about 2 months, move them to the outer edge of the root ball. Over the first year, add emitters farther out toward the edge of the branches as roots grow. Once a plant is rooted, never water only at the trunk.
How big does monk's hood cactus get?
It grows slowly into a column about 1 to 4 feet tall and 6 to 12 inches wide. It is the largest of the star cacti.
When does it bloom?
In summer, with large, scented, lemon-yellow flowers. It usually has to reach about 6 inches tall first, which can take several years.
Does it have spines?
Yes. Stout amber spines line the ribs and turn gray with age. Wear thick gloves and wrap it in folded newspaper to move it.
Does it need shade in Phoenix?
It handles Phoenix heat well and does best in full sun to light shade. Some afternoon shade in summer keeps it looking good.
How often should I water it?
Water in summer when the soil has dried out, about weekly in a pot. Keep it completely dry through winter.
How cold can it take?
It is usually rated to about 20°F. On frost nights, cover it with frost cloth down to the ground, and move pots under a roof.
Is it the easiest star cactus to grow?
It is often called the easiest and fastest of the star cacti, though it is still slow. Good drainage and a dry winter are the keys.
Why are the ribs twisting?
Older plants often grow ribs that spiral around the stem. It is normal and part of the plant's shape.
Monk's Hood Cactus for sale in Arizona, delivered to you
Monk's Hood Cactus (Astrophytum ornatum) is the largest and easiest of the star cacti. This page covers its size, spines, flowers, sun, water and cold in the Valley.
Sourced from trusted Arizona growers and delivered directly to your door, job site, or property. We deliver across the Valley and to nearby towns, and quote delivery anywhere else in Arizona.
What is monk's hood cactus?
It is Astrophytum ornatum, a star cactus from central Mexico with white-banded ribs and stout amber spines.
How big does monk's hood cactus get?
It slowly becomes a column 1 to 4 feet tall and 6 to 12 inches wide, the largest of its kind.
Monk's hood cactus flowers
Large, scented, lemon-yellow flowers open in summer once the plant is about 6 inches tall.
Watering monk's hood in the Valley
Water in summer when the soil is dry, and keep it completely dry in winter to avoid rot.
Is monk's hood cactus cold hardy?
It is usually rated to about 20°F. Cover it with frost cloth on frost nights.
Monk's hood in Phoenix heat
It handles Phoenix heat well. Full sun to light shade suits it, with some afternoon shade in summer.
We deliver across the Valley, from Phoenix, Scottsdale and Mesa out to San Tan Valley, Maricopa and Casa Grande, and up to Prescott, Sedona, Payson and Globe. See delivery areas and rates.