Actual size and flowering may vary slightly based on season.
White Thorn Cereus
White Thorn Cereus, also known as gray ghost organ pipe, is a Mexican column cactus with powdery blue-green to gray stems. Young stems carry reddish-brown spines that turn white with age, which gives it its name. It grows into a shrub or small tree with branches from a short trunk, and opens white to pinkish flowers at night. It takes full sun and needs little water once rooted.
Best for: a pale gray-blue accent, full-sun cactus beds, and large pots where it stays smaller.
The stems carry a dusty white coating that makes the plant look gray-blue, like a ghost. Set it against darker plants so the pale color stands out.
It wants full sun and little to moderate water. Let the soil dry fully between waterings.
In the wild it can reach 20 feet, but plants in cultivation often stay under about 6 feet. It works in a large container with a fast-draining mix.
It is frost tender, rated to about 26°F, so cover it on cold nights. Soggy soil rots the roots.
- Single plants15 ft apart
Wait about a week after planting before the first water. Then water every other week while nights stay above 60°F. In cooler weather, water only after two to four weeks without rain.
Water deeply in the warm months only when the soil is dry, and give little or none in winter. Plants in pots dry out faster and need water more often than plants in the ground.
Plant it with the same side facing the sun as in the nursery. Cover a new plant with light shade cloth its first summer, then remove it.
Below about 26 to 32°F, frost can scar the stem tips. Cover the tips with foam cups or frost cloth that reaches the ground, not plastic. Take covers off in the morning.
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.
Why is it called white thorn or gray ghost?
The stems have a dusty white coating that looks gray-blue, and the spines start reddish-brown and turn white as they age. Use it as a pale accent against darker plants.
How big does it get?
It can grow up to about 20 feet tall and 10 feet wide in the wild, but plants in cultivation often stay under about 6 feet. It grows fast, so give an in-ground plant room to branch.
How often should I water it?
Keep it on the dry side. Let the soil dry out completely between waterings, water more in the warm season, and keep it nearly dry in winter.
Is it frost hardy?
No. It is rated to about 26°F and cannot take a hard frost. Cover it with frost cloth on nights near freezing, or move potted plants under cover.
Does it flower?
Yes. White to pinkish, funnel-shaped flowers open at night in spring and stay partly open into the day. Look for them on spring mornings.
Is the fruit edible?
Yes. The fruit that follows the flowers is edible, so pick it when ripe.
Does it need full sun?
Yes, full sun suits it best. A new plant can sunburn its first summer, so keep the same side facing the sun and use light shade cloth that first summer.
What soil does it need?
Plant it in fast-draining soil, or a gritty cactus mix in pots. Soggy soil rots the roots, so let pots drain freely.
White Thorn Cereus for sale in Arizona, delivered to you
White Thorn Cereus, the gray ghost organ pipe, is a Mexican column cactus with powdery blue-gray stems and pale spines. It suits full-sun beds and pots. Below are the questions Valley homeowners ask before planting one.
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Gray ghost organ pipe in Phoenix
White Thorn Cereus has powdery gray-blue stems and pale spines. It suits full-sun beds and large pots.
How big White Thorn Cereus gets
It can reach about 20 feet in the wild, but often stays under about 6 feet in cultivation. Stems are about 4 inches thick.
Frost care for White Thorn Cereus
It is frost tender, rated to about 26°F. Cover it with frost cloth on cold nights.
Watering White Thorn Cereus
Let the soil dry fully between waterings and keep it nearly dry in winter. Fast-draining soil keeps the roots from rotting.
White Thorn Cereus flowers and fruit
White to pinkish night flowers open in spring. The fruit that follows is edible.
Where White Thorn Cereus comes from
It is native to south-central Mexico, in states such as Chiapas, Puebla and Oaxaca.
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.