The short version
- A cactus fruit grows from the base of the flower, which sits inside stem tissue. Its skin can carry scales, hairs, spines or glochids (tiny bristles that are painful in skin).
- Some cacti cannot set fruit with their own pollen, among them Peruvian apple and several dragon fruit varieties, and growers find San Pedro behaves the same way. Cuttings or pups of one plant count as one plant, so these need 2 genetically different plants in flower at the same time. The prickly pear Opuntia ficus-indica can fruit on its own.
- A flower that drops within a few days with no swelling at its base may not have been pollinated. One that withers but stays on while its base swells has probably set fruit.
- From the flower opening to ripe fruit takes about 30 days for Peruvian apple, about 30 to 40 days for dragon fruit, 85 to 100 days for Opuntia ficus-indica, and usually a few months for San Pedro.
- Leave fruit on the plant until it is ripe: fully colored with a smooth peel on Peruvian apple, fully colored on dragon fruit and prickly pear. San Pedro fruit tends to split open on the plant.
- For seed, wash it free of pulp, let it dry and label it. Each seedling from a cross is a new plant, different from both parents.
What a cactus fruit is
In a cactus flower, the ovary (the part where seeds form) sits below the petals, sunk into the tissue of the stem. After pollination it swells into a berry: a fleshy fruit full of seeds, wrapped in tissue that grew as part of the stem.
Like stem skin, the fruit skin can carry scales and hairs, and areoles, the small pads that a cactus's spines grow from. Prickly pear fruit is covered in glochids, even on kinds sold as spineless. Other fruits, such as Peruvian apple, ripen to a smooth peel.
What it takes to set fruit
Pollen has to reach the stigma, the tip of the stalk at the center of the flower, carried by an insect or by your hand. For how to move pollen by hand, see cactus flowers and their pollinators. For a plant that has not flowered yet, see when will my cactus flower.
Some cacti are self-incompatible: pollen from their own plant sets no fruit. A cutting or a pup (a small offset growing from the side or base of a stem) is genetically the same plant as the one it came from, and all the plants grown from one original plant this way make up a clone. For pollination, 5 pots grown from one plant are still one plant. A self-incompatible kind needs 2 plants that are not copies of each other, with flowers open at the same time.
To tell whether 2 plants are different: each plant raised from seed is genetically new, while cuttings or pups taken from the same parent plant are the same clone. If you do not know where a plant came from, ask whoever sold or gave it to you whether it was grown from seed or from a cutting, and from which parent.
Watch the flower in the days after it closes:
- It drops within a few days and the base has not swelled. It may not have been pollinated, or the pollen may have come from the same clone. At the next flowering, move pollen by hand from a second, genetically different plant.
- It withers but stays on, and the base starts to swell. Fruit has probably set. Leave it on the plant until it shows its ripe signs.
Heat can keep a set fruit from ripening. In hot, dry climates, the red torch cactus (Echinopsis huascha) typically sets fruit that dries and browns before it is fully ripe, because of the heat. On that plant, a fruit that browns before it turns red set but did not ripen.
San Pedro
San Pedro (a Trichocereus) has white flowers. Growers find that it generally needs pollen from a genetically different plant to set fruit, so 2 cuttings of the same clone will not give fruit on each other. If you have only one San Pedro, or several cuttings of one plant, pair it with another San Pedro or Trichocereus that was raised from seed or comes from a different clone, and that flowers at the same time.
In Trichocereus, the flower base that becomes the fruit carries a dense coat of hairs and fairly numerous, close-set scales. Growers usually see it ripen over a few months. When ripe, it tends to split open on the plant, exposing white pulp packed with small black seeds. That split is the sign to collect it.
Other fruiting cacti
Prickly pear, dragon fruit and blue myrtle bear edible fruit, and Peruvian apple has been grown and sold as a fruit crop.
Peruvian apple is sold as Cereus repandus or C. peruvianus, now generally treated as one species. It is a tall, branching column with night-opening white flowers up to 6 inches across, and it is self-incompatible: where it is grown as a crop, plants from different clones are mixed so they pollinate each other. About 30 days after the flower opens, the fruit is ripe: round, red, up to 2.5 inches across, with white pulp and a smooth, fully colored peel. Fruit picked before that does not ripen properly off the plant.
The prickly pear Opuntia ficus-indica sets fruit with its own pollen or another plant's, so a single plant can fruit; other prickly pear species vary, so if you do not know yours, treat it as needing a partner. In Opuntia ficus-indica, the fruit takes 85 to 100 days from the flower opening to full color, inside and out. It does not keep ripening once picked, so leave it on the pad until then, and handle it with cactus gloves and tongs because of the glochids.
Dragon fruit (Selenicereus undatus, long sold as Hylocereus undatus) is a climbing cactus, not a column. Each flower opens for one night. Several varieties are self-incompatible, so grow 2 or 3 genetically different types, not cuttings of one plant. Moving pollen by hand, and between different plants, gives more fruit and bigger fruit. The fruit ripens about 30 to 40 days after the flower opens; pick it once it is fully colored.
Blue myrtle (Myrtillocactus geometrizans), a Mexican column, bears blueberry-like fruits 8 to 20 mm (about 1/3 to 3/4 inch) long, sold in markets in Mexico. Plants can flower when close to 2 years old. See the blue myrtle cactus.
Ripe fruit and seed
A fruit that splits on the plant exposes its seed. In saguaro, the fruit turns from green to purple and usually splits while still attached, and rain can then wash the seed out. Collect a splitting fruit as soon as you see it open.
To clean the seed, scoop out the pulp, rinse it in a fine sieve until the seeds come free, and spread the seeds on paper to dry. Washing matters: in saguaro, the fruit pulp holds back germination, and seed washed clean of it sprouts well. Label each batch with the plant it came from and, if you pollinated by hand, the pollen parent (the plant the pollen came from).
A cross is a seed or seedling made with pollen from a different plant. Each seedling from a cross is a new plant that differs from both parents. To keep a plant exactly as it is, grow it from cuttings; see how cacti reproduce. For sowing the seed, see growing cactus from seed.
Sources
Digital Flowers (Cactaceae lecture text). University of Illinois Urbana-Champaign. https://www.life.illinois.edu/help/digitalflowers/Cactaceae/lecture_text.htm
Climbing and Columnar Cacti: New Arid Land Fruit Crops. Yosef Mizrahi and Avinoam Nerd. In J. Janick (ed.), Perspectives on New Crops and New Uses, ASHS Press, 1999 (Purdue University NewCROP). https://hort.purdue.edu/newcrop/proceedings1999/v4-358.html
Cereus repandus. Martin landscape plant library, Arizona State University Library. https://www.asu.edu/lib/camartin/plants/Plant%20html%20files/cereusrepandus.html
Echinopsis huascha. Martin landscape plant library, Arizona State University Library. https://www.asu.edu/lib/camartin/plants/Plant%20html%20files/echinopsishuascha.html
Cereus repandus (L.) Mill. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:130627-1
Reproductive biology of Opuntia: A review. J.A. Reyes-Agüero, J.R. Aguirre R. and A. Valiente-Banuet, Journal of Arid Environments 64: 549-585, 2006. https://doi.org/10.1016/j.jaridenv.2005.06.018
Prickly Pear Cactus (Backyard Gardener #192). Jeff Schalau, University of Arizona Cooperative Extension, Yavapai County, 2024. https://extension.arizona.edu/sites/extension.arizona.edu/files/attachment/PricklyPearCactus.pdf
Eating Cactus: Prickly Pear for Food (FS-16-09). C. Bishop and B. McMurray, University of Nevada, Reno Extension, 2016. https://extension.unr.edu/4h/pub.aspx?PubID=2157
Selenicereus undatus (Haw.) D.R.Hunt. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77163184-1
Pitaya (Dragonfruit) Growing in the Florida Home Landscape (HS1068). Jonathan H. Crane and Carlos F. Balerdi, UF/IFAS Extension, 2020. https://ask.ifas.ufl.edu/publication/HS303
Pitahaya Production and Marketing Considerations. Ramiro Lobo and Gary Tanizaki, UC Cooperative Extension, San Diego County. https://ucanr.edu/sites/sdsmallfarms/files/248314.pdf
Identity and neotypification of Cereus macrogonus, the type species of the genus Trichocereus (Cactaceae). Sofía Albesiano and Roberto Kiesling, Haseltonia 17: 24-34, 2012. https://cactusconservation.org/wp-content/uploads/2020/03/Albesiano_Kiesling_2012_Haseltonia_17_24-34.pdf
Echinopsis pachanoi (Britton & Rose) Friedrich & Rowley. HortFlora, Royal Botanic Gardens Victoria. https://hortflora.rbg.vic.gov.au/taxon/5eb287ff-8e2a-4201-8e6e-fe7d6a10f65b
Myrtillocactus geometrizans. Robyn Drinkwater, Botanics Stories, Royal Botanic Garden Edinburgh, 2012. https://stories.rbge.org.uk/?p=9827
Myrtillocactus geometrizans. Find Trees & Learn, University of Arizona Campus Arboretum. https://apps.cals.arizona.edu/arboretum/taxon.aspx?id=991
Carnegiea gigantea (Engelm.) Britton & Rose: saguaro or giant cactus. Susan E. Meyer, Woody Plant Seed Manual, USDA Forest Service. https://www.fs.usda.gov/nsl/Wpsm/Carnegiea.pdf
Propagation (chapter 13). Extension Gardener Handbook, NC State Extension. https://content.ces.ncsu.edu/extension-gardener-handbook/13-propagation