The avocado tree (Persea americana): botany, history, varieties and growing one from the stone
Sprouting an avocado stone over a glass of water is often a child's first gardening experiment. Behind it lies a remarkable plant: a tree of the laurel family, domesticated in Central America thousands of years ago, whose flowers change sex during the day, and which has become a global commodity in a century, with its successes and its downsides.
A tree of the laurel family
The avocado tree, Persea americana, belongs to the Lauraceae family, like bay laurel, cinnamon and the camphor tree. It is an evergreen tree that, left unpruned, can exceed 15 metres. Its fruit, the avocado, contains a single large seed: the stone.
Unusually, the avocado generally does not ripen on the tree: it can hang there for months and only softens after picking (Arpaia, 2023). This is also why a hard avocado ripens faster next to an apple or a banana, which give off ethylene, the ripening hormone.
Flowers that change sex during the day
Each avocado flower is both female and male, but not at the same time. It opens twice, on two different days:
- type A (Hass, Reed, Pinkerton, Gwen, Lamb Hass): the flower opens as female in the morning, closes, then reopens as male the following afternoon;
- type B (Fuerte, Bacon, Ettinger, Zutano): female in the afternoon, then male the next morning.
By planting both types side by side, growers improve the chances of pollination (Arpaia et al., 2023). A mature tree can bear more than a million flowers in one flowering, of which only a tiny fraction will give fruit.
Three races, hundreds of varieties
Specialists distinguish three horticultural "races", according to their region of origin (Bender, n.d.):
| Race | Cold tolerance | Fruit | Distinctive sign |
|---|---|---|---|
| Mexican | The hardiest | Small, very thin skin, richest in oil | Crushed leaves smell of anise |
| Guatemalan | Intermediate | Thick skin, slow to mature (12 months or more) | Nutty flavour |
| West Indian | The most tender | Large, low in oil, watery flesh | Matures quickly (about 5 months) |
Most cultivated varieties are hybrids of these races:
| Variety | Flower type | What to know |
|---|---|---|
| Hass | A | About 85% Guatemalan; pebbly skin that turns black when ripe; freezes at around −1.7 °C |
| Fuerte | B | Mexican-Guatemalan hybrid; smooth green skin; withstands about −3 °C |
| Bacon | B | Mostly Mexican; withstands about −4 °C |
| Mexicola | A | Mexican; small fruit with black, very thin skin |
| Reed, Pinkerton, Gwen, Lamb Hass | A | Mainly Californian varieties |
| Ettinger, Zutano | B | Green avocados with smooth skin |
The freezing temperatures given apply to four hours of exposure and are only guides: the age of the tree and its hardening also matter (Bender, n.d.). No variety survives a Belgian winter planted out.
A long history
First traces 9,000 years ago
The oldest traces of avocado consumption come from Coxcatlán cave, in the Tehuacán valley (Puebla state, Mexico), between 8000 and 7000 BC. The name comes from Nahuatl, the language of the Aztecs: āhuacatl, which also means testicle, probably because of the fruit's shape. The Spanish made it aguacate, then avocado (University of Southern California, n.d.).
Why such a large stone? One often-cited hypothesis: the avocado evolved alongside large animals now extinct, such as giant ground sloths, which swallowed the fruit whole and dispersed the stone further away.
The postman and the Hass avocado
The world's best-selling avocado owes its name to Rudolph Hass, a Californian postman. In the late 1920s, he bought young seedling trees and planted them on his land in La Habra Heights. One of them produced fruit his children preferred to all the others. Hass patented it in 1935. The mother tree lived until 2002 (California Avocado Society, n.d.). In California, Hass already accounted for nearly 95% of bearing acreage in 2011-2012 (Bender, n.d.).
A global commodity
According to the FAO, world production reached about 10.5 million tonnes in 2023. Mexico alone supplies nearly 3 million tonnes, or about 28%, ahead of Colombia, the Dominican Republic, Peru and Indonesia (FAO, 2025). Europe, which produces few (mainly in Spain), imports most of its avocados, depending on the season, from countries including Peru, Colombia, Kenya and Morocco.
This success has a downside. In Michoacán, Mexico's main producing state, a 2023 report estimates that orchard expansion has wiped out between 16,000 and 28,000 hectares of forest in ten years, with unlicensed wells and violence against those who oppose it (Climate Rights International, 2023). Choosing avocados of traceable or certified origin, and eating them in moderation, therefore also makes ecological sense.
For the nutrition side, see our article on genesora.com: Are avocados good for your health?
Growing an avocado tree from the stone
Sprouting the stone
- Take the stone from a ripe avocado, rinse it and remove any flesh, without damaging the thin brown skin.
- Find the top and the bottom: the pointed end is the top (the stem will come out there), the flatter base will produce the roots.
- Glass of water method: push three or four toothpicks in halfway up and rest the stone on a glass, with the base 1 to 2 cm in the water. Change the water every week.
- Pot method: bury two thirds of the stone in light potting compost, tip above the surface, and keep the compost just moist.
- Patience: depending on warmth and how fresh the stone is, it often takes several weeks, sometimes two months or more, for the stone to split and for a root, then a stem, to appear. A warm room helps.
With the water method, pot up when the stem has a few leaves, without covering the top of the stone. After about three months, the young plant is 15 to 20 cm tall (Plantura, n.d.).
Growing it as a houseplant
- Light: as much as possible, in front of a bright window. Too little light gives a long, bare stem.
- Watering: regular but not excessive; soggy compost rots the roots.
- Shape: if the stem grows long without branching, pinching out the tip encourages new branches.
- Summer: it can go out on a sheltered terrace when nights stay mild, out of harsh sun for the first few days.
- Winter: bring it in before the first frosts. Even Hass freezes at around −1.7 °C.
What about fruit?
In a tropical climate, a seedling avocado tree takes about four years to fruit; in our latitudes, much longer, and often never for lack of light (Plantura, n.d.). And even if it flowers, a tree grown from a stone does not reproduce the variety of the original fruit: it is a new individual, which must first go through a long juvenile phase (Glenn County Master Gardeners, 2015). Growers therefore graft their trees. For a Belgian amateur, the avocado tree remains an attractive green plant, and that is already a lot.
The leaves are the most toxic part of the plant, because of a substance called persin; Guatemalan varieties are the ones most often involved (Merck Veterinary Manual, 2024).
Test yourself
Sources
Arpaia, M. L. (2023, May 17). Why do some fruit ripen only on the tree and others ripen only after they are picked? UC Davis Postharvest Technology Center. https://postharvest.ucdavis.edu/node/7350
Arpaia, M. L., Fetscher, A. E., & Hofshi, R. (2023, July 14). Avocado flowering basics. University of California, Riverside. https://avocado.ucr.edu/avocado-flowering-basics
Bender, G. S. (n.d.). Avocado botany and commercial cultivars grown in California (chapter 2). UC Cooperative Extension. https://ccfruitandnuts.ucanr.edu/sites/default/files/2016-09/166373.pdf
California Avocado Society. (n.d.). Mother Hass tree. https://californiaavocadosociety.org/mother-hass-tree.html
Climate Rights International. (2023). Unholy guacamole: Deforestation, water capture, and violence behind Mexico's avocado exports. https://cri.org/reports/unholy-guacamole
FAO. (2025). FAOSTAT: Crops and livestock products, avocados, 2023. https://www.fao.org/faostat/en/#data/QCL
Glenn County Master Gardeners. (2015, April 25). Growing avocados in the Sacramento Valley, part II: Variety and rootstock considerations. University of California Agriculture and Natural Resources. https://ucanr.edu/sites/glennmg/files/213826.pdf
Merck Veterinary Manual. (2024). Avocado toxicosis in animals. https://www.msdvetmanual.com/veterinary/toxicology/food-hazards/avocado-toxicosis-in-animals
Plantura. (n.d.). How to grow an avocado from the stone. https://plantura.garden/uk/?p=5231
University of Southern California. (n.d.). Avocado: New World nutrient pack. Plants & People. https://scalar.usc.edu/works/plants-and-people/avocado-new-world-nutient-pack