Houseplants

Growing an Avocado Indoors

There are many tropical fruits that can be grown from a seed – oranges, lemons, mangos, date palms, coffee plants, etc. – but the best known is probably the avocado (Persea americana). It is fascinating watching its huge pit split in two and sprout a thick, rigidly upright sprout. The robust seedling is miles away from the skinny little ones most of our vegetables and annuals produce. Growing an avocado also a great experience to carry out with small children in order to teach them how plants germinate and grow. Plus, you get a free houseplant!

Traditionally you’re supposed to germinate the pit over a glass of water, and if you want to do that, no problem. But the “glass of water” treatment is not mandatory. After all, do you think an avocado pit has to hover in the air over a puddle of water in the wild? Of course not. It germinates in contact with the earth just like any other terrestrial plant. Although far from its native jungle, it will still germinate if you just sow it in potting soil. But sprouting it in water at least offers the advantage that you can better watch the plant’s progress as it germinates: after all, the roots will be visible through the glass. This can be especially interesting as a teaching experience for young children.

Here’s how to start an avocado indoors in both water and soil.

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Before You Start

Choose a slightly softened avocado, a sign that it is fully mature. Extract the pit, then clean and dry it. You can remove brown envelope that surrounds the pit if you want or leave it intact. Whether you do or don’t, the results will be the same.

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Over a Glass of Water

If you do you want to germinate an avocado pit over a glass of water, press 3 or 4 matches or toothpicks into the pit. Insert them all around the pit, at about mid-height, spacing them evenly. Suspend the pit over a transparent glass or a mason jar with the pointed end facing up and the flat end down. Pour water into the glass until the base of the pit touches the water. Now set the glass in a rather warm spot (68?F/20?C or higher), adding water as necessary so that the base always remains in contact with moisture.

After a few weeks, the pit will split vertically and a large root will grow down into the water. Soon after, an upright stem will rise from the top of the pit. Congratulations! You have achieved germination!

Do not wait too long before transplanting the plant into a pot: you’ll find it will better tolerate the transition when its roots are just starting to form then when the glass is a mass of tangled roots… and that’s what happens when you leave it too long in a glass of water. Cover the roots with potting mix and set the pit into the pot so that it is half covered with soil and voila! Your young avocado is up and growing!

In Potting Mix

You’ll save time and effort by sowing the pit directly in a pot of growing mix. Simply fill a pot with moist soil up to about to 1/2 inch (2 cm) from the top. A drainage layer of gravel is not necessary nor even recommended; just fill the pot with mix from bottom to top. Next harvest the pit as above, cleaning and drying it, then plant it in the pot, covering its base in soil to about half its height. Set the pot in a warm place (68?F/20?C or more) and wait patiently. With this method, you won’t see the roots appear, but after a few weeks you will see the pit split in half and an upright stem emerge.

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Surprise: You have Twins!

Sometimes more than one stem will sprout from the pit: there can be 2, 3 or even 4 or more. That’s because some pits are “polyembryonic”: they produce more than one embryo. In other words, the pit can have twins! This occurs frequently with some clones of avocado. If so, simply let the extra stems grow. This will give you a plant that is naturally a bit bushier than normal.

Photo: sandySTC.

After Care

Up to this point, light was not necessary, but as soon as the stem has appeared, leaves quickly follow and they need light, lots of light. Full sun is not too much for this plant native to the South American tropics, although it can tolerate partial shade.

From now on, treat your little avocado like the houseplant it is. Fo example, watering it as needed, when the soil feels dry to the touch. Avoid watering with cold water.

In nature, avocado trees grow straight up, not branching until they are quite tall. This is Nature’s way of pushing the plant to quickly grow through overhanging branches to reach the sun above. It’s only once the tree is basking in the sun that it begins to branch.

Pinching

Potted avocados try to repeat this indoors, heading straight for the ceiling as fast as they can grow, making for a rather thin, not terribly attractive plant. You have to force them to become denser by pinching them regularly. Pinching simply means removing the tip of the stem, either between your thumb and forefinger or with pruning shears. Once the stem reaches 6 inches (15 cm) tall, pinch the tip a first time, and from then on, every time the stem gains another 6 inches (15 cm), pinch again. This will slow its race for the ceiling and will force the plant to produce branches (although the avocado is very reluctant to branch abundantly), thus ensuring a denser appearance.

After 4 or 5 months of growth, your plant will be due for repotting into a larger pot. After that, repotting every 2 years should suffice. Your avocado plant will have to spend the rest of its life in a pot, unless you live in the Tropics, in which case you can plant it outdoors at this point.

During the summer, allow your avocado to spend lots of time outdoors, an experience it will really love… but you must always  gradually acclimatize it before exposing it to full outdoor sun.

Fertilizer

The first year a young avocado mostly lives off the reserves contained in its pit. Afterwards, fertilize it like any other houseplant, from spring to early fall, using the fertilizer of your choice at a quarter of the recommended rate.

Avocado foliage tends to suffer from tip burn and brown patches during the winter. These are caused by the dry air in our homes at that season. To counter this, try increasing humidity with a room humidifier. Mineral salt accumulation (look for the telltale formation of a white or yellowish crust on the inner wall of the pot) can cause similar symptoms. Make a habit of leaching its soil every 3 months to reduce the accumulation. Just take the plant to the sink and let tepid water flow through its soil for a few minutes, allowing excess water to go down the drain. This will remove any mineral buildups in the soil.

Photo: C.

To Fruit or Not to Fruit?

Will your avocado bear fruit someday? Probably not. And if it does, even under ideal conditions it can take 7 to 15 years to reach maturity and produce its first greenish flowers. Even then, it is a reluctant self-pollinator. I suggest you simply learn to appreciate the avocado as a foliage plant… and buy your avocados at the nearest market.

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, laidbackgardener.blog will continue its mission of demystifying gardening and making it more accessible to all.

9 comments on “Growing an Avocado Indoors

  1. Some of the best avocado trees that I grew up with grew from seed. With others to pollinate in the neighborhood, they do produce fruit once they are mature. There are two primary concerns though. They are genetically variable, so the fruit may be significantly different from the fruit that provided the seed. Also, they grow very tall and very fast during their juvenile stage, so that when they finally mature and begin to produce fruit, their fruit is too high to reach. Pruning them down helps, but also disfigures their structure. The advantage to purchasing grafted trees is that the scions of such trees are adult growth that branches and fruits right away.

  2. Pingback: Browning Leaves on an Indoor Avocado - Laidback Gardener

  3. Pingback: Browning Leaves on an Indoor Avocado – Laidback Gardener

  4. A couple of months ago, I did this toothpick method on 5 avocado seeds. With a 12” root and growing its 5th leaf, I decided to place this one plant into soil just today. I’m not too sure what’s going on with the others. Your article mentions the rarity of multiple shoots. Believe it or not, each of the remaining 4 seeds I have grown 30+ shoots growing out of them. I’ve been researching on line for answers, but to no avail. I’m hoping someone can tell me if something has caused this mutation.

    • It’s not really a mutation, but the natural situation for certain clones of avocado. When I wrote “fairly rare” in the text, I did so considering that it won’t happen to most people: maybe one person out of 4 or 5, but if you buy certain clones of avocado, almost all the seeds will be multistem. If you bought all your avocados from the same source, you probably lucked out with a variety that is naturally that way almost every time.

  5. Hello there, is it possible to separate the twins and grow them separately?

    • Theoretically, you can, especially if each clearly has its own separate roots, but that could be a delicate task on very young plants. Most people either let both grow or remove all but one.

  6. Super helpful! I have an avocado plant that grew pretty quickly and I’m trying so hard to keep it alive. The other day I found 2 small mushrooms growing in its soil and I freaked out a little haha I’m going to try that rinsing method to get the salt off, then maybe put it outside for a bit.

    • Don’t worry about the mushrooms. Just dig them out and repeat if they grow back. They’re not harming your plant, their living off the potting mix.

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