How To Grow An Avocado Tree From Seed

Learn how to grow an avocado tree from seed from the detailed step-by-step instructions given below.

Avocado (Persea americana) is a nutrient-rich fruit containing healthy monounsaturated fats, and vitamins C, E, B6, and potassium, magnesium and folate. The monounsaturated fat per 100 gram of avocado is 9.8 gram while only 2.13 gram of saturated fat. The potassium content of an avocado is more than that in banana, 485 mg per 100 gram as compared to 358 mg per 100 gram of banana [1].

Avocado and its seed
Avocado and its seed


The next time, when you eat an avocado, don't throw its pit (seed), you can grow an avocado tree from it. It is quite easy to grow your own avocado tree from seed. The kids will love to grow an avocado tree from seeds at home, so involve them in this interesting project.

The avocado fruit is botanically a large berry containing a single large seed [2]. The fruits have a green-skinned, fleshy body that may be pear-shaped, egg-shaped, or spherical.

There are many varieties of avocadoes including West Indian (P. americana Mill. var. americana), Guatemalan (Persea nubigena var. guatamalensis L. Wms.) and Mexican (P. americana var. drymifolia Blake). The cultiver, Hass produces fruits weighing 200-300 grams is widely grown which accounts for 80% of cultivated avocados in the world [3].

The pit size and shape, and fruit size and taste vary for each variety [4]. The top and bottom of the seeds are also different. The top of avocado is generally pointed or slightly elongated, while the bottom is round or flat. The pointed portion of the seed is the top of seed and the round or flat portion is the bottom of the seed.

There is a slight amount of a fungicidal toxin in avocado pits, and on all parts of the tree. This toxin is so small that it is not poisonous to humans, if not eaten in huge quantities. But there is no toxin in the avocado fruit. It is actually very healthy.

Different shapes of avocado fruit and seeds
Different shapes of avocado fruit and seeds
I did the first experiment of growing the avocado tree from seed with my granddaughter several years ago. That avocado tree is now growing in a pot.

The method for growing the avocado tree from seed is the same for all the avocado varieties. The detailed step by step procedure is given below.

Start the experiment in Spring or summer when the temperature is above 20 deg C. In winter, you can try sprouting the avocado seed indoors in hotter areas.

Step 1 : Remove the Seed
  1. Remove the pit (seed) from the avocado carefully and wash it.
  2. Do not use soap for washing.
  3. Do not damage the seed by cuts.
  4. There are reports that removing the outer brown skin slightly speedup the germination (see below). I have sprouted the seed without removing the skin.
Step 2 : Insert Toothpicks
Insert three or four toothpicks into the pit evenly at its circumference. The pit should be able to stay on the rim of a cup or bottle.

Step 3
Top and bottom of avocado seed
Top and bottom of avocado seed
  1. Take a bottle or glass or jar, not too much wide; ensure that the seed you prepared in Step 2, sits on the rim of the container.
  2. Place the prepared seed on the bottle, ensuring that the pointed end is up and the rounded or flat end is in the water.
  3. In my first experiment, I placed the pointed side of the seed up, that sprouted in a few weeks. But in the second experiment with my second granddaughter, I put the pointed side down by mistake, that took more than 6 months to sprout.

Step 4
Place the bottle on a sunny windowsill or a bright place. Change the water every 3-4 days so that bacteria, fungi, mold etc. do not build up and the water remain clean. Also ensure the base of the avocado always remains moist and submerged in water.

Step 5 : Wait For Germination
Wait patiently for the pit to sprout roots. In a few weeks, the pit will begin to split at the bottom and the top. After a few more weeks, a taproot will begin to emerge in the bottle at the base of the pit. The next thing that will happen is the growth of a shoot bearing leaves. An avocado seed will sprout in two to six by this method.
Germination of Avocado Seed
Germination of Avocado Seed

The above picture shows an avocado seed that was sprouted upside down, that is pointed side in the water and the round side out. The positioning of this way took about six months to sprout. So always keep the top of the pointed side of the seed out in air and the bottom down in water.

Step 6: First Pruning
When the plant grows to 6 inch height, prune it back to 3 inches. New branches and leaves will regrow. After the first pruning, pinch off the growing ends. The pruning of tree branches  promotes thicker branches with strong leaves. However, frequent pruning in grown-up trees can stop leaf growth.

The above method of sprouting the avocado seed uses toothpicks. You can, however, sprout the seed without toothpicks. The principle is the same. keep the bottom half of the seed in water and top half in air.

Place a seed in a cup keeping the bottom of the seed on the bottom of the cup.  Pour water so that half of the seed is under water. Place the cup in a warm place away from direct sun, indoors or outdoor.

How to Plant an Avocado Seedling

Transplant the Avocado Seedling

Now how do you plant your sprouted avocado seed in soil? The steps are given below:
Step 1: Prepare Soil
Avocado trees grow best in free draining soil with pH around 6 to 6.5. Soil containing coconut fiber and river sand is good. Fill a terracotta with this soil.

Step 2 : Plant the Avocado Seedling
Remove the sprouted pit from the water container, remove the toothpicks and plant the seedling in a pot. Plant the avocado pit in the soil such the top-half of pit shows above the soil and the roots are buried in the soil.

Step 3. Select Position
  1. The avocado plants need bright light, but not too much direct sunlight. I have kept my avocado tree in a place which receives morning sun light.
  2. The young avocado trees grows well in a temperature of 15 – 30°C (60 – 85°F), and the mature trees can withstand temperature as low as -2.2°C (28°F).
  3. Keep your plant away from cold breeze. In cold weather, keep your potted avocado plant indoors until the temperature rises.
  4. It is better to cover the plants with a blanket during cold weather.
Watering
  1. Keep the soil moist. Do not over-water.
  2. Yellowing of the leaves indicate too much water, while if the leaves turn brown at the tips, the tree needs more water.
Mulch
Mulch your avocado tree with a wood chips. Spread mulch around the tree leaving 6 inch from the trunk.

Fertilizer
Trees younger than 1 year old do not need too much fertilizer. Fertilize your young avocado trees nitrogen fertilizer like fish and bone. You can use any fertilizer for home plants.

Avocado Flowers and Pollination

The flowers of avocado tree 5–10 mm (0.2–0.4 in) wide and greenish-yellow in color, open for two days. A mature avocado tree can produce over a million flowers, most of which fall without producing fruit because of lack of pollination.

The flowers have both male and female parts so they are perfect. But the problem with avocado flowers is that both the parts of the flower do not open at the same time.

The avocado flowers are of two types. The A-type avocado flowers open female in the morning and male in the afternoon, while in the B-type male in the morning and female in the afternoon [5]. Both the male and female parts open and close twice in a two day period.
On day one female flowers open; on day two male flowers open and shed their pollen.

The pollination process for avocados is interesting. It is very difficult for an avocado flower to pollinate itself. So the natural question is do you need to have two avocado trees to bear fruit? Logically, having two avocado varieties should help pollination and fruit production. But it is not always required. Under ideal temperature condition (20°C to 25°C), among millions of flowers, some have overlap in opening the two flower types, providing a small window of opportunity for pollination [5].

When will your avocado tree bear fruits?

The avocado tree grown from seed may not produce fruits in 10-15 years. The grafted avocado trees can produce fruits in 5-7 years. If you want to grow an avocado tree for fruit, you should buy a grafted tree from your garden nursery.

A mature avocado tree can produce 200 to 300 fruits in a year. However, the tree may produce a large crop one year, and a small in the next year.

Storing the Avocado Seeds

One question of interest is can you grow avocado tree from fresh seeds only or can you store the seeds and use for germination later on. Washed and air-dried avocado seeds placed in dry peat moss and stored in a refrigerator in which a temperature of about 42 degrees F did not affect the vitality of the embryo up to 8 months, but it caused delayed germination after that [6].

Hastening The Germination

The avocado seed germination can be made faster by certain methods:
  1. Removing the Seed Coating: Removing the brown seed coating speeds up the germination [7].
  2. Cutting off the Seed before Planting: It has been shown that cutting off a small portion of the top and bottom of the seed promotes and quicker germination [6].
Avocado seed showing embryo and truncated avocado seed
Avocado seed showing embryo and truncated avocado seed


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References

1. Avacado
2. W.B. Storey,  What kind of fruit is the avocado?  California Avocado Society, 1973–74 Yearbook, 70-71, 1973.
3. Stradley, Linda (2004). Hass avocado
4. AVOCADO 101, Grow Your Own Avocado Tree
5. Growing avocados: flowering, pollination and fruit set
6. F. F. Halma and E. Frolich,  California Avocado Society Yearbook 34: 136-138, 1949.
7. E.R. Eggers,  Effect of the Removal of Seed Coats on Avocado Seed Germination.
Calif. Avocado Soc. Yearbook,  41-43, 1942.