Avocado leaves with dry brown edges are usually due to dry air. Source: cantikalami.club
Question: I grew an avocado tree from seed this summer and now the edges of the leaves are turning brown. Why? The plant is 30 inches (75 cm) tall and has only one main stem.
Answer: The avocado tree (Persea americana) rarely does very well under the conditions that prevail in the average home. True enough, it’s relatively easy to grow one from a pit harvested from a store-bought fruit and that’s kind of fun. Plus, it does grow vigorously at first, but it tends not to stay attractive very long … and that’s normal. Indoor conditions are not really much to the plant’s liking. It would really prefer full tropical sun and intense atmospheric humidity, things that are hard to give it indoors.
The plant most often shows its displeasure in the fall and winter, when its leaf edges start to turn brown and dry out, a condition that engulfs more and more of the leaf surface over time.
And the main cause is dry air.
The avocado comes from a humid tropical climate where the atmospheric humidity is usually at least in the 70 to 80% range and often well above that. Indoors, though, relative humidity drops seriously during the heating season. In many homes, it remains below 30% throughout much of the fall and winter. And when the air is too dry, evapotranspiration (loss of water from leaf cells) increases. Soon, the large but thin leaves of the avocado begin to lose water more quickly than the plant can replace it and when that happens, the cells begin to die, leading to browning.
Humidifier to the Rescue
To keep the leaves in top shape, you need to try increasing the humidity as much as possible and the easiest way of doing so is with a humidifier. If you can manage to keep the humidity in the 45–55% range (also, a good level for humans and pets), that will make a huge difference. Of course, this is far from the 70 to 80% the plant really wants, but at least it ought to keep all but the oldest leaves from browning at the edges.
A humidity tray can help too, although it’s more efficient on shorter plants. The humidity it gives off often diffuses into the air around before reaching the lofty leaves of indoor trees like the avocado.
And there is no point in spraying the leaves with water in an effort to increase humidity. The concept that spraying helps plants to cope with dry air is one of those garden myths that refuses to die.
For “perfect” growth (i.e. no browning at all), grow it in a humid greenhouse or seal your avocado tree inside a large clear plastic bag during the fall and winter. The humidity inside will be 80% and above, just perfect for your avocado. Yes, it will be able to breathe inside a sealed plastic bag. Just watch out for too much condensation. If that occurs, open the bag for a few hours … then seal the plant in again.
Note that, even if you increase the humidity, the damaged leaves will not turn green again, but rather new leaves will not turn brown. In other words, high humidity doesn’t cure browned leaves, it only prevents future damage.
Some Additional Suggestions
First, can I assume that your plant is growing in potting soil? If not, pot it up without delay. Many people start their avocado pit over a glass of water, but it won’t live forever that way. In fact, as soon as you see the first signs of root growth, you really should transplant it into a terrestrial environment.
After it has been potted up, regular, deep watering will be necessary. The root ball must never dry completely, because that too can lead to leaf browning. So, as soon as the soil seems dry to the touch, it is time to water again.
Also, hard water is not good for avocados. They prefer a more acid soil without excess minerals and for that reason, the water would ideally be soft. However, not only can tap water be hard, depending on its source, but the chemical treatments given to municipal water to keep it drinkable can increase its hardness. And hard water can also result in browning leaves, especially in combination with dry air.
Ideally, the water would have a calcium carbonate concentration of less than 60 mg/l: i.e., it should be soft. If your water is considered hard or very hard, it would be better to water your avocado tree with rainwater, dehumidifier water or distilled water.
Or Just Ignore the Problem
The good news is that even if you do nothing at all, the condition of your avocado tree should begin to improve all on its own in the spring, as the damaged leaves will eventually drop off and will be replaced by fresh, healthy leaves. And in the spring and summer, the air indoors in most climates is much, much more humid than in the winter: certainly at least in the 50% range. The result is that the new leaves should remain in fine shape … that is, until the next heating season.
Avocados: fun to start, but not such great houseplants. And they really hate dry air!