by
Plant Doctor Christopher Satch
So, you got a plant, and now suddenly, the leaves are turning brown. Maybe they have crispy edges. Maybe they are turning black at the tips. Either way, when houseplants do this, it’s very upsetting. In this article, I’m going to tell you all you need to know about diagnosing leaves, and what the ailments are.
Yellow Leaves
There is so much information online about yellowing leaves on houseplants out there, that you think that some of it would be right. Unfortunately, no, yellow leaves doesn’t always mean overwatering. In fact, yellow leaves really doesn’t mean any ONE thing that’s wrong. Rather, it’s a sign that the plant is stressed, and you have to look at other conditions to see what is going on and properly diagnose your houseplant. Number one is to know the plant you have. Is it a deciduous plant? That’s the first question to diagnosing your plant. Most houseplants are evergreen, but a few succulents, orchids, and most bulbs do indeed die back a bit (or completely) in the fall and winter.
If your houseplant is evergreen and the leaves are turning yellow, then you need to use the following cues to diagnose your plant.
The following all can cause yellow leaves:
- Dry soil – if it’s been too long since the last watering, then your soil will be dry, your lower leaves may start falling off, and the whole plant will droop or wrinkle.
- Wet/moist soil – if the soil/media is still wet after 4-5 days after watering, then your leaves are turning yellow from overwatering. This doesn’t always mean adding too much water. Rather, overwatering is from the plant’s roots staying too wet for too long. Increase heat and light to help the plant dry out. Most commonly, the leaves will be school bus yellow, and drop from bottom to top. Often, many plants if a tad on the moist side will do a blotchy yellow pattern on the leaves. That’s an early warning sign.
- Cold draft – There’s a difference between ambient cold and a draft. A draft implies wind movement. If there is a draft by your window, you can use painter’s tape or masking tape to seal your windows for winter. The coldest parts of the plant will drop yellow leaves first.
- Heatwave – Sometimes, the south-facing window gets a little too hot, though this is rare indoors as long as you have Air Conditioning. Heatstroke causes light yellow leaves to fall off evenly over the plant.
- Nutrient deficiency – If you haven’t repotted in over a year, or if you have propagated in water, or if you simply have had a plant for a long time, but don’t remember when you last fertilized, now is the time. Nutrient deficiencies will manifest in odd ways of yellowing across the plant.
Brown Leaves
Brown leaves are the next most common complaint after yellowing leaves. Most of the time, they are from a fungus, but occasionally can be from nutrient deficiency or drought.
- Irregular Asymmetrical Patterns/Splotches – Fungi/Bacterial spots. They tend to spread and consume more of the leaf and spread to other leaves in a relatively short amount of time, exacerbated by leaf wetness. Stop spritzing the leaves, and that should arrest the spread of the pathogen. Remove leaves that are more than 50% damaged, and spray the plant completely down with a copper fungicide. IF the plant is an orchid, use Physan instead.
- Regular/symmetrical Patterns/Splotches – Often from an abiotic cause like too many salts in the water/salt accumulation. Can also be from drying out too much. May also be from lack of or too many fertilizer salts.
Brown-purple or White Leaf Spots
These are from temperature extremes – often burns.
- White leaf burns – High light/heat burn A.K.A. sunburn of your plants. This is a one-time thing that almost never happens indoors, but often happens when you first place your plants outdoors without acclimating them. Reduce light, and it should be fine.
- Purpley-brown leaf burns that look like watercolor – Often combined with a soggy leaf, this is frostbite of your plants. It’s a one-time thing that only happens indoors with cold drafts.
Black tips
These are almost always salt-related or fertilizer-related. Flush the plant with rainwater or distilled water, and do not fertilize for 6 months. If the tips are brown, then it is from lack of water.
New leaves are smaller than the old leaves
This happens when one of the growth conditions are not met. Most commonly, it’s from lack of light, but can also be from lack of water. Increase light and water.
New leaves are deformed
This is usually pest-caused, but can also be from either nutrient deficiency or lack of water during growth.
My plant is not growing!
Increase light and fertilizer. Your plant may also be dormant. Know your plant, and find out if what you have has a dormancy cycle (some tropical plants do; some just stop growing in the winter because of lack of light, but can be ever-growing if you supplement light).