I have been asked on more than one occasion why someone’s garden or house plant’s leaves are brown at the tips or edges. The cause is simple and yet complicated at the same time. The simple answer lies beneath the soil line. My first suspicion is not a disease or pest. Usually, it is environmental: root/soil interface issues. When leaf edges are browning, it means there is some type of issue with soil water and the root. The edges brown because these are the extreme end points of water flow, the furthest distance the water must travel through the plant. A shortage in water, therefore shows on these extreme edges. This is the basic answer, however many different things can cause issues with the soil water/root interface.
There are several possible specific reasons why the leaf tips and edges are not getting enough moisture.
- Lack of humidity – The most likely culprit for tropical house plants is a dry indoor environment. The winter months especially lead to lower humidity levels. Dry air tends to wick moisture quicker from the leaf interior leading to dead cell tissue and the water supply does not keep up. Palms are notoriously exhibit brown tips. Keeping plants away from drafts, grouping plants together or using a humidifier are all means of increasing moisture content around the leaf surface.
- Improper watering – Under-watering or overwatering can lead to browning as well. Under-watering leads to not enough water being absorbed, but so does over watering. Overwatering leads to root rot and thus not enough water being taken up to meet cell demand. Water only as often and as much as the plant needs. Water until you see water coming out the bottom. I always recommend pots with holes and a separate tray to collect excess. If you cannot see when to stop watering, how do you know if you are watering enough? There are several ways to tell if it is time to water. As the soil dries, stick your finger an inch plus into the soil to feel the moisture levels. An even better way is to stick your finger into the drain holes underneath if possible. The top layer may be dry but the bottom, where most of the active root growth is occurring, might still be thoroughly saturated. You can also pick up the pot and determine by weight soil moisture levels. The usual guide is to water when soil moisture levels have fallen to about 50% or so.
- Salt build up – If you are using a synthetic liquid feed fertilizer, such as Miracle Grow, a white crusty layer can develop on the potting soil surface. High soil salinity inhibits water uptake, thus a water shortage. Remove the crusty layer and replace with fresh potting media, or better yet, do not use a synthetic fertilizer primarily.
In the garden, the cause is exactly the same: roots and water not getting along. The specific cause might also be dry air, too much or too little soil drainage. Regardless of the specifics, it is your plant’s roots not getting along with the water provided. Easy to fix, once you know what to do!
Josh Steffen, Horticulture and Facilities Manager