Have you ever seen your plants weep? Don't worry, they aren't sad! Those little drops of water are actually xylem sap being exuded from the tips of the leaves. What you've stumbled on is called guttation. It's totally normal and nothing to be worried about. If you're interested in why exactly it happens, keep reading!
We know that plants take up a lot of the water and nutrients they need through their roots. To be able to move these things through the plant, evaporation through the stomata (the "pores") happens. This creates a very slight vacuum that pulls nutrients and water from the roots up through the plant in a process called transpiration.
Most plants close their stomata at night, meaning no transpiration is taking place. This is because plants don't always need the same amount of moisture. When it's cooler in temperature or more humid, less evaporation is happening from the leaves. However, the same amount of water is still being taken up through the roots.
This creates root pressure, which is when the pressure inside the cells of the root system causes sap to rise up through the plant and to the leaves. This pressure forces a little bit of water (it's actually xylem sap) to come out of the water glands (or hydathones), resulting in the little droplets we see sometimes in the morning.
So what is guttation made up of? Depending on the plant, its soil, environment, growth stage and health, it could consist of:
- water
- amino acids/nutrients
- sugars
- minerals/metals (including iron, potassium, calcium, sodium and manganese)
- bacteria, fungi, viruses, cell debris, antibacterial/antivirals if the plant has defended itself from a recent attack
Guttation is a phenomenon found in vascular plants, and it's quite common in tropical climates as well as our houseplants. This is because the humidity levels in the air are high, which makes transpiration difficult. In the jungle, it can rain guttation. It's a pretty remarkable thing, imagine being in the middle of the rainforest on a clear day standing under a shower made by plants.
Some plants don't guttate, which makes them more susceptible to edema (cells that become oversaturated and burst. I see edema sometimes in my fiddle leaf fig, where they show up as reddish-brown dots on the leaves). Apparently, ficus does guttate, so maybe my plant is just extra sassy. Many of the citrus family, however, do not guttate at all.
There are few risks that we know of that come from guttation. For indoor plants, the biggest one seems to be when too much guttation happens, it eventually evaporates and leaves white spots on the leaves. These spots are from minerals that are deposited onto the surface of the leaf once the water is dried up. If enough of the minerals are left to accumulate they can damage leaf cells, creating leaf burn spots. This can be avoided by not over-fertilizing, and by wiping your plants down with a soft cloth. Occasionally wiping your plants down is a good idea even if they don't guttate. Getting any dust off of the leaves will improve photosynthesis, and allow you to check for pests.
Another potential risk could be the spread of fungus and disease through guttation moisture. There is some evidence to suggest that it happens if the guttation from a diseased plant is touched, and then another plant is touched immediately after. Wiping the moisture away seems to be the safest bet for avoiding this risk.
All in all, it's nothing to worry about if you do see it on your plants - it's just plants being plants, and doing more cool plant things.
Want a deep dive into guttation?
Photo Credits:
Guttation on a banana leaf is my photo
Crimson guttation on tooth fungus credit to wikepedia
Guttation lining leaf tips credit to plant cell biology masters - they linked the photo to a website to credit that website, but the link is 404 not found. I tried folks.