Guttation and plant diseases, should you worry about those drops?

Guttation on an orchid leaf with beaker and measuring stick

Breakthrough research is analyzing the effect of guttation on the spread of plant diseases. In some cases, guttation is bad for plants. Indeed, when water flows in and out of the plant through thousands of tiny nozzle-like hydathodes on leaves, germs are transported in and out, too.

Is guttation a disease?

In itself, guttation is a natural process. It isn’t a disease that the plant catches. A healthy plant guttates from time to time, when conditions trigger it.

However, there are some cases when it isn’t all that good for the plant.

Guttation favors spread of plant diseases

Bacteria can enter a plant through guttation

Guttation harbors diseaseA study revealed that in greenhouse-grown tomatoes, guttation helped spread bacterial canker responsible for tomato wilt.

  • When plants were handled while guttation was present, they fell sick and the disease spread.

Two lessons were learnt from this:

  • 1/ seemingly healthy plants already had germs and bacteria appearing in guttation drops.
    As in human diseases, plants could contaminate other plants even as it was still fighting off symptoms of the disease. Plants were contagious through guttation during the incubation phase.
  • 2/ And second, to protect healthy, uncontaminated plants, it was best to wait for guttation to evaporate before intervening among the plants.

If any plants in your garden are diseased, wait for guttant drops to dry off before working among them.

The case of lawn disease

In the case of lawn diseases, it usually helps to clear guttation and dew from the grass. This ensures it dries faster. Spores from lawn fungus won’t have time to hatch and contaminate new blades of grass.

  • Simply mow the lawn or run a rake or roller across it early every morning.
  • Drops fall to the ground and don’t linger on the plant anymore, and blades of grass dry off faster.

Plants use guttation to defend themselves, too

Plants know how to counter this, though. It’s been shown that special germ-blocking proteins concentrate around the hydathodes.

Peace lily flower with a drop of guttation at the tipThese proteins react with bacteria, fungus and viruses and try to destroy them before they enter further into the plant.

A healthy plant, well fertilized and watered, will produce plenty of these “soldier proteins”. A plant weakened by disease, drought, or neglect will tend to have less of these proteins available.

Guttation: plants texting each other?

Reports are discovering that the composition of guttation fluid is strongly influenced by compounds floating in the air.

  • For example, methyls and ethylene floating in the air trigger changes as to which proteins appear as a compounds in guttant sap.

This is a fascinating inroad into learning about how plants communicate. It may explain why plants not yet diseased or attacked by pests start producing chemical defenses as soon as one of their kind is attacked by pests or illness.

One possible reason that this might work is that water in the guttation fluid forms a permeable barrier that airborn compounds can cross. They dissolve from the air into the guttation and from there gain access to the entire plant’s immune system.

Plant care and guttation

How should guttation influence the way you care for your favorite plants?

Removing guttation on indoor plants

  • For indoor plants, there is a risk when too much guttation occurs. It evaporates and leaves white spots on leaves.
  • These spots are from minerals that stay behind once water dries up. These form white spots on leaves.
  • When minerals accumulate, they start damaging leaf cells, creating leaf burn spots.  These spots can be either yellow, brown or black.
  • This tends to happen more often on thick-leaved plants such as orchids (shown in the picture at the top of this article) and the jade plant.

Guttation forming at a eye on an orchid stemTo reduce guttation on houseplants, you can do the following:

  • avoid watering in the evening.
  • water with soft water or rainwater, not mineral-laden hard tap water.
  • don’t over-fertilize. Too much of it keeps adding minerals to the soil. Better to repot or topdress a plant instead.
  • wipe the spots off gently with a soft moist cloth.

What about outdoor plants, is guttation dangerous?

  • For outdoor plants, the answer is no: guttation is and remains perfectly safe for plants outdoors.
  • Rain rinses off any deposits early enough to avoid any damage.
  • The only risk is poisoning neighborhood relationships if your tree spatters guttation all over your neighbor’s prize car or favorite sitting bench.

Indirectly, though, guttation may attract a series of pests. Aphids, scale insects, caterpillars, thrips and many others are attracted by the free source of water and nutrients.

In rare cases, guttation fluid may also stay on the plant for a long time in moist weather; this increases the risk of having sooty mold develop on the plant.

All in all, this is a phenomenon that shouldn’t worry you. And it’s amazing when you see those perfect drops on the tips of leaves and flowers!

Images: CC BY 2.0: Maja Dumat, Shelly and Roy Johnson; own work: Rosalyn & Gaspard Lorthiois; Pixabay: AP