Monday, May 26, 2008

Guttation

Maybe I'm just like my pothos
She's never satisfied
Why do we scream at each other
This is what it sounds like
When Dieffs cry1


About every two or three months on Garden Web's houseplant forum, someone will show up sounding alarmed because their Dieffenbachia, Philodendron, Monstera, or some other plant, is dripping water from its leaves.

If you are that person, and you've been referred here in response to that very question, don't be alarmed. It's good that you're paying enough attention to your plants that you noticed. A lot of people wouldn't. And to get the scary part out of the way first: it's harmless.

The phenomenon has a name. It's called guttation. There's a very good explanation of the phenomenon at this page, which I couldn't improve on if I tried (and I did try), so if you want the grisly scientific details in layman-readable form, that's the best account I managed to find.

Not all plants are capable of guttation; I think I've only seen it personally in the Monstera, Dieffenbachia, Ficus, and Philodendron genera, though I hear that Marantas do it too, as well as Alocasia spp. and several (many? most? all?) grasses. Monstera and Dieffenbachia are the most likely and consistent guttators, in my experience.

With Ficus in particular, the water exuded by the plant often has other substances (sugars, minerals, proteins, whatever) dissolved in it, which will build up over time to leave a small lump of white material on the underside of the leaf, or sometimes at regularly spaced intervals around the outermost edge of the leaves. On very large, old Ficus benjamina in particular, these deposits can get big enough that you might think they're a batch of mealybugs (I've been fooled more than once): the difference is more obvious with a magnifying glass, or you can get sophisticated and use the "squish test." If water comes out when you squish it, or if it kind of disintegrates, it's more likely to be a bug; if it's kind of waxy and solid all the way through, it's probably guttation. (Also mealybug fluff tends to be opaque, a shade or two whiter than white, and distributed kind of randomly around the plant, where guttation buildup is more translucent, very very light gray, and always on the same spot on several different leaves. It's subtle, but once you've seen both, it's pretty easy to tell them apart.) On Ficus benjamina, guttation buildup is always at the spot right where the petiole ends and the leaf begins:



Well, that's not the best picture, but it's a young leaf, so there isn't a lot of buildup to be seen. You get the idea. I couldn't convince any of my plants to guttate on demand, but it just looks like a water droplet on a leaf: there's not high dramatic potential anyway. I haven't had the weird waxy buildup thing happen with any plants besides Ficus benjamina.

The best way to induce guttation is to water a plant heavily, at night, when it's humid. I don't actually recommend this for houseplants: generally speaking, watering late is a good way to get a plant to rot, though some plants cope better than others. If you have a plant that is consistently guttating every time you water, this might signify that you're overwatering, but the cause-and-effect relationship isn't solid enough to worry about. If you are overwatering, there will almost always be some other, less ambiguous, signal that you're doing something wrong.

So guttation doesn't mean anything bad in and of itself. Your plant's just trying to freak you out.

-

1(from Prince's little-known first draft of "When Doves Cry." He changed it later when representatives from his record company said not enough people would know what Dieffenbachias were. It's a pity: if he'd left it alone he might have had a big hit.)


10 comments:

Water Roots said...

I have seen my Aglaonema, Pothos and a few of my Dracaenas do this (particularly the Dracaena Reflexa - Song of India & Song of Jamaica), although they seem to be a little more subtle about it (tiny, hardly noticeable drops). But my Philodendrons and my Dieffenbachias seem to do this most often, and with large, obvious drops. When I first started growing houseplants, I had no idea what this was. Experience teaches you many things along the way, including guttation.

Tracy said...

I remember noticing this occurrence with my plants and looking around for the answer. I may have asked this on gardenweb at one time.....lol.

Isn't is unreal the questions we ask once something has caught our interest, never mind become an addiction....lol.

I bet almost everyone has tasted "guttation" at one time....lol.

erikamckenzie said...

Hello-recently my Philodendron started doing this, and where the drops fell, it left a little bleached spot on my desk-top. It's almost like it stripped the wood where the drop landed. Why is this?? Is there anyway to prevent that from happening? Thanks!

mr_subjunctive said...

erikamckenzie:

It sounds like the wood needs to be sealed. The Philodendron isn't doing anything particularly corrosive to the desk; it's just that the water's getting absorbed into the wood and leaving a mark, they way glasses of ice water will leave a ring on a wood surface.

The husband, who knows about such things, tells me that if you sand the desk down where the spots are and then apply an oil-based stain, or a coat of polyurethane, you can give the wood a water-repellent coating that will keep this from happening in the future.

Anonymous said...

I was shocked to see my Spathiphyllum with water on its leaf tips! I guess you really do learn something new every day.

gr8ful_life said...

I think my Tricolor Dracaena was doing this, but I'm not sure. The "water" drops were on the underside of the leaves, and they were the slightest bit sticky. Because of this I thought "pests, right?" But as there were no bugs to be found, and the plant is very healthy, I'm wondering if it's guttation. I only noticed after topping my plant, as I inspected for signs of infestation before planting the tip I removed (to propagate). Can anyone else give their description of a dracaena marginata "crying?" or any other suggestions to what may be going on with my plant.

mr_subjunctive said...

gr8ful_life:

I think that is, yes, just guttation. It's at least something I've seen D. marginata do before, with no other sign of pests. I mention it in the D. marginata profile, under "grooming."

themysticalmansionandgarden said...

I have a lot of Alocasias that do the very same thing, especially after watering. But they like moist soil, so it's a pretty common thing...I think!

Nick TheFool said...

My Homalomena is guttating. unfortunately the points where the sugary water is coming out are starting to grow fungus and rot.... the obvious treatment i've been administering is keeping it very warm and drying it off. Does any one have any other suggestions?

mr_subjunctive said...

Nick TheFool:

Have you ruled out mealybugs, aphids, and scale? Guttation should be almost entirely water, which evaporates or drips off quickly, and would probably not support mold growth. Honeydew (from mealybugs/aphids/scale) is clear and looks the same, but is sticky, persists on the plant for a long time, and is very sugary, so it would support mold.

Some aroids also produce sticky stuff spontaneously (I've mostly seen it on Aglaonema and Philodendron; see extrafloral nectary at Wikipedia), which are also sticky and sugary, and in the right circumstances could support mold growth. I'm not aware of any Homalomenas producing extrafloral nectaries, but I'm only familiar with a couple varieties personally, so it's conceivable that you have one that does.

Finally, and forgive me for asking -- I don't mean to be insulting -- are there flowering plants above the Homalomena, like on a shelf or in a hanging basket? A lot of houseplants will drip nectar when flowering, to some degree or another, and that could cause mold. (Hoyas in particular could do this, but also I've seen Aeschynanthus drip a lot of nectar, and I'm told blooming Dracaena fragrans does too.)

My gut feeling is that you probably have an undiagnosed insect pest, but I could be wrong. Feel free to e-mail me pictures (directions for how to get my e-mail address are in the right sidebar of the blog) of the droplets, the mold, or any suspicious-looking spots (especially white/gray/lavender ones, which might be mealybugs, or brown/black ones, which might be scale).