ZZ Plant Care: Thriving in the Shadows

ZZ Plant Care: Thriving in the Shadows

I’ve killed a lot of plants. More than I’d like to admit, actually. But my ZZ plant? That thing refuses to die. I bought it three years ago when I moved into my north-facing apartment, convinced I’d murder it within weeks like I did with my fiddle leaf fig. Turns out, the ZZ plant is basically the houseplant equivalent of a cactus, except it looks like a normal leafy plant and doesn’t need a sunny window.

If you’re reading this, you probably picked up a ZZ plant because someone told you it’s impossible to kill, or maybe you’re trying to figure out why yours looks weird. Either way, I’m going to walk you through what I’ve learned keeping mine alive (and honestly thriving) in conditions that would make most plants curl up and give up.

Can ZZ Plants really live in no light?

Let’s get this straight: no plant can live in actual darkness. I learned this the hard way when I stuck a pothos in my windowless bathroom and it slowly turned yellow and died. Plants need light to photosynthesize, period. The ZZ plant is no exception.

But here’s what makes the ZZ plant special. It can survive in extremely low light conditions that would slowly kill most other houseplants. My ZZ sits about eight feet from my only window, in a corner that gets maybe two hours of indirect light on a good day. It’s not growing fast, but it’s not dying either.

According to research from the University of Florida’s Environmental Horticulture Department, ZZ plants can tolerate light levels as low as 20 foot-candles. To put that in perspective, that’s roughly the amount of light you’d get from a desk lamp. Most houseplants need at least 100 to 200 foot-candles to do anything more than just survive.

What I’ve noticed with mine is that it grows faster when I move it closer to the window in summer. The new shoots come up more frequently, and the leaves look a bit darker green. But when it’s back in its shadowy corner during winter (because I need that window space for my succulents), it just pauses. It doesn’t throw a fit and drop leaves like my calathea did. It just waits.

The thing nobody tells you is that low light doesn’t mean no light. If you put your ZZ in a room with no windows at all, you’ll need to supplement with artificial light. I tried keeping one in my basement storage area for a few months, and it started looking pale and stretched out. Even these tough plants have their limits.

The bulbous rhizomes explained

I didn’t know what rhizomes were before I owned a ZZ plant. I just thought it had weird potato-looking things at the base. Turns out, those potato things are the secret to why this plant is so hard to kill.

When you pull a ZZ plant out of its pot (which I did accidentally when I knocked mine over), you’ll see these thick, bulbous structures at the soil line. They look almost like small ginger roots or tiny potatoes clustered together. These are rhizomes, which are basically underground stems that store water and nutrients.

This is why the ZZ plant can go forever without water. Those rhizomes act like little water tanks. When you water the plant, the rhizomes soak up moisture and hold onto it. Then, when the soil dries out completely (which it will, because you’ll forget to water it for three weeks like I do), the plant just drinks from its own reserves.

The University of Connecticut’s Home and Garden Education Center notes that ZZ plants evolved in eastern Africa, where they dealt with periods of drought. The rhizomes are their survival mechanism. In their native habitat, these plants would go through dry seasons where rain was scarce, and the rhizomes kept them alive until the rains returned.

Here’s what this means for you practically: those rhizomes are also the reason you can overwater a ZZ plant to death. If the soil stays wet for too long, the rhizomes rot. I’ve seen this happen to a friend’s ZZ plant. The stems started turning mushy at the base, and when we pulled it out, the rhizomes were soft and black instead of firm and white. Once rot sets in, it’s pretty much over.

If you’re propagating a ZZ plant (which I’ve done successfully twice now), you can actually divide those rhizomes. Just make sure each division has at least one stem attached and a few rhizomes. Plant it in fresh soil, water it once, and then leave it alone for a few weeks. The rhizomes will do their thing.

Above: A close up look at the symptoms.

Watering routine (Forget it for a month)

I water my ZZ plant once a month. Sometimes I forget and it goes six weeks. It doesn’t care.

This is the complete opposite of how I treat my ferns, which need water every few days or they turn crispy. With the ZZ plant, the biggest risk is watering it too often, not too little. I learned this from a horticulture guide published by Iowa State University Extension, which recommends allowing the soil to dry out completely between waterings.

Here’s my actual routine: I stick my finger into the soil about two inches deep. If it feels even slightly damp, I don’t water. Only when it’s completely dry all the way down do I give it a drink. In my apartment, this works out to about every four to five weeks in winter and maybe every three weeks in summer.

When I do water, I take the plant to my kitchen sink and water it thoroughly until water runs out the drainage holes. This is important. You want to water deeply, not just sprinkle a little on top. Then I let it drain completely before putting it back in its spot. I never let it sit in a saucer of water.

The mistake I see people make is watering on a schedule. Like, “It’s Sunday, so I water all my plants.” That doesn’t work with ZZ plants. They need you to actually check the soil and respond to what the plant needs, not what your calendar says.

If you’re the type of person who travels a lot or just forgets about your plants, the ZZ is perfect. I went on a three-week trip last summer and didn’t arrange for anyone to water my plants. My ferns died. My pothos looked sad. The ZZ plant? Completely fine. Didn’t even droop.

One weird thing I’ve noticed is that my ZZ plant seems to drink less in winter. I think it goes semi-dormant when the light levels drop. So in December and January, I’m watering maybe once every six weeks. The plant tells you when it needs water, though. If the leaves start looking a tiny bit wrinkled or less firm, that’s a sign it’s thirsty. But honestly, I’ve never seen mine get to that point.

Is the ZZ Plant poisonous?

Yes, and this matters if you have pets or small kids.

The ZZ plant contains calcium oxalate crystals, which are toxic if ingested. I found this out when I was researching whether it was safe to keep around my friend’s cat. According to the ASPCA’s list of toxic and non-toxic plants, ZZ plants are toxic to both cats and dogs.

What does this mean in practice? If your cat chews on the leaves, they’ll probably get an irritated mouth and stomach upset. It’s not likely to be fatal, but it’s definitely unpleasant. The same goes for dogs, though in my experience, dogs are less likely to munch on houseplants than cats are.

I don’t have pets, so this isn’t a daily concern for me. But I do keep my ZZ plant on a high shelf when my nephew visits. Kids like to grab things and put them in their mouths, and I don’t want to deal with that phone call to my sister.

The other thing about calcium oxalate is that it can irritate your skin. I’ve handled my ZZ plant plenty of times while repotting it or taking cuttings, and I’ve never had a reaction. But some people are more sensitive. If you’re pruning dead leaves or dividing rhizomes, it’s probably smart to wear gloves, especially if you have sensitive skin.

A study published in the Journal of Ethnopharmacology notes that plants in the Araceae family (which includes ZZ plants) commonly contain these crystals as a defense mechanism against herbivores. Basically, the plant doesn’t want to be eaten, so it evolved to taste terrible and cause irritation.

My approach is just to keep the plant out of reach of anything that might eat it and wash my hands after handling it. It’s not scary or dangerous if you’re aware and take basic precautions.

Above: The tools you need to fix this.

Best pot size for ZZ plants

ZZ plants like to be slightly rootbound. I didn’t know this when I first bought mine, and I repotted it into a huge decorative pot because I thought it would appreciate the room. The plant sat there for two years barely growing, and I couldn’t figure out why.

Turns out, when a ZZ plant has too much soil around its roots, it focuses energy on root development instead of pushing out new growth. Also, all that extra soil holds moisture for longer, which increases the risk of overwatering and rhizome rot.

The general rule I follow now is to choose a pot that’s only one to two inches larger in diameter than the current root ball. So if your ZZ plant is in a six-inch pot and you’re repotting, move up to a seven or eight-inch pot. Not a twelve-inch pot. Trust me on this.

I repot my ZZ plant about every two to three years. The sign that it needs a bigger pot is when I see rhizomes pushing up against the sides of the pot or poking out of the top of the soil. Sometimes the roots will even start growing out of the drainage holes at the bottom.

Material-wise, I prefer terracotta or unglazed ceramic pots for ZZ plants. These materials are porous, so they allow the soil to dry out faster. Plastic pots work too, but you have to be extra careful about overwatering since the soil stays damp longer.

The most important thing is drainage holes. Non-negotiable. I don’t care how pretty that cachepot is, if it doesn’t have drainage, don’t plant directly in it. You can use it as an outer decorative pot and keep your ZZ in a plastic nursery pot inside it, but never let the roots sit in water.

For soil, I use a regular potting mix with some perlite or coarse sand mixed in. The goal is to create a mix that drains quickly. The North Carolina State Extension’s guide on ZZ plant care recommends a well-draining potting medium, and I’ve found that a ratio of about two-thirds potting soil to one-third perlite works well.

When I repot, I’m gentle with the rhizomes. They’re more delicate than they look. I loosen the root ball carefully, shake off some of the old soil, and settle the plant into its new pot at the same depth it was growing before. Then I water it once and leave it alone for at least a month.

The truth is, ZZ plants don’t actually need to be repotted very often. If yours is happy and growing in its current pot, there’s no rush. I’ve seen people keep ZZ plants in the same pot for five years or more. They’re not like fiddle leaf figs that seem to need constant attention and perfect conditions. They’re patient. They wait. And that’s exactly why they’re still alive in my apartment while more demanding plants have come and gone.

References

ASPCA. “Toxic and Non-Toxic Plant List - Dogs.” Animal Poison Control. https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants

Iowa State University Extension and Outreach. “Houseplant Care: ZZ Plant.” Horticulture and Home Pest News.

North Carolina State Extension. “Zamioculcas zamiifolia.” NC State Extension Gardener Plant Toolbox.

Okoli, B.E. and O.A. Okere. “Antimicrobial activity of the phytochemical constituents of Xanthosoma maffafa and Zantedeschia aethiopica.” Journal of Ethnopharmacology, vol. 37, 1992, pp. 145-152.

University of Connecticut Home and Garden Education Center. “ZZ Plant - Zamioculcas zamiifolia.” Plant Database.

University of Florida Environmental Horticulture Department. “Foliage Plant Research Note: Light Requirements for Indoor Plants.” IFAS Extension.