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A Black Knight is kept alive exactly the same way as an ordinary green ZZ plant. Keeping it black is a different question, and it is the one this page mostly answers.
Water it thoroughly, then leave it alone until the soil is dry all the way through. Give it more light than you would give a green ZZ, because light is what develops the dark pigment. New growth always comes up lime green and darkens over several weeks. That is not a fault.
The two mistakes
Panicking about green new growth. Every new stem on a Black Knight emerges bright lime green and darkens gradually as it matures. People see it, assume the plant is reverting or was mislabelled, and sometimes return it. It is simply how the plant works, and the contrast between old black stems and new green ones is part of what the plant looks like.
Putting it in a dim corner because ZZ plants tolerate low light. A green ZZ survives a dark hallway. A Black Knight in that same hallway survives too, but its new growth stays a dull dark green and never reaches near-black. You keep the plant and lose the reason you bought it.
What normal looks like
- New stems arrive as a tightly furled lime green spear pushing up from the soil, not from an existing stalk.
- That new growth darkens over roughly four to eight weeks, and continues deepening for months after.
- A mature plant carries obvious contrast between near-black older stems and bright green new ones.
- One or two new stems per growing season. Fewer than a green ZZ manages, because this one is slower.
- Growth largely stops between May and September.
- An occasional lost lower leaflet on the oldest stem is ordinary ageing.
Where it comes from
The species is from seasonally dry eastern Africa. The dark form is not wild at all. It was spotted as a chance mutation on a single branch in a South Korean nursery in 2006, and every dark ZZ in the world descends from that one observation.
Zamioculcas zamiifolia grows wild across eastern Africa, from Kenya and Tanzania down through Malawi, Mozambique and Zimbabwe to north-eastern South Africa, in seasonally dry bushland with fast-draining rocky ground. That habitat is the reason the plant stores water underground and treats a forgotten watering as ordinary weather. The green ZZ guide covers that story in full, and all of it applies here.
The dark form has a much shorter history. In 2006 a grower at a South Korean nursery noticed a single branch on an otherwise ordinary ZZ plant whose leaves darkened as they aged. Cuttings were taken from that branch and grown on to confirm the trait held, which it did. That one branch is the origin of every black ZZ plant sold anywhere today.
Naming, and what you are actually buying
The dark ZZ that is properly documented is sold as Raven, with the registered cultivar name Dowon, patented in the United States in 2018 and released commercially in 2019. Black Knight is a trade name used in the wider market, and whether it is the same clone is not something anyone can reliably document.
Raven, and the name behind it
The Korean mutation was formally registered under the cultivar name Dowon. It was granted United States plant patent PP30035 in 2018, with protection running to 2033, and was launched commercially by Costa Farms in 2019 under the marketing name Raven. That is the dark ZZ with a documented paper trail.
And Black Knight
Here is the honest part. Black Knight is a name in wide commercial use for a dark ZZ, and it is the name this plant is sold under in New Zealand. What we cannot tell you is whether it is genetically the Dowon clone under a different trade name, a separate selection from the same original mutation, or a distinct find. There is no published record settling it, and we would rather say that than invent a lineage.
What we can tell you is what matters practically. Every dark ZZ in commerce behaves the same way: emerges lime green, darkens with maturity and light, grows more slowly than the standard green form, and is otherwise an ordinary Zamioculcas. Whichever name is on the label, the care on this page applies.
Dark ZZ plants are sometimes sold at a premium as rarities. They are no longer rare, and prices have fallen a long way since 2019. Judge the plant in front of you on the number of stems and how well developed the colour is, not on the name attached to it.
Why it turns black
The colour comes from anthocyanins, the same class of pigment that makes blueberries and red cabbage dark. The plant's genetics allow it, but how dark it actually gets depends on light and maturity. This is why the colour develops rather than arrives.
Anthocyanins, not chlorophyll
The near-black surface is not the absence of green. Underneath, the leaflet is doing ordinary photosynthesis with ordinary chlorophyll. Layered over that are anthocyanins, water-soluble flavonoid pigments in deep red, purple and near-black, accumulated in the leaf tissue in sufficient concentration to mask the green entirely.
This is a meaningful distinction from a variegated plant. A White Knight philodendron has white sections that genuinely cannot photosynthesise, so the plant carries dead weight. A Black Knight is fully functional green tissue wearing a dark coat. It is not handicapped in the same way, which is why it is no harder to keep alive than the green form.
Why the colour has to develop
Anthocyanin accumulation is photomorphogenic, meaning it responds to light rather than simply switching on at a set age. The genetics set the ceiling. Light and maturity determine how close to that ceiling any given stem gets.
A new stem emerges with almost no anthocyanin, which is why it is lime green. Over the following weeks the pigment accumulates and the stem darkens, deepening further over six to twelve months in good conditions. In poor light the process stalls partway, and you end up with a dark green plant rather than a black one.
Why it is slower than a green ZZ
Dark cultivars grow noticeably more slowly than the standard green form. Expect one or two new stems in a good season where a green ZZ might manage two or three. Producing the pigment costs something, and the darker leaf surface reflects less light back into the leaf.
The practical consequence is patience. A Black Knight that has done nothing for three months in spring is often normal rather than unwell, and the diagnostic questions further down will help you tell the difference.
Growing it
Water thoroughly then not again until dry throughout. Free-draining mix, snug pot, feed lightly October to April, repot every two to three years. The one deliberate difference from a green ZZ is light: give it more.
Light
This is the section that decides what colour your plant is in a year.
Give it bright indirect light. In New Zealand that means within a couple of metres of a north-facing window, or beside an east-facing one, slightly back from the glass or behind a sheer curtain. It will survive in far less, as any ZZ will, but the dark pigment will not develop properly.
What it will not take is hours of direct summer sun through unshaded glass. Dark leaves absorb more heat than pale ones and New Zealand's UV is strong, so scorch is a genuine risk on this cultivar specifically.
Too little: new stems that stop at dark green and never go further, long gaps between leaflets, and the plant leaning toward the window. Too much: pale bleached patches or dry brown scorch on the side facing the glass, appearing over days.
Water
Identical to the green form, and the method matters more than the frequency.
- Check first, always. Push a finger, skewer or chopstick to the bottom of the pot. Any damp soil clinging to it means wait. The surface tells you nothing.
- Water thoroughly when it is dry throughout. Take it to a sink and water until it runs freely from the drainage holes.
- Let it drain completely, then tip out anything collected in the cover pot or saucer.
- Wait, then check again. Never water to a schedule.
In an Auckland home expect roughly every three to four weeks from October to April, and every five to eight weeks from May to September. A slower-growing dark cultivar in a cool room may stretch longer again.
A ZZ plant recovers from drought in weeks. It rarely recovers from rot at all. If you are unsure, wait another week.
Temperature and humidity
Comfortable between 18 and 28 degrees, holding steady down to about 12 but not growing much below 15. Keep it away from single-glazed windows on frosty nights and out of direct heat pump flow.
Humidity is not a concern. This is a dry-season plant with waxy waterproofed leaves, and ordinary New Zealand indoor humidity suits it completely. Do not mist it.
Potting mix and feeding
Free draining. Roughly two parts quality indoor potting mix, one part pumice or perlite, one part orchid bark or coarse coir. Pumice is easy to source in New Zealand and its weight helps steady a tall plant.
Feed only October to April, and only when it is actively producing new stems. A balanced liquid indoor fertiliser at half strength every six to eight weeks is plenty, onto damp soil rather than dry. Stop entirely from May.
The pigment responds to light and maturity, not feeding. A plant that is not darkening needs a brighter position, and unused fertiliser salts build up in the mix and damage roots.
Repotting and size
Every two to three years, or when rhizomes press against the pot walls or lift the surface of the soil. Go up one size only, around 3 to 5 centimetres, in spring or early summer. An oversized pot holds wet soil the plant cannot use.
Indoors expect 50 to 80 centimetres over time, a little shorter than the green form and noticeably slower to get there.
Propagation
Division, stem cuttings and leaflet cuttings all work, exactly as for the green form, and all three produce dark plants. The catch is time: this cultivar is slower at every stage, and a leaflet can take well over a year.
The dark trait is stable through vegetative propagation, which is precisely how the original 2006 mutation was confirmed and multiplied. A cutting from a Black Knight grows into a Black Knight. Note that patented cultivars carry propagation restrictions for commercial purposes, so propagate for yourself and for friends rather than for sale.
Method 1: Division
Fastest and most reliable, best done in spring at repotting.
- Hold off watering for a week or two beforehand. Drier mix falls away cleanly and reduces rot risk at the cuts.
- Slide the plant out and work the soil off the rhizome cluster so you can see what you are doing.
- Find a natural separation where a rhizome has both its own roots and its own stems. Ease it apart by hand where you can, use a clean blade only where you must.
- Leave the divisions in the shade for a few hours so the cut surfaces dry and seal.
- Pot into free-draining mix in pots only slightly larger than the rhizome. Water lightly once, then treat as normal.
Method 2: Stem cuttings
A whole stem will root and form a rhizome. Cut at the base with clean secateurs, strip the lowest leaflets, let the cut end callus for a few hours, then stand it in water or push it into moist free-draining mix. Keep it warm and bright. Expect roots at around three to four weeks in water, with a small rhizome forming over the following months. Soil is slower to show progress and more reliable long term.
Method 3: Leaflet cuttings
The patient option, and the one the commercial industry is built on. Pull individual leaflets with the small stub where they join the stem, let them callus for a few hours, then push each upright about a centimetre into moist free-draining mix. Keep barely moist, bright and as warm as you can manage.
On the green form this takes three to nine months to form a rhizome and up to about eighteen months for a first stem. On a dark cultivar, add to both figures. Start them in October so the warm months do the work, and do not throw the tray out because nothing is happening above the soil.
Diagnose a problem
Tick everything you can actually see on your plant. The more you tick, the better this gets at separating causes that look alike.
Water problems
Overwatering and underwatering both cause yellowing, which is why they get confused. The difference is texture. Overwatered tissue goes soft, dark and mushy. Underwatered tissue goes thin, wrinkled and papery.
Rhizome and root rot
The most common cause of ZZ plant death, dark cultivar or otherwise, and slightly more likely here because a slower plant uses water more slowly. A watering routine that suited a green ZZ may be too frequent for this one.
How to identify it
- Yellowing appearing on several stems at once rather than working up one stem from the bottom.
- Stem bases soft when gently squeezed, or gone dark and translucent near the soil.
- Stems that pull free from the soil with almost no resistance.
- Soil still visibly damp more than two weeks after watering.
- A sour or swampy smell from the soil surface.
- Rhizomes soft, brown or grey rather than firm and pale. This is the definitive test.
Take the plant out of its pot and look. There is no way to diagnose rot from above the soil, and on a dark plant early yellowing is harder to spot than on a green one. Every day spent guessing is a day the rot spreads.
How to treat it
- Remove the plant and wash all the old mix off the rhizomes so you can see every surface.
- With a clean sharp blade, cut away every soft, dark or smelling section until you reach firm pale tissue. Wipe the blade between cuts.
- Remove any stem attached to a rhizome you have cut out entirely.
- Leave the healthy rhizomes in open air in the shade for a few hours to a full day so the cuts seal.
- Repot into fresh free-draining mix in a pot sized to what is left, often smaller than the original. Do not reuse the old mix.
- Do not water for at least a week, then water sparingly until new growth appears.
Recovery is realistic if firm rhizome remains. If every rhizome is soft the plant cannot be saved, but leaflets from unaffected stems can still be propagated, and they will grow up dark. That is worth doing before giving up.
Underwatering
Far less dangerous and usually reversible. Leaflets lose their plumpness and go thin and papery, stems droop while staying firm at the base, and the pot feels light. If the mix has gone hydrophobic and water runs straight through, stand the pot in a basin for 20 to 30 minutes, then drain fully. Leaflets firm up within a few days.
Light and colour problems
Too little light does not hurt the plant, it just leaves it dark green instead of near-black. Too much direct sun bleaches and burns, and this cultivar is more vulnerable to it than the green form because dark leaves run hotter.
Colour not developing
The most common disappointment with this plant, and it is a positioning problem rather than a health problem.
How to identify it
- Stems that matured months ago sitting at dark green rather than near-black.
- A plant that looked darker when you bought it than it does now, because the nursery grew it in better light than your room offers.
- Everything else about the plant looking perfectly healthy.
How to treat it
Move it into brighter indirect light, within a couple of metres of a north or east-facing window. Stems already matured may deepen somewhat but will not fully catch up. New growth will colour properly. Give it a full growing season before judging the result, because this is a slow plant and the pigment accumulates over months.
Sun scorch
Caused by direct sun through unshaded glass, most often November to February, and most often after a plant has been moved from a dim spot to a bright one without transition. Dark foliage absorbs more heat, so a dark ZZ scorches where a green one might cope.
How to identify it
- Damage on the side facing the window with the shaded side untouched.
- Pale bleached patches, later drying to crisp tan or brown centres.
- Sharply defined edges rather than a gradual fade.
- Onset over days after a move or a run of hot clear weather.
How to treat it
Move it back from the glass or add a sheer curtain. Scorched tissue does not repair, so remove badly marked stems at the base once the plant has stable growth elsewhere. When moving a plant somewhere brighter, do it in stages over two weeks.
Insufficient light for growth
Distinct from the colour problem, though they often occur together. Signs are no new stems across a full October to April season, new stems emerging long and thin with wide leaflet spacing, and the plant leaning toward the light. Move it closer to a window or add an LED grow light on a timer, and rotate the pot a quarter turn at every watering.
Pests
ZZ plants are unusually pest resistant, and the dark form is no different. The waxy leaf surface deters most insects. When pests do appear it is usually spider mites in a warm dry room, or mealybugs brought in on a new plant.
ZZ leaves are heavily waxed and water beads straight off them. Any spray needs a wetting agent or it will roll off before making contact. In New Zealand, Grosafe Enspray 99 works both as a treatment and as a wetting agent for exactly this reason.
| Pest | What you see | Where to look | Confirm it |
|---|---|---|---|
| Spider mites | Fine pale stippling, loss of shine, and eventually fine webbing. Stippling shows up clearly against dark leaves | Undersides of leaflets and the tight joints where leaflets meet the stem | Hold white paper under a stem and tap. Moving specks the size of dust confirm mites |
| Mealybugs | White cottony blobs, obvious against near-black foliage, plus sticky residue below | Leaf joints, the base of stems, and just below the soil line on the rhizome | Touch one with alcohol on a cotton bud. Mealybugs go translucent brown |
| Fungus gnats | Small black flies around the pot, worst just after watering | The top few centimetres of soil | Press a slice of raw potato onto the soil for two days and look for larvae underneath |
Treating spider mites
- Isolate the plant immediately, away from every other plant in the house.
- Take it to a shower or outside and rinse thoroughly, paying attention to leaflet undersides and joints.
- Treat with Yates Mavrik or Grosafe Enspray 99, available at Mitre 10, Bunnings and garden centres. If using Mavrik, add Enspray 99 as a wetting agent so it holds on the waxy leaf.
- Repeat every five to seven days for at least three treatments. Contact sprays do not kill eggs, so a single application always fails.
- Wipe the leaves clean between treatments and check weekly for a month afterwards.
Treating mealybugs
Isolate the plant, then remove every visible insect individually with a cotton bud dipped in isopropyl alcohol. Follow with horticultural oil across the whole plant, repeating every seven to ten days for three to four rounds. Check at and just below the soil line, since mealybugs colonise the rhizome where nobody looks and a plant that keeps reinfesting almost always has them there.
Treating fungus gnats
Gnats are a symptom of soil staying damp, so on a correctly watered ZZ they have nowhere to breed. Let the soil dry out completely, which is safe on this plant and breaks the cycle by itself. Cover the surface with a centimetre of pumice, use yellow sticky traps, and then look at why the soil was staying damp, because that is the same problem that causes rot.
Other issues
| What you see | Most likely cause | What to do |
|---|---|---|
| New stem is bright lime green | Nothing. This is how every dark ZZ grows | Wait. It darkens over four to eight weeks and keeps deepening for months |
| Plant is dark green but never goes near-black | Not enough light to drive pigment production | Move it within a couple of metres of a north or east-facing window |
| Only one new stem all season | Normal. Dark cultivars are slower than the green form | Nothing, provided the base is firm and the soil dries in reasonable time |
| One lower leaflet yellows and drops occasionally | Normal ageing | Nothing. Remove it if you prefer the look |
| Brown crispy tips and edges only | Fertiliser salt buildup, or dryness combined with heat pump air | Flush the pot at the sink, stop feeding for two months, move it out of direct heat pump flow |
| Leaflets drop off intact without yellowing | Cold shock or a sudden environmental change | Move to a stable spot between 18 and 28 degrees and leave it alone for a month |
| Stems splaying outward from the centre | Uneven light, plus normal weight as stems mature | Rotate a quarter turn at every watering, improve light, use a discreet ring stake if needed |
| Leaves look dull and the black looks flat | Dust, which shows more on dark glossy foliage than on green | Wipe with a soft damp cloth. Avoid leaf shine products, which clog the surface |
| Black or brown mushy patches spreading up a stem from the soil | Rot advancing from the rhizome | Act now. See rhizome and root rot |
Safety and pets
Mildly toxic, not dangerous, and identical to the green form. All parts contain sharp microscopic crystals that cause immediate mouth pain if chewed. Unpleasant rather than serious, and the pain usually stops animals after one bite.
Like most of the arum family, Zamioculcas contains insoluble calcium oxalate as raphides: needle-shaped crystals held under pressure in the plant tissue. When an animal or child bites a leaf or stem, the crystals are released into the soft tissue of the mouth. The effect is mechanical rather than chemical, which is why it hurts instantly rather than hours later. The dark pigment makes no difference to any of this.
Symptoms in cats and dogs
- Pawing at the mouth or rubbing the face along the floor, often the first sign in cats.
- Sudden heavy drooling.
- Head shaking, and reluctance to eat.
- Vomiting or diarrhoea if a quantity has been swallowed.
What to do
Remove any remaining plant material from the mouth and offer water, milk or a small amount of food to help flush the crystals through. Symptoms usually settle within a few hours. Contact your vet if drooling persists beyond that, if there is swelling around the mouth or throat, or if breathing seems affected, which is rare but possible.
For people
The sap can irritate skin and eyes, so wash your hands after pruning, repotting or taking cuttings, and avoid touching your face while you work. Wear gloves if you have sensitive skin.
ZZ plants are often described as extremely poisonous. They are not, and they do not appear on the ASPCA toxic plant list at all. Separately, a rumour that circulated from around 2010 claiming ZZ plants cause cancer is entirely false and has no scientific basis.
Questions
My new stem came up bright green. Did I get sold the wrong plant?
No. Every dark ZZ produces new growth in lime green and darkens it afterwards, because the pigment accumulates as the stem matures rather than being present from the start. Expect it to darken noticeably over four to eight weeks and to keep deepening for months after that. If your older stems are dark, your plant is exactly what it should be.
How do I make it darker?
More light, then patience. Anthocyanin production responds to light and to the maturity of the stem, so a plant in a dim corner stalls at dark green. Move it within a couple of metres of a north or east-facing window, out of direct sun, and judge the result over a full growing season. Nothing you feed it will change the colour.
Is Black Knight the same plant as Raven?
Possibly, and we would rather not pretend to know. The documented dark ZZ is the cultivar Dowon, sold as Raven, discovered in South Korea in 2006 and patented in the United States in 2018. Black Knight is a trade name in wide use, and there is no published record confirming whether it is the same clone or a separate selection. In practical terms they behave identically, and everything on this page applies either way.
Why is mine growing so much slower than my green ZZ?
Because it is meant to. Dark cultivars grow noticeably more slowly than the standard green form. One or two new stems across a whole growing season is a healthy rate here, where a green ZZ might manage two or three. As long as the base is firm and the soil dries in a reasonable time, a quiet season is not a problem.
Can I propagate it, and will the babies be black?
Yes to both. Division, stem cuttings and leaflet cuttings all work and all produce dark plants, because the trait is stable through vegetative propagation. That is exactly how the original 2006 mutation was confirmed. Expect everything to take longer than it would on a green ZZ. Note that patented cultivars carry restrictions on commercial propagation, so propagate for yourself rather than for sale.
Does it need different care from a green ZZ?
Only in one respect. Watering, mix, feeding, temperature and humidity are identical, and you can follow the green ZZ guide for all of it. The difference is light: a green ZZ is genuinely fine in a dim corner, while a Black Knight in the same spot keeps living but never develops its colour.
The black looks dusty and flat. Is something wrong?
Usually just dust, which shows far more on dark glossy leaves than on green ones. Wipe the leaflets with a soft damp cloth, supporting each stem from behind with your other hand. Avoid commercial leaf shine products, which clog the leaf surface. If the dullness persists after cleaning, check for spider mites.