Light is food. That’s the whole story… but because this is the 2026 edition (and you’ve already survived a thousand “bright indirect light” posts), let’s actually turn the numbers on your light meter into real-world leaf growth.

You don’t need a physics degree or a $600 PAR meter. You just need to know whether your Monstera is getting “holiday buffet” levels of light… or living on two crackers and a Berocca.

This guide is about taking the numbers you see in lux and translating them into what you actually care about: new leaves, fenestrations, variegation, flowers and that general “wow, that looks happy” vibe.

Want to go full plant nerd? We’ve got a deeper breakdown in our main Indoor Light Guide – this one’s the houseplant-only, quick-reference version. Check out the full light guide here.

1. Lux, PPFD and DLI – In Plain English

Lux is how bright light feels to your eyes. It’s a measure of illuminance – one lumen per square metre. Our eyes are extra sensitive to green-yellow light and less bothered by deep red and blue.

Plants don’t care about “brightness” the way we do. They care about how many useful photons hit their leaves, especially in the red and blue range. That plant-usable light is usually measured in:

• PAR / PPFD: How many useful photons are hitting a square metre of leaf each second.
• DLI (Daily Light Integral): How much useful light a plant gets over the whole day – basically intensity × duration.

So:

• Lux = “How bright does this look to me?”
• PPFD/DLI = “How many plant-calories is this leaf getting over the day?”

The good news: for sunlight through windows and decent white LEDs (around 4000–6500K), lux is still a handy proxy. It’s not lab-accurate, but it’s good enough for houseplant decisions, as long as you remember that:

It’s not just how bright it is – it’s how bright, for how long. A few hours of decent light is very different to 10 hours in the same range, and that’s where DLI lives in the background.

2. Lux Bands as Ballparks (Not Gospel)

Outdoors, even an overcast day can be 10,000–25,000 lux. Full sun can smash 80,000+ lux. Inside our homes? Most spots away from windows are shockingly dim in comparison.

These ranges are ballpark bands for houseplants, assuming you’re getting roughly 8–10 hours in that zone on a typical bright day. Shorter days need more intensity; longer days can get away with a bit less.

0–100 lux: “Looks nice, doesn’t grow”

• Feels like: A dim hallway or moody bookshelf.
• Plant reality: Survival mode for tough plants only (ZZ, snake plant, cast-iron plant). You’re not really “growing” here, you’re babysitting.

100–500 lux: “Low light, not no light”

• Feels like: Standard living room away from windows, interior office desks.
• Good for: True low-light plants if you’re okay with very slow growth – peace lily, some ferns, Aglaonema, ZZ.
• What to expect: They can hang in there, but if you want lush, full plants, this is still a compromise zone.

500–2,000 lux: “Decent indoor light”

• Feels like: A light, open room near (but not right in) a window.
• Good for: A lot of classic foliage plants – pothos, Philodendron, Monstera deliciosa, rubber plant, peperomia, many aroids.
• What to expect: Healthy maintenance and moderate growth. Some fenestrations and variegation, especially on the easier species.

2,000–10,000 lux: “Growth zone”

• Feels like: Right by a bright window (east or west), or within a couple of metres of your sunniest window.
• Good for: Most aroids, Ficus, Hoya, many flowering plants and sun-lovers.
• What to expect: Faster growth, bigger leaves, better colour – assuming you’re matching water and nutrition.

10,000–20,000+ lux: “Indoors pretending to be outdoors”

• Feels like: Sunrooms, north-facing glass, under serious grow lights.
• Good for: Light-hungry plants – Bird of Paradise, many succulents, cacti, and advanced projects like indoor citrus or bougie Anthuriums under lights.
• What to expect: Strong, compact growth once acclimated; scorch risk for true shade-lovers if you go too hard, too fast.

You don’t need to memorise all that. Think of it like this:

• Under ~500 lux: Survival/slow-motion zone.
• 500–2,000 lux: “Doing fine.”
• 2,000+ lux: Where the magic happens, especially if you keep it going for enough hours.

3. How to Actually Measure Light at Home

Option A: The zero-tech method

Do this around midday on a bright day, at leaf height:

• Shadow test:
  • Sharp, crisp shadow with clear edges → high light.
  • Soft, blurry shadow → medium light.
  • Barely any shadow → low light.
• The “would I read here?” test:
  • If you’d happily read a book without flicking a lamp on → at least medium.
  • If you instinctively want a lamp → low.

Option B: Phone lux apps (with realistic expectations)

Most smartphones can run a light meter app that reads in lux. They’re not lab instruments – phone sensors auto-adjust, cameras react to what they’re pointed at, and different models give different numbers – but they are great for comparing spots in your own home.

Quick tips:

• Measure at leaf height, where the plant actually lives.
• Take readings at a few times of day and note the typical low and high.
• Repeat in different seasons – winter numbers will crash compared to summer.
• Treat the numbers as relative guides, not gospel. Perfect for “this corner vs that window,” less useful for winning arguments on the internet.

Option C: Dedicated lux / PAR meters

If you’re running grow lights or you’ve got a full indoor jungle, a basic lux meter is cheap and more consistent than phone apps. Up the nerd ladder are PAR/PPFD meters that measure plant-usable light directly – brilliant if you’re tuning serious grow-light setups.

For most plant parents though, phone meter + common sense + watching the leaves is plenty.

4. From Numbers to Leaves: What Changes with More Light?

Once you’ve got rough lux readings, here’s what more and better light usually buys you:

• Faster growth – shorter breaks between new leaves.
• Bigger leaves – especially on aroids and Ficus.
• Better variegation – whites stay white, patterns stay crisp.
• More fenestrations – Monstera, Rhaphidophora and friends doing their holey-leaf thing.
• Tighter internodes – plants look full and compact instead of stretched and spindly.

Classic “not enough light” signs:

• Thin, stretched stems leaning toward the nearest window.
• New leaves smaller than the older ones.
• Loss or fading of variegation and patterning.
• Soil staying wet for ages because the plant isn’t using water.

If you’re seeing that and your readings are under ~500 lux for most of the day, light is at least half the problem. You can have great watering habits and still have an unhappy plant in a dark corner. Of course substrate, pot size and watering frequency still matter – but light sets the upper limit on what’s possible.

5. Windows and Real Homes (Southern Hemisphere Edition)

Because we’re in Australia, let’s start with the Southern Hemisphere version. In general:

• North-facing windows: Brightest, most direct sun. Great for sun-lovers and most “bright indirect” plants placed a bit back from the glass.
• East-facing: Gentle morning sun, then bright but softer light. Lovely for most tropicals and aroids.
• West-facing: Softer mornings, harsher afternoon sun. Fantastic for strong growers, but you may need sheer curtains in summer.
• South-facing: Softest, lowest light. Think low-light plants right up at the glass, and/or grow lights in winter.

If you’re reading this from the Northern Hemisphere, flip the north/south logic – your south-facing windows are the bright ones.

Then there’s all the real-world stuff that throws the compass out:

• Deep eaves, balcony overhangs or neighbouring buildings chewing up your sun angles.
• Privacy glass, films or heavy tinting soaking up a big chunk of lux.
• Blinds and curtains softening glare but also stealing photons.

This is why even one round of measurements is so useful. Your eyes adapt; your light meter doesn’t.

6. Simple Lux Targets for Common Houseplant Types

These are happy growth ranges – not the bare minimum for survival. More light (within reason) usually means better growth, as long as you acclimate plants slowly.

• True low-light crew (ZZ, snake plant, cast-iron plant, some ferns)
  Aim for around 300–800 lux for most of the day.
  They’ll survive and gently plod along here. If you want them lush and full rather than just alive, nudging them up into the 800–1,500 lux band is a big upgrade.

• Standard foliage plants (pothos, Philodendron, Monstera deliciosa, rubber plant, peace lily)
  Aim for roughly 800–2,000+ lux for 8–10 hours where you can.
  This is the sweet spot for most “living room jungle” plants – enough energy for continuous, decent growth and good leaf size.

• Light-hungry aroids & Ficus divas (Fiddle Leaf Fig, variegated Monstera, many Anthuriums, Thaumatophyllum, some Philodendron species)
  Aim for around 1,500–5,000 lux, with at least a few hours closer to the upper end once they’re acclimated.
  Variegated and collector aroids in particular usually look their best toward the higher end of that range or under well-set-up grow lights.

• Succulents & flowering plants (cacti, many Hoyas, Bird of Paradise, indoor citrus projects)
  Aim for 2,000–10,000+ lux if you can manage it indoors.
  Succulents and Bird of Paradise love that “pretend we’re outdoors” energy. Citrus can be grown indoors, but they really belong in the “very high light / sunroom / serious grow-light” category rather than a standard living room.

If all of this makes your inner-city apartment suddenly look very dim, you’re not alone. Most “average” rooms are sitting firmly in the low to very low bands once you step away from the windowsill. That’s why plant placement and, sometimes, grow lights make such a difference.

7. Grow Lights (2026, Without the Drama)

If your windows are doing their best but still not cutting it, grow lights are just… extra daylight you can control.

• Check real wattage, not just marketing numbers. As a rough rule, anything under ~10 W total is décor more than growth, unless it’s very close to a small plant. Bars and panels around 20–40 W placed well can do a lot indoors.
• Stick to 4000–6500K white LEDs. They’re efficient, plant-friendly and don’t turn your lounge room into a purple rave cave.
• Distance matters a lot. Double the distance from the light and the intensity at the leaf plummets. Keeping plants roughly 20–40 cm from the light is usually far more effective than a brighter light stuck on the ceiling.
• Use a cheap timer. 10–12 hours a day, every day, beats “whenever I remember to flick it on.”
• Watch heat and acclimate. Stronger lights up close can warm leaves and burn sensitive plants if you go too hard, too fast. Start higher or shorter, then gradually bring them closer or run them longer over a few weeks.

There’s no single “perfect” setup – stronger lights closer to plants can run fewer hours; weaker or further ones need longer hours. The trick is to pick something realistic for your space and then watch how your plants respond.

8. Easy Tweaks & a Real-Life Example

Small moves that make a big difference

• Slide plants 30–60 cm closer to the window. Lux can jump dramatically with even a small move.
• Rotate pots every few weeks. Helps avoid lopsided, one-direction growth.
• Clean the glass and the leaves. Dust, grime and fingerprints steal free light. A quick wipe can boost light without changing anything else.
• Group by appetite. Fiddle, variegated Monstera, Hoya? Window squad. Snake plant, ZZ, Aspidistra? Back-row, low-light bench.
• Seasonal shuffle. In summer, pull scorch-prone plants out of harsh afternoon sun. In winter, nudge everyone closer and lean more on grow lights.

A quick “from lux to leaf” makeover

Let’s say your variegated Monstera is 3 metres from a south-facing window, and your phone app reads 150–250 lux most of the day. You’re getting:

• Long gaps between leaves
• New leaves smaller than the old ones
• Variegation fading to a muddy green
• Soil that takes 2+ weeks to dry

You move it to within 1 metre of your brightest window, where readings jump to 1,000–1,800 lux for 8+ hours. Same potting mix, same fertiliser, same you. Over the next couple of months you notice:

• New leaves arriving more often
• Leaf size catching up or surpassing old growth
• Variegation looking sharper and whiter
• Soil drying faster, so your watering rhythm changes naturally

You didn’t reinvent yourself as a plant whisperer – you just upgraded the energy budget. That’s “from lux to leaf growth” in real life.

9. When in Doubt, Trust the Plant (with a Meter as Backup)

Light meters, apps and charts are great, but they’re still just tools. Your plants get the final vote.

Whenever you tweak light – moving a plant, adding a grow light, changing curtains – give it 6–8 weeks and watch:

• Are new leaves bigger, the same, or smaller?
• Is the plant stretching, or getting fuller and more compact?
• Is variegation holding, improving or fading?
• Is the pot drying at a sensible pace for the species and pot size?

If growth tightens up, leaves size up and your watering rhythm feels more natural, you’re on the right track. If not, adjust again – a little closer, a different window, a longer light period – and keep iterating.

And if this has unlocked your inner light nerd, jump over to our main Indoor Light Guide for PPFD charts, window-by-window setups and more plant-obsessed detail than you probably asked for.

Read the full Indoor Light Guide