Hey Nah,

Rich here, with day two of 7 Days to Houseplant Mastery.

Yesterday was watering. Today it's the thing sitting quietly underneath almost every other problem you'll ever have: light.

In the course I put it like this. Light is the fuel, everything else is the fire. Perfect soil, perfect feeding, perfect watering, none of it does much if the plant hasn't got the energy to use it. That's why "water once a week" works for one person and rots another. Nine times out of ten, the difference is light.

The annoying part is that your eyes are terrible at judging it. They adjust so quickly that the windowsill and the sofa two metres back both feel "bright" to you. To a plant, they're different planets. Light drops off far faster as you move into a room than it looks like it does.

And it's about to get worse. We've just tipped into autumn. The sun's sitting lower and the days are shrinking fast. A spot that was perfect in July can be nowhere near enough by November, which is a big reason plants sulk in winter and people blame themselves.

Try this: the shadow test. Hold your hand between your plant and the window. A crisp, sharp shadow means bright light. Soft and blurry means medium. Barely a shadow at all? That plant is running on fumes. It takes ten seconds and it's usually a bit of a shock.

The shadow test is the rough version. In the Light module of Houseplant Mastery, I show you how to actually measure it, with the free phone app I'd start with and the numbers that separate "surviving" from "thriving." There's also why variegated plants need more light than green ones (my variegated tradescantia started pushing out plain green leaves on me, and it wasn't being awkward, it was hungry), how to set up grow lights without scorching anything, and how to move a plant into brighter light without shocking it.