Direction Of Light

Direction of Light

Plant care gets easier when your plant matches your light. We spend a lot of time talking about watering, soil, humidity and what a plant “should” need, but the environment it is growing in changes all of those things. Light is a major part of that environment, and understanding where your light comes from is a good place to start.

Start with your windows

Window direction changes the type of natural light that enters your home and when that light is available throughout the day.

north-facing window generally receives the lowest natural light, with softer, more diffuse light throughout the day.

east-facing window receives morning sun. Light is strongest earlier in the day and becomes softer as the day progresses.

south-facing window generally receives the strongest and longest-lasting natural light throughout the day.

west-facing window receives stronger light later in the day, including afternoon and early-evening sun that can also bring more heat near the window.

But window direction is only the beginning. Two people can both have east-facing windows and have very different growing environments. Window size, trees, buildings, overhangs, season and where the plant sits in relation to the window can all change how much light actually reaches its leaves.

Direction tells you where the light comes from. Intensity tells you how much reaches the plant.

Light changes quickly as you move away from a window. A plant sitting close to the glass can receive considerably more light than another plant several feet into the same room.

This is where measuring light becomes useful.

Foot-candles and lux are measurements of light intensity. Instead of guessing based only on how bright a room looks to us, they give us a way to measure what is actually reaching the plant.

If you measure your light, measure at the leaves where the plant actually sits, not at the window.

And remember that the number isn't permanent. Natural light changes throughout the day and throughout the year.

Your windows don't have to decide what you can grow

If the natural light in your home doesn't provide enough light for a plant you want to grow, you can add a grow light.

A grow light can supplement the natural light coming through a window or become the primary source of light for a plant. That means a room with limited natural light doesn't automatically have to be a low-light plant room.

But choosing a grow light can get confusing quickly.

Kelvin. Lumens. Lux. PAR. PPFD. Coverage. Distance.

Those numbers don't all tell you the same thing, and a bigger number doesn't automatically mean a better light for your plant.

Understanding grow-light numbers

Kelvin (K) tells you the color appearance of the light. For a natural daylight appearance, I generally look for full-spectrum lighting around 5,000–6,500K.

Lumens tell you how much visible light the fixture produces. They're useful for understanding the overall output of a light, but they don't tell you by themselves how much light your plant is actually receiving.

Lux measures the light intensity reaching a particular area. Unlike the lumen rating printed on the box, lux can help you understand what is actually reaching the plant where it sits.

PAR refers to the range of light wavelengths plants use for photosynthesis, approximately 400–700 nanometers.

PPFD measures how much PAR light reaches a particular area. This is especially useful when comparing grow lights and understanding what is actually reaching the plant rather than simply looking at the fixture's advertised output.

Light spread matters too. A powerful light concentrated over one small area behaves very differently from a fixture spreading that output across a large shelf.

And then there is distance. Moving a plant closer to or farther away from a grow light changes the intensity reaching its leaves. That's why there isn't one universal number of inches that works for every grow light and every plant.

Rooted plant descriptions are changing too

I want the information on each plant to help you actually place it in your home, whether you're growing with a window, a grow light or a combination of both.

Rooted plant descriptions already help you understand the natural-light environment a plant prefers. We're expanding that lighting information so the descriptions can also give you more useful guidance when you're growing under plant lights.

The goal isn't to give you another complicated set of rules to memorize. It's to give you enough information to look at your window or grow-light setup, understand what your plant is receiving, and make a better placement decision.

Because “put it under a grow light” isn't enough information. The light itself, its output, its coverage, the distance from the plant and the amount of light reaching the leaves all matter.

Why this changes everything

Light is energy for your plant. It affects how quickly the plant grows, how quickly it uses water, the size and spacing of new growth and how the plant develops over time.

In lower light, growth generally slows and the plant uses water more slowly. With more usable light, the plant has more energy available for growth and will often use water more quickly.

When a plant isn't receiving enough light for the growth you're asking from it, changing the watering schedule doesn't solve the underlying problem.

That is why light and watering can't really be separated.

Light changes when your plant needs water

Watering is not a schedule.

Your plant uses water in response to its environment, and light is a major driver of that process. The same plant can need water at completely different times in two different homes. It can even need water differently in the same home as the seasons change.

This is why I teach:

Water when your plant needs watered.

Instead of deciding that a plant gets watered every seven days, watch the plant, watch the root zone and understand the environment driving its water use.

Placement matters

Sometimes the answer isn't a new product or a different watering technique. Sometimes the plant simply needs to move.

A few feet can dramatically change the natural light available from a window. A few inches can significantly change the intensity beneath a grow light.

If something about your plant's growth or water use starts to change, its light and placement should be part of what you evaluate.

When your plant matches your light

When the plant and its environment work together, plant care becomes much easier to understand.

Water use becomes more predictable. Growth becomes more consistent. The plant gives you clearer signals because you're no longer trying to compensate for an environment that doesn't support what it needs.

You're not following a generic rule. You're learning to respond to your plant.

Start with the light you already have, or create the light you need.

If you want to understand light beyond the simplified version here, The Rooted Light Guide takes you much deeper into measuring, placement, windows, grow lights and understanding what your plants are actually receiving.

Start by choosing your light below: