Light is one of the primary energy sources of our houseplants. As such, when we are unable to give plants the light conditions they need in order to survive, they’ll exhibit changes which warn us that we need to give them more or less light. In this post, I’ll briefly cover the signs that you need to alter the light conditions your plants are subject to.
Signs that your plants are not getting enough light
Some monopodial plants like Phalaenopsis orchids, Sarcochilus orchids, Vandas and Clivias tend to create leaves that are thinner and longer if they do not get adequate light. I like to think that this is an adaptive response because in the natural world, many of these smaller plants grow on the ground or on trees, so by increasing the span of their leaves, they effectively increase the odds of their leaves finding a spot where light shines through the canopy of leaves above them.
A similar phenomenon can be observed in cacti and succulents, which etiolate when they are not given enough light. This means that their stems extend, causing the succulent to deform. This can cause echeverias to look like funky, slightly odd graptopedalums. Again, the extended stem may be seen as an attempt to grow taller to thwart the influence of taller plants which are competing against them for light and blocking the sunlight, or search for light by crawling horizontally across the ground until they find a spot where the sun hits the leaves.
When they’re not given enough light, the leaves of variegated plants can revert to being plain green leaves. This is because the plant needs to increase the green surface area of the leaves, as chlorophyll (the green pigment in plant leaves) allows the plant to photosynthesise. Likewise, most plants will turn a darker shade of green when they do not receive enough light. The build up of chlorophyll allows them to photosynthesise more effectively. Plants that do this include syngoniums and
Signs your plants are getting too much light
Okay, to be 100% clear, it is very rarely the case that a plant gets too much light. If a plant gets sunburned, it is because of a range of factors: heat, poor air circulation and strong light together are the main culprits. A good indicator that your plant is getting too much heat and light is that the leaves feel warm and just a little bit less firm than they usually do.
Some plants can also produce leaves that are overwhelmingly purple or red. Note that this is normal in some plants. Some degree of purple pigmentation is to be expected in some plants. For example, Phalaenopsis and Sarcochilus orchids naturally have a healthy purple flush on the underside of their leaves. Some ornamental citrus trees and their relatives also produce new leaves that start off purple, but turn green as they age. This is because of a pigment produced in many plants called anthocyanin, which is red in colour and acts as “plant sunscreen” while also boosting the immunity of plants.