The Succulent Manual- Basic Tips: Light
I'm not going to lie. I come across a lot of photos from proud new succulent owners and think, "That's gonna die," BUT only if some minor yet urgent changes aren't made. One thing I see a lot of is signs of light deficiency. Sometimes it's very obvious that a succulent isn't getting enough light, especially when it comes to the rosette-forming varieties. Many plants are heliotropic, meaning, 'sun turning' or facing. They literally reach for the sun, growing taller with increasingly weak stems in the process. This is called etiolation. The first sign of etiolation in a rosette is when the top layer of leaves start to turn towards the light. Rosette leaves are meant to grow in compact patterns with very little space between each layer of 'petals.' When an Echeveria doesn't have enough light, there is more spacing between the rows of leaves than desirable and eventually the rosette becomes unrecognizable. Even with the proper amount of light, it's sometimes necessary to intervene a tad to keep rosettes looking rosy. I have a very pretty Echeveria Lola that I'll use as an example. Looking directly down at her and from the side, I can see when she has started to tilt her head towards the sun ever so slightly. I then simply turn her 180º so her tilt is facing away from the sun. In a few days I check again and repeat as necessary. The reward for my minimal effort is a fascinating mandala-shaped Lola who turns all the heads of those who walk by her.
It's harder to identify etiolation in plants that aren't such sticklers about compact growth, such as with some Aloes, Jades, Haworthias, and Cacti. Etiolated succulents don't always die but they certainly don't thrive. They're hungry for the light they need to photosynthesize and make food, which means they're more likely to succumb to other deficiencies. One of the coolest things about succulents is their eagerness to survive and ability to generate new plants from just about any part of the main plant. Not all succulents share this feature, but many do and we can use it to our advantage when repairing an etiolated plant if we don't fix the problem in time. We'll cover that in Succulent SOS but for now we're going to talk about preventing etiolation and finding the right amount of light for different varieties.
Not only does sunlight help feed the plant and keep it warm, it regulates the water retention of soil and directly influences the shape of its growth. Determining the differences between full sun, shade, and everything in between can be a challenge, especially since the sun's position changes with the seasons. So natural sunlight is a dynamic element and we need to observe how it moves across our homes and yards to see what we're working with light-wise. Let's settle on a basic key for talking about sun levels in this discussion. The 'dosage' of sunlight hours don't need to be consecutive either. Three hours of morning sun and another five in the afternoon qualify as a day of full sun.
Full Sun: Six or more hours of unfiltered sunlight per day.
Partial Sun: Four to six hours of unfiltered sunlight per day, towards the high end if filtered or indirect.
Partial Shade: Two to four hours of filtered/indirect sunlight per day.
Shade/Full Shade: Less than four hours of unfiltered sunlight per day. (Don't get excited—there aren't very many sucs that will do well in the shade. I know, I know.)
In my opinion, care labels can never provide enough information on the plant with these limited terms. I prefer those with more detailed descriptions like 'bright indirect light' and 'bright filtered light.' These refer to sunlight that is tempered by the sun's position in the sky, or by items like leafy branches, sheer curtains, and other plants. To clarify, if we're sitting on my covered back porch on a sunny spring day, the screened windows face south and west, and the walls are to our north and east, blocking the direct sun all day. The front of the house faces east, and as the sun rises and moves up and over the roof, the intensity of the light increases from our position. There are a few small trees to the south that filter the sun from that direction until about 1 o'clock. This is 'bright filtered light.' When the sun rises high over my house, but the roof blocks it from directly hitting us, this is 'bright indirect light' — the most desirable lighting for most succulents. The sky is reflecting the light but we can't see the sun yet. Around 2pm, the sun will pass over the roof and be visible to our eyes, resulting in full/direct sun for a few hours until it starts to set.
By late spring, there is more shade from the tree canopies, but the sun's path is higher so it's also brighter sooner and the heat is on. This pattern changes with the seasons as the trees drop their leaves and the sun's path moves lower on the horizon, which means plants may need to be moved several times throughout the year to satisfy their light requirements. I think of it as learning a new dance…a year-long dance with a lot of different partners.
To reiterate, filtered and indirect light simply refer to what is happening between the sun and the plant. It's important to find a way to filter or block the sun from directly pounding your plants with its light. As an old cacti keeper explained while pointing to a big oak outside of a plant sale, standing under the shade of a tree on a clear summer day, you'll see plenty of blue sky but be protected from the direct rays of the sun. This is bright indirect light. Step out from under the tree and you might burn after a few hours. Just like us, plants can easily get too much sun, especially if it's hot outside, resulting in succulent jerky. Be very observant of how much direct sun your plants receive, especially if they aren't used to being blasted by solar rays. When bringing home new plants that require full sun, especially if you have them shipped in a box to your door, and doubly especially during a hot summer, it's very important to be careful not to let them get too much sun right away. Acclimate them by potting them up and placing them near their final home. Leave them for a few hours each day then give them some bright shade, like on your porch or under a tree. Increase the amount of time they spend in full sun over the course of a week or two while paying attention to their reaction and inspecting for any signs of sunburn. Avoid watering while the sun is out—we'll get to why in the 'Watering' section.
So while a plant variety might call for full sun, this is too general of an order for all the nuances that need to be accounted for that aren't printed on care labels—but don't fret, that's what I'm here for! I love discussing the details that don't fit on the vague plastic inserts. Morning sun tends to be gentler while still being bright, and south-facing garden beds and windows are perfect for an all-day dose of bright light. An overcast day can still be bright enough to provide what qualifies as partial sun, depending on the cloud coverage. The afternoon sun burns hotter and more directly for west-facing gardens, so much that many folks in this category rely on trees or shade-screens to protect their plants. West-facing windows often need a sheer curtain to shield nearby leaves from getting poached and scarred with sunburn.
Speaking of sunburn, many succulents produce a natural sunblock called farina. It's an epicuticular (outer layer) waxy powder that covers the leaves in a thin layer, and it not only protects against sun rays but repels water so the leaves don't rot if they get wet under a hot sun. It's a common mistake for those new to succulents to think this coating is dust or some other weird reaction and try wipe it off the leaves. Whatever you do, DO NOT rub it off! The leaf only produces farina during growth and doesn't do touch-up repairs. The farina contributes greatly to the final aesthetic form of numerous plants. It's like a magical coat that enrobes each leaf with a highly transparent matte-white finish, transforming ho-hum leaf colors into ethereal hues rarely seen on our planet, let alone from a plant.
To be safe, don't touch someone else's succulents or you run the risk of being cursed every time they see your fingerprint marring their otherwise perfect specimen. It's not so terrible when new leaves will eventually replace those that get smeared, but there are succulents like columnar cacti which don't have that luxury, and a decade of growth can be 'ruined' with one loving caress. So don't touch them. Handle your plants by the roots as often as possible if they're a farinose variety, or at least hold them from the bottom like a little bird, to avoid touching the visible tops of the leaves. As with pregnant bellies, hands off plants that aren't yours. Don't worry, there are plenty of succulents that beg to be touched and it's perfectly okay. I'll cover those in a future section.
*See the Supplies page on my website for sources and links for the products I use.
Table of Contents of The Succulent Manual