Fixing Etiolation & Light Acclimation Guide

  Fixing Etiolation and Light Acclimation

A Detailed Guide

Written by Miles Ridgway - Henrys Haworthia (owner)

Etiolation is a natural stress response that is common to all plants (Etiolation, 2009). When a plant is not receiving all of the light it needs, it will grow toward the light (called phototropism), and the stems will elongate. More specifically, internode (stem between leaves) length will increase. Since Haworthia stems are very short and generally not visible, the most common early symptom of Haworthia etiolation is an unnatural lengthening or flattening of the leaves (see photos below). In extreme cases, Haworthia will grow a long, brittle stem out of the center of the rosettes, like many other succulents will.

Etiolated H. cooperi var. truncata
Image credit: reddit.com u/mong_gei_ta

Severely etiolated H. cooperi
Image credit: reddit.com u/mong_gei_ta

Perhaps you have noticed etiolation in your own Haworthia plants and want to know what you can do about it. The purpose of this guide is to help you recognize etiolation, prevent it, and "fix" a plant that is already affected.

The Light Needs of Haworthia Plants

Haworthia are sometimes thought of as "shade succulents," but in fact, most varieties will etiolate with no direct sun exposure. "Shade" is defined in horticulture as four hours or less of direct sunlight, and most Haworthia need a minimum of 2~4 hours of direct sunlight to remain compact. Depending on your climate and latitude, many Haworthia varieties can adapt to as much as 8~12 hours of direct sun. In central Pennsylvania, we keep our plants in full sun all day through the summer. 

H. turgida var. suberecta grown in full sun, fully adapted, with beautiful "stress" colors
Image credit: our image

Other Causes of Etiolation

In addition to light intensity, other environmental conditions can cause or exacerbate etiolation. If a Haworthia is not receiving the light it needs, being overfertilized will greatly accelerate etiolation. Temperature also comes into play. In their natural environment, temperatures are generally lower in winter, when the photoperiod is the shortest. The lower temperatures work to slow their growth during this season of reduced lighting. In homes, however, temperatures are usually relatively consistent throughout the year. Sustained temperatures in the 70's combined with reduced light during the winter may cause a plant to etiolate during this time, while in the summer, it may not. If providing more light during the winter is not an option, consider purposefully rationing water with the goal of halting its growth. Let the container sit dry for much longer periods of time, and provide water only when the leaves are noticeably shriveled.

What to Do With a Haworthia that is Already Etiolated

Unfortunately, the deformities caused by etiolation cannot be reversed. The best you can do is fix the circumstances that caused the etiolation in the first place and wait for the etiolation to "grow out." If caught early enough, removing a few stretched leaves may be all that you need to do to improve its appearance. With increased light, new growth will be more compact and will slowly replace the etiolated growth, but this can take many months. If the etiolation is severe, you can remove elongated stems and ~50% of the elongated outer leaves from each rosette, which will make the effect less noticeable and make room for healthy new growth. If you remove etiolated material, hold off on watering the plant for a week in order to allow its open wounds to callous over.

Etiolated H. cymbiformis - 8 or 10 of the large flattened leaves can be removed, and would go a long way toward improving this plant's appearance.
Image credit: our image

If you have a severely etiolated Haworthia with long, stretched stems, you can cut the stems off and discard them, or cut them into segments (see photo below), allow them to dry and callous over in a shady place, and plant them. They will root within a few weeks, and you will have more plants or a fuller pot.

Here is that etiolated H. cooperi again - red lines indicate places where the stems can be cut and propagated.
Image credit: reddit.com u/mong_gei_ta

Acclimating a Haworthia to Brighter Light

It is very important to introduce an etiolated Haworthia to brighter light very carefully. Since it has been growing with little to no direct sun, sudden exposure to sunlight has the potential to cause permanent sunburn. We recommend a process of increasing direct sunlight exposure by approximately one hour every two weeks. This can be accomplished by moving the plant closer and closer to a sunny window or by putting it outdoors in the sun with a shade cloth, then gradually removing the shade cloth. 

Previously etiolated H. cooperi 'blue lens' is slowly adapting sunlight, as indicated by uniformly dark coloration. Once acclimated, color will slowly change to a more natural shade of green.
Image credit: our image

While acclimating to brighter light, the plant's color will change. Haworthia plants that are not accustomed to direct sunlight may turn brownish-green when first introduced to it. The unsightly dark colors are most pronounced in plants that have been heavily fertilized. This is normal, and the unappealing color is temporary. Closely observe the coloration while acclimating a plant. If the color remains green or darkens, the plant is adapting well. However, if the color grows pale, becomes tan or grayish, or if the leaves develop whitish spots or streaks, light has been increased too quickly, and the plant is in danger of sunburn. Reduce the light to the previous level until its color darkens again, and increase the light more gradually. In extreme cases, it is possible for a plant to be severely sunburned before any color change is noticed. 

Below is an example of a plant that we moved from artificial light to about 6 hours of direct sun. Clearly, this was too much, and by the time we realized the plants were getting too much sun, the damage was already done. They were moved to shade but still developed sun scalding over the next couple of weeks. For a plant that was kept in full shade or 100% artificial light, start with only 1 or 2 hours of direct sun and increase over time from there.

This H. cuspidata has suffered irreversible sunburn. Lightening of pigments, soft wrinkled spots near leaf tips, uneven or splotchy pale tan or white spots are signs of sunburn.
Image credit: our image 

Works Cited:

• "Etiolation" Encyclopedia of Microbiology (Third Edition), 2009
• www.haworthia.com
• Personal experience

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