Well-bred Haworthia hybrids can have dazzling colors. One of the most captivating features of these plants is the vivid pigmentation decorating their leaves. A prime example is the standout sibling from my PP247 Haworthia hybrid series. This series is a result of a cross between one of my darkest "Scarlet Begonias" F2 hybrids and a carefully chosen PP22 hybrid. Since the turn of the century, I've been dedicated to breeding Haworthia hybrids to enhance their coloration. The intensity and variety of hues in these hybrids have been astonishing.
Don’t stress out your plants! I'm sometimes asked if the vibrant colors of my Haworthia hybrids are the result of stress. It leaves me taken aback because I toil tirelessly to ensure their growth environment is stress-free. I stress out when I think my plants are under stress, I can’t help it. There's much misunderstanding around the correlation of red hues and stress in Haworthia, particularly on social media platforms. Adequate light is key to brining out the beautiful reddish and darker pigments in Haworthia. However, it's crucial to understand that providing sufficient light is not equivalent to imposing stress. The precise light requirement varies with each plant's unique genetics, but many of my hybrids maintain their crimson hues, even during the dimmest winter days. It's true, Haworthia without a genetic inclination for red can turn red under intense and stressful light conditions, but that's a method I neither endorse nor employ.
The Color Mystery: The specific pigments responsible for the red and dark hues in Haworthia are not definitively known, but they could be anthocyanins, which color other plants, such as red maple leaves. This question would make a fascinating research project – if you're interested in collaborating or funding research on this topic, do reach out!
The G x E Equation: The G x E interaction, or Genotype x Environment interaction, is a vital concept in genetics. It illustrates how genetic and environmental factors interact to influence the traits, or phenotypes, observed in organisms.
In the context of color in Haworthia hybrids, the plant's genotype determines its potential for coloration (such as having red hues). However, this potential's expression (the phenotype, i.e., the actual color the plant exhibits) depends on environmental conditions like light exposure. If a Haworthia genetically predisposed to red coloration receives adequate light, it will display intense red hues. The same genetically predisposed plant grown in low light may not exhibit intense red coloration. Thus, the plant's final color is a result of the interaction between its genetic makeup (genotype) and its environment. This is a Genotype x Environment interaction.
Let there be light: You might wonder, how much light is ideal for your Haworthia to unleash their full color potential? Bear in mind that exposing them to the blistering midday summer sun (from noon to 3 PM) can be damaging, not just for Haworthia but for other succulents as well. For many years, I've successfully nurtured most of my plants on a north-facing deck in California, where they bask in the direct morning sunlight and enjoy shade from around 10 or 11 AM onwards. I have some succulents in a more exposed location in my yard and these are under 50% shade cloth from spring to early fall.
The cool summers in Northern California, where I reside, create an optimum environment for Haworthia cultivation. However, if you're located in areas with hotter summer climates, you'll need to exercise caution. When temperatures soar above 87 F, it's best to keep your Haworthia under shade and slightly on the drier side. During the winter months, give them as much sun exposure as possible.
What about artificial lights? Many inquire about growing Haworthia under artificial lights. I'm always hesitant to advise on this topic due to my limited experience. For several years I have been growing Euphorbia francoisii under artificial lights in my home. The exact system I use I purchased on Amazon:
Gardener's Supply Company Indoor Greenhouse Gardening 3-Tier Plant Stand with Three Watertight Shelf Trays High Intensity 6500K Color LED Grow Light Spectrum for Optimal Plant Growth
Starting more than a year ago I placed some Haworthia including one of my “Scarlet Begonias” hybrids under these lights with the Euphorbia. I did this in order to test how these lights would affect coloration in Haworthia. I am happy to report the plants look beautiful. I was a bit concerned about the lack of air circulation but after a year in these conditions they are quite healthy: