Well, a recent social media post in the PNW Plant Geeks Facebook group has just sent me down a rabbit hole on this plant, Acanthus ‘Whitewater’. Turns out, I am not the only one who has had some issues with it putting out albino, or almost completely albino, leaves. Take a look at several pictures taken from around the Pacific Northwest.
The original post came from a local horticulturist who was wondering if others in the group were having problems with Acanthus ‘Whitewater’. She had planted it in three clients’ gardens and said that “it always just pumps out completely white leaves”. Hmmm. Sounds familiar. Follow-up comments by 14 others from around the Pacific Northwest (from Seattle, WA down to the mid-Willamette Valley, OR) suggested that many of us are having a hard time in keeping this plant alive and looking good in our gardens. I wondered how mine was doing after all the problems I had with it last year (here), so I went to take a look.
Sadly, it doesn’t look too good. Once again, all of the new leaves have emerged almost completely albino and some of those leaves are already starting to turn brown and die from the lack of chlorophyll. Not only that, but the leaves are absolutely covered in holes (slug damage), making them look like pale Swiss cheese that is starting to dry out at the edges. You can still see the greener, healthier leaves that grew out last summer after things warmed up (upper left and lower center of the photo). So, what’s going on here?
Looking back at the other pictures that were posted, I noticed they all have something in common. All of the new leaves that have emerged this spring are albino or almost completely so. Double hmm. Then, someone in the group wondered if this situation was heat related. Click. That sounds familiar. My piqued my interest further and down the rabbit hole I went.
Temperature can affect the amount of variegation that occurs in plants. Probably the best known example of this is the ornamental kale that we see in nurseries starting in the fall. The purple and white colors don’t really develop until temperatures fall below 50-60°F (Mahr 2010; Martin 1959). And, note how the central, newly emerging leaves on the ornamental kale are completely white (or purple), which mirrors what we are seeing with our ‘Whitewater’ plants.
A similar situation also occurred in a patch of variegated Japanese butterbur (Petasites japonicus) at the Fukuoka University of Education campus in Japan (Yamasaki and Akiyoshi, 2014). There, plants had more variegation in April, when temperatures were cooler (bottom row, panel a), than in August, when temperatures were warmer (bottom row, panel b). Experimentation later confirmed that plants grown at 18°C/64°F developed more variegation than plants grown at 25°C/77°F.
The opposite effect also occurs. Below, is an example where the amount of variegation increased as temperature increased in a mutated form of Arabidopsis thaliana (bottom row). Note how much larger the leaves of the non-mutated, non-variegated form of Arabidopsis are in the top row. Variegated plants can be less vigorous than their non-variegated counterparts.
In the end, the effect of temperature on variegation all depends on which plant species you are dealing with and on the mechanism that causes the variegation (there are different reasons for why variegation can occur). Looking around my yard, it also seems like there are probably many variegated plant cultivars where temperature doesn’t affect the amount of variegation much at all. For example, I have a variegated dogwood that has the same amount of variegated tissues regardless of whether the leaves come out in spring or later in summer.
One final, bit of supporting information on the whole white leaf issue comes from the website of the nursery that developed Acanthus ‘Whitewater’, which states “Plants often emerge in spring with white leaves”. Based on this, I would bet that the majority of our plants will revert to their normal green/white coloration as our regional temperatures begin to warm up.
So, there you have it. My hypothesis is that the large amount of white leaf tissues on our Acanthus ‘Whitewater’ plants this year is due to the cooler temperatures that the plants experienced during winter and spring. I don’t know the exact mechanism for this phenomenon, as it depends on how the variegation develops in the plant’s tissues. Perhaps the chlorophyll doesn’t form when temperatures are cold, or perhaps it is due to something else. Regardless, it is incredibly cool to see how environment can so dramatically alter the visual quality of the plants in our own gardens.
Given the troubles that I and others have had with this cultivar, I doubt I am going to keep it around for much longer except for curiosity’s sake. It certainly has not been the vigorous plant described on the tag and the slug damage is ugly. I bet there are conditions under which it performs wonderfully, but I apparently don’t have those in my yard. At this point, I am mainly interested in seeing if the new leaves will emerge more green later this summer.
Currently, I have my Acanthus ‘Whitewater’ in a partly shady (morning sun), fairly moist location in our yard, where I had hoped it would brighten up a rather dreary corner. I was thinking of moving it to a warmer, sunnier position to help prevent the albino leaf issue (and maybe minimize slug damage), but then I read other people comments that it seems to do better in shade. Oh well. A few others also commented that it does better in pots, but right now I don’t need another potted plant to water this summer… Or do I? I just remembered that I actually have an empty pot that I’ve been struggling to figure out what to put into it. Hmm.
Acknowledgements: Thank you to the following people, who allowed me to use their photos from the PNW Plant Geeks Facebook group. Lindsay Phillips Osborn (Plant 1), Tim Batog (Plant 2), Patty Lynn (Plant 3), and Magi Treece (Plant 4).
Resources used in this post:
England, T. 2019. The effects of temperature on leaf morphology and variegation in the geranylgeranyl diphosphate synthase 11-1 (ggpps11-1) mutant. Thesis – Master of Science. Southern Illinois University.
Evenari, M. 1989. The history of research on white-green variegated plants. The Botanical Review 55: 106-139.
Mahr, S. 2010. Ornamental cabbage and kale Brassica oleracea. Link to extension webpage here. Accessed 7/4/2022.
Martin, P.G. 1959. Temperature-induced reversal of dominance of variegation in ‘Ornamental kale’. Experientia 15: 34-35.
Yamasaki S. and Akiyoshi, Y. 2014. Low-temperature-induced variegation in variegated Japanese butterbur (Petasites japonicus) leaves. Environ. Control Biol. 52: 253-257.