An important criterion for what temperennials star in my garden is ease of preservation/propagation from year to year. Variegated tapioca a.k.a. variegated cassava root (Manihot esculenta variegata) almost failed the test until I learned how to handle its idiosyncrasies.
My history with this plant illustrates the adage about believing a plant hardy until you have killed it three times. I very nearly did.
I knew I had to try it when I first saw it in a nursery catalog, sporting multilobed (palmately lobed, for you botaniphiles) leaves in shades of green, chartreuse and creamy yellow. My first plant arrived one fall in a 2 1/4 inch pot, a spindly specimen that I was sure I could overwinter under fluorescent lights in my basement garden. No such luck - it gradually dwindled and perished before it could be placed outdoors in warmth and sunshine. A second attempt ended like the first. Finally I wised up, and ordered my plant in spring. This one, transplanted outdoors to a six-inch pot, grew moderately over the summer and displayed its characteristic foliage to good effect. But I wanted a large sweep of variegated tapioca, so I needed to propagate and grow it successfully indoors over the winter. This was easier planned than accomplished.
It turned out that tip cuttings of M. esculenta variegata could be rooted, but only with difficulty. At least two thirds of the cuttings, taken in my usual fashion and placed in pots in a flat under a humidity dome (or simply covered with a plastic bag) rotted instead of rooted. The survivors had to be babied and watched for their worst indoor pest, spider mites. If I wasn’t careful, the first sign of trouble would be subtle minute leaf speckling, followed rapidly by development of fine webbing where leaf lobes joined the (petiole). This could be controlled by use of a Neem/horticultural oil spray, but required diligent repeat applications.
All that fussing paid off the next summer, when surviving plants began to strut their stuff, growing rapidly in full sun and attaining a mature height of five to six feet. When it came to utilizing this plant in the garden, I quickly learned to disregard expert advice to keep the plants in a display pot on the grounds that they couldn’t be counted on to make an impact when mingled with other garden inhabitants. This is nonsense - the striking leaves put on a great show, especially when displayed with strong solid foliage colors (i.e. deep green, red, purple-black) for contrast. One year’s especially memorable pairing involved a foreground planting of variegated tapioca against a backdrop of Canna ‘Wyoming’, with large bronze-purple leaves.
Given full sun and at least monthly feeding with a balanced fertilizer such as a 20-20-20 formula, variegated tapioca develops stout woody stems and reaches a height of six feet or more. It can be pruned for an extra bushy appearance but I’ve never found this necessary. Small, non-showy greenish-white flowers may appear late in the growing season.
Propagation difficulties were solved when I discovered that instead of trying to root tip cuttings under conditions of high humidity, the way to go is to utilize woody stems, the thicker the better. I take 4-6 inch lengths with several nodes, scraping some superficial tissue off the bottom half of each cutting (use a sharp scissors or blade of pruning shears), placing several vertically into a pot and sinking at least half their length into soil, which should be a freely draining lightweight potting mix. Alternatively, short cuttings can be placed horizontally in the pot and two-thirds covered with soil (the bottom surface of such cuttings is scraped before planting to promote root growth). Some cuttings won’t “take”, which is the reason for placing several in a pot. A covering for extra humidity is not required, and only increases the chances of rot. Bright light is not needed until new growth is well underway; if initial lighting is too strong i.e. sun or close placement under bright artificial lighting, top growth may be prematurely stimulated and subsequently shrivel if root growth has not sufficiently advanced to support it. Plants can be trimmed back as needed to keep size under control and should be frequently misted (especially the undersides of foliage) to discourage spider mites. Gradual introduction to outdoor conditions in spring can take place once nighttime temperatures are consistently 50F or greater. Once true summer heat arrives, growth takes off.
While M. esculenta variegata is generally regarded as hardy only in U.S.D.A. climate zones 8 and higher, intrepid souls may want to give overwintering a go further north with diligent protection. My first attempt was unsuccessful, but I’m going to try again, while continuing to hedge my bets by taking cuttings. It’s too good a tropical accent to ever do without.
*note: M. esculenta variegata roots are described by online sources as being as edible as those of its plain-leafed counterpart, which is utilized as a food source when properly prepared and cooked (the cyanide content of raw cassava is a drawback to the fine dining experience).