| By William Scheick
Contributing Editor |
I imagine there might be readers whose eyebrows raised at the topic of this article. Admittedly, there’s good reason for such skepticism.
New Zealand is a land of amazing floral diversity. But because of their geographical isolation, most New Zealand plants are indigenous nowhere else. So a skeptical gardener might reasonably wonder, what is the likelihood of successfully growing those plants somewhere else?
History, however, is on my side in this matter. Many striking New Zealand plants have already become established favorites in European gardens and, increasingly, some have been showing up in U.S. plant markets. Consider, for example, ‘Platt’s Black’ Leptinella, a ferny New Zealand groundcover once included in the Stepables Program at the Calloway’s Nursery retail stores in the Dallas and Fort Worth area. Also the gorgeous June-blooming, coastline-preferring New Zealand Christmas tree or pohutukawa (Metrosideros excelsa) is now celebrated as a West Coast option in Waterwise Plants for the Southwest (2010).
Another example is ‘Avalanche’ clematis, an evergreen hybrid derived from two New Zealand natives (C. paniculata and C. marmoraria). Cold hardy to 10–15º F, this prolific bloomer has been available at North Central, Central and East Texas plant nurseries for many years. It’s a lovely, attention-grabbing plant when regularly watered in part-shade. However, if the roots of this clematis get too dry, its brilliant yellow-buttoned white flowers will become damaged.
Which brings us to a skeptical Texan’s likely second concern: the fact that most New Zealand plants are accustomed to plenty of cooling moisture. How probable, then, would be success with these plants in our notoriously hot and droughty state?
This concern is harder to dodge, I admit, especially considering our demoralizing statewide droughts of 2009 and 2011. If these record-setting years of devastating aridity and heat are indicative of our future in this state, then quite a number of presently popular ornamental plants will become much less feasible as in-ground possibilities. Last year’s extraordinary heat and aridity ended the years-long run of several of my most reliable standbys, including my sturdy fall asters and Italian jasmines (Jasminum humile). Even my extensive Asiatic jasmine (Trachelospermum asiaticum), a super-tough groundcover, was challenged. A glance at nearby fields, too, suggests that many Texas native plants did little better than our ornamentals beneath the daunting onslaught of our recent weather.
Yet despite severe environmental conditions, gardeners still crave exotic plants. The beauty of unique foliage or flowers makes these plants worth the extra effort. New Zealand plants are no exception to this allure of the exotic, except that in general they tend to be much more limited as viable prospects for Texas gardeners. Many New Zealand plants can be managed in containers, of course, but most of them, accustomed to ample rain, would be hopeless choices as in-ground selections for Texas.
That’s the case, for instance, with cultivars of the New Zealand tea tree (Leptospermum scoparium). It is a beautiful shrub that can flower continuously for half a year and it is marketed widely at Texas plant outlets — making it an impulse purchase just waiting to happen. I have to resist that impulse every time I see one of these beauties for sale because in hot Texas the coolness-craving New Zealand tea tree is hard to please even in an indoor environment. And it doesn’t stand a chance of surviving as an outdoor plant.
There are, though, New Zealand plants that thrive in our kind of heat. Like New Zealand plants generally, they do need some moisture. That fact might simply rule them out as possible choices except that the three profiled here endure Texas heat with the least amount of extra water. They are worth a little added attention because their unique features bring something special to the garden.
NEW ZEALAND CORDYLINE
Cultivars of giant dracaena (Cordyline australis) — not to be confused with the popular houseplant known as the good luck or Ti tree (C. fruticosa) — probably form the largest group of New Zealand plants sold at Texas plant markets. (Australis, incidentally, means ‘southern.’) There are numerous cultivars of this New Zealand cabbage palm, including ‘Southern Splendor’ and ‘Kiwi.’ For other striking cultivars, consult the March/April 2009 issue of Texas Gardener
Spiky cordy selections bring unusual and colorfully bold vertical features to the garden. Generally, cordys can thrive in overwintered containers utilized during warm seasons as “dot plants” strategically placed in garden beds for special effects. While some are cold hardier than others, many can serve as in-ground plantings from Central Texas southward. The safest cold-hardiness bet for an established in-ground C. australis is ‘Red Sensation,’ an auburn-pink cultivar reported to withstand a brief deep freeze.
Young codys are best planted in early March to give them time to become established, and they benefit from excellent drainage, pine-bark mulch, dappled light (to prevent leaf-burn) and protection from frost. They are drought tolerant, but their spiffy appearance will be compromised by prolonged periods of dryness.
Here’s a fun-fact about cordyline: To control height or to nurse a frostbitten cordy top, lop off its head in spring and a new shoot should appear somewhere along that trunk (if it is sound), possibly at its base. The growth pattern of cordylines is similar to many dracaenas and yuccas. So as lower old leathery leaves die — to be annually sheered rather than torn off — a fresh crown of foliage ascends.
NEW ZEALAND FLAX
New Zealand flax (Phormium tenax) is another clump-forming perennial offering boldly colorful strappy foliage. Like cordyline, its cultivars come in varying heights between two to eight feet high. So consider tag information before purchasing one. Also like cordyline, New Zealand flax cultivars come in many colors — commonly variations on burgundy and green — to provide dramatic vertical focal points in the garden.
Rich and well-drained soil is a must for New Zealand flax. As its strappy foliage implies, it’s a tough plant, capable of enduring dry periods and also temperature lows at least to 20º F, though some have survived 0º F (zone 7). Even so, freezes damage foliage, and this phormium is also harder than cordyline to keep attractive during our long hot summers. So sometimes Texans grow this medium-shade flax as in-ground annuals or as overwintered potted evergreens deployed as “dot plants.”
Either way, various cultivars of this flax can get fairly wide and in ideal settings their rhizomes (underground stems) will spread. These rhizomes are not invasive, but can spread enough to require thinning, a task similar to our autumnal division of lilies and irises. Over time, too, the older flax foliage fans become an unsightly brown and can be sheered (not torn) off to maintain the plant’s appearance. Pruning will also tidy up fans frayed or “burned” by freezing temperatures. Although the sword-shaped foliage is itself the sought-after prize for garden display, flax can (in the manner of aloes and yuccas) produce tall spikes with red floral “vases” filled with nectar.
NEW ZEALAND SEDGE
New Zealand hair sedge (Carex comans) and orange sedge (C. testacea) are cold hardy in most of our state and both thrive in our heat. Neither is drought tolerant, unfortunately. Instead, both of these arching mounders require shady moist settings with good drainage — perhaps along a pond edge or in a large pot. In such settings, they are low-maintenance, needing only an occasional pruning of dead foliage and also division of their spreading rhizomes every few years.
Location for moisture is not the only consideration with these sedges. Location for aesthetic effect is also important since bronzy brown is the dominant hue of these sedges. After an early greenish stage of growth, these rust-hued sedges tend to look like clumped dead grass, though they are not dead at all. I admit that bronzy brown is not my favorite color in a plant, but I have seen these sedges make a dramatic “bright statement” when spilling over rocks or the edges of a large container.
A good selection for container or in-ground planting, ‘Frosted Curls’ hair sedge (C. comans) offers a two-foot spread of densely tufted silvery-green foliage preferring part-shade. ‘Bronze’ (C. comans) provides the same effect in coppery tones. Even more dramatic is orange sedge (C. testacea), another two-footer. In sunlight its coppery-green foliage with orange highlights looks like a non-stop flowing fountain — in short, a great in-ground or “dot” accent plant capable of withstanding 20º F.
And don’t overlook striking reddish-bronze cultivars of curly top sedge (C. buchananii), especially nearly three-foot-tall ‘Red Rooster’ and ‘Fox Red Curly.’ Two-to-three-foot ‘Toffee Twist’ (C. flagellifera), cold hardy to 5º F (zone 7b), was recommended for North Central Texas by the Dallas Arboretum, but it can be used farther south in our state. This sedge, which particularly stands out when positioned among blue-green plants, can sequence from pale green to brown to (in cooler conditions) autumnal orange.
Cordyline, phormium and carex are three New Zealand plants that can withstand Texan heat. Succeeding with them, though, means adjusting the standard care information for these plants. Although “full sun” is usually recommended, for instance, in fact our blazing Texas sunlight is too much. It is better to provide cordyline, phormium and carex with only morning exposure or partial shade or even dappled light.
Such positioning will keep their roots cooler, as would midday shadows cast by a wall, fence, house or treetop. The roots of cordyline and phormium can also be kept cooler by applying pine-bark mulch and watering as needed.
That cordyline and phormium (not carex) are drought tolerant does not mean they will continue to look great in prolonged dryness-stressing conditions. If their roots get too parched, the prized foliage of these plants becomes noticeably damaged — something to keep in mind particularly during our triple-digit weather. Their foliage can take the heat, but their shaded, mulched and watered roots should be kept as cool as possible.