In Praise of Winter Rest
David Bar-Zvi, Former Curator of Herbaceous Monocots
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| Curcuma alismatifolia ‘Chiang Mai Pink’ at Nong Nooch Botanic Garden |
That this is the “winter” edition of Garden Views is an indication that those of us who live here in South Florida year-around acknowledge the march of the seasons. This perception is in contrast to that of visiting gardeners and seasonal garden-loving residents who assume that perpetual summer reigns and the gardens remain the same throughout the year.
Local gardeners have long since turned off the air conditioners and are enjoying the cooler evenings and the subtle changes in light. Most tropical trees and herbaceous plants have responded to the shorter day length. Lavender silk floss (Chorisia speciosa) has presented its glorious flowers. Tropical almonds (Terminalia catapa) now disclose their presence by dotting the landscape with crimson leaves. Vermilion Gloxinia sylvatica is carpeting parts of the garden after hiding underground through summer and into autumn.
Seasonal shifts in vegetation are familiar to temperate area gardeners. Spring and summer bulbs are a favorite of many, and sorely missed as seasonal markers. We often hear dismissive remarks about South Florida having no seasons in which to enjoy the annual renewal of hope and inspiration that emerging, unblemished foliage and flowers represent as they push forth from bulbs, corms, pseudobulbs and rhizomes. This is a very incorrect assumption and tends to leave our landscape palate poorer than it ought to be.
It's true enough that we cannot have the grand displays of spring tulips, hyacinth and crocus so fleetingly enjoyed in temperate zones. We could, instead, have longer lasting displays of tulip-like gingers, exotically colored gingers reminiscent of large hyacinths and orchid-like “Indian crocus,” followed by ornamental leaves that look like those of some Hosta species. Promotion of these beauties is lagging and demand has been slow: Nurserymen are correspondingly reluctant to provide plants for which there seems to be little demand. I hope that the botanical garden display will demonstrate some of the ornamental possibilities of these plants. As budget allows, I will be developing more areas where ornamental gingers can be displayed.
The ginger family (Zingiberaceae) has been a source of spices, perfumes and spices since ancient times. The use of some, e.g., the common spice ginger of commerce (Zingiber officinale), is so ancient that the origin of the species is lost knowledge. Ancient India? Ancient China? Ancient peninsular Malaysia? No written record is conclusive. The beauty and usefulness of these plants has ensured that they have spread far from their origins, where ever those origins may be.
In some cultures, including ours, aesthetic appeal is a big factor in choosing which plants to grow. Asian nurserymen have sought out, selected and bred superior ornamental plants that they hope will appeal to the eye of wealthy Asians and the travelling middle class of the whole world. Mass displays, along with more modest exhibits of floral color are constantly in demand and many gingers fill the bill perfectly.
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| Hybrid Curcuma alismatifolia at Selcon Nursery in Thailand |
Imagine grand vistas of lavender pink or white “tulips” lasting for months on end, or in your own garden, or consider a more modest display, using gingers at the same scale you would use tulips in a temperate garden. Curcuma alismatifolia, the so-called “Siam Tulip” is certainly an outstanding choice for garden use. A rhizome pushes forth two, three or more shoots in the growing season. Each shoot is able to produce a stalk of a tulip-sized inflorescence. Pouched bracts that hold the small, orchid-like true flowers are long lasting in color. As new shoots emerge and mature, new inflorescences are produced, extending the flowering season for months. Even without flowers, the blue-green foliage is ornamental and surprisingly tulip-like.
From late June to September, more shoots and flowers are produced in response to the warmth, humidity, bright light and regular rains of summer. In the shorter, cooler days of late October, the leaves begin to droop and dry up in preparation for winter rest. At this time, any insect pests and blemishes are shed, signaling the perennial gardener that it's time to step in and clean up the garden.
The sparse literature about Curcuma culture is aimed mostly at nursery growers, but the principles are useful for any grower. Curcuma is routinely dug up while dormant and kept dry until replanted in spring in soil newly enriched with slow release fertilizer. It isn't strictly necessary to dig the rhizomes every year, but as any grower of perennial plants knows, plants almost always respond with renewed vigor when lifted and replanted into new, fertile soil. As a practical matter, they seem to prosper in one place for a few years, provided organic mulch is added as a top dressing. They should be liberally fertilized at least three times a year, in March, June and September. I use “Palm Special with Micronutrients,” which seems to work well with monocots. Additionally, in June, a “bloom booster” fertilizer seems to promote additional flowering.
Curcuma alismatifolia requires strong light to thrive. At the time of rest, while it is dormant, it is important that the growing area does not remain wet. In winter, plants are susceptible to rotting if the rhizomes stay wet and cold. When growing in pots, they should be kept perfectly dry and at about 60F. In the ground, especially in mulched soil, there is a certain amount of protection from great temperature fluctuations and prolonged periods below 50F; which are undesirable, are rare.
Other species of larger leaved Curcumas may be treated similarly to Curcuma alismatifolia.
Some of these plants are dramatic enough to be treated as specimen plants, many have striking foliage,
several have red or purple markings on the petioles and mid ribs, and usually they are attractively pleated.
In general these species will perform well in the garden, even in medium shade.
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