|No. 189||BATON ROUGE, LA||February 2000|
Searching for IBWO
Year of Discovery
Yard List ‘99 Final Call
The Botanical Birder
Selasphorus ID Article
Selasphorus Figure 1
Selasphorus Figure 2
Selasphorus Figure 3
Selasphorus Figure 4
LOS Pelagics 2000
Winter Meeting Report
Waxwings Poem Rare Bird Alert
LOS NEWS: Page    
|by BILL FONTENOT|
Native Nectar for Spring Ruby-throated Hummingbirds|
Within the realm of animal-plant interactions, one of the more fascinating aspects involves the manner in which plants align their flowering periods in order to offer maximum numbers of blooms at the time(s) when the maximum numbers of their major pollinators are present. On second glance, of course, such adjustments can be readily explained via the natural selection process, whereby a given plant's major animal pollinators "choose" the period(s) of that plant's peak bloom over successive generations of interaction (i.e., those plants which offer maximum blooms at times when pollinators are at peak density are "chosen" to pass along genes which will ensure that their future progeny will be blooming at the best possible time as well).
Here along the U.S. Gulf Coast, the spring migration period for Ruby-throated Hummingbirds begins in late February and extends through early May. During this period - and in this region - their menu of natural nectar sources is somewhat small. Fortunately for them, the plant species involved happen to be among the most adaptable and widespread. A number of minor or "secondary" nectar sources exist as well. These include plants that bloom at the proper time for spring Ruby-throated migration, but whose flowers are not specifically "selected" for hummingbird pollination. A perfect example of such a plant is the ubiquitously-distributed exotic weed, Brazilian vervain (Verbena brasiliensis). Time and again, I've noted hordes of spring-migrating Ruby-throateds working the minuscule lavender-purple blooms of this plant (selected much more for pollination by small flying insects), particularly within the coastal zone itself, where the hummers arrive tired and hungry.
What follows is a discussion of spring-blooming native plants that possess flower characteristics that best accommodate usage by migrating Ruby-throated Hummingbirds throughout Louisiana and most of the U.S. Gulf Coastal states.
Trumpet or Coral Honeysuckle (Lonicera sempervirens) is a woody, evergreen vine, which was featured as a good nectar source for overwintering hummers in the last issue of this newsletter. Indeed, this plant produces its gorgeous clusters of elongate blooms on an opportunistic basis (whenever the combination of moisture, temperature, and sunlight levels are appropriate), but it also exhibits two definite periods of peak bloom here in Louisiana each spring (Feb-April) and fall (Sept- Nov) - each of which perfectly tracks spring and fall Ruby-throated Hummingbird migration through our state.
Trumpet honeysuckle natively occurs within sandy/acidic pine and mixed forests throughout north and central Louisiana, as well as in the Florida parishes. Fortuitously for south Louisiana hummingbird gardeners, it adapts beautifully to alluvial-based circumneutral soils. It is a much more mannerly grower (to 12') than its weedy/exotic cousin, Japanese honeysuckle (Lonicera japonica), which has itself developed into a major nectar source for Ruby-throateds throughout its naturalized U.S. range. Trumpet honeysuckle appreciates about a half-day of direct sunlight for best blooming. Use it on trellises, arbors, fences, and other vertical structures/situations.
Red Buckeye (Aesculus pavia) is naturally distributed throughout most Louisiana woodlands. It even follows the "gallery" forests along natural levees of several bayous and rivers all the way down to the coast, particularly around the northern edge of Vermilion Bay. For gardening purposes, it is among the most adaptable of all native plant species, thriving in sun (half-day best), shade, wet, dry, sand, clay, or loam.
Compared to other native deciduous plants, red buckeye's foliage schedule is certainly quirky. New foliage appears in January - long before that of any other deciduous plant - and easily withstands any number of early spring freezes. Buckeye leaves are palmately-compound (like fingers on a hand), faintly glossy, and exceedingly handsome. As early as July (depending on relative soil moisture, sun exposure, etc.), however, it begins defoliating into fall/winter dormancy. At such times, gardeners should resist the urge to over water, thinking that something might be wrong with the plant.
Red buckeye produces its lovely spikes of coral-pink to blood-red tubular blooms from late February through early May. From personal observation in both natural and cultivated landscapes over the past 15-20 springs, this plant looks to be an extremely important nectar source for spring migrating Ruby-throateds. Size-wise, red buckeye averages 6-8' in height and width in heavily shaded positions, 8-12' in "high shade," and 15-30' in more direct sun and moisture-retentive soils. Its large fruits or "buckeyes" are produced in fall, and probably should be picked up and discarded in most cultivated settings, as germination rates are high, and seedling thickets are sure to form.
As a longtime grower of 10-12 species/cultivars of Louisiana irises, it has become apparent to me that spring-migrating Ruby-throateds routinely nectar off of Copper Iris (Iris fulva), while routinely eschewing the others. While other iris species are often "visited" by Ruby-throateds, it is plain that bumblebees are the primary pollinators of those. By contrast, the relatively small bloom size, reddish bloom color, and early bloom period of copper iris point to at least a possibility that the Ruby-throated Hummingbird may function as this plant's primary pollinator.
Interestingly, further anecdotal testimony regarding hummingbird affinity to copper iris blooms is reported by Lafayette birder George Broussard, who regularly visits a large wild colony of this species each spring blooming season (March) in the vicinity of Lake Martin (St. Martin Parish). During his March 1998 and 1999 visits, Broussard observed single Rufous-type hummingbirds nectaring off of the copper iris blooms there – apparently attempting to fatten up for their pending northwestward journeys.
As with other native Louisiana iris species, copper iris foliage emerges from its rootstocks in late fall, after a 5-month period of aboveground dormancy. As with red buckeye foliage, copper iris leaves seem immune to freezing temperatures. Copper iris is the first of the native Louisiana iris species/cultivars to bloom. Here in south Louisiana, bloom-scapes appear by late February; and by early March its smallish russet flowers unfurl. Blooming continues through at least the third week of April. By July, the last vestiges of foliage have withered, and the dormant season begins.
In Louisiana, copper iris naturally occurs mainly along the shores of the Red, Mississippi, and Atchafalaya Rivers and their tributaries, but it is also found in small woodland depressions away from these streams.
All Louisiana irises appreciate as much moisture as they can get, so gardeners are well-advised to plant them in perennially damp areas such as edges of pools, ponds, and gutter-spouts, as well as just outside the drip lines of unguttered roofs. Most species/cultivars can handle "high shade" (bright, filtered light) as well as direct sunlight.
Just as copper iris and red buckeye blooms begin to fade, the bloom cycle of Eastern Coralbean (Erythrina herbacea) begins. Distributed throughout most woodland habitats throughout Louisiana, eastern coralbean mirrors red buckeye in its ability to thrive in most any soil, moisture, and sunlight regime. Dubbed "mamou" by early Cajun settlers (nobody knows why . . . ), both the toxic seeds and woody rootstocks of the plant were used medicinally by this cultural group.
A member of the legume family, eastern coralbean is classed as a "perennial shrub" because its delicate aboveground parts normally freeze back completely each winter. By early spring, its trademark triangular leaves unfold from thin stems regenerated from its massive bulb-like root system. By mid- March to April, thick bloom-stalks appear at the center of the plant, and rise up to 1-2' above the surrounding foliage. Soon afterward, its magnificent lipstick-like flowers pop out to form 6-15" bloom spikes. In moister soils, blooming can extend to early June.
In the garden, eastern coralbean can be used anywhere except under deep shade, where it will not bloom much. In moisture-retentive soils, expect a specimen of 6'X6' dimensions - occasionally even larger. In average soils, it will top out at 3-4'.
In terms of sheer hummingbird utility, none of the abovementioned natives can really compare with Tropical Sage (Salvia coccinea). Said to be native throughout much of the U.S. Gulf Rim, tropical sage's native Louisiana range is limited to the coastal cheniers, where it grows beneath canopies of live oaks and hackberries, alongside equally "quasi-tropical" plants such as pigeon-berry (Rivinia humilis), turk's cap (Malvaviscus drummondii), bird pepper (Capsicum sp.), and eastern coralbean. In garden settings, however, it will grow absolutely anywhere, from deep shade to full sun.
Though horticulturally classed as a reseeding annual, tropical sage often escapes winter freezes in southern Louisiana, particularly when it grows under evergreen canopies and other protected locations. In such instances, it is known to bloom 12 months out of the year! Hummingbirds and sulfur butterflies favor it heavily. Because several genetic "sports" of tropical sage have been selected and are commonly offered within the nursery trade, it is important to distinguish the "species" from these cultivars. Species tropical sage commonly grows to 30-36" in height, and bears fire engine-red blooms. As with many Salvia species/cultivars, tropical sage should be cut back on a regular basis in order to encourage reblooming and to keep it tidy. In fact, one of the most effective uses of this plant that I've seen involved a mass planting of it beneath a live oak, where it was kept short (ca. 6") through regular passes with a weed-eater. Another important thing to remember about "species" tropical sage is that it is a vigorous reseeder. New seedlings spring up at various times of the year in the vicinity of mature plants. These seedlings can either be left in place to thicken a planting, or can be lifted and moved to other areas or given to friends.
Tropical sage cultivars, on the other hand, reseed at much less vigorous rates. Thus, a planting of one or more of the cultivars is more apt to "give out," and must be replanted from year to year. Some of the more popular cultivars include the pink-blooming, 20-24"‘Coral Nymph', the white-blooming, 20" ‘White Nymph', the pink/white-blooming 20-24" ‘Bicolor', and the candy apple-red-blooming, 12-18" ‘Lady in Red'. Like the species, all of these cultivars should receive regular "deadheading" in order to encourage reblooming.
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