A. PALMETTOS: OLD-TIMERS OF THE SCRUB

The Florida scrub-jay collects tan-colored threads from scrub palmetto fronds at the beginning of nesting season and weaves them together to make a soft lining for its oak-twig nest. The blue tortoise beetle spends its entire life on the leaves of either a scrub and saw palmetto. With its tiny jaws, it scrapes away at the palmetto leaf, leaving a thin yellowish line behind it as it moves along the leaf. When alarmed, the blue tortoise beetle clamps itself down on the leaf holding on with its yellow feet. Each foot is covered with hundreds of oily hairs, which stick to the wax that covers the palmetto leaf. The larva of the blue tortoise beetle also feeds on palmetto leaves. It covers itself with curved bits of waste material so that it looks like a tiny, upside down bird's nest. This beetle is never common enough to damage a palmetto plant. Although Florida scrub might seem too dry for frogs, squirrel tree frogs are quite common. They can find shady places that are cooler and more humid among the leaves of plants. This is another example of a microhabitat, like the ones in the leaf litter discussed in Unit Three. Palmettos are often a good place for tree frogs, because the frog can tuck itself down in a folded palmetto leaf out of sight during the day. Tree frogs eat spiders, crickets, and katydids also found on the palmettos. Some areas near scrub habitat are often marshes during the rainy season (summer, fall) and dry during the dry season (winter, spring). Because these seasonal wetlands do not have fish that eat tadpoles, these marshes are good places for tree frogs to lay their eggs. Estimating the Age of a Saw Palmetto Dr. Warren Abrahamson of Bucknell University has been conducting research at Archbold Biological Station in Lake Placid, Florida, for more than 20 years. He discovered that the age of a saw palmetto could be estimated by examining the relationship between the growth rate of the palmetto stem and the stem length. For four years, he measured the growth of more than 400 palmettos in two different habitats. The averaged growth rates for all palmettos in both habitats was 1.2 cm per year. By measuring the length of a saw palmetto stem and dividing the length by 1.2, the approximate age of any saw palmetto can be determined. Intermediate-sized saw palmettos in his study typically had a stem length of 100-150 cm with an estimated average age between 75 to 200 years. However, longer palmetto stems were not uncommon and Dr. Abrahamson judged that some saw palmettos he measured could be well over 700 years old! Scrub palmettos have a subterranean, curved stem so their age cannot be estimated using this method.

Plants that thrive in the Florida scrub are tougher than Indiana Jones in Raiders of the Lost Ark. And like Indiana Jones, it is amazing that plants can survive at all. They must prevent their leaves from drying out in the intense summer heat or from baking under the broiling sunlight. They must be able to survive weeks without water, yet be strong enough to survive a deluge during summer storms. They must grow and thrive with almost no nutrients. When fire approaches, they cannot run away, but must either sprout back after being burned to the ground or recolonize from seeds that were protected from the flames. Scrub plants must defend themselves against an abundance of insect and animal predators and from being overwhelmed by molds and fungus during the wet season. Yet despite all the conditions that seem to work against them, some scrub plants seem to grow with great ease.

Palmettos demonstrate some of the water conserving features found in many scrub plants:

• The leaves are covered with a coating of wax that prevents water from escaping from the surface of the leaf. One reason why Florida scrub burns so fiercely is that the heavy wax coating on palmetto leaves ignites once the leaves are heated sufficiently.
• The leaves are tough and thick, and not easily damaged in ways that could expose the moist inner tissue.
• The leaves are held upright when the plant is growing in open areas, so the rays of the sun hit the flat surfaces of the leaves directly during morning and afternoon, but not in the middle of the day when the sun is hottest.

There are other water-saving adaptations in scrub plants. Some of these are discussed later in the section on oaks. How is a cactus adapted for drought?

The saw and scrub palmetto are two rugged species found throughout the Florida scrub in peninsular Florida. (Scrub palmetto is not found growing in the Panhandle.) These tough, slow-growing plants are well adapted to scrub and live very long lives--sometimes as long as 600-700 years! Palmettos play an important role in scrub habitat by providing food and cover for animals and material for nest building. Because your students are probably very familiar with palmettos, they will have lots of fun discovering so many new things about these plants. Both species of palmettos bloom during a predictable period, so your class can plan on visiting a few flowering plants to see what kind of insects drop by for nectar! Your students can easily locate and estimate the age of saw palmettos by measuring the length of the stem (or trunk) during Part One of the activity.

Both types of palmetto grow slowly out from the bud end and produce between 3 to 7 leaves a year--depending on the type of palmetto. Each leaf can live for 1 to 2 years. When a leaf dies, it loses its color and stays attached to the stem for about a year. Palmetto leaves are covered with a waxy coating which make them highly flammable. Palmetto leaves burn easily, but the growing bud of the saw palmetto is well protected by fiber that covers the stem and thick palm boots (the bases of old fronds). Because the stem is so well protected, it never burns down to the ground. After a palmetto burns, the charred stem can produce a new leaf within a week of the fire. Palmettos are one of the quickest scrub plants to respond after a fire. The stem and growing point of the scrub palmetto are usually under the sand and stay protected from fire.

Although palmettos respond quickly after a fire and are difficult to kill, young palmetto seedlings take a long time to get established and mature enough to produce flowers. Saw palmettos are clonal, so are more likely to spread underground than to produce new seedlings from fruits. Most populations of saw palmettos are made up of very old, well-established individuals. Saw palmettos grow in dense impenetrable thickets and can reach heights of 6 to10 feet or more. As the stem grows along the ground, it sends out roots to collect moisture from the soil. In moist, shady areas, the stem grows toward the light and is more erect. Scrub palmettos, on the other hand, are not clonal, so do not grow in thickets as saw palmettos do.

Both kinds of palmettos produce a cluster of white flowers in the spring. Saw palmettos typically bloom during March-April and scrub palmettos during April-May. Some plants will bloom at other times during the year--usually as a result of a recent fire. During a warm, sunny day, you can find many insect species as well as a great number of individual insects visiting the sweet-smelling palmetto flowers. Palmetto berries develop soon after the flowers drop. Initially, the fruit is green. As the fruit slowly ripens, it changes to yellow, then orange, and, finally, turns black by October.

The interactions between palmettos and animals are almost endless! Many animals are dependent on palmettos for survival. More than 100 birds, 25 amphibians, 61 reptiles, 27 mammals, and hundreds of insect species use palmettos as food, cover, or for nest material. Black bears, white-tailed deer, raccoons, opossums, gray fox, wild turkeys, bobwhite quail, and gopher tortoises eat palmetto berries. Feral pigs and bear dig out the growing tip from the stem (which kills the plant) and eat the newest leaves and "heart of palm." Gopher tortoises and cattle eat parts of the leaves. Florida scrub-jays, grasshopper sparrows, and wild turkeys collect parts of the plant to use as nesting material. Panther, black bear, and white-tailed deer use the protected cover provided by palmettos as a birthing den. Spiders and wasps commonly build nests and webs in the fronds and blue tortoise beetles "glue" themselves to the leaves. Vines often use palmetto for support and mosses and lichen grow along the stem if it has not recently burned.

Humans are known to have eaten the palmetto berries in the past, but the berries are said to have a "rancid tobacco juice" flavor. Today, saw palmetto berries are used by pharmaceutical companies to manufacture certain drugs and medications. In one season, well over 7,000 tons of palmetto berries are harvested. Wildlife researchers worry that if demand for palmetto berries increases, the loss of available berries will be harmful to wildlife that eats the berries.

• Tough leaves provide protection from drought and damage.
• Waxy leaves keep the plant from drying out.
• Vertically-held leaves in open areas mean less exposure to the noon sun.
• Less vertically-held leaves in shaded sites allow a plant to capture more light.
• Fibrous layer in the trunk insulates the plant from fire.
• Clonal growth from root system allows the plant to colonize quickly in open patches after a fire.
• Blooming after fire means plants can take advantage of nutrients from ash, and produce more seeds when open areas are available.
• Flowers produce large amounts of nectar which attract many species of insects for pollination
• Edible fruits attract raccoons and other animals that disperse fruit
• Extremely hard, indigestible seeds are excreted unharmed from an animal that may eat them.

• Leaves as food: example-blue tortoise beetle
• Nectar as food: examples-bees, wasps, flies, butterflies
• Palm hearts as food: example-black bear
• Berries as food: example-raccoons, deer, black bear, gray fox, wild turkey
• Seeds as food: example- palm seed weevil
• Fibers for nesting: example-grasshopper sparrow
• Shelter in leaves: Examples-frogs, lizards, spiders, insects
• Shelter in thickets: examples-panther, black bear, deer, raccoon, gray fox, opossum, wild turkey, eastern towhee, snakes
• Habitat maintenance for wildlife: since palmettos burn easily they can help carry fire through the scrub habitat
• Medicine: example-humans