There are more than 700 species within the Eucalyptus genus and most, if not all of them evolved in Australia 196 The taxonomy is complex and not completely agreed upon. Some of the more well-known members of the family are the species of Eucalyptus and of bottle-brush ( Callistemon), as well as guava ( Psidium guajava), allspice ( Pimenta dioica), and cloves ( Syzygium aromaticum).
Most species have numerous brightly colored stamens, leaves with strongly-scented oils, and fruits that are either capsules or fleshy berries. Juvenile leaves are often distinct from mature leaves. The evergreen leaves are simple and mostly opposite with entire margins. They range throughout the world’s tropical and subtropical regions and make up a large part of the tree and shrub population of Australia. All species are woody and have floral parts in fours or fives. The myrtle family contains as many as 3000 species in 130-150 genera, mainly in the Southern Hemisphere. Red gum is a dicot angiosperm in the myrtle family (Myrtaceae). The rounded top of the ovary projects from the center, and tiny angular seeds are released through four triangular valves in the top. In red gum, the fruit is generally less than 1/2 inch in diameter. Each gumnut is a compound structure of hypanthium and ovary, which becomes woody when mature.
The fruit of a eucalypt is often called a gumnut. The main flowering time of red gum is in spring, 7 but we have found flowers in mid-summer. The “flower” of a red gum is a spray of numerous white stamens, nestled within which is a stout, green pistil the pistil becomes receptive after the stamens have shed their pollen, minimizing self-fertilization. Just prior to flowering, the stamens expand and push off the bud cap. In red gum, the bud cap is conical with a long, projection. Instead, these have united into a bud cap that covers the end of the hypanthium, protecting the immature pistil and stamens. Traditional petals and sepals are absent. 197 In red gum, the base of the flower, the hypanthium, is a bowl-like structure, which encloses the developing pistil and stamens. The structures of eucalypt flowers and fruit are unique Johnston gives an excellent photographic description of one species. Red gum flowers occur in small umbels of creamy white flowers from leaf axils of young shoots. Unlike the young leaves of many eucalypts, juvenile leaves are not markedly different from adult leaves. Numerous tiny glands are embedded between the veins of each leaf these produce the volatile oils that give the red gum its distinctive aroma.
Long, slender twigs are reddish and droop downward with blue/olive, leathery leaves that are lanceolate or sickle-shaped, two to eight inches (5-20 cm) long and less than two inches (5.5 cm) wide with smooth margins. The bark sheds in long strips leaving a smooth, mottled trunk of white, tan and gray. The wood is dark red, giving this species its name.
Red gums are large evergreen trees, with deep roots and a full crown of leaves it may grow to 100-150 feet (30-45 m) in height. The immediate effect is not pretty, but restoration plans are well underway and in a few years we will have a healthy and diverse association of native riparian plants blending natural marsh and upland oaks. Last month (October 2017) a program was initiated to remove these red gums and replace them with oaks, and riparian trees such as cottonwoods, sycamores and willows. They are invading our elfin forest on the southwest and our marsh on the north. Over the years, red gums in the Reserve have grown and fallen and reseeded. In San Elijo they are in conflict with our goals as an an ecological reserve and are unwelcome. It is one of a few species have escaped into natural areas where they displace native species and create a fire hazard. It has been called “miracle tree” and “noxious weed.” Red gum ( Eucalyptus camaldulensis) is one of many species of eucalyptus, or eucalypts, that were introduced into California for wood, shelter, landscaping and for their presumed curative powers. Gerald Durrell, (My Family and Other Animals, 1956)įew plants are as controversial as a Eucalyptus. “I can’t be expected to produce deathless prose in an atmosphere of gloom and eucalyptus.” Lawrence Clark Powell (speaking at Mills College, 1956) “…no tree is more beautiful in the wind or against the sky, and none provides better nesting