Introduction:
Common ironwood (Casuarina equisetifolia)
Casuarina equisetifolia is an evergreen conifer-like angiosperm. It has been introduced to new locations for coastal landscaping and erosion control. It has become invasive in Florida (USA) where it interferes with prime reptile nesting sites. Casuarina aggressively colonizes sandy beaches where it forms monocultures and degrades habitat in the Cayman Islands.
Description:
Casuarina equisetifolia is a member of the Casuarinaceae (beefwood) family; it is an evergreen tree with a soft wispy pine-like appearance and an open irregular crown. The tree can attain heights of up to 50 meters, with a diameter of up to 18 centimetres; however, it generally only reaches 15 to 25 meters in height. It bears a resemblance to coniferous plants due to the production of cone-like fruits and pine-needle-like leaves.
It has reddish brown to grey bark; the bark is rough, brittle, peeling. Branchlets are pine-needle like, greyish green, jointed, thin (less than 1 millimetre wide), 10 to 20 centimetres (four to eight inches) long, minutely ridged, hairy in furrows. Leaves are reduced to tiny scales, six to eight in whorls (this is a distinguishing feature, see Similar Species), whorls encircle joints of branchlets. Flowers are unisexual/monoecious, inconspicuous, female in small axillary clusters, male in small terminal spikes. Fruit is a tiny, one-seeded, winged nutlet (samara), formed in woody cone-like clusters (fruiting heads), these clusters are brown, two-centimetre-long (3/4 inch) and 1.3 centimetre-wide (1/2 inch).
Occurs in:
Coastland, estuarine habitats, riparian zones, ruderal/disturbed.
Common ironwood (Casuarina equisetifolia) Distribution in North America shown in green.
Habitat description:
Casuarina equisetifolia occurs in open coastal strand habitats in subtropical and tropical climates, including: sandy and shelly beaches, rocky coasts, sand dunes, sand bars and estuarine/mangrove habitats. Its natural habitat has been described as coastal herbaceous swamp and broad-leaved hammock communities, however, C. equisetifolia frequently colonises disturbed sites such as filled wetlands, roadsides and cleared land.
General impacts:
Casuarina equisetifolia is a fast-growing plant which produces heavy shade and a thick blanket of leaves and fruits beneath it, reducing habitat value. Its dense monoculture thickets displace native dune and beach plant species. Once established, C. equisetifolia alters light, temperature, soil chemistry and hydrology of the habitats it invades.
Management:
Common ironwood (Casuarina equisetifolia) Is a beach weed also.
Physical: For small infestations the manual removal of seedlings and saplings is recommended, however, it should be noted that cutting often induces sprouting.
Prescribed fire has been used for large infestations in fire-tolerant vegetation communities. Fire control is reported to be effective in dense stands with sufficient dry fuel on the ground. Periodic fires coupled with the use of herbicides may be an effective method of controlling Casuarina. However, too frequent intense fires that kill over story native pines may actually encourage Casuarina species to establish. Burning Casuarina in peat soils may be hazardous. Fire may be an effective control method for trees greater than eight centimetres (three inches) in diameter and in dense stands; burning could be potentially harmful if the soil pH is changed such that native species cannot establish.
Chemical: For heavier infestations application of a systemic herbicide to bark, cut stumps or foliage is likely to be most effective. Chemicals such as 2,4,5-T, 2,4-D or Garlon 3A can be used to tackle Casuarina. A 2% mixture of Garlon 4 in diesel oil applied using the basal bark method or the hack-and-squirt method is most commonly used against Casuarina in the USA. Garlon 3A is also effective.
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