by Lalith Gunasekera
Creeping water primrose
(July 5, 2017, Mackay – Queensland, Sri Lanka Guardian) Creeping water primrose (LUDWIGIA PEPLOIDES) is another ludwigia species either floats on water or sprawls across the ground. Native range is from North America to Australia. This plant can be seen in several water bodies in Central highlands of Sri Lanka.
The stems are light green to red and alternately arranged leaves along these stems. The leaves are usually glossy green in appearance, up to 6 cm long and 2-3 cm wide on stems up to 4 meters long. The leaf bases taper gradually into slender petioles about 1-5 cm long. Individual flowers develop from the axils of the middle to upper leaves on erect to semi erect pedicels about 2-6 cm long. Each flower is about 2.5 cm across, consisting of 5 yellow petals, 5 green sepals and 10 yellow stamens. Flowers are diurnal (during the day).
Stems typically develop a dense clump of roots covered with numerous fine root hairs at lower to middle nodes.
Seed pods are a hard, narrowly cylindrical capsule. It has 4-5 chambers, 2-4 cm long, 2-4 mm in diameter, 5 sided on a stalk to 9 cm long that is typically bent downward. Seeds are ovoid, triangular in cross section, 1-1.5 mm long.
Creeping water primrose reproduces mainly by seed and vegetatively from creeping stems and stem fragments. Seeds and stem fragments disperse with water and soil movement and probably by clinging to the fur, feathers, feet and beaks of animals.
Floating stems can encroach for some distance into waterways, obstructing water flow in some situations.
Gal goraka (CLUSIA ROSEA)
Gal goraka originated in North America and widely grown as an ornamental plant in tropical countries around the world. It was introduced to Sri Lanka as an ornamental plant through horticultural industry. This plant has shown some invasive characters in hot humid climate like in Sri Lanka especially in central highlands. Plant can grow well in dry barren areas to steep cliffs in wet areas. It tolerates many different soil types but most rapidly on moist soils.
Gal goraka plant spreading widely, densely foliated and rounded as shown in the picture. This is evergreen tree that has a short trunk and broad, thickened, dark green leathery leaves. The leaves are opposite, obovate shape, pinnate, 20-30 cm long. Leaves can be written on with a finger nail. Thick and succulent waxy blades are used by the plant to store water and last for a long time.
Showy disk shaped flowers are large (1 cm diameter) pink or white. Seven fleshy snow-white petals surrounded a button sized, green central pistil surrounding the numerous yellow stamens. Flowers solitary, terminal or in the axils open facing downwards in the late afternoon or evening are probably bat pollinated. By morning they have already begun to turn brown and die. Fruits begin to grow immediately thereafter, from the expanding ovary. They mature 5 months later as glossy green globular capsules (5 cm diameter). Fruiting commences as each capsules splits in to a flower like star. It has eight narrow compartments hold many small orange ariled seeds which contain s sticky sap.
Fruits attract and consumed by birds. Some of the seed of gal goraka will end up high in the branches of other trees and can germinate in the crotch in sending down aerial roots. A unique shaped fruit that is sometimes used in flower arrangements.
Wedelia or trailing daisy (SPHAGNETICOLA TRILOBATA) native of Central America and cultivated widely as an ornamental ground cover in many tropical countries. This species was introduced to Sri Lanka as a ground cover and now occurs in invading as an invasive plant in natural forests, riparian zones, and agricultural areas in central highlands as well as in wet regions.
Wedelia is a creeper with mat forming perennial herb with fast growing rounded stems up to 40 cm long. Leaves are opposite and simple, obviate to elliptical, 2-9 cm long and 2-5 cm wide, acute at the apex. They are attractive, bright, shiny green somewhat fleshy and irregularly toothed on the margins, commonly with three shallow lobes.
The single attractive bright yellow daisy like flowers are borne on the end of terminal stalks about 2-9 cm long.
Wedilia plant is mainly spread by vegetative parts. Seeds are not fertile.
To be continued
Dr. Lalith Gunasekera is an Invasive Plants Specialist based in Mackay – Queensland, Australia