Colubrina oppositifolia is a 15 to 40 foot tree. The bark is brown to gray and comes off of the trunk in large round flakes. The new twigs are reddish changing to light brown as they mature.
As the name implies, the leaves grow opposite each other on the stems; the next pair of opposite leaves forms at a right angle to the first pair. The leaves are thin and flexible with smooth edges. They are oval with a pointed end and range in size from 2 1/4 to 4 3/4 inches long and 1 1/4 to 2 3/4 inches wide. The leaves on seedlings are larger than those on mature plants. The veins of the leaves are light green and show clearly on the upper surface of the leaf. The leaf stems are about 1 inch long and reddish.
The flower clusters form where the leaf stem grows from the branch. The flowers are yellowish green to greenish yellow. They are about 1/4 inch in diameter and have 5 sepals and 5 petals. There are 10 to 12 flowers in each small bunch. (Lamb 1981; Wagner 1990)
Propagation by Seeds
The fruit of Colubrina oppositifolia is a almost round capsule 1/2 inch in diameter. The capsule has 3 parts and there are generally several seeds in each capsule. The dark brown to black oval seeds can be up to 1/4 inch long. The fruits ripen from late spring through early fall. The capsule opens explosively when it is mature. Culliney advises that full-sized fruits that have not completely dried and are still greenish-brown often contain more viable seeds than completely mature capsules. These not-quite-mature fruits should be ripened in a dry location free from insects for a few weeks. The seeds can be extracted after this process.
In his germination studies, Obata found that untreated seeds of Colubrina oppositifolia had germination rates ranging from 5 to 30%. Culliney notes that some individual trees do not produce viable seeds. These seeds do not contain an embryo.
Stratton's survey respondents had three pre-treatment recommendations. The first was to soak the seeds for 3 days in tap water. Soaked seeds germinated in 2 weeks to 2 months with a 65% germination rate. The second treatment was scarification with a clippers or file. Scarified seeds germinated about 5 days sooner than soaked seeds and also had a 65% germination rate. The third treatment was to soak the seeds in 170 degree F water for 24 hours. These seeds germinated in 2 weeks to 2 months with a 40% germination rate. Untreated seeds took 3 weeks to 3 months to germinate with a 40% germination rate. If a soaking pre-treatment is used, discard any seeds that float.
Lilleeng-Rosenberger's notes show similar findings. Fresh seed which had been soaked for 36 hours in cold water germinated in 2 to 4 weeks and had 59% germination. Scarified seeds also germinated in 2 to 4 weeks and had 80% germination. Culliney et al suggests soaking the seeds in water for 24 hours though their reported germination percentage ranges from 25% to 75%.
Seeds should be planted in a shallow container in a well-draining medium such as a mixture of 3 parts #2 perlite to 1 part Sunshine Mix #4 or a mix of 4 parts cinder to 1 part soil; Culliney recommends 100% vermiculite. The planting medium should be keep moist until germination and the containers should be kept in a covered shaded area for better control of moisture levels in medium. Seeds germinate in 2 to 4 weeks.
According to Stratton's survey, Colubrina oppositifolia roots grow slowly and the seedling may benefit from a foliar application of phosphorus. Koebele reports that powdered sulfur can successfully be used to control fungal diseases on Colubrina oppositifolia seedlings.
To store seeds of Colubrina oppositifolia, remove them from the capsules and keep them dry. Store them in a paper container in a cool, dry (relative humidity 25%) location. Stratton recommends storage in an airtight container with desiccant. However, Lilleeng-Rosenberger's notes indicate that seeds stored for 2 months at 80 degrees F and 25% relative humidity experienced a decrease in viability. Only 30% to 35% of these seeds germinated even when treated. (Culliney 1999; Koebele 1999; Lilleeng-Rosenberger 1996; Obata 1967; Stratton 1998)
Culliney, John L., and Bruce P. Koebele. 1999. A native Hawaiian garden: how to grow and care for island plants. Honolulu: University of Hawai'i Press. p. 72-75.
Koebele, Bruce P. 1999. Sulfur paste: an effective treatment for a fungal disease that attacks Lama (Diospyros sandwicensis) seedlings. Newsletter of the Hawaiian Botanical Society 37 (4):67.
Obata, John K. 1967. Seed germination in native Hawaiian plants. Newsletter of the Hawaiian Botanical Society 6 (3):13-20.
Stratton, Lisa, Leslie Hudson, Nova Suenaga, and Barrie Morgan. 1998. Overview of Hawaiian dry forest propagation techniques. Newsletter of the Hawaiian Botanical Society 37 (2):13, 15-27.
Lamb, Samuel H. 1981. Native trees and shrubs of the Hawaiian Islands. Santa Fe, New Mexico: Sunstone Press. p. 81.
Lilleeng-Rosenberger, Kerin. 1996. Plant propagation notebook. Unpublished materials: National Tropical Botanical Garden.
Wagner, Warren L., Darrel R. Herbst, and S. H. Sohmer. 1990. Manual of the flowering plants of Hawai'i. 2 vols, Bishop Museum Special Publication 83. Honolulu: University of Hawaii Press and Bishop Museum Press. p. 1094.