The leaves are generally oval in shape ranging in size from 1/2 to 3 inches long and 1/2 to 2 1/4 inches wide. The mature leaves are generally leathery and smooth dark green, but some forms are woolly or hairy underneath and may appear grayish. The leaf buds (liko) can range in color from pale green to pink to red.

Metrosideros polymorpha blooms mostly in the spring, but can bloom sporadically throughout the year. Weissich notes that there can be as many as 3 blooming periods per year. The powder puff like flowers are most often a shade of red, but yellow, orange, salmon, and pink forms are also found. There are eight recognized varieties of Metrosideros polymorpha. (Criley 1999; NTBG 1996; Rauch 1997; Wagner 1990; Weissich 1995)

Some researchers have found that light is required for germination of Metrosideros polymorpha seed while others have found that it greatly improves germination. Bright light, however, is not required for germination; Metrosideros polymorpha seeds germinate well at low light levels. In any case, it is best to sow Metrosideros polymorpha seeds on the surface of the medium. Drake found that Metrosideros polymorpha seeds germinate at any constant temperature from 50 to 93 degrees F. However, the fastest germination was at a temperature of 72 degrees and the slowest at 93 degrees. Interestingly, he also found that seeds from plants with fuzzy leaves germinated somewhat faster overall and better at higher temperatures. (Burton 1982; Drake 1993)

Use a moist sterile potting medium such as 1 part potting mix to 1 part fine cinders (NTBG 1993). Stratton's survey respondents suggested either the same mix as NTBG or a mix of 3 parts #2 perlite to 1 part Sunshine Mix #4. After sowing the seeds, water the medium as gently as possible; a mist system is ideal. Drake germinated seeds on find basalt sand using 6 seconds of mist every 3 minutes. Keep the medium moist and place the seed containers in a covered, shady location to control soil moisture and reduce damage from rain.

Both Drake and Burton found that a less than 20% of the seeds in a Metrosideros polymorpha capsule are viable; most of the seeds do not contain embryos. The viable, embryo-containing seeds are plumper than the others. Burton feels that the low percentage of viable seeds may be a result of partial self-incompatibility since this has been shown in some New Zealand members of this genus. This low seed viability rate results in a low germination rate. The most current NTBG publication (1996) states that the seeds germinate in 7 to 14 days. Drake also found that the majority of viable seeds germinated in 10 days and over 90% germinated within 15 days. Criley gives 10 days as the germination time.

Metrosideros polymorpha seeds should be sown while they are fresh since storage greatly reduces seed viability. Seeds stored at room temperature (55-84 degrees F) and ambient humidity (58-98%) for only a few months show significant losses in viability. If it is necessary to store the seeds, Stratton et al suggests removing them from the capsules as outlined above and storing them in a paper bag or envelope. Then place the paper container in an airtight container with desiccant in a cool, dry location. Some seed will germinate even after 3 years of storage in a refrigerator. (Bornhorst 1996; Burton 1982; Criley 1998; Criley 1999; Drake 1993; NTBG 1993; NTBG 1996; Stratton 1998; Yoshinaga 1998)

Rauch et al tested 4 dilutions of rooting hormone with a 2 to 1 indolebutyric acid (IBA) to naphthaleneacetic acid (NAA) ratio (Dip'n Grow) on 4 inch cuttings of yellow flowered Metrosideros polymorpha. The dilutations ranged from 500 to 5,000 parts per million (ppm) of IBA. Vermiculite was used as the rooting medium and the cuttings were placed under intermittent mist of 6 seconds every 2 minutes. They reported that best results were obtained with 2,000 ppm IBA. One hundred percent of the cuttings in that treatment rooted and they had the longest average root length of all of the treatments. They found that the higher concentration was detrimental to both root length and rooting percentage.

Criley reports success with rooting hormones in solution having a 2 to 1 ratio of IBA to NAA. In this work, successful total auxin concentrations ranged from 2,000 parts per million (ppm) to 4,000 ppm, but higher concentrations may be needed for more difficult to root varieties. Bornhorst suggests dipping the cutting in a strong rooting hormone such as 10% Dip-N-Gro for 10 seconds.

Put the cuttings in a very well draining medium. Some recommended media are 1 part perlite to 1 part peat moss to 1 part vermiculite or 100% perlite. Criley uses either 1 part coarse perlite to 1 part vermiculite or 100% vermiculite.

Bornhorst states that cutting material from some individual plants roots more reliably than material from others. Criley suggests that cultivated forms may root more easily. (Bornhorst 1996; Criley 1998; Criley 1999; Rauch 1997; Stratton 1998)

Tanabe and Frazier report that the ring girdle air layer technique was successful on vigorously growing branches of younger plants. In their work, they used 3 to 4 foot long air layers. They tested a range of indolebutyric acid (IBA) concentrations and found that a 3% IBA talc dust (30,000 ppm) improved both rooting percentage and root quality of Metrosideros polymorpha air layers. This level of rooting hormone produced an 80% rooting rate after 15 weeks. They found that higher levels of IBA reduced rooting success.

Some individual plants seem to air layer more easily than others. Bornhorst suggests that the presence of aerial roots indicates that the plant may be propagated by air layering relatively easily. (Bornhorst 1996; Tanabe 1985; Stratton 1998)

Bornhorst, Heidi L. 1996. Growing native Hawaiian plants: a how-to guide for the gardener. Honolulu: The Bess Press. p. 61-64.

Burton, Philip J. 1982. The effect of temperature and light on Metrosideros polymorpha seed germination. Pacific Science 36 (2):229-240.

Criley, Richard A. 1998. Propagation of indigenous and endemic ornamental Hawaiian plants. Combined Proceedings of the International Plant Propagators' Society 48:669-674.

Criley, Richard A. 1999. Aloha Hawai'i. American Nurseryman 190 (3):50-61.

Drake, Donald R. 1993. Germination requirements of Metrosideros polymorpha, the dominant tree of Hawaii lava flows and rain forests. Biotropica 25 (4):461-467.

National Tropical Botanical Garden (NTBG). 1993. 'Ohi'a lehua. In Native Hawaiian plant information sheets. Lawai, Kauai: Hawaii Plant Conservation Center. National Tropical Botanical Garden. Unpublished internal papers.

National Tropical Botanical Garden (NTBG). 1996. Ten native Hawaiian trees for urban landscapes. Lawai, Hawaii: Education and Plant Science Departments. National Tropical Botanical Garden.

Rauch, Fred D., and David Hensley. 1997. 'Ohi'a lehua, Ornamentals and Flowers OF-11. Honolulu: Hawaii Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. (Also available as a PDF file at Free CTAHR Publications.)

Rauch, Fred D., Kelly Niino, and Jan McEwen. 1997. Vegetative propagation of yellow ohia lehua, Horticulture Research Notes HRN-3. Honolulu: Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. (Also available as a PDF file at Free CTAHR Publications.)

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.

Tanabe, Michael J., and Ben Frazier. 1985. The influence of auxin on the airlayering of ohia-lehua. In Proceedings: Second fertilizer & ornamentals short course, edited by F. D. Rauch, W. W. McCall and K. W. Leonhardt. Honolulu: Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. p. 68-69.

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. 967-969.

Weissich, Paul R. 1995. Hawaiian native plants in the landscape. Combined Proceedings International Plant Propagators' Society 44:332-335.

Yoshinaga, Alvin. 1998. Storing seeds of some native rain forest plants: some simple methods. Newsletter of the Hawaiian Botanical Society 37 (2):28-32.