Hawaii falls into the USDA winter hardiness zones of 10 and 11. Most of the islands have a winter temperature of 40 degrees Fahrenheit and above, except mountain tops where freezing temperatures may occur in winter. Hawaii only has two seasons. Summer is from May until October, and winter is from November until April. The Pacific Ocean surrounds the islands creating mild temperatures. Average winter temperature is 72 degrees Fahrenheit, and summer is 78 degrees Fahrenheit. Plants growing in Hawaii enjoy the sunny tropical conditions.
Dwarf iliau (Wilkesia hobdyi) is a member of the sunflower family. This shrub is a short-lived perennial that grows branches from its base. It only reaches 23-1/2 inches in height. Clusters of narrow, sword-shaped leaves grow in whorls at the ends of the branches. Clusters of tiny flowers form cream-colored splashes amid the green leaves. Flowers are seen in June, September, October and December. The dwarf iliau grows on the dry cliffs along the coast. This shrub is threatened by predation from feral goats.
Island spleenwort (Diellia erecta) is called palapalai lau li'i by native Hawaiians. This ground fern produces 8-inch long fronds. These green fronds are deeply lobed with 20 to 26 pairs of small leaves. The island spleenwort fern is extinct on most of the islands. It is federally listed as endangered and is facing extinction as alien plant species take over its natural habitat.
Kamakahala (Labordia spp.) is a shrub or small tree growing in the drier areas of Hawaii. The leaves are shiny green on the top and pale green on the undersides. The funnel-shaped flowers have five, thick petals that flare out at the end of the funnel. The flowers are yellow, greenish-yellow or white and are followed by green or white capsules. There are 15 species of kamakahala growing in the Hawaiian Islands.
Kanawao (Broussaisia arguta) is an understory shrub that grows in the Hawaiian rainforest. This shrub grows up to 20 feet tall, which is the size of a small tree. Kanawao has elliptical leaves with short-tapering points and finely serrated edges. Two or three leaves cluster together hanging off 1 to 2 inch long leafstalks. Gray brown, smooth bark covers the trunk and branches. Flower clusters are 2 to 4-1/2 inches across form on the ends of the branches. The small, five-petaled flowers are white, blue and pink. Kanawao produces small blue and dark red berries.