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A native Hawaiian plant is a plant that existed in Hawaii long before humans arrived. Native plants came to Hawaii by three methods: Wind, Water (Ocean), and Wings (Birds).
Getting to Hawaii was just the first hurdle these plants faced. Once they were transported here, these plants needed to grow and adapt to their new surroundings.
The founder plants that were established during this time of pre-human contact are categorized as indigenous plants. Indigenous plants are plants that were found growing in Hawaii, but are also native to other parts of the world. Beach naupaka (Scaevola sericea) is an example of an indigenous plant because it is native to Hawaii and can also be found growing in other areas like the South Pacific Islands. As time went by, some of these indigenous plants changed to better adapt to Hawaii's environment. This process is known as adaptive radiation. The changes in these plants made them unique to Hawaii or endemic. Endemic plants are plants that are native ONLY to Hawaii. An example of an endemic plant is our State flower, the yellow hibiscus, Ma'o Hau Hele (Hibiscus brackenridgei).
In general, Hawaiian plants, when planted in the correct habitat and once established in the ground, will be able to grow with less irrigation and be able to handle drought conditions better than some of the other landscape plants currently being used.
When selecting plants for your landscape, there are a few things to keep in mind.
It is illegal to collect wild plants and seeds without the proper permits. It is best that you obtain plants for your landscape from local nurseries, friends, and plant sales. If you do acquire the proper permits to collect from the wild, remember to collect sparingly from each plant, and know what you are collecting. Some plants are on the Federal and State endangered species lists and require additional permits in order to collect.
Do you know what type of soil is in your yard? For a quick test, take some soil and add a little water to it if it's dry. Roll the soil it into a ball and then press it lightly. Does it stay in a compact ball shape? If so, you most likely have clay soil, which retains moisture, has poor drainage, and forms cracks on the surface when it dries out. Does the soil crumble without forming a ball? You have sandy soil, which has excellent drainage, but sometimes doesn't retain moisture long enough for the plants to consume it. The ideal situation is if the soil forms a ball, but can be easily broken apart. This means your soil is loamy. Loamy soil retains moisture, but also has good drainage. Clay or sandy soils can be improved by adding organic matter (i.e., mulch or compost) to the soil. To learn more about your soil, contact your local agricultural extension office.
When planting your native plants in the ground, regular irrigation is initially needed to help get the roots established. Once the plant is established in the ground, irrigation can be reduced. When watering the plants, it is better to do periodic, deep soaks to encourage downward root growth. Irrigate with a slow trickle for several minutes (for example 10-15 minutes 2 or 3 times a week in loamy soils, decrease the frequency of irrigation for clay soils and increase for sandy soils), which allows the water to filter into the soil rather than just running off the surface. This type of irrigation schedule encourages deeper root growth and will increase the plant's chances of survival during drought conditions. If the soil is moist do not water, because over watering reduces the oxygen in the soil and can kill the plant. If you irrigate frequently and for a short period of time (for example, 1-3 minutes every day), the roots will grow only where there is moisture near the surface of the soil. Shallow rooted plants do not have good anchorage in the soil and are more susceptible to drought conditions.
Plants will vary in how long it will take to become established in the ground. It may range from a few months to a few years. Usually, vigorous new growth is a good indicator that the roots have expanded into the surrounding soil and is well underway to becoming established in the ground.
Native plants do not need very much fertilization. In fact, over-fertilization can harm or even kill native plants. If you want to fertilize your plants, it's best to apply it at half the recommended dosage. Adding compost to the soil is another way to add nutrients without adverse affects and it will also improve the soil structure.
Mulch is an excellent way to retain soil moisture, reduce weed emergence and add a finished look to your landscape. Mulch comes in various colors and materials- ranging from wood chips to cinder to shredded rubber. Wood chips breakdown rapidly in Hawaii's climate and adds beneficial organic matter to the soil. When spreading the mulch, do not place it right next to the bark of the plant. There is a chance the bark will rot wherever the mulch is touching due to excess moisture, and the plant may die. It's best to leave a three (3) inch buffer around each plant base.
The two primary ways plants are propagated are by seeds or cuttings. A couple of handy reference books to have in order to learn more about how to propagate native plants are: Heidi Bornhorst's book, Growing Native Hawaiian Plants, and A Native Hawaiian Garden: How to Grow and Care for Island Plants by John Culliney and Bruce Koebele.
Interested in seeing native Hawaiian plants growing in the landscape? Check out the following places on Oahu to get an idea of what the plants look like and how to use them in the landscape. Please contact the gardens for visitor hours and other information.
University of Hawaii Botany Department: Native Hawaiian Plant Website