Hawaii has a year-round growing climate conducive to many tropical and subtropical plants. This might sound like an ideal growing situation, but some plants can present challenges because of their need for water, nutrients and the correct type soil. Native plants are perfectly adapted to the conditions in their natural environments.
Work With the Land
Where lava has covered an area in the past few hundred years, soil is almost nonexistent and the landscape is uneven and rocky. Many homeowners, especially on Hawaii Island, choose to utilize a large bulldozer to "rip" the rock and grade it into a barren, flat surface. If you simply clear the land of invasive species and unwanted plants that manage to grow in this harsh environment, you'll be preserving the natural landscape and saving the native plants and animals that call it home.
Raised beds are a good way to create your landscape. You can build a raised bed right on top of solid rock if you surround an area with rocks. Fill it with purchased topsoil mixed with compost, peat moss, grass clippings, cinder and other organic materials. Make your raised beds as high as you want. Smaller plants will do well in shallower beds while larger plants such as trees require a deeper growing environment.
Fill cracks or holes in the rock on your property with a mixture of topsoil and organic materials. This results in some interesting shapes and sizes of beds.
Hardy Native Plants
Native Hawaiian plants can be difficult to find in nurseries. Check with local botanical gardens for annual sales and search for other retail sources for plants. Learn a bit about your climate zone. For example, the windward side of the islands receives significantly more rain than the leeward side. Find native plants specific to your area or an area with very similar conditions. Altitude is another consideration; many native plants that grow near the ocean, where it is warmer and drier, will not survive at higher elevations and vice-versa.
The early Polynesian settlers of the Hawaiian Islands brought many important plants with them on their canoes. Plants we think of as typical of Hawaii are often on the list of the "canoe plants." They include coconut palms, kukui nut trees, kava kava and others. These plants are often included in native landscapes in Hawaii because they have proven themselves to be hardy, drought resistant and well adapted to the areas where they have grown and naturalized. Don't forget about them when you are choosing the plants for your landscape.
The windward sides of all the Hawaiian Islands receive large amounts of rain. However, short droughts of two weeks to two months sometimes occur. During these dry periods, give many plants supplemental irrigation. Setting up a drip system or a series of soaker hoses is a good solution for keeping your landscape as green and healthy as possible. Using a timer with a drip system is not always a good decision because rain can occur at any time. To avoid overwatering and wasting water, opt for manual control of your irrigation system.
When native plants grow in the wild, they survive without the help of humans. They drop their leaves and fruit to the ground around them, forming a humus or mulch that helps to keep the soil moist and also provides nutrients to the plant when they decompose. You can help your native plants by introducing a 2- to 3-inch layer of organic materials as mulch around their base. Suitable materials include organic compost, peat moss, fallen leaves, grass clippings and chopped up plant parts such as the spent flowers and leaves cut from other plants. However, avoid using any plant material that has signs of disease or a serious insect attack.