What has the Easter Bunny and eggs have to do with Easter? Actually, the return of Jesus after the Crucifixion, has little to do with bunnies and eggs. However the concept of rebirth and resurrection was based on the pagan holiday of Eostra that celebrated new life and fertility. Early Christians connected the two events and thus we celebrate with joy rather than sorrow. The date palm is associated with the Easter Holy Week because it was the leaves of that palm used to wave as Jesus rode into Jerusalem. In many Catholic countries, the leaves are now woven to create intricate art forms used during Holy Week.
Easter and spring remind us that our gardens burst with new life even in the tropics. Last year, folks were complaining about too little rain. Now West Hawaii is getting greener. Even the koa haole and kiawe are lush green from makai Kona to Kohala. Climate warming definitely seems to be affecting us locally as temperatures have also hit record highs in the last few years. How does this affect our gardening practices and our state of mind?
We should remember that a healthy green landscape helps minimize the extremes of hot and cold. Vegetation helps reduce noise, pollution and produces oxygen that makes us feel better. Also the color green is a very restful color.
A garden planted with no thought given to dry spells will do well in rainy periods but deteriorates without irrigation in dry periods. Even in East Hawaii, we need to use plants that will tolerate extremes of wet to dry conditions. Fortunately, many garden plants in Hawaii are fairly hardy when it comes to short water supply, so we have a long list from which to draw. It’s important to vegetate these areas so that our Islands don’t look like Arizona in years to come. A good reference to help you select the right plants is “Sunset’s National Garden Book”
There are two factors that make plants able to survive moisture stress.
First, some plants are notably resistant to drought. This quality is centered largely in the cellular structure and has a bearing on the economy with which the plant functions. Some plants have the ability to carry through extended dry periods because of a happy faculty of closing the pores of the leaf against transpiration, or turn the leaf back or edge-on to the sun. Others root deeply to tap and have available for day periods, any accumulated moisture of sub-soil.
The garden environment is the other critical factor. Water use is a process controlled by energy. The source of that energy is the sun. To move water out of the soil directly or through the plant and away into the atmosphere requires energy. The amount of energy available and the nature of the conducting medium that is the soil, plant and atmosphere complex, determine how much water will be used in a given time.
This is why the more shade and wind protection from trees we have in the garden the less water is required to keep moisture levels up. And conversely, the more asphalt and concrete to heat up, the more rapidly our planted area dries up, even in normally high rainfall areas like Hilo. Our lava lands are unusually prone to moisture loss, so when we develop these areas and plant trees, shrubs and grass, we actually create a cooler more comfortable environment. We may increase the rainfall in places like Hualalai, Kukio, and Mauna Kea Beach when we change lava flows to develop urban forests, parks and gardens.
Besides the moisture of the soil, the nature of the plant itself has considerable effect on the amount of water lost into the air. The height of the plant and the roughness of the surface have an effect on the wind movement and mixing of air across the surface of the vegetation. A rough surface will cause more water loss than a smooth surface.
Plants that are tolerant of salty beach conditions often use less water than many soft, luxuriant jungle plants because they are streamlined for water conservation. Beach naupaka is a great salt resistant shrub but is also used in the landscape inland. Plants like bird of paradise, dracaena, monstera and many philodendrons give a luxuriant look and are still drought resistant. Many palms also have this quality. Heritage plants like noni, hala and kukui are very drought tolerant but will also grow in our wet humid lowlands.
What can we do in managing the soil to take advantage of our knowledge of the factors affecting water use rates? First of all, we can irrigate only when the soil moisture becomes low and plants begin to show evidence of wilt during the hottest part of the day. This forces deep rooting. Daily watering tends to promote shallow roots.
We can understand that we will have to irrigate sooner following a previous irrigation than following a general rainfall. And we can provide soil with good physical and chemical properties for deep rooting of plants.
Proper fertilization will help accomplish this. Also, poor soils should be improved with the necessary amendments to help the plants develop good root systems. Addition of well rotted organic matter or compost often helps increase moisture and nutrient holding capacity. In many Hawaiian soils, available phosphorus is lacking. This is essential to root growth, so addition of this element is particularly important. The use mulches will also help conserve soil moisture.
Proper planning and maintenance of your garden will help in the short run, but we must do something about the overall future of the islands as well.
For our mental and physical health, we need to focus on our own gardens and at the same time, work with our local politicians and planners to keep Hawaii the green paradise it is meant to be!