Diana Duff is a plant adviser, educator and consultant with an organic farm in Captain Cook.
BY DIANA DUFF | SPECIAL TO WEST HAWAII TODAY
The evidence of dramatic, global climate change seems clear … West Hawaii included. We often experience less rain in winter but nearly year-round drought conditions have been extreme over the last several years.
Despite a wet summer in mauka areas, plants that don’t receive regular irrigation are showing evidence of extreme thirst. Wilting leaves, as well as fruit, flower and leaf drop, are signs of water stress. Though we may experience more rain as spring approaches, we need to start thinking about xeriscape gardening year-round using drought-tolerant species and techniques that require less water.
Though all plants require water when first planted, xeriscape or drought tolerant plants are able to survive most dry periods once they are established. Many native Hawaiian plants are good choices for a xeriscape garden since they have adapted over the centuries to our seasonal fluctuations and can tolerate long dry periods. Consider a food-producing tree like ulu (breadfruit) or a drought- tolerant ground cover like pau-o-hiiaka (Jacquemontia ovalifolia). Several local nurseries, including Amy B.H. Greenwell Ethnobotanical Garden in Captain Cook and Aikane Nursery in Hawi, carry a wide variety of natives and can advise on drought tolerant species.
Check out mature landscape specimens that qualify as xeriscape plants by visiting botanical gardens containing such plants. Pua Mau Place in North Kohala is challenged by very low rainfall, high winds, rocky soil and occasional flooding. It has chosen plant material and placement that works in its environment and it employs many water-saving techniques. For example, it has installed several ground covers to help hold the soil and its moisture. The hardy grass-like lippia (Phyla nodiflora) is one example.
Using a variety of water-saving techniques can help keep your plants alive and your water bills down in dry times. Installing a drip irrigation system avoids water loss from evaporation or waste that can occur using overhead sprinklers. A properly installed system puts adequate water in the root zone, where the plants need it most.
Mulch, mulch, mulch. By placing green waste or any organic matter on top of the soil around your plants, you can control weeds, retain moisture, prevent soil erosion and improve the quality of your soil. Mulch works best when placed several inches from the trunk and inside the drip line, covering the plant’s root zone. You can make your own mulch from palm fronds, green trimmings, used cardboard boxes or shredded paper, or you can get free mulch from several green waste dump sites.
Gardening in containers is another xeriscape technique as water stays in the plant’s immediate root zone. Many plants do well in pots and production can sometimes be expanded and better controlled when contained. Consider growing edibles in containers for food production using less water.
Herbs are well-suited to pot gardening and can be placed throughout your garden, as well as on your lanai or inside your home. Oregano, rosemary, thyme, lavender, borage, fennel and chives can all be cultivated with very little water. Using them creatively can expand their usefulness.
Greens and lettuces also grow well in containers. They can be attractive in a window box or placed anywhere in your landscape.
Beans can also thrive in pots, providing a protein source for your table while gathering nitrogen from the air to add fertility to the potted soil. Try snow peas, winged beans or purple string beans to add interest to your garden and table.
Drought-tolerant veggies such as potatoes, squash, tomatoes and peppers also can be grown successfully in pots and can produce well with minimal water though they will not do well if we have another wet summer. It’s best to plant these in the fall.
Some tropical trees can also thrive in dry times as potted plants. Large half barrels or 15-gallon pots can contain dwarf citrus varieties, as well as flowering ornamentals that will produce well year after year.
During dry periods, tropical perennial greens like Okinawan spinach, with purple-backed leaves, as well as tree spinach or chaya can add charm, save water and provide food.
However you decide to deal with drought in your garden, remember water is a precious resource in Hawaii. Keeping your water use under control is a favor to your plants, your purse and our island environment.
Tropical
gardening helpline
Andrea asks: We got some beautiful orchids for Christmas but now the flowers have died. What shall we do with them to encourage more flowers?
Answer: Orchid plants will thrive and bloom again and again if you care for them properly. Most of the orchids for sale here are native to warm, wet climates and will do best if they are kept warm and moist.
Many tropical orchids are also epiphytes and prefer to have moist air space around their roots. Orchids do well even when their roots are crowded though, so you don’t need to repot even if roots are coming out of their current container. If you do repot, do so in a very loose mix of wood chips or stones that can hold moisture in the root zone while allowing adequate drainage to prevent the medium from becoming soggy.
You can attach epiphytic orchids to tree crotches outside as long as you keep the roots misted. In dry areas, it is best to lightly mist orchid plants daily and keep them out of full sun. They absorb water through their roots, so be sure to hit the root zone with your spray.
A good plan is to give your potted orchids a good shower every week or two. You can share a shower with them or let them have a light shower of their own. If you can close the bathroom and let them remain in a warm (not hot) misty environment for a while, they’ll be very happy.
In Hawaii, orchid lovers maintain multiple plants outdoors and place blooming specimens into living areas during flowering. Some varieties will bloom several times a year. Keeping several plants on hand allows you to rotate bloomers. Outdoor areas with partial shade or afternoon cloud cover are good orchid maintenance sites.
The blossoms on orchid plants are long lasting and can survive in low light. It is important to support blooming stems by attaching them to small stakes, especially when the flowers are heavy or the blooming spray is long.
Keeping your orchid plants healthy and happy will provide you with years of rotating beauty and pleasure.
Email plant questions to konamg@ctahr.hawaii.edu for answers by certified master gardeners. Some questions will be chosen for inclusion in this column.
Diana Duff is a plant adviser, educator and consultant with an organic farm in Captain Cook.