With so much flooding during these last few months of Kona’s summer rainy season, we may not be thinking about water conservation. But, even with the climate confusion we are experiencing, dry times will likely come and planning for those is a wise idea. Once you start watering your landscape again, these tips can help you reduce your water bill.
If you or your irrigation system is watering your garden daily, you may be able to save as much as 25 to 30 percent on water usage by adjusting your schedule or performing a simple irrigation programming adjustment on your irrigation controller. It can take just a few minutes at no cost, if you do it yourself.
The EPA says “50 percent of outdoor water use is wasted due to inefficient watering methods and systems.” It’s common to see daily watering programs used for irrigating landscapes on this dry, leeward side of Hawaii Island. Not only are we wasting massive amounts of water and increasing water bills substantially, but also daily watering contributes significantly to plant pest and disease outbreaks.
Start by taking a look at the programming on your irrigation controller, also sometimes called the “clock” or “timer.” You’ll need to be familiar with the programming and functions of your irrigation controller to be successful. If you have lost the manual, a few clicks on the Internet will turn up many instructional resources and how-to videos.
First, it’s crucial to understand that different parts of the landscape have different water requirements. Turf grass, for example, has a much shallower root system then the root system of a tree. Therefore, turf needs more frequent watering. Shrubs are somewhere in the middle, with a deeper root system than grass but not quite as deep as trees. Key point: The watering schedule should match the root system you are watering. Daily watering produces shallow, poorly developed root systems that can lead to disease and pest attacks. Watering less frequently, like twice a week instead of daily, helps plants develop robust root systems, making them healthier and more resistant to pest infestations and diseases.
Turf is the largest water consumer in the landscape and requires an extensive sprinkler system with even coverage for good results. According to the University of Hawaii College of Tropical Agriculture and Human Resources, turf grass should receive 0.75 to 1 inch of water (465 to 620 gallons per 1,000 square feet) when the grass shows its first sign of wilt. Through my own process of careful observation and experimentation, I’ve determined the first sign of wilt to be about every three to four days in the cooler winter months and every two to three days during summer for warm season turf grass in Hawaii. Therefore, the optimal schedule for turf grass is to be watered two times per week in the winter months and three times per week in the summer. For planter beds containing shrubs and trees, the watering schedule that works best is two times per week year-round. If your trees are planted in soil more than 4 feet deep, then a long soaking once per week is the absolute best schedule for water conservation and tree health. The duration of watering or run time on your controller is dependent on the type of heads and nozzles in your system. Expert advice can help determine this for you.
Another extremely wasteful landscape management practice to be aware of is the bare soil condition. We create this by picking up all the leaves and blowing the soil “clean.” This practice increases water requirements by 10 to 20 percent because of harsh sun and wind exposure on the bare soil. Just mulch it. Apply any type of mulch such as wood chips, cinders or even stone at a minimum of 4 to 6 inches thick. For the best results, ensure full plant coverage whereby plants and trees also shade and shelter the mulched soil to reduce soil heating and moisture loss.
When used together, these techniques yield significant savings to the water-wise homeowner. To learn more, attend the annual Landscape Management Conference and Trade Show on Oct. 24 at the Hapuna Beach Prince Hotel. This year’s theme is “Waiola — the water of life: preserving and conserving our most precious natural resource.” Visit hilahawaii.com or call 322-4884 for more information and to register.
Micah Barker runs the organic landscaping company Bio-Scape Hawaii LLC. He also serves as secretary for the Hawaii Island Landscape Association.
Tropical gardening helpline
E-mail plant questions to konamg@ctahr.hawaii.edu for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.
Doug asks: I am having trouble with several plants, including my Okinawan spinach. They get dark spots on their leaves and they seem to spread over the leaves and on to other leaves. Sometimes the leaves turn yellow and drop off. What’s going on and what can I do?
Answer: As you might have noticed we are having a very hot, wet summer. Lots of diseases are encouraged by high heat and high humidity. This summer we have both.
What your plants probably have is a fungal disease. Though it may go away as we get cooler, drier weather, you can try some control practices now or treat it with an organic product that may take care of it more immediately.
Fungal diseases are spread by spores. If you want to control the disease naturally, start by removing the leaves with black spots and disposing of them off-site. Don’t remove more than one-third of the leaves, however, or your plant will go into additional stress. Increasing air circulation around and within the plant and avoiding overhead watering or splashing around the plant can also help. Okinawan spinach usually recovers and the black spots do not appear on new leaves once the weather dries out and cools off.
Serenade is an OMRI -approved organic product that contains Bacillus subtilis, a soil-dwelling bacterium that controls foliar fungal diseases like anthracnose, bacterial spot, leaf blight, early and late blights, rust, powdery mildew, gray and black molds, scab and others.
Be sure to read and follow the label instructions including wearing personal protection equipment and clothing when using the product. According to the label, it can safely be used on fruits and vegetables up until the day of harvest and it can treat fungal diseases on flowering plants and other ornamentals. The product will likely be effective at controlling the spread of the black spots. It should be available locally in either a ready-to-use or concentrated form.
Gardening events
Friday and Saturday: The 2015 Fall Horticultural Show and Plant Sale from 5 to 9 p.m. Friday and 9 a.m. to 2 p.m. Saturday at the Afook-Chinen Auditorium in Hilo, sponsored by the Big Island Association of Nurserymen, offers plants, plant producers and educational booths. For more information, visit hawaiiplants.org.
Saturday: “Saving Seeds for the Future” is held from 10 to 11:30 a.m. at the Kailua-Kona Public Library with Jill Wagner of the Hawaii Island Native Seed Bank. It is a free presentation on saving and storing seeds. For more information, call 508-264-7335, email nehamah47@gmail.com or visit folkhawaii.com.
Farmers markets
Wednesday: Hooulu Farmers Market, 9 a.m. to 2 p.m. at the Sheraton Kona Resort & Spa at Keauhou Bay
Wednesday: Sunset Farmers Market, 2 p.m. to sunset at the north makai corner of the Kmart parking lot
Saturday: Keauhou Farmers Market, 8 a.m. to noon at Keauhou Shopping Center
Sunday: South Kona Green Market, 9 a.m. to 2 p.m. at Amy B. H. Greenwell Ethnobotanical Garden in Captain Cook
Monday to Saturday: U-Pick greens and produce, 10 a.m. to 4 p.m. Tropical Edibles Nursery in Captain Cook
Plant advice lines
Anytime: konamg@ctahr.hawaii.edu
Thursday: 9 a.m. to noon at UH Cooperative Extension Service in Kainaliu, 322-4892.
Monday, Tuesday and Friday: 9 a.m. to noon at UH CES at Komohana in Hilo, 981-5199 or himga@hawaii.edu.
