Planting for the dry times ahead


Rainfall reports indicate that drought conditions are continuing throughout Hawaii. Climate change studies indicate that increasingly hotter and drier weather can be expected in many parts of the world. A good time to practice growing drought-tolerant plants in West Hawaii is during our drier winter months – mid-October through mid-April.

Xeriscape gardening involves growing plants that do well in dry climates, while implementing water saving techniques. Though all plants require thorough watering when first planted, xeriscape or drought tolerant plants are able to survive longer periods with less water, once established. Fully mature xeriscape plants can thrive through months of dry weather.

Making the most of limited water is good xeriscape gardening. Growing plants in containers requires much less water and many plants adapt well to container life. Mulching might be one of the best water conservation ideas. Use dry leaves, grass clippings, composted wood chips or garden compost placed on top of the root zone of your plants. Mulch helps hold moisture in the soil while suppressing weeds and helping maintain cool soil temperatures to reduce evaporation.

Planting fewer plants and keeping your garden weed-free means more water to go around. Choosing planting sites that are protected from drying winds can also help maintain soil moisture. Water deeply to water plants less frequently. Using drip irrigation systems or well-placed soaker hoses are good ways to be sure that water soaks into the soil where it is needed. Once established, plants that are deeply watered can occasionally go for long periods without additional water.

Overfertilizing plants can cause leafy growth spurts that may require more water. Fertilizing and watering minimally can keep excess plant growth in check and encourage deep root development rather than thirsty top growth.

Select plants carefully from the large palette of xeriscape varieties. Be sure to check for drought tolerance in their description. Dwarf varieties or smaller cultivars often require less water. Include ground covering varieties where possible to help protect the soil from drying winds and sun exposure.

A sure way to make the best use of limited water is to grow plants that are attractive as well as edible or otherwise useful. Several ground covering plants might be a good place to start.

Okinawan spinach is a good choice. It is an attractive ground cover with dark green leaves with purple undersides. Sweet potatoes come in several varieties and also make an attractive ground cover. Rosemary, especially prostrate varieties, is very drought tolerant and has many culinary and medicinal uses.

Herbs such as thyme, sage, lavender and lemon verbena also grow well in dry climates. Sprawling squash vines can fill in a garden with lovely large leaves and flowers. Kabocha is a reliable variety for Kona, but other pumpkin and winter squash varieties also do well. The vining chayote, sometimes known as pipinola, needs support to grow well and produce but requires limited water.

Many tomato varieties do well when “dry farmed.” Though they need a good supply of water to get started, they have fewer disease problems and produce tasty fruit with less water as they mature. Peppers and eggplant are also good candidates for gardening in dry times.

Check out UH seeds at ctahr.hawaii.edu/seed for more ideas.

However you choose to deal with dry times, remembering that water is a precious resource can inspire you to minimize its use as a favor to our environment as well as your wallet and your plants.

Tropical gardening helpline

Arielle asks: I think we have seed borers attacking our cherimoya. Is there anything we can do about them?

Answer: Two different species are known to attack cherimoya, Annona cherimola, seeds. I’m not sure which one you have, perhaps both.

One is the wasp Bephrata maculicollis. It deposits eggs near the surface of small immature fruit. When the eggs hatch, the larvae invade the fruit and begin consuming the seeds. Their presence causes the fruit to ripen prematurely or defectively. When the larvae leave the fruit to pupate, the tunnel of exposed fruit makes it susceptible to fungal diseases.

A second seed borer, Talponia batesi, is a moth that lays its eggs on flowers or fruit as it is developing. The larvae then bore into the fruit to feed. This pest also exits the fruit to pupate in the leaves of the tree.

Both pests are difficult to control or combat. The adults can be killed on contact with a soap and oil mix. Safer soap and neem oil are good choices for the mix. Use 2 to 3 tablespoons of each in a gallon of water. Spraying this mix on the fruit may leave an odor that could possibly deter the adult insects. To kill them, the spray must contact them and cover their exoskeleton, thus suffocating them.

Some lab tests using the fungus Beauveria bassiana were effective at killing the adults. If you are using this product against the coffee berry borer, it may also kill any seed borer adults it contacts. The organic formula of Beauveria bassiana is sold as Mycrotrol O.

The best way to combat the larvae’s damage is to prevent them from entering the fruit. Bagging the fruit is a good way to protect it. The bags should be somewhat air permeable. Wax bags will resist water damage somewhat. Check out horticultural bags online. The website greenharvest.com.au/PestControlOrganic/ExclusionProducts.html has a variety of bags to consider.

These two pests also attach other Annona family fruiting plants including soursop, atemoya and custard apple.

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 an organic farmer, plant adviser and consultant.