Monday, March 20, 2017

Growing Corn in the Tropics

In Hawaii, as well as other tropical areas of the world, corn can be planted year round. This will give gardeners three and possibly four crops a year.  

A major complaint from backyard  growers, however, is that the individual ears of corn produce few kernels. Poor pollination is the most common cause. Since corn is wind pollinated, it needs to be densely planted in order to achieve good pollination. Planting a compact square or a dense circle will ensure better pollination than a few plants or long rows. The best recommendation is to plant a minimum of 4 rows about 8 feet long rather than 1 or 2 long rows.
Weather patterns can adversely affect the corn crop.  Too much wind or heavy rains during the pollination period, or very dry weather will impede pollination. In addition, from pollination to harvest, corn plants need adequate water to insure full kernel development.

Corn varieties are classified into two groups, tropical and temperate. The tropical supersweet corns are bred in Hawaii. Popular ones include Supersweet #9 and #10. If residing in the tropics, growers should be aware that many seed company catalogs list only the temperate hybrids: Bantam, Golden Cross and Jubilee. Some of these seed packets are also found in local stores. These temperate varieties have, in general, been very disappointing when grown in Hawaii and presumably in other tropical regions.

Tuesday, February 28, 2017

Volcanic Emissions VOG in Hawaii

On the Big Island of Hawaii, heavy volcanic emissions (VOG) have recently covered the Hilo side  (East) with a bluish-grey cloud. Discharges include sulfur dioxide, sulfites, ash and hydrochloric acid.

                           No VOG                                          VOG
Many gardeners, especially those living near the volcanic area, have experienced the distressing effects of VOG on their plants. Sulfur dioxide  enters the leaf through the stomata.  The degree of injury will depend upon its concentration and duration, and upon the sensitivity of the specific plant. The symptoms of low concentrations of sulfur dioxide are general chlorosis (yellowing) of the plant foliage. Higher concentrations cause a bleaching or browning of tissues between the leaf veins.

Volcanic ash appears as a dust and is composed of fine rock particles from the volcano. The ash does not damage plants directly but can block sunlight on foliage as well as detract from the appearance of the plant. Harvested fruits and vegetables should be thoroughly washed prior to their consumption.

There is not much that can be done about the harmful chemicals the volcano churns out. However, as far as the plant is concerned, leaves should be rinsed with adequate water after exposure. Susceptible plants can be grown under cover such as greenhouses, and during periods of intense VOG, valuable plants can be temporarily covered with fabric or plastic.

Different plants have varying degrees of susceptibility to VOG.  The following is a list of plants documented to be susceptible to VOG:

Ornamentals - African lily, Oriental lily, cypress, Dutch iris, eucalyptus, ginger, hydrangea, heavenly bamboo, pine, podocarpus, rose and tuberose.

Native plants -  koa, naio, pilo, uki, akala.

Vegetables - broccoli, cauliflower, Chinese cabbage, daikon, lettuce, Swiss chard, tomato and watercress.

Some of the more resistant plants are asparagus, celery, coffee, corn, and ohia, the ubiquitous native tree.

For a more in depth look at the volcano’s effects on plants with some excellent photographs read, “Volcanic Emissions Injury to Plant Foliage” by Scot Nelson and Kelvin Sewake, UH Department of Plant and Environmental Protection Sciences. The publication can be found on the CTAHR website -

Photos USGS

Sunday, February 19, 2017

Small Fruit Size

Many people are disappointed with the size of their home grown fruit.  “Why isn’t it as big as the fruit I see in the store?” First, with most commercial operations, fruit is run through a packing house where it is cleaned and sorted by quality and size.  Then the larger-sized fruit are sent to market where they get the best price.  

Second, most commercial farms put into practice a sophisticated fertilization program, including tissue analysis, which maximizes plant nutrient usage.  Homeowners, on the other hand, do not spend that much time or money to optimize their fertilization program and they don’t necessarily have to!

There are several specific conditions, however, that will contribute to poor fruit size:   
  •   Lack of irrigation – young fruit is particularly susceptible.
  •   Lack of sufficient heat units, i.e., a cool growing season
  •   Lack of nutrients including potassium
  •  Desiccating winds    
  • Viral diseases, nematodes, root-attacking fungi, and insect infestations.