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.

Friday, February 3, 2017

Algae on Walkways

Living in the tropics, we are often plagued with unsightly and dangerous moss and algae growing on driveways and pathways around our homes. When the rain stops, the green growth will dry up but will regenerate again with the next rain. 

There are many different products on the market to help you clean up the driveway. Look at the active ingredients on the label; most products will contain bleach, copper, or soap. Be sure to follow the directions on the label. Most are sprayed on, left for a while and then washed off with a hose – sometimes with the help of a shovel-scrapper. Often times the buildup is so great that a power washer is needed. Bleach is often recommended at one cup per gallon of water. 

When using copper and bleach, there is always the potential for these products damaging desired plants either from the direct spray or from the solution saturating the soil. Take caution when spraying near desirable plants. The damage is lessened in high rainfall areas through the leeching action of the rain.

Another option is to use one cup of vinegar per gallon of water; bleach is sometimes added to fortify the solution.  I have not had any feedback on how well the soaps and vinegar work.