Cotton in Hawaii

In Hawaii, the cotton plant, Gossypium tomentosum, is a perennial shrub lasting about 3-5 years, depending on growing conditions. In Hawaiian, it is called Ma’o. This plant can be found growing in coastal plains and dry forests primarily on the leeward sides of the main Hawaiian Islands. Ma'o naturally grows in hot, dry, windy coastal areas tolerating the salty spray. Conversely, the plant does not do well in locations with continuous high rainfall and in waterlogged soil.

Periodic pruning is necessary to control the height, to keep the shrub full and to prevent low lying branches from spreading.

In 1838, a commercial cotton industry was actually started in Kailua on the Big Island of Hawaii. Although it lasted for about a century, cotton never became an important trade item. Even though early Hawaiians stuffed pillows with the fibers, the cotton was not used as a fabric. 

 For more information on Ma’o, see the website for native plants in Hawaii at  http://nativeplants.hawaii.edu/plant/view/Gossypium_tomentosum 
and refer to the UH CTAHR publication entitled, “Ma’o (Hawaiian Cotton). 

Photos by Forest and Kim Starr

Propagation of Blueberries

Blueberries are propagated from either softwood or hardwood cuttings.  

Hardwood cuttings are collected in late January or February, after sufficient chilling has occurred. Follow these simple directions: collect shoots from the previous summer, 12 to 36 inches in length. Select healthy material, avoid propagating from plants that have odd-looking or stunted foliage. Divide the shoots into pieces 5 to 6 inches long, removing any flower buds. Place cuttings in a propagation bed at a depth of one-half to two-thirds of their length. Finally, keep moist.

Softwood cuttings are taken in late spring from the current season's growth, 4 to 5 inches long. Here are the directions: collect these cuttings when the stems have developed woody tissue but are still somewhat flexible. Remove all leaves with the exception of two or three terminal leaves.  Place cuttings in the propagation bed, under mist at a depth of one-half to two-thirds of their length.

Rooted cuttings are eventually transplanted into pots and held for about one year.  During the time of rooting, keep beds moist while being aware not to over water.

For the propagation process, a greenhouse is not necessary, but some type of propagation bed/chamber, under 40 to 70 percent shade with a mist system is recommended; an area as small as 3x3x3 can be used.

The mist system should keep the media uniformly moist but not soggy.  An intermittent-mist system with frequent, short misting intervals is recommended in order to keep the humidity near 100 percent.  However, keeping the cuttings at this constant moisture also creates an ideal environment for pathogenic fungi to grow. Thus cleanliness is very important; use new or sterilized planting mix and pots, keeping them raised off the ground.

  

Potting media containing various mixtures of coarse sand, ground pine bark, perlite, sawdust, and peat moss have proven satisfactory. According to a publication from the University of Hawaii, a good rooting medium recipe is a mixtures of coarse sand, ground pine bark, and peat moss at 1:1:1, or perlite and peat moss at 1:1.

Spittlebugs

Are your plants foaming at the leaves?

A white frothy substance on plants may be a spittlebug. Inside all that froth is a tiny bug about ¼ - ½ inch long.  The immature stage of this insect sucks the plant juices just as aphids do. But in the process, spittlebugs remove so much water and carbohydrates, that excess fluid is produced. They then cover themselves with this fluid. The spittle is produced when the insect bubbles air from the tip of the abdomen into the liquid. This is an ingenious method to protect themselves from predators and  from drying out.

Although the removal the plant fluids can weaken the plant, rarely are spittlebugs a serious problem. Simply spraying a strong stream of water can physically remove the pest. A soap/oil spray can also be used.

In addition to basil, the spittlebug attacks other common plants such as rosemary, mint, hibiscus and some pine trees.

Avocados with Black Strings

Why are some avocados stringy?

The strings in the fruit are vascular tissue, part of the conductive system of the plant bringing water and nutrients to the fruit.  They are always in the fruit but are unnoticeable in high quality fruit. From non-grafted trees, or seedlings where a genetic mix takes place, fruit can exhibit darkened, thicker strands as a natural characteristic, especially as it reaches maturity and beyond.  

These strands are usually the same color as the fruit pulp but can discolor or blacken for various other reasons. The most common reason is cold temperatures. This is true in avocado growing in areas like California where temperatures can reach freezing or below. Cold weather, however, would not apply to fruit growing in tropical regions such as the Hawaiian Islands. 

The blackened vascular tissue can also be caused by a disease. There are a number of fungi which enter an avocado at the stem end of the fruit.  Some of these pathogens will cause vascular discoloring as a precursor to decaying the flesh. 

These stem-end rotting fungi are present in the soil and on dead plant tissue and assist in the breakdown of organic matter. The spores of the fungi spread by wind and splashing water. This disorder is clearly made worse in a rainy environment. Infection typically occurs when the fruit is still on the tree, but it does not develop until after the fruit is picked due to anti-fungal compounds present in unripe fruit. Fruit will continue to decay as it ripens.

Control Measures For this Fungal Disorder 

• Clean out dead limbs and twigs which helps to reduce the incidences of fruit rot.  
•  Keep trees healthy with proper nutrients and water.
• Maintain a thick layer of mulch under the tree’s canopy which will help to minimize the disease.   
• Place avocados in the refrigerator after picking them, if not eaten soon. Caution: Temperatures below 41 degrees Fahrenheit can cause fruit injury in some varieties.
•  Spray trees with a copper fungicide to limit infection if the problem is severe.

Watering Houseplants

How often should I water my houseplants?

• Although is may seem the easiest method, do not water plants by the calendar. Using this method would assume that in regards to environmental conditions (temperature, humidity, wind etc.), each day of the year will be the same.

• Water by inspection of the soil or potting mix. If it is wet, wringing wet, don’t water; if it’s dry, water. If the soil is moist, but not soaked, wait a few days and check again. If you actually observe the plant wilting, you should have watered yesterday. When assessing the soil, do not examine the surface, which usually dries out rather quickly. To truly evaluate the condition of the soil, place your finger about a third of the way down the pot or take a mini trowel and pull up some dirt. In reality, you may end up watering somewhat by the calendar, but at least you will have arrived at it through observation and inspection. 

• The lifting method also works well. If the pot isn’t too big, simply lift the pot off the ground, if it’s heavy, it’s got plenty of water. In comparison, if it’s relatively light, it’s time to water. Putting these methods together, you’ll soon get the hang of it.

A major problem lies in the fact that wilting and lack luster growth can be symptoms of both under watering and over-watering. In the case of over-watering, the roots will begin to rot, with or without the help of soil pathogenic fungi. Once some of the roots are gone, the plant will not be able to pick up enough water, especially on hot days, and the leaves wilt.

It is important to note that under watering a plant will lead to lackluster growth and low fruit production (for fruit producing plants), but over-watering can easily lead to the death of the plant.

As you can see knowing when to water will take some trial and error. It is important to use a well-drained potting mix and never leave water standing in the tray. Plants that have been in the pot a long time may have become pot bound, meaning that most of the space in the pot is occupied by roots rather than soil. If this is the case, you will find that these plants need very frequent watering because there is simply no soil to help hold the water.