Monday, February 24, 2014

Bananas vs Plantains


The tropics are abundant with bananas. Some are sweet when ripe, peeled and eaten, and some are starchy and bland, cooking varieties of bananas otherwise known as plantains. For all practical purposes, the distinction between the two is based solely on how the fruits are consumed: cooked or eaten fresh out of hand. 

The common banana is sweet, easily digested and ready to eat when the skin is yellow. Plantains, on the other hand, are thick skinned and must be boiled, steamed, roasted, baked or deep fried to make them soft and palatable. When the peel is green to yellow, the flesh has a starchy texture with a bland flavor. As the peel changes to brown or black, the plantain losses some of its starch and becomes slightly sweet. At this stage plantains have more of a banana aroma but are still unsuitable until cooked. The interior color of the fruit is creamy, yellowish or lightly pink.

Plantains are native to India and are popularly grown in tropical climates, especially in Western Africa and the Caribbean countries.  They are often used in soups and stews or simply mashed.

There are over 500 different types of bananas; this means that if you eat a different variety of banana every day, it would take almost a year and a half to eat every one.

Photos by Forest and Kim Starr

Sunday, February 16, 2014

Citrus Brown Rot

The fruit in this picture is infected with a fungal disease called brown rot of citrus.  Not only will the fungus infect fruit, but the trunk and roots as well.  The fungal spores will splash up on low hanging fruit during a heavy rain storm. The spores germinate, grow and cause the fruit to rot and eventually drop.  As the rain continues, so does the disease, spreading to fruit higher and higher in the tree. Infected fruit will turn light brown and become soft and leathery.  Eventually the whole fruit will rot.

A copper fungicide is often used as a preventive spray - it will not, however save the already infected fruit. Repeat applications of copper will be needed if the rain continues. Another method of control is to mulch the ground underneath the tree. This will help in preventing fungal spores on the ground from splashing up into the tree and infecting the fruit.  In dry years, the disease will be mild, but it will thrive in years of high rainfall.

Sunday, February 9, 2014

The Invasive Australian Tree Fern

Although the Australian fern (Cyathea cooperi) is being sold in Hawaii at many commercial plant nurseries, it is invasiveAccording to Dr. J.B. Friday with CTAHR Extension, Department of Natural Resources and Environmental Management, it is fast growing and aggressively outcompetes native plants in the forest understory. It is a threat to the forests and eventually displaces the native ferns, including the slower growing hapu’u.  

Dr. Friday suggests cutting out the Australian fern and removing it while wearing long sleeves and gloves since the hairs are irritating.The best diagnostic characteristic is the hairs on the leaf stems. With the Australian tree fern the hairs are broad and white. On the native hapu’u they are either fine and red-brown for hapu'u pulu (Cibotium glaucum) or fine and black for hapu'u i'i (C. menziesii). 
                                                                    C. cooperi

The Australian tree fern grows to 40 feet tall. It tolerates full sun in cool wet areas. Their spores are spread by wind and can travel over 7 miles from the parent plant.

In comparison, the Hawaiian tree fern, or Hapu’u is native to most of the Hawaiian Islands. Although once common, hapu’u stands have been reduced due to a large number of ferns being harvested for orchid media and landscape use. The last remaining large stands of native hapu’u are found on the Big Island.

The Hawaiian hapu’u  are very slow growing; the young ones grow at about 3.5 inches per year while the older plants grow even more slowly, eventually growing to  15-20 feet tall.  The unfurled fronds are covered with silky, red-brown wool -like fibers called pulu.  In the past, pulu was used for stuffing pillows and mattresses and for dressing wounds. 

The Hawaiian tree ferns are relatively easy to grow. They grow best in well drained slightly acid soils and partial shade; they will tolerate full sun in cloudy upland areas. They need a steady supply of water and occasional light applications of a complete, slow release fertilizer. Old and injured fronds should be pruned. It is illegal to ship tree ferns or products from the ferns internationally. 

Photos by Forest and Kim Starr

Sunday, February 2, 2014

Lemongrass Rust

Lemongrass is commonly grown by backyard gardeners as an ornamental plant. It is popular in Thai cooking and other Asian dishes.  Leaves can also be dried for herbal tea. The lemon-scented oil is used as a fragrance.

Unfortunately, lemongrass is susceptible to a fungal infection known as rust disease.  The environmental conditions that favor this disease are high rainfall, high humidity and warm temperatures.  

The disease initially begins as tiny yellow spots on the leaves. They merge together developing streaked patterns of brownish, purple lesions running up and down the leaf.  Both upper and lower surfaces of the leaf are infected. Wind and rain spread the spores.

The good news is that, normally, the disease is not fatal, but defoliation, poor yields and reduction in oil can occur. Diseased plants are safe to use in cooking recipes.

Here’s what to do:
·        Keep plants growing vigorously with adequate fertilizer.
·        Avoid planting large numbers of plants together.
·        Try growing plants under cover to protect their leaves from        rainfall.
·        Thin out diseased leaves and destroy the material.

Although the University of Hawaii has not evaluated this fungicide, Trilogy (neem oil) is the only registered material in Hawaii for use against this disease on lemongrass.