Monday, December 28, 2015

Banana Basics

The banana plant is actually a perennial herb. The fruit is harvested 11-15 months after planting. Individual bananas turn light green to yellow and angular corners become rounded.

Bananas require a well-drained soil, with a pH range of 5.5 - 6.5. They also need rainfall of 100 inches or more, well distributed throughout the year along with full sun, wind protection and an average temperature of 81degrees Fahrenheit.  

In general, banana plants need a fertilizer with high amounts of potassium (K), along with nitrogen (N) and phosphorus (P). Around the Hawaiian Islands, soils vary, some being richer than others. The University of Hawai`i recommends applying 2 lbs. of a fertilizer similar to 10-5-20 (N-P-K) three times a year . This amount is applied per mat. When referring to bananas, a group of plants is known as a mat. A properly maintained mat will have one plant in fruit, one plant half-grown and one plant just emerging from the soil. Applying compost to the surface of the banana mat is beneficial, but most likely will not supply enough nutrients, especially nitrogen, for optimum growth. 

Green bananas can be stored up to seven days at room temperature or up to 20 days under refrigeration. Neither green nor ripe bananas, however, should be stored at temperatures lower than 58 degrees Fahrenheit.  Cooler temperatures will cause surface damage. 

Monday, December 7, 2015

Orange Trees with Vigorous Shoots

My neighbor recently asked this question:
"I have an older orange tree in my front yard. One of the branches is very vigorous, has large thorns on it, and the fruit is very sour.  Why is this branch different from the rest of the tree?" 

This is a fairly common problem in oranges and other sweet citrus fruit. The vigorous shoot, or branch, originates from the rootstock, that is, below the original graft or budunion. This branch, therefore, is not genetically part of the grafted orange variety. 

Rootstocks are chosen because they possess resistance to disease or some other cultural quality desired by the grower. The fruit borne from the rootstock, although a citrus species, is often sour, bitter and with little juice. Occasionally a bud will break from the rootstock, develop into a branch and grow up through the tree. Eventually this branch can set fruit, but as noted, usually of inferior quality. These sprouts or branches should be cut out. Since they are usually more vigorous than the grafted portion of the tree, they could eventually dominate the entire tree if not removed.

Sunday, November 15, 2015

Sandalwood Trees in Hawaii

Sandalwood trees (Santalum sp.) are classified as hemi-parasites. The term describes a plant that is green and can produce its own food but also derives water and some nutrients by attaching to the roots of other plants. This process can effectively join together whole plant communities through their root systems. The plants that donate nutrients to sandalwood are called hosts; sandalwood trees do not grow well without a host. In fact, this ‘inter-cropping’ is not only possible but necessary. 

According to the publication, Species Profiles for Pacific Island Agroforestry, S. ellipticum, one of four species known as Hawaiian sandalwood, can “… successfully develop into relatively large individuals when growing with endemic species such as Wikstroemia sandwicensis (‘ākia) and a fan palm Pritchardia remota (loulu) in windward, lowland areas. In more xeric (dry) environments it has developed successfully in association with the endemic shrub Chenopodium oahuense (‘āheahea) and Chamaesyce hypericifolia. Apparently S. ellipticum, is flexible in the species it can parasitize for needed nutrients.”
Santalum ellipticum is endemic to the Hawaiian Islands. It is found as a sprawling to bushy shrub near the ocean shore. It is occasionally found as a larger shrub to small tree in dry gulches, on slopes, and frequently in rocky habitats. S. ellipticum is adapted to arid habitats with typical summer drought in leeward lowland locations.
Hawaiian sandalwood species generally resist most insect attack; sometimes infestations of whitefly or scale insects can be found. Insecticidal soap may be used to treat such infestations. Slugs and snails will also feed on newly sprouted plants. The trees generally tolerate a broad range of soil conditions but show a preference for well drained neutral to slightly alkaline soils.  Since many Hawaiian soils tend to be acidic, an application of lime would be appropriate to bring the soil closer to neutral. The wood of the sandalwood trees is often used for carving handicrafts, art, musical instruments and decorative furniture.  

Tuesday, November 3, 2015

Avocados and Clay Soils Don't Mix

Avocado trees, planted in a clay soil in an area of high rainfall, will frequently be unhealthy. Various species of trees can tolerate ‘wet feet’ such as the great magnolias of the South which grow in the swamps. Other trees, like avocado and citrus, do not like to sit in water. In order for most trees to thrive in places of high rainfall, they must either be able to tolerate lots of water or be grown in well-drained soils. Unfortunately, a clay soil does not facilitate good drainage.

A key element to remember is that roots need oxygen as much as they need water. When it rains, water fills the air pockets in the soil. For good plant health, a portion of that water needs to quickly drain away to allow the air to come back. In clay soils this does not happen; the clay holds onto the water.  

In arid climates, farmers who have clay soils simply apply water less often. In tropical climates, the clay soil has little or no chance to dry out; oxygen is excluded, and the roots die. In the case of avocados, it has been shown that after 72 hours in a water logged soil, their roots begin to decline.  Once this happens, leaves turn yellow and drop resulting in twig and small branch dieback.

Clay and rain are a bad combination for many plants. There is not much to be done for existing trees; the soil can’t be changed neither can the rain be stopped. A good recommendation is to plant on a slope where there is better drainage. Sometimes trees can be planted on mounds about 3 feet high. It won’t do any good to dig a hole, put the tree in and fill the hole with a different type of soil. That is like putting sand in a bathtub, plugging the drain and planting a tree in it.