Sunday, November 26, 2017

Dry, Flavorless Citrus?

Overly mature fruit is a major cause of dryness in citrus. In other words, if the fruit is left on the tree too long, drying occurs.  A few other reasons include:
 1) the application of too much nitrogen. 
 2)  At times, dryness may occur when a tree is young; the fruit will improve as the tree ages.  
 3) Trees budded on certain vigorous rootstocks will make the problem of dry fruit worse. 4) For citrus grown in temperate climates, dry fruit is the result of low, freezing temperatures.  
Overall, certain varieties of citrus, especially mandarins, seem to be more susceptible to producing dry fruit. 

In Hawaii and other tropical areas, a further complication is the fact that citrus fruit does not color well. In other climates, such as California, fruit develops a deep orange color due to the great differences between day time and night time temperatures.  And under these conditions, oranges may actually turn color before they are sweet enough to pick. 

In the tropics, however, where there are less temperature fluctuations, the orange coloration does not develop well and therefore is not a good indication of ripeness. In fact, fruit is often sweet but will still show a green coloration; by the time the fruit shows good color, it may have dry segments already forming.

 If you don’t know the harvest season for your particular fruit, I would suggest picking one good sized fruit, even though it may still be greenish in color.  If it is not sweet enough, pick one every 1-3 weeks until it tastes sweet. Fruit will develop more sugar the longer it is held on the tree. 

Wednesday, November 15, 2017

Sweetness in Citrus Fruit or Lack of It!

Warm sunny days: The accumulation of heat units is most important in determining the sugar content in citrus. Simply put, citrus fruits become sweeter the longer they remain on the tree up to a point. If the fruit seems ready to pick, but the taste is not sweet enough, then leaving it on the tree a little longer should sweeten it.   

Location, location, location: In certain places, fruit from a given tree will simply not produce enough sugars. Of the hundreds of citrus varieties, not all are adapted to a specific area. For a given region, some varieties won’t produce good quality fruit!

The rootstock factor -  There are numerous citrus rootstocks. They impart a variety of characteristics to the fruit. Some rootstocks will enable the tree to produce an abundance of fruit, but with poor quality, in this case, low sugar content. For commercial growers, choosing the right rootstock is an important factor when selecting new trees for an orchard. Homeowners on the other hand, have few choices in rootstocks when purchasing a tree.

  Will citrus fruit get sweeter by adding potassium or lime to the soil?
The notion of adding potassium or lime to sweeten citrus fruit has been around for a long time, but it has not been substantiated by scientific research. Fruit from trees deficient in potassium are small and thin-skinned, yet they can be juicy and have a good acid and sugar content. Adding potassium to deficient trees will increase the size of the fruit. This has also been noted in other fruit trees, such as apples and peaches.  An excess of potassium makes fruit large with coarse rinds, thick skins and poor eating quality.

 A classic chart taken from the University of California’s Citrus Industry Volume II, shows that as the percent of potassium in the leaf rises, there is a slight decrease in the sugar content of the juice in the fruit.  The vitamin C, however, content increases.
If soils are truly potassium deficient, by all means apply potassium. This being said, sweeter fruit will not be a result of adding potassium.

In regards to lime (calcium carbonate), an old study (1958) in South Africa, on calcium deficient orange trees, noted that the fruit was acidic and low in sugars. The trees were stunted, chlorotic (yellow), sparsely foliated and exhibited profuse blooming and excessive young fruit drop. If the soil is truly calcium deficient, adding lime may increase the sugar content of the fruit. A soil analysis can determine whether the soil is deficient in calcium, as well as other nutrients. Contact a local university cooperative extension to inquire about where an analysis is available.

Friday, October 20, 2017

The Beautiful Vireya

Vireya are part of the rhododendron family, classified as a subgenus. They are native to Southeastern Asia - New Guinea, Borneo, Sumatra and the Philippines, growing quite often in the cooler mountainous areas. On the Big Island of Hawaii, vireya, also called tropical rhododendrons, are successfully grown from Volcano down to the coast.  There are about 300 species of vireya. Azaleas are part of this group.
Vireya grow well in the sun.  Yet locations of intense sunlight along with high afternoon temperatures should be avoided. In this case filtered sun is best. On the other hand, planting vireya in the shade will produce leggy shrubs with inferior flower production. No hot summer sun, no heavy shade.
It is important to plant vireya in soils and potting mixes that have excellent drainage. In addition to growing them in the soil, and sometimes in cracks and crevices, they can also be found growing as epiphytes. An epiphyte is a plant that grows upon another plant such as a tree, but is not a parasite on that tree.  The epiphyte derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it.
Vireya are well adapted for growing in pots and may even grow well indoors in a well-lit room. They come in a variety of beautiful, vibrant colors such as salmon, pinks, orange and yellows.

For those interested in learning more about vireya, join the Hawaii Chapter of the American Rhododendron Society or search to see if there is a chapter in your area.