Monday, December 18, 2017

Poinsettias are NOT Poisonous

This is the time of year many people buy poinsettias. Yet, some are concerned because they think the plants are poisonous.  Are poinsettias truly poisonous? No, this myth has been around since the early 1900’s. The American Society of Florists has been trying to dispel the myth for a long time. They say that no other commercial plant has been tested for toxicity more than the poinsettia.

According to the American Medical Association’s Handbook of Poisonous and Injurious Plants, ingestion of the poinsettia plant has been found to produce no ill effects except an occasional case of vomiting. According to the POISINDEX information source, a child who weighs 50 lbs. would have to consume over 500 leaves before he reaches a potentially toxic level. Since the taste of poinsettia leaves is reportedly unpleasant, it is unlikely that a child or animal who attempts to eat or chew the leaves, will continue to do so after the first taste. Some people, however, can develop a skin and eye irritation from contact with the milky sap of the plant.
  • Poinsettia plants prefer indirect light, six hours daily is ideal.
  • Poinsettias require daytime temperatures of 60 to 70°F and night time temperatures around 55°F for best growth; high temperatures will shorten the plant’s life.
  • Standing water can be harmful for the plant. Remove any wrappings from around the pot or at least punch holes in the foil so water can drain into a saucer; discard excess water. 

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.

Wednesday, September 20, 2017

Basil - a Great Aromatic Herb

Basil is a member of the mint family and is one of the world’s most popular herbs.   In colder climates it is generally grown as an annual, but in Hawai`i   can be grown as a perennial.  After flowering, when seeds have matured, basils will stop producing new leaves.  To ensure continued growth, cut off any flower buds that begin to form. Be sure to cut the branch rather than just the tips, otherwise, new flower buds will quickly appear.  By pruning basil often (every 3-4 weeks), plans remain vigorous with many harvests throughout the season. 

Sweet basil is the variety most widely grown on the Islands, but there is also Thai basil, lemon basil, cinnamon basil and royal basil.  Basil prefers a sunny location with a well-drained soil.  Typically, the best time to harvest basil is in the morning when the essential oils are strongest. However, University of Michigan researchers have found that harvesting basil in the evening between 6 and 10 p.m. increases its shelf life.

This aromatic herb can be used in soups, stews, and rice dishes, and with fish, chicken, and other meat. It can also be a key ingredient in cheeses, vinegars, oils, jellies and teas.  Even basil's flowers are edible and can be candied or added to salads and other dishes. For optimum flavor, add fresh basil in the last few minutes of cooking; the dried spice just doesn’t have the same robust flavor as the fresh.

Cooks often notice that fresh basil will quickly turn black.  This is due to oxidation of some elements in the leaves. To prevent this blackening and insure the best flavor, add basil to salads and other cold dishes soon after cutting. 

Pests – Basil is often grown with few or no pests.  But some of the more common problems encountered are thrips, leafhoppers, whitefly, spittlebug, scale and leafminers.  Insect pests that would be causing chewing damage to the leaves include the Chinese rose beetle, beet armyworm, a pinkwinged grasshopper and flea beetles.  If you see worms (caterpillars), pick them off, or you can spray the plant with an insecticide with the active ingredient, Bacillus Thuringiensis (Dipel, Javelin). Bt is an organic, bacterial preparation which will control the caterpillar but is harmless to humans.  

Thursday, September 7, 2017

Japanese Maple in the Tropics

Being a deciduous tree, the Japanese maple is indeed adapted for cold climates. Hawaii, as well as other tropical locations, does not provide the best growing environment; yet the trees will grow in these areas. I have one Japanese maple that is now 9 years old. Admittedly, it is not the most vigorous tree, and I think it is continually looking for winter. Sometimes it goes dormant in spring or even in the middle of summer, but it still grows. A question might be, how many years can it survive without experiencing a dormant period?

There are over 1000 cultivars of Japanese maple. Obviously some will adapt to tropical regions better than others. Usually, nurseries select those varieties best suited for their area.

Regardless of the climate, another problem is an insect called Chinese rose beetle. This beetle makes holes in the leaves weakening the tree. 

In the evening, when beetles are feeding, placing a cover or netting over the small trees will exclude the pest. Another choice for control is to use a systemic insecticide with the active ingredient imidacloprid. Granules can be applied to the pots and watered in. 

On this website, I have a detailed report on this pest; search Chinese rose beetle in the space on the left of the screen.

Saturday, August 19, 2017

Trouble with Palms

"The bottom fronds of our triangle palm started to die, and then suddenly the whole palm fell over," a friend complained.
A significant pest of Pritchardia palms is the banana moth, Opogona sacchari. The triangle palm is also attacked by this moth. It seems that the female moth targets wounded or stressed palm tissue to lay her eggs. Stresses can include drought, flooding, mechanical wounding, poor nutrition, and herbicide injury. The larvae generally feed on decaying and dead plant tissue but will feed on living tissue, too, causing extensive damage. In affected palms, larval tunneling, along with the characteristic frass (insect droppings), can often be seen. Fully developed caterpillars measure just over an inch. The adults have greyish brown wings are 3/8 to 5/8 inches long.

The main treatment is prevention: keep palms growing well; give them adequate fertilizer, and supplemental water during a drought. Gardeners also need to be careful with the weed wacker! Female moths are looking for wounds to lay their eggs. Bt (Bacillus thuringiensis), an organic insecticide, can be applied to these wounds, as well as those caused during pruning.

For more information about this pest see the CTAHR Cooperative Extension Service publication, “Banana Moth – A Potentially Fatal Pest of Pritchardia and Other Palms”, by Scot Nelson and Mark Wright.  CTAHR stands for the College of Tropical Agriculture and Human Resources at the University of Hawaii. 

Thursday, July 20, 2017

Ohia Trees (Metrosideros sp)

There are four distinct species of ohia tree that are endemic to Hawaii. In addition to genetic differences, environmental factors will cause physical variations in the trees. Elevation, rain, and temperature all have an effect upon these trees. 
In general, the shapes of leaves from trees growing in hot, dry deserts are often small in order to conserve water loss through the leaf. Contrast this to the large-leafed plants of the tropics. Ohias occur in a wide range of habitats, from just above sea level to 8,200 feet: from dry forests with less than 16 in annual rainfall to wet forests with more than 33 feet of annual rainfall. This along with its genetic propensity for variation will produce trees of diverse appearance. The species name, polymorpha which actually means many forms has eight varieties. Thus tree height and form, leaf shape and flower color are highly variable.
Concerning the care, ohia trees can be damaged and even killed from a lack of water. During periods of drought especially, supplemental watering will be needed. Trees growing in the pahoehoe lava (exhibiting a smooth, billowy, ropy surface) may do well when young and water requirements are low. Nevertheless, as trees increase in size, if adequate water is not supplied, they can dry out and even die.  Mulch will help, but of course, not piled against the trunk.

Since ohias are adapted to grow in low nutrient soils, beware of over-fertilizing. Slow-release fertilizers or natural compost is best. 

Tuesday, July 4, 2017

Start a Garden

Here are some fundamental points to help along the way: 

·      Plant only as large a garden as you can easily maintain. Don’t over plant and become overwhelmed with the many garden chores: weeding, planting, pest control, soil preparation. 

·      Choose recommended varieties for your region. Midwest and Eastern US seed catalogs, with pictures of giant tomatoes are fine, but those varieties are not necessarily adapted for a tropical climate. University of Hawaii CTAHR seed program develops and sells vegetable seeds suitable for the Hawaiian Islands.

·      Consider locating the garden within easy walking distance to your house in order to carry tools there and eventually return with baskets of produce. 

·      Select a site that receives at least 8 hours of full sun each day.  Plant vegetables where they are not shaded by trees, walls or fences. Nearby trees and shrubs with roots reaching into the garden will compete with the vegetables for water and nutrients.

·      For those with minimal space, grow crops that produce the maximum amount of food for the area available.  You can harvest a lot of radishes, onions, lettuce, bok choy and tomatoes in a small plot.  Plants like pineapple, watermelon and pumpkin squash take up lots of space for what is harvested.  In addition, consider planting vegetables that can be grown vertically instead of horizontally. Vining crops such as tomatoes, squash, cucumbers and pole beans can be trellised or staked to minimize ground space and increase garden productivity.

·      Plant perennial vegetables such as rhubarb and asparagus to one side of the garden so they are not disturbed as you prepare the ground for subsequent annual crops.

·      And finally, try succession planting. A crop like indeterminate tomatoes can be harvested over a long period of time; one planting will last for many months. With other crops like corn, beets and lettuce, the entire crop will mature at approximately the same time. Unless you want to eat all your corn in a short period of time, stagger the plantings at 2-3 week intervals, or more. Read more about growing vegetables by clicking on the column on the right.