Wednesday, November 30, 2011

Sweetness in Citrus

  Will citrus fruit get sweeter by adding potassium or lime to the soil?
Although the notion of adding potassium and/or lime to sweeten citrus fruit has been around for a long time, it has not been substantiated by scientific research.  Fruit from trees deficient in potassium are small and thin-skinned but are 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 fruit’s juice.  However, the vitamin C content increases.
If soils are truly potassium deficient, by all means apply potassium.  However, 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.

Monday, November 28, 2011

Citrus pruning

Lemon trees grow vigorously, especially the Lisbon variety. If not pruned on a regular basis they will develop a very dense canopy, allowing little light to penetrate into the interior of the tree. Under this condition, the tree will produce few interior blooms and subsequently a small amount of fruit.  In addition, pesticide sprays become ineffective because of the inability of the spray to penetrate the dense foliage.  Left unpruned, a lemon trees will also become quite tall, making picking difficult. 
Other citrus trees like orange and grapefruit are not as vigorous in their growth, and therefore do not need as much pruning as lemons. These trees can be left unpruned without serious consequences. If desired, a large tree can be pruned by simply removing a few of the interior branches to open the tree up to more light. Note: studies have shown that yields are reduced in proportion to the severity of pruning. To rejuvenate an older tree, pruning may range from moderate thinning of the canopy to heavy pruning. This pruning will stimulate a new flush of growth; however, the recovery will be temporary unless the cause of the trees decline has been corrected.
When to prune
 The timing for pruning is not critical.  After the last piece of fruit is removed for the season, is generally a good time.  Citrus like Valencia oranges and some mandarins tend to alternate bear. That is, they produce heavily one year followed by light production the next.  In this case, it would be best to prune during the ‘off’ or light year. In addition, if you have the time, it is prudent to remove the dead twigs from a tree. These harbor disease spores which, during a rain, will splash and infect nearby fruit causing the fruit to blemish. 

Friday, November 25, 2011


Inconsistent fruit production in lychee.
 When it comes to producing fruit, lychee trees, as well as longans, are very temperamental.  In order for the tree to bloom profusely, there are certain requirements that need to be met:  a combination of a dry period, usually about 4-6 weeks, along with low temperatures. The cool temperatures then need to be followed by warm weather for good fruit development. Among the many varieties of lychee, kaimana requires less cool temperatures and is therefore a good variety for warm areas.
 It is apparent that in order for lychee trees to produce well, they need a very specific climate. When this is not met, inconsistent fruit production will occur.

Monday, November 21, 2011

ALBIZIA – Beautiful tree or a true menace?

The albizia trees that quickly spring up in vacant lots or recently cleared land have become one of Hawaii’s worst invasive species. It has been called  “the tree that ate Puna”.

This albizia tree, Falcataria moluccana (it is also named Albizia falcate, A.moluccana and others), is a native to such places as Papau New Guinea, the Bismark Archipelago, and the Solomon Islands. The wood is used for light weight construction, cabinets, furniture, toys, and match sticks.
It is a fast growing tree to over 100 ft. tall. The tree can reach heights of more than 20 feet in the first year and to 60 feet by the end of ten years. It is described as a deciduous tree with wide-spreading branches, capable of shading over half an acre.  The tree produces large seed pods 4-5 inches long and about ¾ inch wide. It grows from sea level to about 3,200 feet elevation.  It is a nitrogen fixer, meaning that with the help of some bacteria residing in its roots, it can pull nitrogen out of the air and convert it to a form that roots can absorb. Because of this ability, it is used in many countries to improve soils as well as provide shade in coffee plantations.

This may make it sound like a pretty decent tree. But Dr. J.B. Friday, Extension Forester with the University of Hawaii, states “In Hawaii this tree is invasive in native`ohi`a forests as well as on land disturbed by human activities (especially bulldozing). It will causes the`ohi`a  to die off and makes it easier for other invasive species like strawberry guava, clidemia and possibly miconia to grow under it and further degrade the forest. It also improves habitat for the coqui. It is a distinct threat to our native wet lowland forest ecosystems such as there are in Puna.”

Because of their brittle wood and weak structure, these trees are an even more serious problem to homeowners. Strong winds can cause large limbs to drop onto whatever may be underneath them, causing costly damage to homes, other structures and power lines. The fragile branches often cause traffic hazards by dropping branches on the highway.

A major problem, especially in Puna, is that people sometimes hire a bulldozer to clear their land. They clear the native ohia/uluhe forest, which is somewhat resistant to albizia invasion. If they are absentee landowners, they may not return for a few years and when they donreturn, an albizia forest has sprung up. Albizia is much bigger and faster growing than ohi`a, so the native trees cannot compete. To complicate matters, there is now a source of seedpods for the alibizia to invade the neighbors' land. Dr. Friday advises not to clear the native forest on your lot unless you have another use planned for it. Otherwise albizia will come in and take over and you'll have a huge problem

What to do: Leave the natural vegetation untouched—don’t bulldoze—until you are ready to utilize the land. Eliminate albizia seedlings and small trees before they become a problem.
Methods of control:  
After trees are cut down, immediately apply herbicide to cut stumps. Triclopyr amine is effective at concentrations of 7-10%.  For larger trees near buildings it may be advisable to first contact an arborist to determine the safest and most effective course of action to take in removing the tree.

The US Forestry Service in Hilo has an excellent publication entitled “Albizia – The Tree That Ate Puna” authored by C. Sumida, F. Hughes and Kathleen Friday.   For a copy contact Veronica at or write to USDA Forest Service, Institute of Pacific Islands Foresty at 60 Nowelo St, Hilo 96720; or call at 933-8121       

 Ask the Garden Guy, Science Based Answers to Garden Questions, is an excellent resource book for gardeners. Some popular topics include Slugs and Snails, Organic Pesticides, Reasons, Why Vegetable Seeds Do Not Germinate, What’s So Hot about Manure? Mushrooms in the Lawn.  Purchase by clicking on the image of the book above.   

Friday, November 18, 2011

Macadamia nut tree

 Can I plant a macadamia nut and get a good producing tree? 
Probably not.  When buying fruit trees, including a macadamia tree, I would recommend buying a grafted, budded or air layered tree – not a seedling.  There are a few exceptions:  papayas, coffee and mangosteen are usually grown from seed.  Most citrus seedlings (perhaps 80%) will run true. But with citrus it is still a good idea to buy a tree budded onto a rootstock which is resistant to root decaying fungi.   The macadamia seedlings will grow into a nice looking tree, but most of the time the nuts will have lower oil content, and production will be poor. 

Wednesday, November 16, 2011


The leaves of tomato seedlings – as well as many other vegetables and ornamentals - are riddled with tunnels.

The tunneling is caused by the immature stage, or larval stage, of a group of insects called leafminers, which for the most part are flies (Order Diptera).   The tunnels are made as the larvae feed between the upper and lower surface of the leaf, meandering their way throughout the leaf.   Sometimes, black thread-like strips of frass (insect droppings) can be seen in the tunnels.  

In most cases, leafminer damage can be tolerated because of the several species of parasites (the good guys) which attack the larvae while they are feeding within the leaf tissue.  Many times, damage is confined to seedlings. Once they are set out in the garden, the plants tend to outgrow the pest - while the parasites take over and keep damage to a minimum.   Chemical sprays are generally not recommended because the larvae are well protected inside the leaf tissue. In addition, the spray would kill the parasites.  Some people pick off the infested leaves and discard them.  This may not be a good idea because inside those leaves many parasites are waiting to emerge to attack more leafminer larvae.

Monday, November 14, 2011


Asparagus, touted on some lists as a superfood, is low in calories and carbohydrates and rich in vitamins and minerals. Compared to other vegetables, it is relatively rich in protein.  Asparagus is an excellent source of potassium, vitamins A, C and K, riboflavin, thiamine, folic acid and vitamin B6.   Asparagus is also a very good source of dietary fiber, niacin, phosphorus, and iron and suitable for use in low-sodium diets.  
Asparagus boasts both anti-oxidant and anti-inflammatory agents as well as having antifungal and antiviral properties.  There are even claims that asparagus fights hair loss, varicose veins, high blood pressure and kidney stones.
Asparagus is in the lily family along with onions, leeks and garlic.  It is a perennial vegetable, with individual plants lasting 10 -20 years.  The mature plant looks like a small shrub with lacy, fern-like foliage.  Seed can be sown in 4 inch pots and be ready for transplant within 3 months.  A quicker method of establishing plants is to order 1-2 year old crowns from a Mainland nursery.  Mary Washington is a common variety sold, but some newer California varieties such as Apollo, Atlas and UC 157 seem to be more suited for Hawaii’s climates.

Asparagus prefers a sunny location with well-drained soil. It will not grow well in an extremely acidic soil (about pH 5.9 or less). Since asparagus does not compete well with weeds, diligent weed control is a major task. 
In areas where summers are dry and warm, like California, asparagus ferns begin turning yellow during the hot summer and will eventually die back.  Then, in the beginning of the year, the roots, actually the crown, will send forth numerous asparagus spears. These are what we harvest and eat.  If left to grow, they will become the tall, fern like leaves. 

In warm, wet climates like Hawaii, the ferns do not die back and the plants grow all year around. One method of harvesting is to cut down the entire fern plant.  Then, for approximately 4-6 weeks, harvest the subsequent spears that emerge.  After this time, allow the spears to grow into ferns. These will replenish the crown.  Then, after 5-6 months start the procedure all over again.   If you have enough plants, the procedure can be staggered to allow for year around harvesting.   An alternative method is to harvest newly emerging spears from a fully bushed plant. But at some point it is best to cut the existing fern.

When harvesting asparagus, it’s important to keep in mind that the green ferns (leaves) replenish the crown with starches (energy for the plant). Continuous harvesting will deplete the crown of starch, and the plant will produce poorly and even die.  After a period of harvesting, the plant must be allowed to grow in order to replenish the starches lost in harvest.  In fact, newly planted asparagus should not be picked for at least one year and preferably two, in order to build a healthy crown.   For more on harvest methods and other aspects of growing asparagus, check out the University of Hawaii CTAHR publication entitled, “Asparagus.” 
On the Big Island of Hawaii, asparagus plants are relatively pest free.
The following nurseries carry one or more of the California varieties Apollo, Atlas and UC157, either seed or crowns.

1. West Coast Seeds – website:; 888 804-8820.
2. Cutter Asparagus Seeds, Arbuckle, CA – website:  Tel 530 476-3647
3. Seeds of Change – website:
4. Reimer Seeds, North Carolina – website:
5. Pendleton’s Asparagus Crown - Lawrence, Kansas.  Email at; website –; Tel. 785 843-1409 . Does not ship to Hawaii.
6. California Asparagus Seed and Transplants, Inc – website:   Tel. 530 753-2437  Seeds only, minimum order.

Friday, November 11, 2011

Moss/Algae on sidewalks

After abundant rainfall, what to do about all the slippery growth on driveways and paths around the home. (often referred to as slimy blobs of olive green matter similar to what one would expect floating on a pond).
Living in the tropics, we are often plagued with unsightly and dangerous moss and algae growing on driveways and pathways around our homes.  When the rain stops, the green growth will dry up but will regenerate again with the next rain. 
There are many different products on the market to help you clean up the driveway.  Look at the active ingredients on the label; most products will contain bleach, copper, or soap. Be sure to follow the directions on the label.  Most are sprayed on, left for a while and then washed off with a hose – sometimes with the help of a shovel/scrapper.  Often times the buildup is so great that a power washer is needed. Bleach is often recommended at one cup per gallon of water. 
When using copper and bleach, there is always the potential for these products damaging desired plants either from the direct spray or from the solution entering the soil. Take caution when spraying near desirable plants. The damage is lessened in high rainfall areas through the leeching action of the rain.
Another option is to use one cup of vinegar per gallon of water; bleach is sometimes added to fortify the solution as vinegar alone may not always work.   An application of Roundup herbicide will kill the algae and moss, but the plant residue still needs to be scrapped off. 

Monday, November 7, 2011

Lychee mite

The rust like appearance on the leaves of the lychee tree is a very common occurrence.  It is not a disease but rather is caused by a tiny mite (Erinose mite) about 1/200 of an inch long. The foliage has been described as curled, distorted and galled, with a velvety brown to brownish-red appearance on the underside. These mites attack new leaves at the onset of growth flushes. 
Mites infesting young trees may cause a stunting of the tree.  At this stage, when trees are manageable, infested leaves can be removed and discarded. This will help reduce the mite population and allow the young trees to grow more vigorously. Generally as a tree becomes larger, removing infested leaves is difficult. However, mites seldom kill a tree. It’s probable that the tree will continue to be plagued with mites, but you should be able to harvest a normal crop of fruit.

Friday, November 4, 2011


 In Hawai`i, ants can be a major nuisance in and around the home.  Although they usually don’t cause serious damage, an exception might be the white footed ant that can cause electrical switch damage. There are some 40 to 45 species of ants in Hawai`i. Their feeding habits vary, ranging from sweet to greasy foods, starches and even plant and animal material. 

Ant control in and around the home requires persistence. With a few exceptions it is not necessary to know which type of ant you are dealing with. The control measures are often the same.

Physical exclusion and sanitation are the most feasible non-chemical treatments. While spraying chemicals inside the house may seem effective, it will not prevent more ants from entering the home. The reason for this is that most ants live outdoors and pesticides used indoors are short lived.  Spraying around the foundation will not provide long-term control either because only foraging ants are killed without eliminating the colony. Perimeter treatments may appear to knock down the population, but ants will quickly build back up and invade again. Instead, focus efforts on keeping ants from entering the house.
  • Caulk cracks and crevices that provide entry points.
  • Store attractive food such as sugar, syrup, honey, and pet food in closed containers.
  • Clean up grease and spills.
·        Wiping up ants with soapy water may be as effective as an insecticide spray in temporarily removing foraging ants from the home, because the soap also removes the ant’s scent trail. Some products such as window cleaners will kill ants on contact but leave no residue.

Baits are a key tool in managing ants. The key ingredients in a good bait are a toxicant (something that will kill the ants) and a materials that will attract the worker ants as they look for food. The success of the baits is dependent on a couple factors. First, the workers must be attracted to the bait. If they are not, try another brand. Once they are attracted, they will recruit other workers to it. Workers carry small portions of the bait back to the nest where it is transferred mouth-to-mouth to other workers, larvae, and queens to kill the entire colony. Second, baits must be slow-acting so that the foraging ants have time to make their way back to the nest and pass the poison on to other members of the colony before they die.  If many ants die too soon, live ants will abandon the bait area.  It may take 5-10 days before fewer ants are observed, and actually, several weeks may lapse before the entire colony is eliminated.  If ants are gone in a day, they have NOT been wiped out, they just relocated. When properly used, baits are more effective and safer than sprays.

From University of California at Irvine, here is a simple recipe for ant bait for sugar loving ants.  The bait is made of boric acid, sugar and water. Boric acid powder, specifically labeled for ants or cockroaches, can be purchased at drugstores and in retail centers. To prepare the bait solution, pour 1 cup of hot tap water into a jar. Hot water makes it easier to dissolve the sugar and boric acid. Add 8 teaspoons of sugar and 1 teaspoon of boric acid. Mix well until all solids dissolve. Mark the jar clearly that it contains poison, and store it for future use out of reach of children, in non-food containers.  Never store pesticides in common food containers like catsup or coke bottles.
For bait stations you can use small glass jars. Mark the jars clearly that they contain poison. Make a small hole in the jar lids, just enough for ants to enter. Put some cotton balls inside. They make it easier for ants to walk to the bait solution. Pour some bait solution into the jars, and soak the cotton balls.
Place the bait stations next to or on the ant trail. Avoid direct sunshine.
Every few days check and add more bait solution if needed.

You can also check out the Texas A&M University website for more recipes -  

Wednesday, November 2, 2011

Ohia lehua

Ohia or Ohia lehua (Metrosideros polymorpha)  is a slow growing tree 30-80 ft high. Beautiful red-orange, orange, pink, white or yellow flowers are produced periodically throughout the year. The flowers are popular for leis. Ohia is the official flower of the Island of Hawai`i. 

The trees are sometimes used as a windbreak or hedge plant. Ohia can grow in full sun or partial shade in a well drained soil. New leaf growth is often pink or reddish. Seeds germinate readily but do not produce trees that are true to type.  If you want an exact duplicate of the tree you have - usually for the desire flower color - new trees must be started by cuttings or airlayering.  Success with these methods is not always consistent.

 Cuttings should be soft, not having turned stiff and woody, about ¼ inch in diameter, vegetative, that is, only with leaves, no flowers,  taken from the end of the growth and approximately 4 inches in length.  Rooting hormone like Dip’n’Grow can be used.  Place cuttings in a well-drained potting mix (some recommend a media of 1 part perlite to 1 part peat moss to 1 part vermiculite) and kept moist.  The key to success is the concentration of the Dip’nGrow.  The best rooting is achieved by using Dip’nGrow at a 1:5 dilution rate (explained in the directions).

 The wood from Ohia has been used for flooring and furniture and in construction