Have gardening tips to share?

If you're gardening in the Kohala Ranch area, give us your words of wisdom.  With your help, this page will grow.  And if you’re willing to field questions from other residents, include your contact information.  (Be sure to include what location you’re referring to, since conditions can be quite different at different elevations.)

You can email us at

Other sources of information

You can find information on many of the topics below by contacting the University of Hawaii Cooperative Extension Service.  (If you get a blank screen, scroll down, and the page should appear.)

The Extension Service's Master Gardener program is designed to answer questions from the general public.  For current phone numbers for the master gardeners, look in the State Government section at the front of the phone book, under University of Hawaii at Manoa, College of Tropical Agriculture & Human Resources.

If that doesn't get you the answer you need, you can search the University's horticultural database for information on specific plants and, if you don't find the answer to your question, ask it there.

The University also has write-ups on various insect pests and landcaping issues, as well as livestock management.  The Extension Service website has information on the commoner pests here.

Of course there are many, many websites with useful information.  A great source of gardening lore is, which includes input from gardeners all over the world.  They also have a free newsletter you can sign up for. is a handy source of information on the cultivation needs of many different plants.


A lot of plants will do well at Kohala Ranch, but some require much more water than others.  So we’re especially interested to hear about plants that do well with little water, and in the face of strong and drying winds.

Because of our mild climate, we’re also interested in plants that flower year-round, or at least have long blooming periods.


The County of Hawaii provides free mulch at their facility in Kona.  It's next to the recycling area to the east of the police station.  There are loaders there that will deposit the material into your truck.  You can also drop off trimmings you want to get rid of. 

The University of Hawaii has a soil testing service which can advise you as to what you need to do to correct pH or nutrient deficiencies.  For more information, click here.  The charge for this service depends on what kind of analysis you need. 

One family that imported cinder soil from a dealer in Kona found that it allowed the irrigation water to vanish too quickly, leaving little evidence of it's passing.  They had previously purchased topsoil that seemed to form a hard crust, which they didn’t like; now they wish they could get some more of it.  

Unfortunately, they can no longer find that company, and they are experimenting with taking apart diapers and putting the absorbant material into the hole with what they're planrting.  You can buy something specifically made for that at gardening stores, but it’s quite expensive.


The salinity of Kohala Ranch water is higher than you might be used to elsewhere and, though that may be good for some plants, it's borderline for the tolerance of certain salt-sensitive plants.  In addition, because of the dry conditions here, and the extensive use of drip irrigation, salt may build up in the soil.  If you suspect a problem, try giving the area a good soaking to push the minerals down below the root zone.

You might want to consider fertigation (or chemigation).  This involves adding fertilizer, pesticides, etc. to the water supply.  It reduces the amount of chemicals you have to use, increases nutrient absorption and, because an increased root mass allows the plants to trap and hold more water, it reduces irrigation requirments.

Resident Michael Wald is using the system and says it has so far reduced his water usage by 15%.  You can reach him at 882-4440 if you want to discuss it with him. 

Netafim irrigation lines have emitters built in at one foot intervals.  One user reports that after a year or two, many of the emitters have stopped emitting, and others seem more sluggish than they should be.   

This problem may result from not flushing out the filter at the beginning of the line, which should be done regularly.  In any case, it's possible to punch holes in the line and insert emitters designed for the black drip irrigation systems. Conversely, Netafim accessories can be used in the black lines, and may be both superior and cheaper.


One you’ve got everything set up properly, the biggest threats to your plants are insects.

If you’re growing fruits – which includes "vegetables" that contain seeds – fruit flies are a big worry, and are hard to control.  These are not the little Drosophila flies, or vinegar flies, that hover around ripe fruit on the ground or on your kitchen counter.  Those are annoying but cause little damage.

The real problem in Hawaii is a group of related large flies called the Mediterranean fruit fly, the Oriental fruit fly, the melon fly, and the Malaysian fruit fly, which lay their eggs in the fruit while it is still on the plant. The larvae can quickly ruin your crop.  To see photos of these flies and get information on control efforts, click here.  (You can get to the same site through the University Extension link above, but it's harder to find.)

Stink bugs will puncture your tomatoes and drink the juice, but the damage is more aesthetic and psychological (the yuk factor) than anything else.

Chinese beetles will eat holes in the leaves of your plants.

If your banana trees don't look quite right, it could be banana bunchy top.  You may have noticed signs around Kona announcing a banana quarantine area, and bunchy top is why.

If your dog is taking naps in your flower beds, try throwing in coffee grounds.  We have limited data on the effectiveness of this approach, but it seems as though it may work.  Presumably this could eventually change the pH of the soil, so that might be something to watch for.

Of course there are many other pests and things that can go wrong, but there's also a lot of help available.  See the section on sources of information near the beginning of this page.  And rememer, there's always good ol' Google.

Specific plants

Seed sources

The University of Hawaii sells seeds adapted to Hawaii conditions.  For availability and prices, click here.  There’s a link there to the order form.  Most of the packets cost $1, though a few are $3.

Perpetual bloomers  

Madagascar periwinkle (Catharanthus roseus or Vinca rosea) – small bush; sun or part shade; white, 
pink and red varieties; moderate water.
Bougainvillea - the flowers don’t last long, but the colorful bracts that most people take for petals are 
Non-deciduous plumerias (Plumeria pudica and Plumeria obtusa); may be less fragrant than other types.

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Kabocha squash grows as though it’s in the Little Shop of Horrors, and suffers only minor insect damage.

Spinach doesn’t do well in hot climates, but a reasonable substitute is vine (aka climbing, aka Indian, aka Ceylon, aka Malabar) spinach.  The Latin binomial is Basella alba (white Basella).  For more color, you might want to try the red-stemmed variety, Basella alba var. rubra (red white Basella).  In our estimation it gives a better approximation to real spinach if used as a potherb than served raw in salads. 

Another spinach substitute is the heat-, salt- and pest-resistant New Zealand spinach, a slightly fuzzy relative of ice plant.  Despite its kiwi name, the Maori rarely ate it, according to Wikipedia.  But Captain Cook took it on the Endeavour to help ward off scurvy.  Wikipedia also says you should blanch it for one minute in hot water and then rinse it, to remove the oxalate.

Taro makes a good spinach substitute, but the jury is still out on how well dry-land taro will grow in the Kohala Ranch area.

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Difficult plants  

Avocados need good wind protection, can be damaged by too much inorganic fertilizer when young, and need good drainage.

A lot of orchids will not do well in the lower portions of  Kohala Ranch.

Watch out for invasive roots on Schefflera and on Ficus trees – they may get into your sewage and irrigation systems.      [expand this item & this section]

Invasive plants

Invasive roots are covered in the preceding section.  For a surprising list of plants considered invasive by the Hawaii State Alien Species Coordinator, click here.  The State requests the public's cooperation in stopping the spread of these plants, but many of them are available at local nurseries, and several are recommended in an appendix to the Kohala Ranch Design Guidelines.   A lot of the species seem unlikely to run rampant in a dry place like Kohala Ranch.  Of course, animals may distribute the seeds to nearby environments that are more hospitable to them.

Lantana is on the list and, in fact, grows as an invasive weed at Kohala Ranch.  But it’s possible to buy sterile hybrids in a variety of colors, and these are not a problem.  The ivy gourd vine that is smothering so many other plants in Kona has been spread to Kohala Ranch by birds, and should be pulled up when you find it.  

Animals that impact humans directly

When you bring a plant into Kohala Ranch, please check it carefully for coqui frogs or their eggs.  Adult frogs are less than an inch in length.  The eggs, which transition from white to pinkish to greyish to black, are 3 to 6 mm in size, so the new hatchlings are tiny. The males of these frogs make such a racket that they disrupt people’s sleep and, in some locations, their populations can increase to an incredible density.  For information on how to distinguish the coqui from the more benign greenhouse frog, and for methods of control, click here.  If you hear a coqui, please report it ASAP to the property manager or a member of the maintenance staff.

The stinging nettle caterpillar is not dangerous, but a touch from its spines is painful, and it has reached West Hawaii.  Eventually it will get to Kohala Ranch.  If you leave outside lights on all night, you might want to rethink that, since they will attract  the adults of these moths as well as many other insects.

The adult is a small brown moth with a curving white line near the tip of each wing.  It usually lays its eggs on monocots (grasses, palms, lilies, orchids, bananas, etc.).  Once the moths have reached our area, you may want to take precautions when working around such plants - or any plants.  Watch where you put your hands and/or wear good gloves.   Some horses have been stung on the face while grazing, and it’s suspected that, when eaten by a pregnant mare, they could cause her to abort.    

The good news is that a helpful parasitic wasp may be released soon.

But there’s no good news regarding the little red fire ant, which is also headed this way and, though only 1/16” long, can blind pets and livestock by stinging them in the eyes. They can get onto you from any vegetation, even falling on you from trees.

If you find either of these pests, call 323-7594, 322-2484 ext 103, or 974-4140.  Don’t try to poison the ants until the experts have assessed their distribution. (The larger tropical fire ant has an irritating sting but is much less harmful.)

A rare parasitic disease may be on the rise in Hawaii, though not yet in our area.  Rat lungworm is a type of nematode that can be transferred from rats to snails and slugs.  The latter may be small enough to escape notice on raw fruits and vegetables.  Ingestion by humans may not cause any symptoms, but one Hilo resident ended up in a coma.  The worms typically die out within a few weeks, but in the meantime they are capable of causing great pain, so be sure to thoroughly inspect and rinse raw produce.  More at rat lungworm.