Monday, September 29, 2014

Passionfruit - Hawaii’s Favorite Flavor

The yellow passionfruit, Passiflora edulis f. flavicarpa, and the purple passionfruit, Passiflora edulis, are grown in most tropical and subtropical parts of the world. The yellow passionfruit is a tropical plant while the purple is considered subtropical, being able to survive some freezing temperatures.

Of the hundreds of species in the genus Passiflora, these two, P. edulis, and P. edulis f. flavicarpa, are solely designated as passionfruit.  In Hawaiian, the fruit is called lilikoi and in Portuguese, maracuja peroba.  When the seeds of purple passionfruit first came to Hawai`i from Australia in 1880, they were planted in East Maui in the District of Lilikoi and that name stayed with the fruit. The seeds of the yellow passionfruit were brought to Hawai`i from Australia in 1923. 

In 1951, there were only a few acres of passionfruit plantings. It was then that the University of Hawai`i chose passionfruit as the most promising crop for development. And by 1958, there were 1,200 acres of primarily yellow passionfruit, and the industry was firmly established.

The lilikoi vine is a shallow rooted perennial, displaying beautiful, fragrant flowers, 2-3 inches wide. The fruit is nearly round approximately 1 ½ - 3 inches wide.  Inside, the fruit is filled with an aromatic mass of juicy pulp and within are as many as 250 small, edible seeds.  These vines, especially the yellow, are fast-growing and will begin to bear in 1 to 3 years. In fact, some vines can flower and fruit within a year after being started from seed. In Hawai`i, passionfruit matures from June through January; the ripe fruit will fall to the ground.

Carpenter bees are efficient pollinators for the yellow passionfruit. Honey bees and the hover fly also help in pollinating but are much less efficient. Wind is ineffective as a pollinator because of the heaviness and stickiness of the pollen.

The yellow lilikoi vine tends to be more vigorous and the fruit generally larger than the purple. While the purple appears to grow better at higher elevations, 400 to 3,000 feet, the yellow fruit is best adapted to lower elevations, from sea level to 1,500 feet. Furthermore, the yellow will yield 3 to 4 times that of the purple, yet the purple fruit is considered to have better flavor and aroma with the pulp being less acid with a higher proportion of juice.

Passionfruit vines are usually grown from seeds.  If the seeds are planted soon after being removed from mature fruit, most will germinate in 2 to 3 weeks. Fortunately, seeds do not require cleaning, drying or storage. They can be planted immediately after being removed from the fruit, even separation from the pulp is not necessary. In fact, allowing the pulp to ferment for a few days may hasten germination. In contrast, seeds that have been cleaned and stored actually have a lower and slower rate of germination. 

Propagation of passionfruit can also be accomplished through air layering and cuttings. Good soil drainage is essential for successful plantings.

Commercially, vines are trained on wire trellises. For backyard production, however, the yellow passionfruit is more productive and less subject to pests and diseases if allowed to climb a tall tree.

In Hawai`i, Oriental and melon fruitflies will deposit eggs in young fruit. This may cause fruit to shrivel and fall from the vine. If older fruit is pierced, the only ill effects will be an external scar. Other pests include aphids, scale, thrips and mites. In spite of all these, passionfruit or lillikoi vines flourish on fences and in trees, in backyards and vacant lots around the Islands.

The juice with its distinct flavor and aromatic bouquet is a key ingredient in making sauce, candy, ice cream, sherbet,  iced tea, or in cocktails.  In the Hawaiian Islands lillikoi is a favorite flavor enjoyed by young and old alike. 

Photos  by Forest and Kim Starr

Monday, September 15, 2014

Ways of Adding Phosphorous to the Soil

 Primary nutrients of plants include nitrogen, phosphorus and potassium; they are the ones indicated on each fertilizer package. For example, 5-10-15 printed on the label signifies that the fertilizer contains 5% nitrogen, 10% phosphorus and 15% potassium.

Many soils are deficient in phosphorus, especially those red Hawaiian soils high in iron and aluminum oxides.  When growing vegetables, or any annual crop, phosphorus can be incorporated into the soil before the crop is planted. It can also be incorporated before trees and shrubs are planted. The difficulty comes when attempting to apply a phosphate fertilizer to an established tree or shrub with existing roots already deep in the soil.

In contrast to nitrogen fertilizers which are water soluble and move well in the soil, phosphate fertilizers do not move well. In fact, years after a surface application of a phosphate fertilizer, the majority of the phosphorus will still remain near the soil surface. How then can a phosphate fertilizer be applied and penetrate down to the roots of mature trees?   Here are some better ways of applying a phosphate fertilizer to existing plants

1. Remove a core of soil at the drip line of the tree, at the four corners, 1 – 2 feet deep. Cores can also be removed going around the drip line of the tree in a circular manner. Apply a measured amount of phosphate fertilizer to these holes, either dry and mixed with soil, or in a water solution.  Ammonium polyphosphate is especially good. Admittedly, this involves a good deal of labor when treating many trees. 

2. Similarly, fertilizer spikes, although expensive, can be placed in the ground around the drip line. In both cases, roots will gradually gravitate to the higher nutrient content and flourish.

3.  Foliar applications of a phosphate fertilizers do not work well. Frequent applications of 3-4 times per year, however, can potentially meet the trees requirement.

4. Perhaps the best alternative in improving phosphate availability and movement into the soil is to apply it in its organic form; for example, manures, fish meal and blood meal. Likewise, adding organic mulch is beneficial. As the organic material breaks down, the end product is humus. Humus is loaded with negatively charges sites that are able to hold onto positively charged plant nutrients such as potassium, calcium, magnesium, manganese and iron. Keeping the tree under a bed of mulch will supply a small but constant supply of various essential nutrients.  Roots will eventually grow into the mulched area and proliferate, picking up essential nutrients. In addition, because of the abundance of new surface roots in this area, it now becomes an ideal place to apply a phosphate fertilizer.  

Monday, September 8, 2014

Coconut Palms Bearing Fruit

When can I expect my coconut palms to begin to produce? 

In general, coconut palms will flower in 4 - 6 years. They may not actually produce fruit, however, until they are 6 – 10 years old. And if growing conditions are unfavorable, they may not bear until they reach 15 – 20 years of age. Full production is at 15 -20; they can potentially produce until they are about 80 years old.

Although coconut palms are tolerant of dry soil conditions, for optimum fruit production regular irrigation is recommended, especially during drought conditions. Palms can also endure temporary waterlogged soil conditions. Yet they will decline and even die when exposed to prolonged periods of wet, poorly drained soils. Coconut palms will tolerate saline water and soils, as well as salt spray, but this does not mean they prefer it.

Coconut palms respond to applications of a balanced fertilizer, such as
10-10-30. Organic mulch and fertilizers are good and highly recommended.

Monday, September 1, 2014

Controlling Broadleaf Weeds in Grass

Controlling a grassy weed in a lawn (grass) is difficult since most chemicals cannot distinguish between good and bad grass species. Fortunately, certain herbicides can distinguish between grassy plants and broadleaves. It is the chemical composition of the herbicide and the morphology of the plant that will cause certain herbicides to affect broadleaf plants but not affect grasses. Therefore, controlling broadleaf weeds in a grassy environment is relatively easy. Purchase an herbicide with the active ingredient 2,4-D, MCPP (mecoprop), or dicamba (Banvel). These products are often sold in combination, giving better management and a wider spectrum of the broadleaf weeds controlled.

For light weed infestations, spot treating is more appropriate than treating the entire lawn. Apply just enough of the solution to wet the leaf, do not apply to the point that the herbicide is dripping off the leaf. To insure maximum absorption, stop mowing 2 or 3 days before treatment and allow 3 or 4 days before mowing again. This allows sufficient time for the weeds to absorb the herbicide and transport it to their roots.
Caution: these materials are volitle, espectially 2,4-D. The drift can damage other valued broadleaf plants; tomatoes and hibiscus are particularly sensitive.

Controlling weeds however, should begin long before chemical herbicide applications are considered. Cultural measures ought to be employed from the beginning. These include: 
  • Proper irrigation -  weeds often invade lawns that are either over-watered or under-watered. Perhaps the worst possible irrigation schedule, yet common, is daily watering for 5–10 minutes. Light, frequent irrigation creates a shallow-rooted lawn which is more susceptible to weed invasion, as well as being less tolerant to drought.  In dry areas, where irrigation is employed, water should penetrate to a depth of 6 to 8 inches. The best practice is to allow the soil to partially dry out between irrigation. The top 1 to 2 inches  should be fairly dry before watering again. For more information on irrigating lawns, see UH CTAHR publication, “Watering Lawns”, at

  • Proper fertilization – apply suitable amounts of fertilizer on a regular basis; nitrogen is the key nutrient for turf.
  • Proper mowing heights – each turfgrass species has an appropriate mowing height. Mowing some grasses too short can weaken the lawn and predispose it to weed invasion.  A typical guide is to remove no more than one-third of the leaf blade at each mowing. If too much is removed, it will take more time for the grass to recover, giving weeds a chance to invade.
  • Thatch is a layer of organic matter - stems, stolons, roots - that develops between the turfgrass blades and the soil surface. Regular thatch removal will help keep turfgrass healthy and competitive with weeds.  For Hawaii residents, see the UH CTAHR publication “Removing Thatch from your Lawn” for more information on this procedure.
  • Any activities that lead to soil compaction will contribute significantly to turfgrass stress. This in turn, will make it easier for weeds to invade. These activities may include heavy foot traffic as well as vehicles traveling over the area.

It is very impossible to get 100% weed control in your lawn. Weeds will occur, but the problems can be minimized with a well-managed, vigorously growing lawn. By combining cultural methods with herbicide applications when needed, weeds will  be minimized.