Monday, February 23, 2015

Propagating Plumaria Trees

Plumaria trees can be propagated from cuttings, normally 1-2 feet long. This method preserves the characteristics of the selected cultivar. Before placing the cutting in the ground, they need to “cure” in a dry place for at least two weeks. Then, it is important to plant them in a well-drained soil; they may also be planted in a pot. Although not required, treating the base of the cutting with a rooting compound (0.3% indolebutyric acid) will enhance rooting.  

Plumeria can also be propagated from seeds collected from the tree. It is interesting to note that seeds from trees with white flowers produce mostly white-flowered seedlings; dark red will produce red, and yellow will produce yellow. On the other hand, pinks and multicolored plants will produce a range of colors in their seedlings.

Plumeria blooms can easily be strung into a fragrant flower necklace known as a "lei" in Hawaii.

Monday, February 16, 2015

Onions, Pungent or Mild

Sulfur is an essential element required by onions. But high levels of sulfur in the soil can contribute to pungency, that is, a strong flavor. The compound responsible for this is called allyl propyl disulfide. Furthermore, the term sweet, when referring to onions, is a misnomer.  Mild is the correct description for onions with low pungency.

Growing onions in high sulfur soils can give them a pungent flavor. In Central America, "sweet" onions for export are not grown on soils that have sulfur levels above 18 ppm (parts per million). Yet, for the average gardener, it is not realistic, or even necessary, to treat the soil in order to lower the sulfur content.  In most soils, sulfates move well in the soil profile. Since onions are a shallow rooted crop, it is easy for the sulfate to move below the root zone of onions.

What is practical is to eliminate or limit the application of sulfur fertilizers. Definitely do not apply them after bulbs begin to form. As long as high levels of sulfur are not applied, pungency should not be an issue.

Constant applications of large amounts of organic matter (OM), especially manures, can potentially increase the sulfur content of the soil. Though with ample rainfall, excesses should be leeched beyond the onion roots. 

In addition to sulfur in the soil, pungency or the strong flavor in onions can also develop when growing at high temperatures. Twice as much pungency may be expected when the temperature is 90°F compared to 50°F at the time the bulbs form. This increase may be due to a greater uptake of sulfur because of the higher temperatures. Pungency also rises under dry growing conditions.
Attention Big Island Residents: I will be teaching a class, Vegetables in the Home Garden, on Saturday, February 21, 9:30AM -12:30PM at UH-Hilo Campus. Call 974-7664 to register; there is a fee. 

Tuesday, February 10, 2015

Growing Gladiolus in the Tropics

    Gladiolus produce enjoyable blooms and are relatively easy to grow. The plants require well-drained soils in a sunny location. Bulbs, actually a corm, which are 1 1/2 to 2 inches in diameter, will produce full, attractive flower spikes. Small corms produce foliage but may not bloom. Planting depth varies with the size of the corms. Large corms should be planted 4 to 6 inches deep and 6 inches apart. Small corms should be planted at a depth of 3 inches and about 2 inches apart. A general rule of thumb is plant deeper in sandy soils and shallower in heavy soils. Supporting the flower stem may be required in windy areas and in rocky soils where it is difficult to dig a deep hole.

Unfortunately, gladiolus blooms can be plagued with thrips. These are tiny, slender black insects, often difficult to see with the naked eye. They will cause white streaking on the blooms as well as the leaves. Flowers can also become misshapen and discolored.

Note: These insects are the culprits which also cause silvery to brownish scarring on the surface of avocado and citrus fruit. This damage, however, does not harm the internal fruit quality and is strictly cosmetic.

To save the bulbs for next year’s planting, they can be dug up at the end of the season, cleaned off and stored in a dry, cool place. Pack bulbs in dry peat moss or wood shavings in a brown paper bag or cardboard box.   In high rainfall areas, bulbs that are kept in the ground are susceptible to rot. Sometimes it is just better to buy new bulbs each year.

Certain hardy, spring flowering bulbs like tulips and hyacinth generally require a chilling period in order to produce blooms. When these bulbs are grown in mild winter climates, a 6-8 week chilling period in the refrigerator is required.

Planting bulbs in large containers is also a good idea. Containers will provide good drainage and the bulbs are easily planted and dug up. And, if need be, containers can easily be moved out of the rain.  

Attention Big Island Residents: I will be teaching a class, Vegetables in the Home Garden, on Saturday, February 21, 9:30AM -12:30PM at UH-Hilo Campus. Call 974-7664 to register; there is a fee.