Will roses bloom on Big Island?


I come from Northern California where I grew beautiful roses. The climate in Hawaii is so much warmer, I am wondering if I can still grow good roses in the tropics. Thanks for your help, enjoy your column.

Roses indeed are associated with cool climates like San Francisco, Portland and even England. They will, however, do well in a variety of climates here in Hawaii.

The early missionaries brought the old-fashioned type roses to the islands. Roses can flower throughout the year in the warmer, sea level climates. They can also be in continuous bloom in the cooler mauka (mountain) communities.

In order to reap the benefit of these beautiful flowers, some care must be invested when growing and maintaining the plants.

Here are a few essential points to consider:

— Roses require at least six hours of sun each day, well-drained soil, and adequate protection from strong, continuous winds. Rose bushes grown with less sunlight than six hours will tend to be tall and leggy with fewer blossoms.

— Roses will benefit from mulch, at least four to six inches. This reduces the temperature of the root environment, helps to control weeds, supplies nutrients to the ground and improves the physical characteristics of the soil. A fertilization program should be guided by a soil analysis.

For more information on nutrition and other rose topics, contact the University of Hawaii College of Tropical Agriculture and Human Resources Office. An old, but good publication, “Rose Growing in Hawaii,” is available online.

When growing roses, they will not be free of pests.

Rose beetles are a frequent and serious pest of roses. These critters come out after sunset and chew on the leaves. Tiny spider mites, aphids, thrips and grasshoppers will also trouble the plants.

Diseases like powdery mildew, black spot and rust are common.

The rust appears on the underside of the leave as powdery pustules of bright orange spores.

For more information on pests and diseases in the garden, visit my website at gardenguyhawaii.com

Aloha, Nick: I had a nice crop of tomatoes this year, but when I harvested them they were not ripe at the top. The top part was usually yellow while the rest was nice and red. I’ve left some on the vine hoping that this area would eventually turn red, but it doesn’t.

Your tomatoes have a physiological disorder called yellow shoulder, also known as green shoulder. As you described, it is when the stem end of a tomato, known as the shoulder, remains green or yellow, and even whitish, while the rest of the fruit ripens. The shoulder area may also be noticeably harder than the rest of the fruit.

Here are three potential causes:

1. Environmental: The disorder can occur when high temperatures, above 90 F, remain for a prolonged period and the fruit receives too much direct sun exposure.

2. Nutritional: It can be triggered by insufficient potassium and a soil pH above 6.7.

3. Varietal: Because many hybrid tomatoes have been bred to alleviate this problem, the newer hybrid varieties are less prone to the yellow shoulder disorder. Unfortunately the problem is prevalent in the heirloom varieties.

Switching to another variety is one solution. If needed, apply additional potassium. Creating some partial shade cover during hot weather will also help.

Letting the fruit hang longer on the vine in order for the fruit to color will not help and can increase the potential for rot.

What do the numbers on a fertilizer package mean?

All fertilizer packages have three numbers printed on them, for example, 10-15-5. These numbers represent the percentage of the three primary plant nutrients — nitrogen, phosphorus and potassium. In this example, the fertilizer would contain 10 percent nitrogen, 15 percent phosphorus and 5 percent potassium. This is important since various plants and different situations require distinct types of fertilizer.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net.

 

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