By Russell T. Nagata
University of Hawaii at Manoa College of Tropical Agriculture and Human Resources Komohana Research and Extension Center, Hilo
Here in Hawaii, summer squash (Cucurbita pepo) can be grown year round and enjoyed every day of the year. When we talk about summer squashes, we are referring to squash with thin skins and tender fleshy fruit which are harvested and eaten in the immature stage. Due to the immature stage of fruit development, post-harvest storage life is short. Summer squashes are differentiated from the winter squashes, also Cucurbita pepo by the aforementioned characteristics.
The winter squashes are harvested mature, have a tough skin, and store very well. The most common types of summer squash grown in Hawaii are zucchini, crook neck, straight neck and scallop. Zucchini commonly has a smooth, green skin with a torpedo shape. Those with light green stripes are referred to as cocozelle or Italian zucchini. Golden or yellow types are also common, as well as those with round, ball-shaped fruit. The crook and straight neck squashes are yellow or golden in color with slight bumps on the fruit surface. The crook and straight neck refers to the portion of the fruit right below the stem and is self-explanatory. The scallop or patty pan squashes resembles a flying saucer with scalloped edges and is normally whitish green or yellow in color.
The cucurbita squashes are native to the Americas and were used extensively as food by early American natives. Explorers to the America’s transported seeds to Europe, where the squashes were quickly accepted. As European immigrants made their way to the Americas, they reintroduced the various forms of summer squashes.
Summer squash is a relatively easy crop to grow in Hawaii. Squashes prefer areas with plenty of sunlight and well-drained soil that is medium-textured with a slightly acidic to neutral pH. Higher levels of soil organic matter can improve soil condition and favor better plant growth. Prepare your garden bed by loosening the soil to a depth of 8 to 10 inches. Preplant fertilizer application of 1-1.5 pound 10-30-10 per 100 square feet of garden should be placed in a band 2-3 inches to one side of the plant row and 2 inches deep. Four weeks after sowing, a second application of 1-1.5 pounds of 10-30-10 should be applied as a sidedress application. To prolong plant vigor and harvest, an additional side dressing of nitrogen fertilizer after the first harvest should be made. Summer squash enjoy good soil moisture, but not water-logged soils.
Insect and disease control is critical for the success in growing summer squash. Fruit flies, pickle worms, leaf miner, aphids and mites can be a problem and prevent a successful harvest. Common diseases of squash in Hawaii are powdery mildew, various viruses and damping off of young seedlings. Powdery mildew can be managed by various treatments, including both organic and conventional chemical methods. Squash plants infected by viruses can only be controlled by the elimination of infected plants. Other virus management procedures to prevent virus infection involve control of alternate host plants that harbor the virus and serves as a virus reservoir, control of insect vectors such as aphids, and by growing virus resistant cultivars.
Since squash is a monecious species with male and female flowers on the same plant, the presence of insect pollinators to transfer pollen to the female flower is critical for proper fruit development. In the absence of insect pollinators, you the gardener need to do the work of the pollinator early in the morning. When applying pesticides, it is very important not to injure your insect pollinators while controlling other insects. It is critical to read any pesticide’s label carefully and follow label directions. Pesticide can only be used on crops listed on the label.
Summer squash is harvested young when the fruit is still soft. It is best to use a sharp knife to cut fruit from the stem, as breaking fruit from the stem may leave a rough wound from which opportunistic diseases could enter. Fruits have a thin skin and will desiccate rapidly upon harvesting. After harvesting, quickly clean fruit and use immediately or store for later use.
For more information on this and other gardening topics, please visit the CTAHR electronic publication website at http://www.ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices around the Island. I can be reached at firstname.lastname@example.org.