Urban Gardener: Cucumbers thrive year-round in Hawaii’s climate

Cucumber is a warm-weather crop that can be grown all year in Hawaii. Best growth is obtained when the temperature is 70 degrees or higher.

Many cucumber varieties require pollination. In areas where bees are not abundant or when cucumbers are grown in a greenhouse, parthenocarpic (P) varieties — generally seedless — can fruit without pollination.

Many cucumber varieties do well in Hawaii. Varieties resistant to powdery mildew (PM) are noted below. Here is a partial list:

>> Western slicing type: Dasher II (PM), Genuine (PM), Sweet Success (P), Diva (P) (PM)

>> Japanese: Tasty Green (PM), Spring Swallow, Tasty Bright, Tasty King, Southern Delight, Tokiwa, Summer Delight (PM), Soarer

>> Korean: Summer Express (PM)

>> Persian: GVS 609 (PM) (P), Socrates (PM) (P), Sultan (PM) (P)

Cucumbers can be grown in any type of soil that holds water well, has good drainage and a pH range of 5.5 to 7.0. Applying manure or compost — 10 to 20 pounds per 100 square feet — will improve soil condition and fertility. Work the soil to break up any hardpan (dense layer of soil), then work in the manure or compost to a depth of 6 to 8 inches.

Cucumbers can be grown on the ground or on trellises 5 to 6 feet tall. Trellising protects against slug and snail damage and soil rot.

Cucumber seeds may be started in small pots and transplanted, but when transplanting be very careful not to damage the roots. Spacing between rows should be 4 to 5 feet and between plants, 15 to 18 inches. Plant seeds directly into the seedbed at a depth of 1/2 to 3/4 of an inch.

Frequency of watering is largely dependent upon soil type and weather conditions. In general, lighter soils require more frequent watering. If growing in containers, daily watering is necessary after the plant begins to set fruit.

The University of Hawaii’s Agricultural Diagnostic Service Center can test your soil and make lime and fertilizer recommendations. If you haven’t done a soil test, here are general instructions for organic fertilization: 4 pounds of Sustane 8-2-4 or 8 pounds of Sustane 4-6-4 can be applied per 100 square feet. Apply half at planting, 2 to 3 inches away from the seeds and 3 inches below, in a single band. The remaining half can be applied three to four weeks later. Additional nitrogen may be applied at the beginning of harvest to prolong vine vigor and fruit production.

Insects that commonly attack cucumbers are melon flies, pickleworms, whiteflies, aphids, slugs, snails and leafminers. Covering young fruit in brown paper bags will help prevent melon-fly and pickleworm damage. Slugs and snails can be managed by picking them off by hand into a slug jug. Leafminers and whiteflies are usually kept at tolerable levels by natural enemies.

Diseases that commonly affect cucumbers are damping-off, root knot nematodes and powdery mildew. Planting in well-drained soil and not over-watering will help to minimize damping off. Adding high amounts of organic matter to soil may help with root knot nematodes. Planting varieties resistant to powdery mildew is ideal.

Elihu Isele is the coordinator of the East Hawaii Island Master Gardener Program in Hilo.