Last month I wrote about the challenges that summer heat poses to vegetable gardeners. Though the high temperatures typically persist partway into October, we should notice cooler weather soon or already as the fall season is underway. The cool season is a great time for planting, starting a garden and other heavy work. Hard work is more bearable, and plants are less stressed as well.

With rain and shorter, cooler days, stressed plants in the landscape may become greener and put on healthy new growth. The rainy season is also planting season for our many hardworking conservation groups and forestry professionals restoring native plants and habitats. Arbor Day Hawaii falls on the first Saturday in November, as tree planting is generally more successful in the cool rainy season.

Many leafy greens can grow through the summer. Kaneshiro Farms in Waianae has been putting out beautiful kale, choy sum and lettuce this summer, with careful variety selection and irrigation management. However, most gardeners will be more successful at growing greens during our cool season. Plan to start seeds beginning in September so plants will be growing when the weather starts to cool. Many vegetables can be started through February, March or April, so the harvest can occur before the heat really increases in May or June.

In most of our lowland urban areas, broccoli and cauliflower typically do best when planted in October or November. They generally prefer warm temperatures during the early growing season, then cooler weather as the heads begin development. Cauliflower is typically less heat tolerant than broccoli. The Puakea variety from the University of Hawaii may have a better chance of growing at low elevations compared to other varieties. You can find Puakea and other vegetable varieties adapted to our local conditions at the UH Agricultural Diagnostic Service Center (ADSC) Seed Lab. In addition to providing local seeds, ADSC also provides soil, plant and water testing services which can be very helpful for gardeners as well as farmers.

Finding heat-tolerant vegetable varieties can help with growing in Hawaii. In addition to our UH Seed Lab, search through online seed retailers such as Johnny’s Selected Seeds, High Mowing Organic Seeds, Burpee Seeds, Baker Creek Heirloom Seeds and others for varieties that are heat-tolerant and resistant to diseases such as powdery mildew and viruses.

Learn more about seasonal gardening in Hawaii at the Oahu Urban Garden Center on Saturday from 8:30 to 11:30 a.m. for our Second Saturday at the Garden event. Come talk to UH master gardeners, stroll the gardens and bring your children to enjoy the themed children’s gardens and hedge maze.

At 9 a.m., certified Master Gardener Amy Teves will teach a class about working with the seasons to grow any vegetable successfully in your area. The workshop costs $5, payable in cash at the door. Call 453-6050 to reserve a spot and for more information.

Find more information on vegetable gardening, you can contact the UH master gardeners on your island by visiting our website ctahr.hawaii.edu/UHMG.

Kalani Matsumura is a junior extension agent with the University of Hawaii’s College of Tropical Agriculture and Human Resources and coordinates the UH Master Gardener Program on Oahu.