Sunday | June 26, 2016
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Start planning now for your summer garden

Once again it’s time to begin thinking about the summer garden. Some gardeners do not realize that many vegetables thrive when grown during the warmer months of the year, and others grow better during the cooler time of the year.

With the mild Hawaii climate, there is more flexibility with planting dates even to the point of growing many vegetables year around. But remember, there is a season in which they will grow better.

Plant now the warm season vegetables — beans, cantaloupe, corn, cucumber, eggplant, pumpkin, squash, tomato and watermelon. Generally, it is not a good time to plant the cool season vegetables such as Chinese cabbage, celery, daikon, head lettuce, romaine and leaf lettuce and Irish potatoes. These frequently do better in cooler temperatures. Once established, certain vegetables like kale, collard greens and Portuguese cabbage will continue to grow year around in cooler areas.

Because there are many different climate zones on the Big Island, for your specific area, feel free to experiment with different planting dates for the various vegetable crops.

Aloha Nick, I am about to start some new container plantings and wonder if there is a good way to recycle/ sanitize old container soil. If you have a link to follow, that would be fine. Mahalo. — D.H.

First, let me address the need to ‘sanitize’ used container soil. Reusing potting soil can work for a while. As long as no pathogen is introduced into the soil via contaminated plants, then the soil can be rejuvenated by adding some nutrients and perhaps some organic matter. But then again, if a pathogen (fungal, bacterial or nematode) is introduced by way of an infected plant, the whole pot is contaminated, and subsequent plantings are at risk of being infected. Have you ever planted seeds in a container and nothing comes up?

This is one reason why. Sanitation is important both for commercial operations as well as for the backyard.

The question arises as to how to ‘sanitize’ or sterilize used soil. There is no easy answer. Fumigants have been taken off the markets for homeowners. Solar sterilization, putting clear plastic over a pile of soil and allowing it to bake for four to six weeks, is a good idea, but hot weather is required. Steam sterilization is also effective, but one must have access to steam. Lastly, and perhaps the most practical for small quantities of mix is the oven. Here are the directions: place slightly moistened soil mix in a covered pan and bake in the oven at 250 degrees for half an hour. The center of the mix needs to reach a temperature of 180 degrees for a t least 30 minutes; use a candy or meat thermometer to check the temperature. This process may produce an unpleasant odor.

When recycling used potting soil, it can be thrown in the compost pile or in its own smaller pile with some added organic material and used only for potting purposes.

This procedure will be relatively safe if the compost pile heats to proper temperatures and the heating is uniform. Proper temperatures range from 104 degrees for five days to 130 degrees F for 4 hours. Many times proper temperatures are not reached. If potting soil is reused, I recommend a crop rotation. Whether vegetables or annual flowers, replanting with the same species of plant or even in the same family is not advisable. Gardeners have been successful in reusing soil mixes; nevertheless, the above information is useful for making an informed decision.

l Annual: A plant in which the entire life cycle is normally completed in a single growing season.

l Perennial: A woody or herbaceous plant that lives from year to year and does not die after flowering once.

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


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