THE COASTAL GARDENER:Gardening challenges in warm climates

Summer is here. And there are two things we know for sure: It will be hot and there will not be a drop of rain.

If we are experienced gardeners, we also know that, regardless of our efforts, many of the plants in our gardens will shut down during the summer heat.

Many in Orange County have lived or traveled in places where it rains year-round. In fact, summer rain is the norm for most of the United States.

These other places have storybook seasons: winter, spring, summer and fall. We see these places in myriad magazine articles, on television and in our travels.

We assume, albeit naively, that we are like them. We often see plants and gardens that we try to reproduce here in Orange County, and nearly as often we are frustrated by those attempts.

We garden in coastal Orange County, where we have just concluded the driest season since record-keeping began in 1948. Our rainfall total this past year was barely more than two inches. Normal rainfall for us is just more than 13 inches. But even in a “normal” Orange County year, no rain falls from June to September.

Whether we know it or not, we garden in a Mediterranean climate, and it is this unique climate that often determines the success or failure of our gardens. Knowing this, we would be wise to make friends with this climate, to garden with these absolute forces, not against them.

Like all Mediterranean climates, there are only two seasons in Orange County: a warm and a cool season. The warm season, which we are in, is characterized by warm, bright, clear days and warm, clear nights. It is a bone-dry period, with low to moderate humidity. The cool season, which runs from about October through April, brings chilly nights and less light intensity due to frequent cloudy periods.

In a Mediterranean climate, it is during the cool season when all of the rainfall occurs, and Orange County is no exception.

Why does any of this matter? Because the plants in your garden can be fairly easily divided into either warm-season or cool-season growers. Once you figure out which is which, you will know when to plant, prune, fertilize, and expect flowers either dormancy or some degree of seasonal stress.

For many gardeners, this cool season-warm season maxim has eventually come to them as an awakening; a moment of light within their gardening efforts. For them it is as if, after years of underlying struggle and frustration, someone had finally enlightened them and given them a great gardening secret.

The needs and personalities of the various plants in their gardens become — suddenly — so much clearer.

So we are midway through the hottest week of the year here in Orange County. Without a doubt, we are in the midst of our Mediterranean warm season. Several plants in our gardens (the cool-season growers) are unhappy right now, and there isn’t much we are going to be able to do about it.

Common examples of cool-season plants struggling through the Orange County summer are marguerite and euryops daisy, phormium (flax), ceanothus, rosemary, lavender, amaryllis, white calla, gazania, blue fescue grass, bluegrass. and even Italian cypress and bay laurel.

These plants, and hundreds of others in your gardens, cannot talk to you. They cannot tell you of their summertime struggles, but to a keen gardening eye they can show you. New growth has stopped, leaves become smaller, yellow foliage appears and below ground their root systems are actually shrinking.

Fertilizer won’t help; they don’t want to grow right now. Heavier watering, although perhaps necessary to simply sustain them, will not perk them up either.

In our Mediterranean warm-season, these are cool-season plants. Don’t expect too much from them right now. It’s not their time.

ASK RON

Question: I cannot get rid of the white fly on my hibiscus tree. It’s too beautiful to remove. Is there anything I can use?

CAROL

Answer: The pest is The Giant Whitefly (Aleurodicus dugesii). It was first discovered in Orange County 13 years ago. Biological controls have reduced its occurrence dramatically, following the first couple of years of near hysteria among local gardeners. Here are a few suggestions, and they may not even require any pesticide.

First, be sure the hibiscus is growing in a full-sun location with very good air circulation. Secondly, wash off the undersides of the leaves, along with the whiteflies, frequently with a strong stream of pure tap water. Third, check for and control any ants that are associating with the whiteflies. Finally, apply a one- to two-inch layer of earthworm castings (an organic product) to the root zone at the base of the hibiscus. I can just about guarantee that whiteflies won’t be a problem if you follow these cultural practices.

ASK RON your toughest gardening questions, and the expert nursery staff at roger’s gardens will come up with an answer. Please include your name, phone number and city, and limit queries to 30 words or fewer. e-mail stumpthegardener@ rogersgardens.com, or write to plant talk at roger’s gardens, 2301 san joaquin hills road, corona del mar, ca 92625.