THE WEST’S CLIMATE ZONES


21


ZONE 23 — See maps on pages 31, 34–37 J


F M A M J J A S O N D


THERMAL BELTS ALONG THE SOUTH- ERN CALIFORNIA COAST The best zone for avocados; good for cherimoyas, ‘Valencia’ oranges, guavas, mangoes, and papayas. But mild winters allow only low-chill pears, apples, and peaches. Winter lows average about 45°F/7°C, and summer highs reach 78°F to 89°F (26°C to 32°C). Frosts are rare, but Santa Ana winds dry plants every fall.


ZONE 24 — See maps on pages 31, 34–37 J


F M A M J J A S O N D


SOUTHERN CALIFORNIA COASTAL STRIP Dominated by marine air but occasionally ripped by Santa Ana winds, winters here rarely dip below 45°F (7°C), and frosts are rare. In late spring, morn- ing overcast rules. July highs hover around 75°F (24°C). Where the beach parallels high cliffs, Zone 24 extends to that barrier; where hills are low or absent, it runs inland several miles.


ZONE H1 — See map on page 41 J


F M A M J J


CLIMATE CHANGE AND GARDENING


“Climate is what you expect,” wrote Robert Heinlein, science-fiction author, “and weather is what you get.” Even so, climate is constantly changing. In the past 30 years, aver- age temperatures in the western United States have risen by a degree or two. While that isn’t enough to affect Sunset climate zones, it does have a practical effect on gardening. “We’ve been seeing more warm- ing in the spring months than in the fall months,” says Kelly Redmond, regional climatologist for the western United States. “Latest spring frosts might be coming 2 to 3 weeks ear- lier than before.” For gardeners, that’s good news: you can probably get away with planting a few days earlier in spring. “Fall frost dates, to my knowledge, haven’t changed,” adds Redmond.


But is climate change to blame


for the West’s headline-stealing bad news: extreme heat, rain, drought, deep freezes, and mudslides? “Extreme events have happened forever,” says Tye W. Parzybok, author of Weather Extremes of the West. The apparent increase in extreme


A S O N D


HAWAII’S MILD VOLCANIC SLOPES Cooler air makes higher volcanic slopes better for growing everything from sweet bulbing onions (Maui onions) to low-chill varieties of apples and even Mediterra- nean herbs. Warm-season highs range from 65°F to 80°F (19°C to 27°C); cool- season lows can dip to around 45°F (7°C), with extreme lows of 35°F (2°C).


ZONE H2 — See map on page 41 J


F M A M J J


weather events, he says, is largely the result of better monitoring and higher social costs than ever—there are simply more people and property affected by bad weather. One downside to plan for: if con-


tinued warming reduces the snow- pack as anticipated by the California Department of Water Resources, it will team up with increasing popula- tion to put significant pressure on water supplies all over the West. Water will get more expensive, less available, or both—and this will change the way we garden.


Protect Your Plants


• As a hedge against water short- ages, install drip irrigation and skew your plant choices to less thirsty kinds, including dry-climate natives.


• Open up big trees by selective pruning so that strong storm winds pass through them instead of blowing them over.


• Where snow cover is unreliable, mulch every fall to protect shallow roots against hard frost.


A S O N D


HAWAII’S COCONUT PALM BELT Most lowland lees here get their heaviest rains from November through March, while May through September is relatively dry. On the wet windward sides, rain comes from passing storms and year-round trade-wind showers. The Kona Coast, however, gets most of its rain in the warm season. Highs hover around 86°F (30°C); lows can dip to around 64°F (18°C).


Storm clouds darken the skies above agaves in Anza-Borrego Desert State Park, California.


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