really mild areas, such as parts of Southern California, Florida, and the Gulf Coast, the entire year is likely to be frost-free and wide open. The rest of us may feel we’re not as lucky (but just remember that those folks, and their plants, have to contend with intense summer heat and humidity, not to mention bugs that are never killed by frost). Look at it this way: If you have a colder winter, you get a break, a chance to stop and relax — and a chance regroup and plan for an even better garden next year, after the last frost is past.
The length of a growing season varies somewhat from year to year but is generally about the same. You probably already have a sense of your growing season, but if you really need to know, finding out is fairly easy. Call your nearest Cooperative Extension Service office, ask a knowledgeable gardener or garden-center staffer, or watch your local newspaper for the frost dates (which can vary from one year to the next). Many gardeners also use frost zone maps, like the ones here:
Bonnie’s Plants (https://bonnieplants.com/gardening/first-and-last-frost-dates/)
National Gardening Association (https://garden.org/apps/frost-dates/)
Here’s how to calculate your growing season: Suppose you live in Denver, Colorado; your last frost is May 3, and your first fall freeze is October 8. That gives you 157 days in which to garden. Or suppose you live in Las Vegas, Nevada; your last frost is March 7, and your first fall one is November 21. You get 259 days of growing.
Zoning Out: Breaking the Zone and Growing Season Rules
Despite all the zone maps and all the research, hardiness remains an inexact science. Although some plants turn out to be surprisingly tough, others succumb unexpectedly. The easiest thing you can do is to set your sights on plants said to be appropriate for your area. Here are some tips on deciding what you can grow, even if you’re not sure about the zone:
Peek at your neighbors’ yards. Chances are that if a type of plant is succeeding right nearby, it can grow well, survive, and thrive for you, too.
Buy local. When you get plants that were raised in your area (not in some distant place or coddled in a greenhouse), they’re much more likely to be able to handle whatever your local weather dishes out. After all, they’ve already experienced some of the harsher conditions and survived so the seller can offer them to you. Production fields out back or right nearby are your cue.
Grow native plants. Plants that come from your area or region — ones you’ve seen growing in the wild, perhaps, or certainly in local parks or botanic gardens — are sure to be well-adapted and set not only to survive but to prosper. How do you know whether a plant is native? Ask where you buy, or look it up.By the way, some local nurseries that promote or segregate native plants may also have nice selections or cultivars for you to choose from — improved versions of native plants (they may have smaller or more-compact size, different flower colors, bigger or longer-lasting flowers, and so forth); keep an eye out.
You can, however, force plants to grow in your hardiness or frost zone by taking advantage of microclimates (pockets of different growing conditions) or by using tools to extend your growing season. The following sections tell you how you can sometimes beat the zone system.
Managing your microclimates
Features in your yard, both natural and human-made, often modify the overall climate and create small areas with distinctly different environmental conditions (including hardiness zones). Here, your zone rating may go up or down by one or possibly even two levels, changing your planting options.
Look for marked differences in these areas:
Water: Proximity to a pond, stream, wet ditch, or the ocean can make temperature fluctuations less dramatic.
Soil: Different types of soil can create protective or stressful growing conditions. For instance, clay soils hold moisture and heat and thus can reduce stress in dry or very cold conditions. Very sandy soils drain well and are great where excessive water is a problem, but in hot and dry conditions, they can put plants under severe water stress.
Wind: See how strong the winds are and how often you get air movement in a particular area. Winds are very drying.
Temperature: One spot may be significantly hotter or colder than its surroundings. Note that cold air often flows over a landscape like water, settling in low areas and creating cold pockets.A useful tool for determining temperature variation is the maximum-minimum thermometer (also known as a Six’s thermometer). This thermometer can measure the high and low temperature during a given time and can measure the extremes of temperature in a location. See Figure 3-1. This instrument is also available in a digital form. Recording thermometers can store temperatures and humidity levels over longer periods of time, and some can be synchronized to a spreadsheet on your computer. Apps come with some of these digital, remote-sensing devices and can track temperatures on you phone.
Light: Note dramatic differences in amount of daily sun and shade. Human-made structures (yours or a neighbor’s) as well as trees can contribute to these changing conditions.
© John Wiley & Sons, Inc.
FIGURE 3-1: A maximum-minimum thermometer gives you an idea of the outdoor temperature ranges in your area.
Cheating the system: Creating microclimates
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