That means that while a particular plant’s hardiness range may tell you that it will survive your region’s winter temperatures, it does not address its heat tolerance. When selecting an outdoor plant, gardeners check to see if it grows in their hardiness zone.
If you are wondering how to use heat zones, look for heat zone information on the plant label or ask at the garden store. You’ll need to know where your area falls on both the hardiness and heat zone maps to make this work for you.
As a founding employee of Gardener's Supply, I wore many hats over the years. Currently, I have my own company called Johnnie Brook Creative.
Many plants are adapted to warmer climates and will die if exposed to freezing. These days, most cold-climate gardeners are very familiar with the U.S. Department of Agriculture's Plant Hardiness Zones.
These 11 zones indicate the average minimum winter temperatures for a given area. Most catalogs, websites and garden centers now provide a Hardiness Zone rating for almost every plant they sell.
But cold hardiness is not the only factor that determines whether a plant will survive in your garden or not. When a plant is not cold hardy, it will simply die, but the signs of heat stress are usually more subtle.
Plants that can't tolerate high heat may stop blooming, the leaves may turn pale, and the plants may become more susceptible to pests. In the late 1990s, The American Horticultural Society (AHS) developed the Heat Zone Map, which parallels the USDA Hardiness Zone Map.
This map is based on the number of heat days” experienced in a given area. A heat day is defined as a day in which the temperature climbs to over 86 degrees F. At this temperature, many plants begin to experience physiological damage and start to shut down their functioning.
Because Heat Zone ratings are relatively new, not all catalogs, websites and garden centers currently indicate a plant's Heat Zone. This plant will survive winter temperatures in zones 5 to 10.
Preciousness A plant's performance is governed by many climate related factors including the length of the growing season, the amount of rainfall, winter lows, summer highs, wind or humidity. Selecting plants suited to your climate will be a key step to success.
Based on the minimum ten-year average winter temperatures, plant hardiness zone maps have been progressively developed, first by the Department of Agriculture (USDA) for the United States and then more or less applied to the rest of the planet. If you are planning to buy a shrub, perennial or tree, you need to make sure that this new plant will tolerate year-round conditions in your area.
Therefore, to ensure your new acquisition will survive and grow year after year, you will need to compare the hardiness zone of your area with the hardiness zone of your plant (included in most American reference books, nursery catalogs and gardening magazines describing plants). It does not include microclimates, humidity, summer heat tolerance either.
To partly resolve some above issues, a Heat Zone Mafias been developed by the American Horticultural Society, based on the National Weather Service (NEWS) daily high temperatures recorded between 1974 and 1995. While the effect of heat is not as immediate and radical as severe cold, it may slowly damage your plants and kill them.
Similarly to the hardiness zones, most garden plants provide heat tolerance information. It is relatively cold hardy, but can't tolerate extreme summer heat.
The reason is that other factors could have an impact on the life of your plant such as a lack of water (resulting from the heat), light (cloud cover, dappled shade), day length (the longer the summer day, the more impact on plant survival), air circulation (fast-moving air on hot days may quickly dehydrate the plants), surrounding elements (hard structures of stone, concrete) emit heat, raise the air temperature and soil pH. A plant's performance is not only governed by its hardiness or heat tolerance but also by many other factors such as the length of growing season, timing and amount of rainfall, winter lows, summer highs, wind, and humidity.
Sunset Magazine has developed a Climate Zones map, which takes all these factors into account and has long been the standard among gardeners who live in the 13 western states. While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates.
Create a membership account to save your garden designs and to view them on any device. On the other hand, heat zone tells you how heat tolerance your respective zone plants are and how many average warm days' temperature over 30 Celsius you get in a year.
These zone map studies help you find out the suitable plants for your garden. In the beginning, it would be a little confusing, but it is not as difficult as you think and the practice field is the best place to learn plant hardiness zone.
Studying the planting zones help you to understand the opportunities with threats for your specific locations. A number of frost-free days you get around the year (Following the USDA Hardiness Zone Map).
Warm zones create longer season, but they invite different pests and insects. Try something new: When you understand the planting zone you will get the confidence to apply new ideas in your garden.
In addition, grow some native plants which can easily survive in your region. The angle of slope of your land and its facing also determine how much sunlight exposure it receives as well as the influence of airflow, water supply and drainage system on your site.
In the heavy rainfall area, a vertical slope causes soil erosion. If the soil has a large portion of clay, it will preserve more moisture than sand.
Besides the soil covered with plants or mulch, evaporates less moisture and heat. Artificial Structures: Your house can play an important role in microclimates.
If your house surrounded by big trees, high walls, high rise buildings or fences, it can protect your area from wind and balance temperature. Similarly, if your garden surface and walkways covered with rocks or pave they can also moderate temperature.
If your garden has shade and shelter for your plants or a greenhouse might affect the microclimates in your location. Besides, if you have a rooftop garden in urban areas, you should also take into consideration the high-rise buildings surrounding the roof, sunlight exposure, airflow, water supply, and other factors.
New gardeners face some troubles to choose the right plant because of the puzzle of the hardy zone. However, it does not give you an exact instruction what to do next after selecting the planting time for your garden.
If your garden located in a microclimate zone you will get some favor or face some challenges. Planting zone introduces you the time frame of cultivation, average extreme minimum temperature, and the climate of a specific region but doesn’t cover all things.
Hardiness zone only shows you the average data of a specific climate and climate calculates last 25 years data of higher and lower temperature and other factors of a specific zone. But, your garden plants affected by the unpredicted weather pattern of the current season.
Weather doesn’t match the hardiness zone map all the time. Besides, you should consider the rainwater ratio, humidity and proper drainage system in your location.
Pests and diseases : Hardiness zone gives you the idea of last and first frost date and the average minimum temperature of a growing season. Heat zone map helps to determine the suitable heat tolerant plants, which can survive in your respective zone where the average temperature over 86° Fahrenheit or 30°Celsius.
Heat zone map selects plant that can thrive in your garden all year round. When you buy seed packets from the market or plants from the nursery, you may notice two sets of numbers.
But you cannot determine plants using the hardy zone map during the season of drought. Therefore, the American Horticultural Society first introduces the AHS plant heat zone map, which is divided into 12 heat zones.
After reaching the temperature at that point can cause physical damage to the plants from heat. This heat zone map makes the job easier to select the suitable plants for your specific garden location.
Hardiness and heat zone maps are the basic guidelines for selecting plants but don’t let them limit you. You better study the zone maps deeply to understand and apply them to innovate something new.
Need to mention that, no matter what your zone maps or plant tags and other statistics say about your location, you couldn’t get it 100% accurate. Start small to reduce the risk and understand the exact situation.