Unless you’ve been living in a cave for the past decade, you definitely notice the manifestations of climate change! There’s no denying that changes in the ecosystem are happening. Sea level rise, glaciers are shrinking, plants and animals are displaced, trees blooming earlier, lengthening of growing seasons, ice on rivers and lakes freezing later and breaking up earlier, and even mirco changes that we can’t see with the naked eye! It is expected that the majority of the states in the US will experience an increase in average temperature as well! (IPCC, 2007).
What does this mean to gardeners? Plants may no longer survive where they used to thrive! All plants need to be in an environment that meets their basic requirements.
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Those requirements are:
- Day length. Day length is usually the most critical factor in regulating vegetative growth, flower initiation and development, and the induction of dormancy. Plants survive only when the day length promotes their growth and prepares them for the seasonal changes.
- Radiation. Most plants respond to radiation in the 270- to 3000-nm region. Cloudy, rainy days coupled with the shade provided by nearby plants and structures can significantly reduce the amount of radiation available. Plants survive only where the amount is within a specified range.
- Temperature. Plants grow best within an optimum range of temperatures; and the range may be wide for some species, narrow for others. Plants survive only where temperatures allow them to metabolize.
- Frost. Plants differ in ability to survive frost, their responses varying from immediate death to sustained performance. The previous environmental and cultural conditions of plants can often shift, but not permanently alter, their tolerance to freezing. Plants survive only when they are adapted to subfreezing weather.
- Heat. The thermal cutoff temperature varies widely from species to species. By tradition we group plants into sun, partial sun, and shade types and plant them according to their light and heat tolerances.
- Rainfall. Gardeners need to know how much water a landscape plant requires in determining its usability in low maintenance landscapes. Rainfall gardening often greatly limits which species can be used successfully. Gardeners also need to know how much and how often to water plants in high maintenance landscapes.
- pH. The ability of plant roots to take up water and nutrients depends on the pH (measure of acidity or alkalinity), presence of soluble and insoluble salts, and aeration of the growing medium. The successful culture of all plant species requires that they be grown in a medium within a definite pH range and with from 10 to 14 essential nutrients in appropriate balance. Although plants may tolerate some extraneous elements and compounds, every plant species and cultivar has well prescribed limits.
While the USDA Plant Hardiness Zone* map has not changed since 1990, the Arbor Day Foundation came up with a new hardiness zone map that reflects the warmer climate. Much of the US has become warmer and that affects how we can plant.
You can help create a shadier, cooler spot for your plants by planting trees. They conserve energy, reduce soil erosion, clean the air we breathe, and help protect rivers and streams. Trees can also provide food, shelter and a place to raise young for our wildlife! Just remember to stay away from invasive species!
Arbor Day Hardiness Zone change press release.
LOOKUP YOUR ZONES:
Arbor Day Hardiness Zone Map (2006)
USDA Hardiness Zone Map (1990)
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References:
- IPCC, 2007 The Intergovernmental Panel on Climate Change: Climate Change 2007: Impacts, Adaptation, and Vulnerability. Cambridge University Press, Cambridge, United Kingdom, 1000 pp.
- * The USDA Plant Hardiness Zone Map was published in 1960 and revised in 1965 and in 1990.
