Dr. Gary Bachman is an associate extension/research professor of horticulture at the Mississippi State University Coastal Research and Extension Center in Biloxi and is the host of Southern Gardening.

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Microclimates in the Landscape
by Gary Bachman Ph.D.       #Environment   #Hardscaping   #Weather

Hosta, impatiens and polka-dot plant (Hypoestes phyllostachya) are good choices for the full-shade garden.
 

One of the most common topics of conversation between gardeners is the weather. Rain, heat, cold and drought all present challenges to maintaining a good-looking garden and landscape. Together, these environmental factors are referred to as the “climate” for a particular area or region. Since these areas can be rather large, we can call these environmental factors the macroclimate for a given area. The USDA Hardiness Zone map is a resource we use to determine growing conditions over wide areas and regions.

Within the larger macroclimates are smaller areas that have different or modified conditions. These pockets may be warmer or cooler, or wetter or drier than surrounding areas. These areas are termed “microclimates” and can be influenced by buildings, trees, bodies of water or elevation changes.

Most, if not all, residential gardens and landscapes have various microclimates. Trees, shrubs and structures influence how water, light, temperature and wind around a home affects gardens and landscapes. It is important to realize that these microclimates can, and will, change over the course of the year. The observant home gardener recognizes these microclimates and takes advantage of the conditions to successfully grow plants. Let’s take a look at some of the common microclimates found in the home garden and landscape.


These hydrangeas enjoy the morning sun in this microclimate between the homeowner’s house and garage.
 

Most home gardeners realize that the sun shines its light at different angles throughout the year. Knowing this helps gardeners determine the location of sunny and shady gardens, as well as where to plant shade trees to cool the house.

Your home, garage and other structures also influence landscape microclimates. These structures, especially southern and western walls, absorb heat from the sun throughout the day. When the sun sets, this heat energy radiates back out into the environment. It is common during the winter months to move container plants against the house when frosts and freezes are in the forecast because that radiated heat provides some protection. This is a good place to plant shrubs, fruit trees and flowering perennials that are considered marginally hardy. During the warmer summer months, these areas can be considerably warmer because the excess heat radiating from these walls can bake plants. Beds next to the house can also be drier because eaves and gutters redirect rainwater elsewhere.


This south-facing wall creates a microclimate with warmer temperatures, allowing the homeowner to grow these bananas (Musa spp.).
 

Shade is another common microclimate created by trees or structures. The amount of light a landscape bed receives can change throughout the year. When planted under deciduous trees, spring bulbs will flourish in the full sun. Once these trees leaf out, the bed can be used for plants that prefer shade, such as hostas and impatiens.

Garden art and overflowing containers add interest in this partially shaded microclimate.

The degree of shade is also important. Partial shade can be described as an area receiving between four to six hours of direct sun each day. Full-shade areas receive less than four hours of full sun, generally early in the morning or late in afternoon, based on the sun’s angle. When the tree canopy is so dense that little rainwater reaches inside the drip-line, this is called dry shade. One last thought about shade: As young trees are planted, the area of shade will expand as the tree grows. Landscape areas that have been in full sun will need to transition to full shade after several growing seasons, and the gardener needs to be aware of these long-term changes and ready to change the plantings accordingly.

 

Left: Ponds influence microclimates in the landscape and create opportunities for more native plants, such as these bald cypress (Taxodium distichum). Middle: Hardscape, such as this brick walkway, can create hot, dry conditions along the edges. Right: The plants selected for this area can tolerate the warmer and drier conditions created by the hardscape materials.


Microclimates also affect temperatures. Water features, depending on their size, can moderate temperatures, creating microclimates. Landscapes surrounding ponds can be slightly warmer in the winter and slightly cooler in the summer. Hardscaping materials and topography can influence temperature in the garden and landscape as well. Spots that are cooler than the surrounding areas are called cold traps. Cold air tends to settle in low areas of the landscape. Fences can also block the winter sun, so areas behind them will be more susceptible to frosts in the spring and fall. Not only the walls of a home, but virtually any hardscape can affect landscape temperatures. Stone, patio pavers and concrete absorb sun’s energy, heating up and therefore tending to be drier. This particularly affects planting beds alongside paths and sidewalks.

 

A version of this article appeared in a July/August 2013 print edition of State-by-State Gardening.
Photography courtesy of Gary Bachman Ph.D.

 

Posted: 06/09/17   RSS | Print

 

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