I live in zone 7. The front of my house faces north and plants that are normally hardy to zone 7 struggle up against the north side since it is colder & shadier than the rest of the yard. They need extra protection in the winter and sometimes don't survive. But plants that don't like our typical zone 7 hot summers do better in the front and will often thrive there when they don't anywhere else in the yard. The back of the house that faces south and gets more sunshine stays warmer and I can get plants that are hardy only to zone 8 to survive there most winters. Both of these areas are considered "microclimates."

Every yard can have areas that are colder, shadier, warmer, sunnier, wetter, drier than is typical of the area. These are microclimates. It takes careful observation of your own yard to find these spots and then some research to see what will do well in them.

Remember that the type of soil one has also affects what plants do well in your zone, also your microzones, or micro climates. I am really zone 4, but almost z5 in temp. these last 5 years, and very southwest for much of my planting. Also, short or long planting season and early or late frosts really get in there. Nancy Ryan

Hi Dirtgal,

That's very interesting about the type of soil having an effect on microzones. Can you elaborate on that a bit please? I ask because I'm attempting to grow a couple of plants that are only marginally hardy in my area. One is a muscadine grape, "ison" and the other is a "Chuck Hayes" gardenia. Both are said to be hardy to zn 7. I planted the gardenia up near my brick south facing foundation. The grape is planted on an arbor on the south side of my house as well. I placed rocks around the base of the plants for added warmth. My soil is a beautiful loam and the PH is 6.5.

I remember reading about the agriculture practices of pre-european influence, southwest indians in and around the Mesa Verde etc.... The archeologists have been uncovering their farming areas and have found they planted crops that needed protection or longer growing periods in swales below the rest of the area. Isn't it amazing that we have only recently rediscovered microclimates? Sandy

GardenerSandy described a microclimate colder than her zone along her north side. One of the gardens I care for has a microclimate warmer than our zone. It not only faces south, but is enclosed by two walls--this means wind protection which is especially important in winter. Because of the southern exposure and the wind protection, this little area is a zone 6 or even 7, where the rest of the garden is a 5 or maybe 6 (zones are crazy in SE Michigan!). This means I was able to overwinter a few plants outside that normally would have died, such as rosemary.

Monica

Gardener Sandy covered it very well. Prevailing winds can make an area cooler and drier as well. Usually the north side of a structure is colder than the south. Proximity to large bodies of water also moderates the temperature. Gentle breezes blowing between our house and our neighbors' become somewhat blustery as they are funnelled through that space.
I have also been able to grow some Z9 plants on the south side of my Z8 yard. The banana tree didn't even lose all its leaves last winter, the ginger finally died down but multiplied generously this spring.

Akapeggy, to be specific I don't think dirtgal was saying soil affected the climate or hardiness zone so much as she was implying that different soils can affect the hardiness of the plants and I suspect this is due to how well established the plant is and how deep the roots run. Regardless, if the plants survive it all equals the same thing. Let us know how the 'Ison' muscadine does. If the muscadine survives then you might be able to grow the fuzzy kiwi also, actinida deliciosa.

You might want to check out Google Search for Gardening Microclimate which has lots of good sites about gardening microclimates.

Soil does have an effect on the hardiness of a plant. Plants that are adapted to a xeric envionment can be hardy outside of the zone that they are listed as if provided with a well draining soil. For instance Hesperaloe parviflora is listed as hardy in zones 7-10 but is hardy to zone five if grown in a sandy soil. The reason is that heavy clay soils hold so much water during the dormant season that the roots and rhizomes rot.