Pick The Right Plant for the Right Place

Sometimes we’ll get visitors to the Alpharetta Community Garden who are from California and they will talk about how they miss all the vegetable and fruit choices from the West coast where, apparently, every fruit and vegetable known to man grows like gangbusters.  Likewise, when I worked garden center retail I would frequently hear our customers from up north complain that their favorite lilac or some beloved tree won’t grow down south.

Each region of the United States has its own growing climate and that’s why there is a USDA Hardiness Zone Map.  Since I am in Zone 7b, when I go to buy flowers or foliage plants, I know to look on the tag in the flower-pot to make sure the plant is hardy to Zone 7.  If it is hardy it will over-winter here; it is perennial. It will survive the freezes and frosts in my area.  The flowers that don’t over-winter are called annuals.  They add seasonal color and then they die off. 

I also refer to the hardiness information when buying trees and shrubs.  As I mentioned above, most lilacs that grow up north do not like Zone 7.  Tropical trees from south Florida aren’t going to be happy here either. 

When buying vegetable starts or seeds, you have to think a little differently.  Most of the vegetables we grow are annuals.  The question really is how soon to get them planted relative to the last and first frost dates and whether or not they will have enough time to mature and produce the food that we want to eat.

Those of us who’ve been planting awhile know that even within our zone the same plant can thrive over here and languish over there. This can be explained by site and microclimates.  For example, the Big Creek Greenway is a low elevation air sink (cold air flows downward) that is swampy and humid.  Compare that to Fulton County’s highest elevation point at the northern end of Freemanville Road in Milton.  This site is a relatively dry, hickory-oak hardwood forest.  Furthermore, the north facing side of that high elevation is cooler and more moist than the sunny and dry south facing side.

What if a creek flows through a site or there is a body of water?  Then that changes things too.  Water adds a moisture and temperature dimension - generally cooling. Likewise, winds influence temperature as well as the rate at which things dry out. 

Temperature from radiant heat is important when determining what to plant and where.  A Japanese maple will thrive in a slightly shaded spot and die an untimely death if planted next to your mailbox.  This is because mailboxes are typically next to asphalt streets and all that radiant heat combined with full sun can overwhelm a Japanese maple. 

And then there are soils.  Think again of that flood plain at Big Creek.  That soil is sandy because flood plains flood.  They deposit silt and sand over and over again. Sites that aren't in flood plain here in Zone 7 are typically red clay soils (with a multitude of variations within that clay type).  

Temperature affects soils as well.  It is because our soils down south warm up so well and so fast that we are able to grow things like field peas and okra and tomatoes and green beans – vegetables that like it hot.  Likewise, with trees, it is good to plant them in the fall in the south because, among other things, soil temperatures typically stay warm enough that tree roots will grow somewhat throughout the fall and winter.  On the other hand, up north, especially way up north, fall tree plantings can be a bad idea because the ground gets too cold for the roots to do much of anything. 

All gardening requires observation, as nature is complex.  You have to know your gardening site and its microclimates.  If you'll start with the Hardiness Zone Map and try to determine what other factors might come into play to determine your specific microclimate, you will be able to buy the right plant for the spot you want to see planted.