There are thousands of plants we can choose from to decorate our lawns and gardens.

There are numerous herbaceous and woody perennial plants and hundreds of annual plants. But when you travel around the country you can also find many, many more plants that we do not grow in this area.

Ever wonder why that is?

I was in Southern California recently, and whenever I visit such places there are numerous plants that I do not know the names of. That is because we do not plant them here.

The reason? They will not grow here.

This is mostly due to three elements of the places these plants thrive. These elements are temperature, rainfall and soils.

The U.S. Department of Agriculture has divided all of North America into regions they call “Cold Hardiness Zones.” These zones are an extremely accurate way to determine if a plant will survive where you want to plant it.

The lower the winter temperature the lower the zone number. Therefore, a plant adapted to growing in zone 9 may not survive the winter in zone 4. Many times, when you are looking at a plant in a nursery or nursery catalog there is some information provided related to these zones.

For example, most orange trees are hardy in zones 9 to 11, and most sugar maples are hardy in zones 3 to 8, so it is not very likely you will find these trees growing in the same place. Orange trees cannot tolerate freezing northern weather and maples cannot tolerate hot southern weather.

Another example is Lantana. This plant is often grown as a permanent hedge in Southern California — zones 8 and 9 — but in Virginia — zones 6 and 7 — it must be brought indoors in the winter or it will not survive.

In Southern California where we were visiting, in particular, San Diego County, the USDA Cold Hardiness Zones range from 8 along the coast to 9 and even zone 10 inland where it is desert. But even along the coast there is very little rain when compared to parts of North Carolina which are also in Zone 8. This is reflected by the types of plants found growing there.

Rainfall is another piece to the growth requirements of plants. Some plants, such as many species of cactus, cannot tolerate wet soils. They have adapted themselves to exist for long periods when there is no rainfall. In the desert southwest, USDA Zone 10, it rains only 2 or 3 times a year. These plants have developed specialized tissues to collect and store the rainwater when it comes so they can survive several months of dry weather. If the wet weather persists too long, some of these plants will suffer health problems. However, in the same USDA zones in the southeastern states, there is significantly more rainfall, the vegetation is green, lush and there is a greater variety of plant species. The rainfall also affects the soils where the plants grow.

In the desert states the soils are sandy, and in many places it seems to be mostly dust. But in the eastern states the soils tend to be richer with organic matter and even the finer soil particles seem to be bound together.

The greater amounts of rainfall in the east keep the plants growing and this means they are dropping more debris such as leaves as they move through their growth cycles.

The soils tend to have more vegetative cover than in the dry deserts. All of this contributes to a higher level of organic material that accumulates on the soil surface, rots (again, due to greater moisture) and breaks down to add nutrients to the soil. Even in the sandy coastal soils there is a much higher amount of organic matter to help hold the soil together and provide a rich environment for plants’ roots.

So when we are choosing plants we need to think about where we are going to put them. In this area we need to use plants that will grow in USDA Hardiness Zone 7. Sometimes this is referred to simply as the Mid-Atlantic Zone. Then we need to use the other localized information about what type of soil and how much water the plant needs. Then we can have better garden success by using plants that are adapted to grow in this area.

Enjoy your garden.

Sutphin is an extension agent with the Virginia Cooperative Extension, Danville Unit Office. Contact him at (434) 799-6558.