There’s a saying in the plant world — “Right plant, Right place.” The challenge to the right plant and right place motto is it really depends on the goals of the owner and other unique factors of the property and its location. Many newbies are overwhelmed by the many terms used for grouping and identifying plants based on exposure, hardiness, tolerance, and resistance. Even seasoned gardeners make mistakes, or willingly overlook recommendations —but your rebellion is not the focus of this blog. Instead, I wanted to briefly explain the key qualities often used to describe a plant’s suitability to certain conditions and how that impacts what plants you choose.
One of the first key factors is the level of sun exposure a plant prefers. Generally it’s divided into three categories, which are in the table to the right. Sometimes a plant is labeled as being good for full sun and part shade, but really its best in sun and may not flower or perform as well in shady conditions. Some plants will also say morning sun only, as afternoon sun is hotter. Especially here in South Texas, where it seems like full sun in July is a heck of a lot hotter than full sun elsewhere, and I see many plants that normally want full sun suffering. In those instances I may provide a temporary shade cover in the afternoon to help mitigate the blazing Texas sun.
Full sun: receive full sun exposure the whole day, or for 7 hours or more
Part sun/shade: receive sun for only a third to half of the day (3-6 hours)
Full shade: sun rarely shines directly in that area, or if it does its only for an hour or so and usually not in the hottest part of the day
Besides sun exposure, most people are familiar with the hardiness zones that were developed by the USDA. These zones are group based on their average lowest winter temperature. The U.S. is broken down into 11 zones with similar climatic conditions. Over time the zones were broken down further and designated with the addition of a letter, such as 8a, 8b, 8c. You can view the map and find your zone here.
As I mentioned, the hardiness zones are based on lowest average winter temperatures. They don’t identify the lowest possible temperatures that are common in that area, which can be 10 or more degrees cooler than the average. So in addition to identifying the hardiness zone, many growers have begin labeling and identifying the specific winter hardiness or lowest winter temperature that the plant can withstand and survive. That temperature may be common in a hardiness zone that is deemed appropriate for that plant, and expose the plant to damaging and life threatening conditions.
For example, here in San Antonio many people like to plant palm trees, because most of the year we have the right conditions to support them. However most are cold hardy down to only 50 degrees. We may be hot as hell most of the year, but we get quite a few cold snaps that drop us down as low as the teens and twenties. In those temperatures, palms can suffer irreversible damage and die. Many folks circumvent this issue by covering their plants, but if you are looking for a low maintenance option, its best to stick with plants that can survive your conditions year round.
On the other hand, there are many plants that need a certain number of cold days or chill hours in order to force blooms. Many bulbs and fruit trees require cold days and nights to promote flowering. You can find charts on chill hours for various bulbs and fruit trees across the internet.
On the opposite side of the spectrum is heat tolerance. Heat tolerance is the highest average temperature that a plant can survive without damage. Since heat is a bigger factor than cold in many parts of the U.S., the American Horticultural Society designed a heat-zone map to help identify heat zones, similar to cold hardiness zones, and give gardeners more information to draw on in making their decisions. Heat zones are based on the average number of days above 86 degrees.
Some growers provide both zones on their labels, but since it is not as well known, many do not. However, many growers will identify a plant as heat tolerant.
In addition to temperature, another key factor that influences a plant’s ability to survive is its water needs. Some plants are designed to grow and thrive in wet conditions, while others have evolved or adapted to handle arid conditions. In the Pacific Northwest and other areas with higher rainfall, drought tolerance may not be a concern, but in the south and southwest, where drought conditions and water restrictions are common, it’s becoming the number one criteria for plant selection.
Another factor many gardeners must consider is disease resistance if a certain type of plant disease is common in your area. Many diseases affect a specific species or genus of plants. Rose Rosette disease largely impacts roses while Pierce’s disease is a common threat to grapes. Many growers have breed varieties that are resistant — though not entirely immune— to specific diseases.
Determinate or Indeterminate
Folks looking to grow edibles in small spaces need to be able to identify the growing habit of common vegetables. Determinate varieties are often called bush or dwarf varieties and have a limit on how big they will get. That’s important when space is a concern. Indeterminate varieties can sprawl and grow without limits. Generally their growth can be trained and cultivated with trellising and pruning. There are a growing number of ornamentals that are also dwarf varieties of their giant cousins, giving urban gardeners more options overall.
Soil pH – Acidic or Alkaline
Preferred soil pH is probably one of the most overlooked qualities. Soils vary dramatically across the country, and even across the state. Many plants evolved and adapted to thrive in their natural conditions. Plants that prefer acidic soils will struggle in alkaline soils and vice versa. Soil pH also affects the chemical availability of many nutrients. Gardeners can amend the soil to achieve the right pH, but it will require reapplications over time and may impact other plants nearby. As a firm that practices sustainability, we recommend planting specimens with different pH requirements in pots instead of in the ground, to avoid changing the natural soil conditions.
Now, one thing I didn’t mention is microclimates. The site conditions of a specific location may vary enough from its surrounding area to create a microclimate that allows the owner to grow plants that normally wouldn’t work in the region. There are a number of homes here where I live that are able to create a high water, full shade, tropical oasis while most of us are opting for full sun, drought tolerant plants. Knowing your site’s conditions and how they change throughout the day and throughout the year and pairing it with plants that thrive in those conditions is what the phrase “Right plant, Right place” is all about.