Defining Sun Requirements for Native Plants

Knowing how much light a plant needs to thrive should be a simple question, but it is often easily misunderstood. There are so many different descriptions for sun requirements or exposure found on plant labels, but they don’t provide all the information you may need to make the right selection for your yard. Are these descriptions for Kansas or Virginia? Can a plant survive in full sun with 30 inches of average rainfall or does it need 50 inches?  Does it need full sun with protection from the hot afternoon sun? 

Plant labeling has been getting better and more consistent, so understanding a few key terms will assist in selecting the right plant for your landscape conditions. Let’s take a closer look.

Terminology

Every plant in the landscape needs sunlight to grow.  Even shade plants with their adaptations need a certain amount of light to grow and prosper. Plant labels identify the amount of sun a plant requires as full sun, part sun, part shade full shade, or dense shade:

  • Full sun – Plants need at least 6 hours of direct sun daily
  • Part sun – Plants thrive with between 3 and 6 hours of direct sun per day
  • Part shade – Plants require between 3 and 6 hours of sun per day, but need protection from intense mid-day sun
  • Full shade – Plants require less than 3 hours of direct sun per day
  • Dense shade – No direct sunlight and little indirect light reaches the ground.

A Closer Look at the Terms

Full Sun

Most prairie plants fall into this category of sunlight exposure. This light is bright, sunny for most of the day like in open areas and backyards. These spaces get at least six hours of direct sunlight and need to be planted with full sun plants. Their deep roots and natural adaptations for direct sunlight will help them thrive in this harsh environment. Silver or gray leaves, pubescent leaves, or leaf orientation are adaptations that help them prosper in these sunny areas. 

There are other plants that appreciate some protection from the hottest part of the days, but they still need at least six hours of direct light. Keep in mind that full sun in the Smoky Mountains and full sun in Texas are different.  So, think critically about your local site, because some experimentation may still be needed.

Kansas Gayfeather in full sun

Part Sun and Part Shade

When I think about part sun and part shade, savannah plants come to mind. They are tucked up close to the margins of the forest. They transition from prairie plants to woodland plants. Some will get sunlight for most of the day, but not often. It is not the hottest direct sun. 

Part sun and part shade are very similar, but there are subtle differences. These two terms can be understood quite differently. Most plants requiring either part sun or part shade do well in filtered light for most of the day. In Kansas, a plant requiring part sun or part shade needs to be protected from the more intense afternoon sun. Give it morning sun to keep it happy.

Plants requiring part shade can be quite sensitive to too much direct sun, particularly in the afternoon, and will need shade during the hottest parts of the day.

Plants requiring part sun can usually tolerate more light and need a minimum amount of direct sun to thrive. These plants may bloom poorly if given too little sun.

For either group, providing a few hours of direct morning sun is a good choice.

Bumblebee on Echinacea purpurea-Purple coneflower appreciates partial sun conditions
photo by Janelle Flory Schrock

Full Shade

Plants requiring full shade are the most challenging in Kansas. Essentially, we are trying to grow shade plants in a prairie environment with lots of sun and inconsistent moisture. Shaded areas typically stay dry and need supplemental moisture to grow full shade plants. Full shade plants require anything less than three hours of direct light such as morning sun and late evening sunlight. Protection from the hot midday sun is very important.  Filtered light, such as that found beneath a tree canopy, is a good setting for full shade plants. This type of light is referred to as dappled shade and offers many gardening opportunities.

Native columbine thriving in the shade of an elm tree

Dense Shade

Dense shade may occur under a dense evergreen tree against a fence, or the north side of your house protected by a deck. These areas get little if any sunlight throughout the day. These problem areas are usually dark and can stay very wet or very dry. There is not much you can do under these conditions, but maybe a ground cover or decorative yard element would be a good choice. Plants need some light and you are fighting nature by trying to grow something without much light. Rather focus on the areas that do have some light to draw your eyes away from this area. 

It is best to become familiar with sun exposure in your landscape by checking on light conditions throughout the day and over the course of a full growing season. Growing plants in Kansas can be a test of your will, so match plants up to your landscape based on light conditions in your landscape. I have found that if you get this requirement right, some of the other elements like soil, water and fertility will sort themselves out on their own.

How to Add Native Plants to an Established Prairie

As we wind down the growing season, now is a great time to take stock of your new prairie garden or established prairie landscape.  Which plants have done well?  What has struggled?  What needs to be moved?  Which plants need to be added?  These questions will help guide your efforts this fall and especially next season. 

If you have an established prairie, it can be challenging to make some desired changes.  To add a few plants to a mature landscape takes some forethought and planning.  The deep rooted natives have a distinct advantage over the immature perennial you are trying to get started.  Here are a few simple steps to help give these new plants a fighting chance.

Choose spots

Maybe you want to add some wildflowers into a prairie setting dominated by native grasses.  Visualize where you want these new plants.  Remember, a prairie has subtle splashes of color.  Sprinkling in a handful of wildflowers will look more natural. 

This couple is slowly adding a few native wildflower into their meadow. Some have even started coming in on their own.

Prepare the soil

With your spots chosen, now it is time to make room for these additions to your prairie.  We flag the spots and then spray them with Roundup.  These spots are usually not more than one foot in diameter.  If you want to avoid spraying, cut the area down to the ground and cover it with heavy cardboard for several months or over winter.  Secure these one foot areas with several inches of mulch or stones. 

Two or three inches of mulch will hold down the cardboard and smother out the existing plants.

Choose the right plant

I keep circling back to this point because it is so important.  If plants have struggled in an area, it is usually because either the soil or the plant is out of balance. Typically, the soil is not to blame. It is more likely that the soil and plant have not been correctly matched. Observe soil, sun and drainage issues and match the proper plant to your area. It is good to have a sense of how some of these natives grow naturally in community.  The more you know, the more successful you will be.   

Establish your plants

After waiting several months or over winter, it is now time to plant.  Establish plants using this method in either spring (April/May) or late summer (August/September).  If you sprayed the small areas, you can simply plant right into the open weed free soil.  If you put down cardboard and covered it with mulch, you can pull back a little of the mulch and slice through the cardboard. Put the plants into the ground and water daily.  Leave the cardboard and mulch to decompose over the next few years, as this will give the new plants a little room to grow with less competition.  The cardboard and mulch will ultimately disappear.

Next Steps

Over the next few years, it will be necessary to monitor these new plants.  It generally takes two to three years for the root systems to get fully established.  Remember to:

  • Water deeply as needed.
  • Make sure they are not getting too crowded by other vegetation. 
  • You may need to cut back nearby grasses so these new plants get enough sunlight.  This will only be necessary during this establishment phase. 
Native grasses are wonderful but a few wildflowers in the prairie make it even more beautiful and dynamic.

This process is not guaranteed to succeed, but we have used it successfully to add some diversity to an established prairie.  This approach can also be used to transform a smaller intensively planted display bed. Either way, plan now so you are ready to plant next season.