Backyard Gardening
Think Outside the Container
Photo credit: Carol Lugg
By Carol Lugg
While container gardening is certainly a popular choice for summer gardening enthusiasts, we may fall into a pattern of using typical summer annuals and don’t consider other options. In today’s Backyard Gardener, we’ll explore ideas for filling containers to reduce potting mix costs, how to attractively arrange plants in your containers for a show-stopping summer of beautiful blooms, and options other than the usual flowering annuals for filling your containers for year-around enjoyment.
Before you begin, take inventory of where you want to place your containers and whether the location is going to be in sun, part-sun, part-shade, or shade. This is an important step as you’ll want to select plants that will thrive when grouped together, based on their shared light needs. As planting season arrives, I start with placing my containers in the areas of my deck, patio, or garden where they will remain through the growing season and then fill the containers with potting mix. This focuses my plant buying decisions, as I consider which plants I want to include in my container based on the location of the container and the amount of light that will be available. It is easy to head off to the local greenhouses and become drawn to an array of blooming plants, but if the plant needs more or less light than will be available, you should determine whether the best future home for the plant is to enjoy it in the greenhouse or choose another spot in your garden.
When selecting a container, be sure to check that the container will have good drainage. Containers without proper drainage will quickly become waterlogged and your plants will eventually die. If your container doesn’t have a drainage hole, use a drill to make several holes in the bottom of your container. If the container is glazed ceramic, you’ll need a diamond drill bit, also known as a masonry drill bit, to make your hole. These drill bits are readily available in most hardware stores.
When ready to fill your container, select an all-purpose potting mix. If your potting mix doesn’t contain perlite or vermiculite, you can purchase these products separately and add per the directions. If you have compost or bark on hand, you can also add this organic matter to enrich your potting mix. If you’d rather, you can mix up your own homemade soil-based mixture by combining sterilized garden soil, sphagnum peat moss, and coarse sand, vermiculite or pearlite. Begin with a gallon of each of the ingredients and adjust based on your planting needs. Consult the Penn State Extension site (https://extension.psu.edu/homemade-potting-media) for further details in preparing your own potting soil. Preparing your own potting medium may be a good economic alternative if you have several containers to fill before planting. If you stored last year’s potting mix, based on Oklahoma State Extension site, you can reuse potting mixes from last year (https://extension.okstate.edu/articles/2023/reusing_potting_soil.html). As long as your plants didn’t show signs of poor health or you battled weeds or insects with last year’s plantings, it is acceptable to reuse. You will need to improve the previously used soil by adding slow-release fertilizer or add perlite to the soil. If your soil remains in the container, you can remove the top 6 inches or so, replacing with your new amended soil and mix in with the previously used soil to prepare the soil for your new plants. Again, water thoroughly before adding your new plants.
Another cost-saving alternative to filling your containers, is to place a plastic pot upside down, basing the size of your plastic pot on the size of your container https://extension.oregonstate.edu/gardening/techniques/container-gardening-basics). By inserting a pot into your container, you will fill space and lessen the amount of potting mix as well as lighten your container if you should want to move the container. Be careful to choose the right size of plastic pot, as you want to allow plenty of space for potting mix for your plants’ roots to grow.
As you begin to fill your container, leave approximately 1” of headspace to allow for a water reservoir so that when you water the plant, the water doesn’t flow up and over the sides of the pot. After you’ve filled your container, you should moisten your potting mix before planting.
Finding the right balance as to how many plants to include in your container can be challenging. You’ll want to leave enough room for your plants to grow and mature, as well as allow for air flow through your container. This University of Illinois Extension website, https://web.extension.illinois.edu/containergardening/blueprints.cfm, features a variety of blueprints for designing container plantings and details the plants, number to purchase, and placement to achieve the results in the photos. Remember, you can always add a plant if your container seems sparse.
Most gardeners are aware of the adage for filling pots: select a thriller, a spiller, and a filler. Think of the thriller as the centerpiece and place in the middle of the container if your container will be viewed from all sides or at the back of the pot if viewed from one side. Typically, only one centerpiece plant is needed and while most gardeners default to the typical dracaena spike, consider ornamental grasses, cabbage palm (Cordyline australis), or a tall blooming flower such as cleome hassleriana, commonly known as spider plant.
The fillers are mounding plants, and you should purchase three to five of these plants, depending on the size of your container. You can include a variety of mounding plants or purchase all the same plant. Other than the typical geraniums or marigolds, consider using a basil or other herbs, fern, or hosta. You can also purchase a perennial plant and move the plant into your garden beds in early fall for next year’s enjoyment.
The spillers tumble over the sides of the container, and in addition to the usual varieties of wave petunia, sweet potato vine, or bacopa, consider nasturtium or one of the many types of ivy (https://extension.psu.edu/the-art-of-container-gardening). There are plenty of sources for inspiration for your planters, however, the fun is in the experimentation.
If you are new to container gardener, you may find this University of Illinois Extension website, https://web.extension.illinois.edu/containergardening/blueprints.cfm helpful as it features a variety of blueprints for designing container plantings and details the plants, number to purchase, and placement to achieve the results in the photos. The site also includes fresh ideas for containers, window boxes, and single plantings.
While container gardening can be an enjoyable summer hobby, some gardeners may want to consider filling containers with plants other than annuals. If you have perennials that need to be divided in your garden, such as hosta, divide the plant and place it in your container as shade-loving filler. At the end of the growing season, you can replant elsewhere in your garden or share with a friend for fall planting. Shrubs can also be used in containers and many of the newer dwarf shrubs are ideal for container gardening. Broadleaf evergreens, such as hollies or boxwoods are ideal for planting in containers for four-season enjoyment (https://web.extension.illinois.edu/containergardening/overwintering.cfm).
You’ll want to select a container that can withstand the freeze and thaw cycle and situate the planter in a protected area. I’ve purchased a shrub for a summer container and transplanted it successfully in the fall months.
Finally, don’t forget to fertilize your plants through the growing season. You can mix in a slow-release fertilizer when planting your container or apply a liquid fertilizer when watering and apply every two weeks. If your container is filled with textured foliage, purchase fertilizers high in nitrogen. If you want to keep your container pushing out blooms all summer, opt for a fertilizer high in phosphorus
(https://web.extension.illinois.edu/containergardening/fertilizing.cfm).
Every spring, as I am dragging my containers out of winter storage, I look forward to the creative opportunity to fill containers with a variety of plants. I’m often surprised at how a container that I originally didn’t think contained a pleasing variety of plants matures into an eye-catching display. I’ve also enjoyed exploring the use of perennials that needed to be divided during my spring garden, filling a role as fillers or spillers in my containers. I’ve also enjoyed my container gardening throughout the winter months with a well-selected shrub and placing a few spillers in the container for summer color. This summer, think outside the typical container plantings and allow your creative side to have some summer fun!
If you’re interested in becoming a Master Gardener, contact Penn State Extension at 570-726-0022, or refer to the Penn State Extension of Clinton County Master Gardener website and look for information on How to Become a Master Gardener.
Carol Lugg has been a Penn State Extension Master Gardener since September of 2022. She can be reached at clintonmg@psu.edu or through the Clinton County Master Gardener Hotline at (570) 858-0198.
