Linn County Master Gardener, Lisa Slattery, provides the following on the basics of container gardening:
I consider a beautiful container of plants as a mini garden. Containers are perfect for people without time and space for a traditional garden. Plus container plantings can be moved around. They add color, beauty and grace to walkways, porches, patios and decks.
There are a few keys to successful containers. First choose a container that fits your space – think window box, hanging basket, wall-mounted pots, and classic terra cotta clay pots. If your container doesn’t have drainage, drill four ¾ inch diameter holes in the bottom. To help fill up space in large containers, place plastic packaging “peanuts” in the bottom, cut to fit a layer of porous landscape fabric (to help separate soil and “peanuts” for clean-up) and top with good potting soil. Don’t use garden soil since it will compact in containers. Choose a commercial potting soil or make your own with equal amounts of soil, sphagnum peat moss and perlite.
Place the tallest plants in the center with shorter plants and trailing plants around the edges. You’ve heard the saying – a thriller, a filler and a spiller? Make sure you set the plants at the same depth they were already growing in the cell-pack or pot. Choose plants that share the same light requirements, sun loving plants for containers on hot cement walkways and shade lovers for pots under trees.
After planting always water thoroughly. Just like light requirements, you’ll want to make sure you don’t mix water hogs with plants that like dry soil. For example impatiens like moist soil and petunias likes dryer soil. Your watering schedule will depend on the container size and placement. All containers should be checked daily. One year I planted way too many pots on my hot, sunny deck and my summer turned into a watering nightmare.
Containers require regular fertilization. Soluble fertilizers can be applied weekly at ¼ the recommended monthly rate or you can opt for slow release fertilizers which release a small amount of fertilizer every time the plant is watered. Check labels for application rates.
Maintain your containers by removing dried leaves and spent blooms regularly. Petunias or other leggy annuals need to be pruned mid-summer. Cut back stems to about four to six inches to promote branching out and more blooms.
So, thriller, filler, spiller, right? What to plant? Choose plants and colors that you like, keeping in mind like light and water requirements. Think about mixing flowers and foliage, upright growers and trailing plants. For a nice list of recommended annuals for containers visit the ISU extension website at http://www.extension.iastate.edu/Publications/RG301.pdf and as always, happy planting!