Perennial Basics from Dallas County Extension

The Iowa State Extension and Outreach of Dallas County provides research-based information on various topics—including horticulture. The Master Gardener program allows for citizens to become formally trained, participate in community projects and become experts in all things lawn and garden. The following are their tips on planting and caring for perennials.
Although perennials do not need to be planted every year, they still require a certain amount of maintenance. Among the list of required tasks are watering, fertilizing, pinching, staking, deadheading and dividing. Before discussing each of these actions, it is important to know how to select a perennial that will work for your yard.
For partially or heavily shaded areas, hostas (Hosta spp.), Jacob’s ladder (Polemonium caeruleum) and bleeding hearts (Dicentra spp.) are wise selections. Also when looking to plant in the shade, don’t forget about native perennials such as woodland phlox (Phlox divaricate), Solomon’s seal (Polygonatum biflorum) and merrybells (Uvularia grandiflora). Many perennials live in the sun, allowing them six or more hours of direct light. Among them are hollyhocks (Alcea rosea), delphiniums (Delphinium x elatum) and foxgloves (Digitalis purpurea). “Perennials for Sun”, an ISU Extension publication is available for purchase at the Dallas County office.
When beginning to plant, take into consideration the soil composition. Most perennials thrive in well-drained soil, so it’s important to avoid planting them in low-lying beds that can accumulate rain. There are, however, certain perennials such as sweet flag (Acorus calamus), queen-of-the-prairie (Filipendula rubra) and Japenese iris (Iris ensata) that will flourish in wet soils. For new bed creation, start in the fall for spring planting and in the spring for summer planting. If unsure about the soil makeup in your yard, contact the Extension office to find out how you can get your soil tested by Iowa State. After results, you can adjust the chemical makeup of your bed.
If working in an existing bed, clean it up by pulling weeds and loosening the soil where you intend to plant. It’s important to know, a hole should be dug as deep as the container the flower comes in. If your hole is too shallow, the roots do not have enough room to spread. Water the plant as soon as you have transplanted it to establish these roots. When it comes to future watering, soak the soil if it is completely dried out, avoiding the actual foliage which could contract disease from excess moisture.  
Because some perennials are tall and shoot straight up, they tend to fall over due to the weight of their flower. Help them stay upright by planting them against structures like fences or fasten them to a wood stake with the use of twine. Sometimes plants such as phlox and sage attempt to grow tall. To make them bushier, you can use a method called “pinching.” Pinching is the process of removing the tips of the plant, resulting in leaves developing on these short stems.
Deadheading and dividing are additional ways to care for your perennial. Deadheading involves removing the “spent” flowers from the plant. Not only does this keep it looking neat and trim, but it eliminates the need for the plant to expend extra energy on fueling an already dead section. By following these tips, you may initially find yourself with a healthy plant, but over time you may observe that your garden is not coming back as full or vibrant as the years before it. This is when division, or relocation, becomes necessary. Dig out the entire plant and clean up the roots by pulling them apart, cutting off roots that appear dead or diseased. Replant the perennial in a different area. Think of this as a time to recreate your garden.
If in doubt when purchasing a plant, check plant labels to find light requirements, recommended water intake and also USDA Hardiness Zones. Remember, just because a plant is a considered a perennial in California, does not mean it will come back every year in Iowa. For additional information or questions, contact the ISU Extension Hortline at (515) 294-3108 or hortline@iastate.eduto speak to horticulture specialists about your gardening needs and questions

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