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Faithful, but not Foolproof

perennials, how long do perennials live

Perennials provide a sense of time and place to a landscape. It is wonderful to see familiar color return each year. Nature’s clock uses flower blooms instead of numbers to display progress through the seasons. The Iris and Baptisia tell us spring is here. The Daylilies and Coreopsis announce mid-summer. The Joe Pye Weed and Goldenrod tell us the children will be going back to school. Year after year, perennials choreograph their burst of color.

Perennials come back each year, at least for a while. Some are more faithful than others. Some are just reliable, self-seeding annuals. Some will come back, but only if you divide them every few years. Some are perennial, but only if the outdoor temperature stays above freezing. Don’t be fooled by the perennial sales pitch. You can count on a perennial living a year or two longer than an annual, but after that, the return each spring is dependent on the species. Perennial is a relative term.

Most perennials go dormant sometime during the year. Perennials are herbaceous plants with soft, tender, watery stems that cannot withstand freezing. During winter months, their foliage will either disappear or dry up and become debris, harboring pests. Bare ground will be an invitation for volunteer weeds, so in winter perennial beds require a cover crop, compatible succession planting with cold-season plants, or a thick layer of mulch. When designing a garden, you will need to anticipate months with bare ground and plan for annual maintenance requirements as the growing season begins and ends.

Many perennials suffer from the donut-hole effect. If you notice declining health of a perennial planting, check to see if the clump needs dividing. As perennials grow each year the mass of foliage and root system fights for soil and nutrients. The center of the perennial clump is the site of fierce competition. In time, usually about three years, the intertwined growth is so thick it squeezes any healthy growth to the periphery of the clump, causing a dead zone in the center. When you see a donut-hole forming with your Daylilies and Iris, it is time to lift the entire clump out of the ground, separate the separate plants, and replant new clumps in areas where there is plenty of room to grow. When planning for perennials in a landscape design, you should also plan for your maintenance specifications to include this essential task. Division is the solution for the donut-hole effect.

The “new perennial” garden movement is the latest trend in landscape design. It is opening up ideas for creating new, natural-looking meadow gardens. The style appears to require a dedicated gardener with a sophisticated herbaceous-plant knowledge base for each site, in order to nuance the interconnected growth of different species. It may bring more die-hard annuals, perennials, and native grasses into the market. The off-season changes for herbaceous plant material can be dramatic! The expanded choices will draw on the professional landscape designer’s horticultural wisdom as well as real-life experience with each species. When you specify perennials in large-scale landscapes, research real-life experiences using them over time.

The Persistence of Perennials