Tips For Perennial Gardens

from Ohio State University Master Gardener Training Manual:

http://www.hcs.ohio-state.edu/mg/manual/index.htm

 

design • Successful color combinations and continual color throughout the season are challenges facing gardeners who choose to grow perennials. Plot the blooming periods of the plants you choose on a linear calendar. This aides in developing continuous bloom and combining color combinations successfully.

Large plants may be planted singly. Plant smaller plants in clumps or “drifts” of 3, 5 or 7. Avoid planting in precise rows. Informal shapes are easier to maintain than formal groupings. Curved lines, varied plant heights, masses and textures result in a more natural appearance.

Careful attention to foliage is important with perennials because few perennials bloom for more than a few weeks. Texture, form, height and color should be combined carefully. In addition to a linear calendar, plotting the garden to scale will ensure that these factors will be combined successfully.

fertilizing • Perennials often stay in the same location for years. This means that selection and preparation of site for new plantings are vitally important. Organic matter worked into the soil at planting time can provide nutrients and improve aeration and drainage.

For perennials that require annual fertilization, apply in spring as new growth begins. Broadcast 1 pound of 5-10-5 or 6-12-6 over 100 square feet of area. Make another 1-pound application 8 weeks later. Wash off any fertilizer that remains on foliage. Astilbe, chrysanthemum, delphinium, lupines and summer phlox are perennials that should be fertilized annually. It is always best to follow recommendations of a soil test. Test soil every 3 years.

mulching • Winter mulching helps to prevent winter injury from HEAVING. After soil has frozen, apply a layer of coarse mulch. Four inches of pine boughs, pine needles or straw are suitable. Pull back mulch from plant crown as soon as new growth begins in spring. Winter mulching of perennials is especially important in the following situations:

·              when marginally hardy perennials are grown;

·              for newly transplanted or divided perennials moved in fall.

supporting • Perennials with heavy flower heads or long thin stems may require staking. The weight of water or wind can easily damage flowers and stems. Examples of perennials that usually need stakes or supports include delphinium, foxglove, Achillea ‘Gold Plate,’ selected asters and mums. Stake when plants are about 6 inches tall so supports are hidden by foliage later in the growing season.

deadheading • The removal of spent blossoms is called “deadheading.” Many perennials will continue to bloom if faded flower heads are removed. This is especially true of dianthus, coreopsis and shasta daisy. Some perennials will bloom again later in the season. Examples of perennials that will produce a second flush of blooms if flower stalks are cut back to the ground include delphinium and false indigo.

There are different methods of deadheading. Some plants will rebloom on the same flower stalk. In this case, it is necessary to remove only the dead blossom. Campanulas and balloon flowers will rebloom if faded blossoms are removed. Other perennials are deadheaded by cutting off old flower stalks down to where the new bud shoots appear. Obedient plant should be deadheaded in this manner. When deadheading, look for the location of the second bud or set of buds.

Although faded flower heads should be removed on all plants, only some will produce new blooms. Others will not rebloom. Removing spent blooms diverts energy that would otherwise go into seed production.

Garden markers and record keeping are very helpful with certain perennials. It is easy to forget about perennials that appear late in spring or die back before the rest of the garden. They are often “rediscovered” by accidentally digging into them. Good candidates for markers are butterfly flowers, Oriental poppies and balloon flowers.

dividing • Most perennials decline with age and should be divided every 3 or 4 years. New growth can be noticed on the outer edges of clumps. Divide perennials when you notice the following:

·              a dead center formed in the crown area with a ring of growth around it;

·              blooms becoming sparse and smaller;

·              plants looking obviously crowded.

Do not divide perennials when they are in bloom. Divide midsummer and late-summer bloomers in spring (April or early May) when growth is 2 to 3 inches high. Divide spring-blooming perennials in late August or September.

To divide perennials, dig the entire plant and separate it into sections, or take divisions from the edge of the clump while it is still in the ground. Ornamental grasses have tightly tangled, tough root systems that are difficult to divide. Do not hesitate to cut through a large clump of roots with a sharp ax.

Some perennials are rarely divided or moved unless absolutely necessary. These include gas plants, peonies, tree peonies, foxtail lilies, goatsbeards, butterfly weeds and bleeding hearts.

After a killing frost, remove dead stems and foliage. Leave a piece of stem a few inches long to assist you in locating plants the following spring.