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Winter Perennial Cleanup.

By Skip Richter
Contributing Editor

Late winter is a good time to do some cleanup work in your perennial beds around the landscape. A little sprucing up now will pay off in a much more beautiful landscape during the coming season.

The term perennial can correctly be applied to any plant that returns for more than two years. This would include shrubs and trees. However. when we say perennial we usually mean plants that die back to underground structures each winter and return the following spring. These plants are more specifically known as herbaceous perennials.

Sometimes also included in the general term perennials are certain herbaceous evergreen plants that don't die back in the winter, such as cast-iron plant. The term is also applied to plants that are rather woody near the base that also don't die back completely in your particular growing zone but which may be cut back like a perennial. An example would be a subshrub such as Salvia greggii.

I should also point out that Texas is one big state. What is perennial in central or southeast Texas may be an annual in the metroplex or the Panhandle. Therefore some adjustments may need to be made as I refer to specific plants as perennials.

For the sake of this article, I will be using the term perennial in this broader sense of including all these plants that die back to the ground in winter and others that don't but may be cut back at this time. Here are a few tips to help you get the various types of perennial plants around your garden in top shape for spring.

Flowering Perennials
The first hard freeze will kill back the top growth of flowering perennials such as cannas, Mexican bush sage (Salvia leucantha), various penstemons, lantana, cigar plant (Cuphea ignea), Mexican mint marigold (Tagetes lucida) and various types of ginger. Cut these plants back to near the ground and chop up the top growth for use in mulching or to include in your compost pile.

Even if the top has not been completely killed to the ground, it is usually a good idea to cut them back since some freeze damage may have occurred in lower areas, and cutting back will provide for a more attractive plant in spring when fresh new growth appears.

If a species is marginally hardy in your area, pile the mulch up several inches over the base of the plant to provide a little extra protection from late cold snaps. Yellow bells or esperanza (Tecoma stans) and butterfly ginger (Hedychium) are two examples of plants not dependably hardy throughout Texas.

Perennials that bloom in the summer and fall are best divided in late winter and early spring. Dig the clumps and use a sharp butcher knife or Japanese Hori-Hori knife to cut them into sections for resetting them in your garden beds. Replant the sections at the same depth they were previously growing and water them in well. Then mulch the soil around the plants.

Subshrubs
This gardening term generally refers to plants that are woody at the base but that may partially die back in winter. Examples include autumn or cherry sage (Salvia greggii) and skeleton-leaf goldeneye (Viguiera stenoloba).

These plants have characteristics and growth habits somewhere between what we think of as woody shrubs and herbaceous perennials. They are often treated more like shrubs or simply left unpruned, resulting in a rangy, unattractive appearance. Cherry sage takes on a more open, woody appearance and does not bloom as well when left unpruned.

These plants should be cut back to 6 to 10 inches high depending on the species. They will resume growth in spring, creating fuller, more compact plants without all the old woody growth. Cherry Sage blooms much more profusely this way. By early summer it will be starting to get rather lanky and its blooms will be fewer atop long spent bloom stalks. That is a time to shear it back by one third, apply a little fertilizer and water it in well to bring on fresh new growth and more blooms.

Evergreen Herbaceous Groundcovers
Liriope stays green year-round and is often left untrimmed from year to year. After a long hot summer or cold winter it can start looking pretty ragged. It's a good idea to cut it back to 2 or 3 inches tall in mid-to-late winter. Your lawn mower or string trimmer can be used for this purpose.

Don't wait too long to do this because liriope will begin its growth very early in the spring and a late trimming will result in ragged tips on the newly emerging foliage. Mondo grass can also be sheared back when it starts looking less attractive.

Vining ground covers, including Asian jasmine, vinca, wedelia, wooly stemodia and ivy, may be left unpruned most years. However, if the plants begin to look worse for the wear they can be cut back to a few inches high with a mower or string trimmer, although this is no easy task. After being cut back, the plants will put on fresh new growth with the arrival of warmer spring weather.

Cast-iron plant can also become unattractive after long hot summers and cold winters. Prune out the old stalks just above the ground in late winter using hand pruners. New growth will soon fill in, creating a fresh, attractive planting.

When you've completed this late winter pruning you may want to go ahead and divide some of these clumping ground covers. Dig up the plants and split the clumps into sections with a sharp spade. You can push two spading forks into the clump back to back and then push the handles apart to pry the clump apart. Then reset the plants and water them in well.

Ornamental Grasses
We have many beautiful types of ornamental grasses in our landscapes. Clumping ornamental grasses, including various types of miscanthus and pennisetum, are attractive throughout the growing season. Their seed heads, which appear in late summer, are especially attractive. I prefer to leave them unpruned through the winter season when the straw colored clumps still serve an ornamental purpose, especially on a frosty morning when ice crystals form on the seed heads and arching foliage.

Prior to the arrival of new growth in early spring, these clumps should be cut back to within 6 to 10 inches of the soil line. If left unpruned, the old dead growth will detract from the attractiveness of the fresh new growth. However pruning ornamental grasses can be quite a chore!

Some gardeners use a pair of hand pruners or loppers to prune their ornamental grasses. With sharp tools as well as some time and patience this will work. Others report that a string trimmer with a brush blade works well.

One Extension bulletin from the southeast suggests wrapping two strips of twine or two bungee cords very tightly around the clump, one at ground level and the other a few inches above it. Then use a reciprocating saw or a chain saw to cut the stalks between the two restraints. I've not tried this technique, but it does sound interesting! I would suggest taking it slow as some grasses can clog up the chain housing on a chain saw if you proceed too rapidly.

Pampas grass often is left unpruned and becomes quite unattractive. Its sharp leaves and incredibly tough stem and leaf tissues make pruning extremely difficult. Have a sharp pair of loppers and wear protective eye glasses, a long sleeved shirt and gloves to protect yourself if you try to take on a clump of pampas grass!

After a few years, ornamental grasses can begin to develop a dead center as the clump spreads outward. At this point they need to be divided and reset to maintain an attractive appearance. Dividing grass clumps is not an easy task because they are extremely tough.

Begin by digging the grass plant up completely. Then use a sharp spade to cut the clump into sections for replanting. A machete or sharp butcher knife may also be used to divide the grass clump. Don't be afraid of harming the grass plants as they are quite resilient. Discard the dead center of the clump into the compost pile. Then reset the grass divisions and water them in well. They will take off growing rapidly with the arrival of warm weather. You may want to pot up some of the extra divisions for sharing with friends or planting elsewhere in your landscape.

Other Tips for Perennial Beds
Late winter is a good time to plant or to re-plant perennials in a new location. Perhaps you have a few plants that struggled in too much sun or shade this past year. Maybe there are some that needed to be in a better drained bed or where they could receive more moisture. Now is a good time to dig those plants, prepare the garden beds and then reset them in their new location.

Make sure to mulch all your perennial beds well. Mulch prevents weed seeds from germinating, protects the soil surface from crusting and erosion, moderates soil temperatures including winter cold and summer heat, and gives a garden bed a more attractive appearance.

Don't throw all those trimmings from your perennial plants away. They are organic matter and therefore contain nutrients that will be released as they decompose in a compost pile. They can also be chopped up and used as mulch or as pathway material.

As the perennial plants in your landscape begin to grow in the spring, apply a moderate application of fertilizer around the plants. Scratch it into the soil surface and then water it in well. This will provide a boost for the growing plants, ensuring good vigor and, in the case of flowering plants, good bloom production.

If you have aged manure to use around the plants, go ahead and apply it in the winter because it will gradually break down and release its nutrients as the soil warms up and microbial activity increases.


 

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