Maintaining wildflower plantings for enduring beauty
Native wildflower plantings are beautiful expressions of the original landscape that once covered much of the country, including the great prairies of the Heartland as well as other types of grasslands that originally existed across the continent. They're not only beautiful, but they attract wildlife and are educational as well.
On golf-courses, an increasingly popular site for native stands, these plantings are functional as secondary roughs and out-of-bounds areas. At the same time, they serve as a good public-relations tool, showing that the course is trying to promote wildlife. In parks, botanical gardens and other public areas, interpretive trails add to the enjoyment and learning that result from wildflowers growing in a natural state.
Native-wildflower maintenance initially requires you to coddle new plantings and remove brush and other invasive weeds. However, for their size and impact, wildflower plantings are relatively low-maintenance landscapes. Plantings often take 3 to 5 years to mature but thrive indefinitely with proper maintenance. America's oldest native wildflower planting--the Curtis Prairie at the University of Wisconsin in Madison--was planted in 1936 and still is a beautiful sight throughout the seasons. Our relatively new planting at Powell Gardens near Kansas City, Mo., though young, already has similar aesthetic appeal.
What's a wildflower? The phrase "wildflower" can mean many different things. Here, however, I'll discuss wildflower plantings for full sun or, at most, partial shade. Sun-loving wildflowers originate from a variety of habitats, such as prairies, savannas, glades, deserts, dunes, marshes and meadows. Because grasses generally dominate these habitats, we typically refer to them as grasslands. Species such as big bluestem, Indian grass, little bluestem and switchgrass were major elements of the original tallgrass prairies but are native to much of the United States east of the Rocky Mountains.
Non-grass flowering plants, or forbs, also are common inhabitants of grasslands. The species listed in Table 1 (page 38) are examples of truly American wildflower forbs, with dozens of species native from coast to coast.
To many people, the word wildflower implies that the species is native. However, many "wildflower" mixes contain species that do not grow naturally anywhere near the locality where you're planting them. Often, these are quick-blooming annuals that will not reappear as the planting matures unless some disturbance of the soil occurs. Such mixes quickly can produce a display of colorful flowers and may be useful as cover crops for other longer-lived plants. For example, cosmos is a common component of some mixes, even though such displays mislead the general public on what constitutes a true wildflower planting.
Unfortunately, some of these color plants can become invasive, and some mixes contain species that conservationists are trying to rid from local native habitats. Dame's rocket (Hesperis matronalis) is one such biennial that spreads vigorously into woodlands in the Midwest. Conservationists worry that it may soon may become a problematic weed. A proposal to ban its sale in Illinois was unsuccessful. Careful use of such plants will head off future attempts at such legislation. Do some reading to find out which plants are local natives. Regional wildflower guides for all parts of the country are easy to obtain and are good references for determining species native to your region. In addition, many local conservation organizations and nature centers readily distribute information on native wildflowers.
Provide a good mix Many native wildflowers make good cover crops (see Table 1, page 38 for some common examples). Some species, such as daisy fleabane and frost aster, are so ubiquitous that they appear in almost every planting on their own. I often receive questions about these two plants and reply that they actually are desirable plants. Native-wildflower cover crops are a major component of young plantings and gradually die out as the planting ages. They often reappear following disturbances such as drought or animal diggings.
Wildflower plantings are most successful when you use them in species compositions similar to those of their original wild state. Grasses usually predominate in such situations and should make up the largest component of any wildflower mix. Grasses provide physical support to many wildflowers that otherwise would be too rank for self support.
Turf managers know that grasses fall into two major groups based on how they photosynthesize: C3 (cool-season) and C4 (warm-season) grasses. For example, Kentucky bluegrass is a cool-season species that thrives in the northern parts of the United States. Warm-season turfgrasses such as St. Augustinegrass perform well in the southern states.
Wildflower plantings should contain both C3 and C4 grasses. Native cool-season grasses (see Table 2, page 42) green up early in spring and remain green late into the fall. In the South and other warm-winter climates, they may remain green year-round. Native warm-season grasses (see again Table 2) thrive in the hottest months. They exist naturally from north to south and often have beautiful fall colors with the onset of frost and cool weather. The management techniques I describe here apply to both warm- and cool-season grasses.
Weed control in young plantings Initially, the maintenance of any wildflower planting must include weed control. While I do promote the use of prescribed fire, mowing is an acceptable substitute for burning. This especially is true during the first season because fire can injure young plants.
The first weeds to appear are annuals, but these will not thrive in the long run if you do not disturb the soil (which stimulates their seeds to germinate). However, if annual weeds are exceptionally heavy, you may want to control them during the first year. To do this, mow your planting using your mower's highest setting (6 inches or higher). Wait at least until August to minimize impacts on nesting birds. If you included color annuals in your seed mix, you may wish to forgo initial mowing and just concentrate on cutting the most offensive annual weeds, which most likely will include giant ragweed (Ambrosia trifida).
For appearance's sake, I also recommend a mowing in late winter or early spring. This allows the planting to get a new start for the next season, providing space for newly emerging grass and spring flowers.
Mowing to control brush I typically do not recommend annual August mowing, because repeated August mowing prevents many late-season plants from blooming and setting seed. This can change the composition of your planting by favoring the spring and early summer-blooming species.
However, if you must mow to control brush, August is the best time to do it. At this time, plants begin to transfer most of their carbohydrates down to their roots for storage through the winter. If you mow off a woody plant at this time, you rob the root system of much of its energy. It then will expend more energy on new growth. This new growth is tender and susceptible to frost, which will not be far off in most parts of the country. Herbaceous plants, however, still have time to regrow by autumn and provide winter cover.
Mowing in August has another benefit: Most nesting birds have finished raising their young by this time. Thus, you will not destroy nests with eggs or young chicks. The goldfinch, which nests in August, is a notable exception, but a quick walk through your planting to flag nesting sites is an easy task.
Fire For optimum results, you should use prescribed fire in addition to mowing. Most of our continent's natural landscape is adapted to and sustained by fire. Since the time of the Smoky-the-Bear campaigns that promoted the suppression of all fire, we have learned that not all fires are bad. In fact, fire is vital for the health of many ecosystems. Fire burns off duff and recycles nutrients back into the soil. It also quickly promotes a vigorous new landscape by exposing the soil and providing a heat-absorbing dark surface which promotes earlier growth. You easily can see fire's effect by comparing adjacent burned and unburned portions of a prairie. Burned areas have vigorous lush grasses that don't have to compete with last season's duff. The same goes for forbs, whose flowering and fruiting improve after a fire. Of course, some exceptions exist, but these mostly are species rarely found in the wildflower seed trade.
Fire can be dangerous, but it also is safe and effective when properly prescribed and controlled. Natural fires typically occur in the fall. However, after 10 years of experience, I have learned it can be difficult to perform controlled burns at that time of the year. Falling, burning leaves from trees, neighboring unharvested crops and wet growth that's difficult to ignite can make fire tricky to work with at this time.
Instead, I suggest late-winter or early spring burning as the most effective and safe. Ensure you perform the burn before the desirable cool-season grasses and forbs have broken dormancy or the fire will set them back or kill them.
Early spring fires do little harm to brush--most of the woody plant's energy still is stored in its roots, and a vigorous flush of new growth will result after a fire. However, removing surrounding brush encourages herbaceous plants by increasing their exposure to more early season sun. Another reason for holding off your burn until early spring is to retain cover and habitat for wildlife through the tough winter months.
You should set fires only under desirable weather conditions, including: * Humidity greater than 65 percent * Maximum wind speed between 5 and 15 mph * Temperatures less than 70 degrees F.
On windy, dry, hot days, fire is explosive and nearly uncontrollable. Conversely, conducting a prescribed fire on a day with no wind can be dangerous because the fire may be erratic and move in its own direction.
Necessary equipment includes a fire starter, flappers, rakes, face masks and, most importantly, the availability of water. Proper buffers around buildings and landscapes also are vital.
You must contact local authorities to obtain the necessary permission to conduct a prescribed fire. In many urban areas, an EPA permit also is necessary. In some locations, you can burn wildflower plantings as landscape waste in accordance with open-burning laws. Local government agencies can provide you with applicable regulations.
After receiving the necessary permits, you should always contact the local fire district. This is important in case you have problems, but mostly because they will certainly get calls from concerned citizens who see the smoke. You also must contact all adjacent landowners so they are aware of the project.
If you are uncomfortable using fire, don't. Mow instead, or hire a firm to perform the burn for you. Numerous such firms exist and, especially if you are in an urban area where regulations are more restrictive, they can save you a lot of time with permits, materials, equipment and labor.
Some concern exists that fire may burn habitat for desirable insects, such as butterflies, and for all sorts of other wildlife. Therefore, it is a good practice to leave some areas unburned. Also, you may want to mow an area after burning to cut off remaining stalks and stems for a uniform appearance. We did this at the Winnebago County Forest Preserve District Headquarters (near Rockford, Ill.) prairie restoration for a neater-looking spring landscape. Incidentally, three uncommon, habitat-restricted (prairie-dependent) butterfly species colonized that prairie despite annual burning.
Controlling woody plants Aside from mowing and burning, controlling isolated woody or brushy weeds probably is the most important management practice for wildflower plantings. Nature wants to grow a forest almost everywhere, and--without mowing, burning and grazing--most areas eventually become brushy and, finally, forested. Mowing and burning keeps this natural succession under control, but isolated woody plants always seem to remain. Spot-treat them with appropriate herbicides. For a better appearance (no standing dead plants), cut out the woody plants and treat the stumps with herbicides. This method usually succeeds in spring when sap flow can flush the herbicide off the cut stems. However, this treatment is more likely to succeed in late summer when the plant is transporting nutrients from its crown to its roots.
I list the worst brushy invaders in Table 3 (above right). Species with rhizomes or stolons are the most difficult to control because they spread quickly and interconnect as one plant. Thus, any treatment must include the whole stand to be effective.
Some woody species (see Table 1, page 38) belong in wildflower plantings and are well-adapted to fire and mowing. Learn to recognize these species and simply treat them as you do the rest of the planting. They should succeed on their own.
Herbaceous weeds In addition to mowing and burning, you may need to perform other weed-control measures. Fortunately, this need will be minimal if you were thorough with your initial weed control. Herbaceous weeds may be annual, biennial or perennial. Annual weeds, whose control I mentioned earlier, are least offensive because they usually do not reappear after the first year. However, biennial invasive exotic weeds (see Table 3, above right), especially thistles, can be long-term pests.
Control first-year thistles with herbicidal spot treatments. Cut second-year thistles below the soil line just before their bloom. If you wait to cut biennial thistles until they're in bloom, they'll probably produce seed even after being cut. Incidentally, many thistle species are native to the United States. Do not remove them--they are not invasive and have high wildlife value. You can identify many native thistles by the whitish or silvery undersides of their leaves, which are less prickly and touchable than those of many invasive species. A picture-identification manual is helpful too. You may need to engage in some public relations to assure people that these plants should remain.
Sweet clover is another serious biennial-weed problem. You can kill sweet clovers by cutting them below their foliage when the plant is in full flower. This timing is important because if you cut too early, the plant may re-flower. If you cut too late, the plant still can set viable seed. If sweet-clover infestations are minor, you should simply pull them by hand.
Perennial weeds (see Table 3, above right) are more difficult to control. It is best to treat them with herbicides before planting the wildflowers. If infestations occur anyway, spot-treat them as necessary. Most state departments of natural resources or conservation provide material on how to control local weeds and brush, and you should consult these for accepted control measures in your area.
In 1987, we planted a native grasses-and-wildflowers prairie as the landscape focus of the Winnebago County Forest Preserve Office. It took 3 years to look really attractive and 5 years to completely mature (the drought of 1988 definitely slowed its establishment, but it ultimately survived and flourished). Once mature, the landscape's ornamental impact made believers out of Winnebago staff.
They burned and mowed each spring, and from that point on, the new growth of grasses and flowers changed continually through each season. The autumn colors were spectacular, and the stalks and stems stood through winter, interplaying with the frost and snow. They enjoyed a greater variety of wildlife as well. The wildflower meadow I currently maintain at Powell Gardens is having similar impact, and we currently are adding several acres to it. After seeing how wildflower plantings can improve your facility, you'll want to do the same!
Alan Branhagen is horticulture manager at Powell Gardens (Kingsville, Mo.).
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