Every month at the Pitt County Arboretum, we hold what we call a Northside Plant Walk, where we walk through the Arboretum (often including a loop on what is known as the Northside Walking Trail) and discuss plants that share a common characteristic. I often have many of the plants in mind well ahead of each month’s tour, but I also like to walk the grounds myself a day or two before the tour to see what else might catch my eye that is not already on my radar. I tell you this because when I was putting together this past month’s tour, the bloom of our Toad Lily in the Perennial Garden called to me so loudly that I simply had to include it. Toad Lily (Tricyrtis hirta), also called Japanese Toad Lily or Hairy Toad Lily, is an herbaceous flowering perennial plant that is excellent for shady sites and average to wet soils. It is native to Island regions of Japan, where it is found growing along shady rocky cliffs and stream banks. It was introduced into the United States in the late 1800s, but was found mainly only in botanic gardens and specialty nurseries for many years, and really only became widely available for the average gardener in the 1990’s. The name Tricyrtis, translates roughly to “three bulges,” a reference to the three swollen nectar sacs found within each blossom. The nectar is a favorite of hummingbirds, and flowers are often visited by various butterfly and bee species as well. Above left: Toad Lily flower. Photo: André Karwath, CC-BY SA 2.5 Above right: Toad Lily flowers and leaves. Credit: Alpsdake CC BY-SA 4.0 It can be difficult to find plants that perform well in heavy shade, and especially difficult to find plants that bloom heavily in shade. As such gardeners with shady gardens tend to rely on plants like hosta, ferns, and astilbe, and lament the relative lack of other options. While these are all fine plants, it is always nice to have options. Enter Toad Lily, which not only tolerates shade, but requires it, and will bloom prolifically from late summer through fall. The typical Toad Lily has blossoms that are speckled purple and white, with petals arranged in the shape of a six-pointed star. Individual flowers are small. Plants have a spread of 18-23 inches. The blooms are colorful, but the intricacy and complexity of the shape and color pattern is best appreciated when the viewer can see the flowers from up close, thus it’s ideal, if possible, to plant them along the edge of a flower bed, or near a path, wall, or other feature that allows close inspection. Toad Lily pairs well in the garden with plants like hosta, astilbe, ferns, and hellebores (Lenten Roses), not only due to their previously mentioned love of shade, but also due to a similar affinity for high organic matter and soil acidity. Toad Lily will probably tolerate wetter soils than any of the aforementioned plants, but as long as soils are at least slightly moist it will be happy. It will not perform well in dry areas. Partial shade is okay, but more than half a day of sun will likely cause some leaf burn or other stress. There are quite a few interesting cultivars of Toad Lily, each of which has slightly different flower colors or foliar characteristics. To quickly summarize just a few of these: ‘Alba’ and ‘White Tower’ have white flowers, ‘Albomarginata’ has green/white variegated foliage with purple flowers, ‘Lightning Strike’ and ‘Miyazaki Gold’ have green/gold variegated foliage with purple flowers, ‘Golden Gleam’ has yellow leaves with purple/white flowers, and there are quite a few others with varying combinations.
Last Northside Plant Walk of 2024 If you’d like to attend one of our Northside Plant Walks, the next one will be at 12 noon on November 8th at the Pitt County Arboretum and will focus on Berries, Twigs, and other Underappreciated Ornamental Attributes. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705.
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One of the great things about gardeners is that no two of us have the exact same taste in plants. Some gardeners prefer neat, ordered, well-mannered landscapes, while others lean towards more of a natural, wild aesthetic. Some of us fill our landscapes with familiar, classic plants, while others gravitate towards plants that are uncommon, perhaps even unusual. Some think of gardening as mainly a springtime activity and thus their landscapes are filled with plants that bloom only in April and May, while others value color and interest throughout as much of the year as possible. As such, no two landscapes end up looking quite the same, and the world of plants provides endless opportunities for creative expression. If your tastes tend toward the unusual and unkempt, and you’re always on the hunt for plants that bloom at odd times, you will probably love Lespedeza, also known as bush clover, a sprawling shrub with purple pea-like blooms in the fall. Although there are several species of Lespedeza, the one most suitable for garden use is Lespedeza thunbergii, a variety that grows three to six feet tall and wide, although plants will usually be a bit wider than they are tall. It is worth noting that many other species of Lespedeza are generally considered weeds and sometimes appear on invasive plant lists. While Lespedeza thunbergii will drop some seedlings and does take up a fair amount of space in the landscape, it is reasonably well-behaved compared to its relatives.
The ornamental value of Lespedeza comes mainly from its intense autumn-bloom. Its long arching branches are loaded with tiny flowers from base to tip. Though obviously different in flower color, the shape of the plant creates a similar effect to plants like forsythia, which blooms golden yellow in early spring, or abelia, with its light pink flowers during summer. The flowers are frequently visited by butterflies and the occasional hummingbird. When the long branches rest against bare soil, they will sometimes root at the point of contact. Once rooted, these rooted stems can be cut off and easily transplanted or shared, if so desired. Lespedeza is native to Central and Southern China, and other parts of East Asia, and is hardy from zones 5 through 8. It typically will die back to the ground in our winters, and if you are growing Lespedeza you should plan to cut it back to the ground every spring, in order to allow it generate a flush of new growth. 'Gibraltar' is one of the larger Lespedeza cultivars, growing six feet tall and twelve feet wide. A few of the cultivars of note include ‘Alba,’ a white-blooming variety, ‘Gibraltar,’ which is slightly larger than what is typical for the species, and ‘Little Volcano,’ which has darker rose-purple flowers. Because of its shape and growth habit, Lespedeza is a good plant to incorporate in areas where it can sprawl, such as slopes, near walls or water features, or in border areas. It is also quite drought-resistant once established, so it will do well in hot, dry areas of the landscape.
Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. The calendar has just turned to October, and while that may mean the beginning of “spooky season” for some, it also means that cold nights are coming! It won’t be long until we have to start watching the news for frost alerts and guidance for protecting tender plants. Take some time to bring in any houseplants that are still outdoors and be prepared to protect any tender plants you want to try to squeeze a few more weeks of enjoyment out of. Inspect houseplants before bringing them indoors, to make sure you’re not carrying along any undesirable pests with the plants themselves. Along with the cold weather of fall comes a change in leaf color for many of our deciduous trees. There’s always something nice about the way the new colors paint our landscape this time of year. This change is not an accident of course, there’s a simple scientific explanation behind how and why it happens. The changing of leaf color is caused by a physiological change that happens in the plant during fall. Leaves produce a number of pigments, the most well-known being chlorophyll. Chlorophyll is a green pigment and is the reason the leaves of most plants are some shade of green for most of the year. However, plants also contain carotenoids and anthocyanin, yellow and red pigments respectively. The amount of each pigment a plant produces depends on the temperature and the length of day. For most of the year, leaves produce much more chlorophyll than these other pigments, but in fall chlorophyll production slows down and the other pigments take over. Trees that turn yellow or orange have a lot of carotenoids present, while those that turn red have a high amount of anthocyanin. A number of other factors seem to play at least some role in how brilliantly the colors of fall shine in any given year. One is rainfall. Colors often seem to be more intense if the weather has been dry and sometimes aren’t expressed as vibrantly if there’s been a lot of rain. his can also dictate when the color change happens, as it may occur slightly earlier in dry years than in wet ones. The weather also affects our perception of the colors as well. Colors appear brighter to our eye on clear days than on cloudy ones, so if it is rainy during peak foliage season, it may not be as impactful to us as viewers.
Though we think of fall foliage primarily as a forest phenomenon, many of the deciduous trees and shrubs we use in our landscapes go through the same color change just prior to their leaf fall. Don’t neglect this characteristic when selecting plants to include in your landscape, as fall leaf color can have incredible ornamental impact at a time of year when flowers are sparse. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. This week, let’s round out our discussions of fall-blooming perennials by considering the aster. Asters, botanically known as Symphyotrichum after a recent name change, are a genus of plants in the Asteraceae family (who would’ve guessed), also known as the daisy family. Their late arriving blooms are a welcome sight in fall gardens, and with flower colors mostly on the blue-purple edge of the color wheel they make a fabulous pairing with yellow and orange blooming fall plants such as goldenrod and assorted chrysanthemum varieties, which I mentioned in previous columns. Let’s look closer at a few of the most prominent species of Aster. We’ll start with Symphyotrichum novi-belgii, known commonly as the New England or New York Aster, a species native to the east coast from Canada to Alabama. It is a herbaceous perennial (it dies to the ground in winter and returns in spring from its root system) with lavender purple petals that radiate from a yellow center, forming its disk-shaped daisy flower head. This aster is often found growing in salt marshes and other moist habitats in coastal areas. In garden settings it requires moist, but well-drained soil, and flowers best in full sun. It is a tall, upright grower, reaching 3 to 5 feet high and only 1-2 feet wide, and though the species is lavender in bloom, cultivars such as ‘Peter Harrison’ and ‘Royal Ruby’ offer pink or red blooms with otherwise similar attributes. Top right: Symphyotrichum novi-belgii 'Peter Harrison' has pink blooms. Bottom right: Symphyotrichum novi-belgii 'Ruby Red' has deep red blooms. Symphyotrichum laeve, or Smooth Aster, is slightly smaller at 2-4 feet high and wide, but otherwise fairy similar. Its native range extends a bit further west into the central part of the country, and is probably slightly more drought tolerant than the New England Aster. Both are quite tolerant of nutritionally poor soils. Next is Symphyotrichum ericoides, or Downy Aster. This is a white-blooming species native to Canada, the central United States, and northern Mexico, typically found in fields, clearings, roadsides, and dry thickets. It’s a bit smaller than the other species mentioned so far, at a height of 18-36 inches tall and 12-18 inches wide. The Downy Aster tolerates shallow, rocky soils quite well, and is actually very useful in preventing soil erosion when grown or planted on slopes. This species has white flowers rather the blue and purple so many other asters are known for. The cultivar ‘Snow Flurry’ grows as a groundcover, creating a dense mat of white flowers 4-6 inches above ground. Above left: Symphyotrichum laeve: The blooms of these Smooth Asters are from a second year plant. Photo: Tom Potterfield, CC BY-NC-SA 2.0 Above right: Symphyotrichum ericoides: The Downy Aster has white flowers. Dan Mullen, CC BY-NC-ND 2.0 As native species, asters are an important part of our ecosystem and attract a number of different insect pollinators. They also provide food for birds and other animals. Pearl Crescent butterflies are known to frequent both the New England and smooth aster, as are a number of different native bee species. Songbirds and small mammals such as squirrels and chipmunks feed on the seedheads that persist after flowering, so consider leaving those throughout the winter before cutting the plants back in spring. Asters can be incorporated in the landscape in mixed perennial gardens, borders, pollinator gardens, native plant gardens, and rock gardens.
Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. To continue with the theme of fall-blooming perennials established with my article about chrysanthemums, I’d like to talk about goldenrod. There are several species of goldenrod within the genus Solidago, most of which are native to North and South America. The genus name Solidago comes from the Latin word solidus, meaning to make whole, and is a reference to the medicinal uses of Solidago that were a common practice among many Native American tribes. Perhaps the most familiar species of goldenrod is Solidago canadensis, which is native throughout much of Canada and the United States. This species of goldenrod is a herbaceous perennial with arching branches and grows to a height of 2 to 6 feet tall, with a width of about 4 to 6 feet. The characteristic golden yellow flowers begin to emerge in August and last through October. As the blooms conclude, brown seed capsules covered in whitish-gray hairs develop. Goldenrod has been unfairly maligned as an allergen because of the vague similarity that these seed capsule clusters have to bloom of ragweed, blown pollen of ragwort, and other high allergen plants. In fact, goldenrod produces pollen that is much denser and damper than the light windblown pollen of ragwort and other high-allergen plants, and therefore isn’t particularly of concern in that regard. It is, however, a favorite of bees and other pollinators, and an important one at that, as there are relatively few pollen and nectar sources in the fall compared to spring and summer. Top left: ‘Fireworks’ is an especially popular compact cultivar and diminutive species of goldenrod. Bottom left: Solidago flowers and leaves. Photo: David J. Stang, CC BY-SA 4. Right: The most familiar species of goldenrod is Solidago canadensis. Solidago rugosa, or rough goldenrod, is a slightly more compact species, growing 3-4 feet high and wide. The common name, rough goldenrod, refers to the stems lined with stiff hairs. For many gardeners, this compact form is a bit easier to find space for in the landscape, and the floral impact is just as substantial. The cultivar ‘Fireworks’ is especially popular, and is even more diminutive, at about 2-3 tall and wide. The flowers radiate in all directions and resemble a burst of fireworks, hence the name.
All species of goldenrod are fairly adaptable, but prefer full or mostly sunny conditions and average soil. The plant will, however, tolerate drought and low-fertility soils. It can be used in the landscape in natural areas, native gardens, pollinator gardens, and as a companion plant to other fall-blooming plants such as mums and asters. Compact cultivars such as ‘Fireworks’ can be used in edging pathways, in the front of perennial borders or foundations, and even in large containers. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. Autumn is approaching quickly, and one of the landscape plants we most commonly associate with the fall is the chrysanthemum, frequently referred to simply as 'mum.' Fall flowers are often in short supply, compared to the relative abundance of blooms in spring and summer, and yet reliably year after year, chrysanthemums are the shining star of fall landscapes with their late-arriving blossoms. Chrysanthemums are short-day blooming plants, meaning their bloom is triggered by the shortening length of daylight and increase in length of darkness that occurs each fall. They are members of the Asteraceae, or daisy, family, with flowers resembling the classic disk-shape we associate with daisies. Many of the mums we buy and plant in the fall are herbaceous perennials, though gardeners treat them like annuals, ripping them out after the flowers have succumbed to frost. Though there are several different types of chrysanthemums, and thousands of cultivars, all of the mums we use in North Carolina like essentially the same conditions, preferring well-drained, high organic matter soils in full sun. They will do okay in a small amount of shade, too, and an hour or two of late afternoon shade may even be a good idea, but more than that will reduce the amount of blooms you see. Mums do use a fair amount of water, particularly large, container-grown mums, but they don’t like to be in wet soil, so adequate drainage is quite important. If you’re planting mums this fall and want to overwinter them, you will need to do a bit of work in the spring and summer to duplicate the show you get in year one. Container-grown mums are pinched back repeatedly throughout the growing season in order to develop large dome-shaped plant shapes and they will need to be pinched back that same way in subsequent years in order to grow to the same size and shape the following year. Even the so-called hardy mums, which are treated more like traditional perennials, including cultivars such as ‘Sheffield Pink’ and ‘Mary Stoker,’ should be pinched back for peak performance. Use mums in your landscapes in containers or in the ground, in lining walkways, edging along the front of a border area, or along a wall or other high-visibility areas. Mums can also be used as companion plants with asters, ornamental kale and cabbage, and other plants that stand out in the fall. Mums can develop some leaf spot fungal diseases, but avoiding watering the foliage and instead directing water to the root area of the plants will lessen those issues.
While mums have relatively low toxicity, there is an oil in the leaves and flowers that can cause redness and irritation in some individuals sensitive to the compound. There is also a natural insecticide made from an extract from chrysanthemum flowers and seeds. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. North Carolina has some truly fantastic native plants and there are great reasons to use these native plants in our landscaping. Native plants are part of our national heritage. Many serve as host plants and/or food sources for beneficial insects and wildlife, while many are simply attractive plants that are not often used in modern landscapes. Plants that are native to the United States, or North Carolina in particular, are naturally well adapted to our local conditions and tend to do well in our landscapes provided they are grown in conditions that mirror where they are found in nature. If incorporating natives into your landscape, use them wisely and with a proper amount of consideration. Remember that the conditions in our landscapes are often quite different than those a native plant might grow in naturally. For example, you’ll often find dogwoods growing naturally on the edges of forests, where they receive a good deal of shade, yet many people plant them in full sun in their front yard. Many other native plants grow naturally in wet, swampy areas but when used in the landscape, are planted in dry, sandy soil. Native plants, like any other, are subject to the 'right plant for the right place' rule, meaning that you should pick a plant that will thrive in the conditions you can provide for it. Any plant, whether native or non-native, that is growing in a less than ideal location is going to struggle. Simply knowing that a plant is native to North Carolina doesn’t tell us enough about that plant to make an informed decision on how to use it in the landscape. Above left: Close-up of flower, photo by Jim Robbins. CC BY-NC-ND 4.0 Above right: The flower, photo by Marcia Boyle CC BY 4.0 One underappreciated native tree that I particularly like is the Carolina silverbell, Halesia tetraptera. This is a medium-sized, multi-trunked deciduous tree that grows up to 30 to 40 feet tall, with a slender upright growth habit. Its greatest ornamental trait is its powerful spring bloom, with white, bell-shaped flowers that hang from the branches for a few weeks in April. Flowers emerge just before the leaves, which allows its bloom to have great impact. Silverbell attracts hummingbirds, bees, and a number of different butterfly species. It has dark green leaves that fade to yellow in autumn and drop early, revealing a small brown fruit that has some unique ornamental appeal. Carolina silverbell likes moist, slightly acidic, organic soils and grows well in mostly sun or light shade environments. Carolina silverbell is in the Styracaceae family, related to Styrax americanus and Styrax japonicus, the American and Japanese snowbells. Each of these is more commonly used in modern landscapes, and the American snowbell is, of course, a native as well. While the snowbells are small trees, 10-25 feet tall, and thus easier to fit in most landscapes, the ornamental features are quite similar to the Carolina silverbell. If you’ve got room in the landscape and the right soil and light conditions, Carolina silverbell would be an interesting plant to add. You probably won’t see at any other house on the block. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705.
Since we’re now in September, it's time to start thinking about pumpkins. My wife recently had me bringing fall decorations out of the attic, so pumpkins are fresh on my mind. You can probably find the pumpkin of your dreams at a local farm, but perhaps next year you’ll want to grow your own. If so, here are some things to consider. Both pumpkins and gourds are members of the cucurbit vegetable family. This means they are relatives of squash, cucumber, watermelon, zucchini, and cantaloupe. As such, they share many of the same pests, and many of the same soil and growing conditions. However, while most of the other cucurbits are used as food, pumpkins and gourds are primarily (but not solely) grown for their ornamental value. Above: At a hefty 1,097 pounds, this pumpkin grown in Nash County won the 2023 NC State Fair’s contest for largest pumpkin grown by a NC resident. If growing either pumpkins or gourds, be prepared to provide a good deal of space, as both are vining crops that will run 4-8 feet or more in each direction. Don’t overcrowd the plants. Avoid using sprinklers or other watering methods that wet the leaves, as foliar diseases will occur when leaf moisture is high and air circulation between plants is poor. Pumpkins and gourds will use a lot of nutrients during the growing season, so test your soil prior to growing, and follow recommendations. Fertilizing with too much nitrogen is a common mistake that will result in lush vine growth with few fruit. Harvesting pumpkins and gourds can be a bit tricky for beginners. For gourds, look for a change in the sheen of the skin. When mature, it will go from shiny to somewhat dull. You also want the outer skin to be hard and not easily scratched with your thumbnail. Pumpkins will also develop a more robust outer shell when mature and will be a deep orange color (for most varieties, anyway). Perhaps the most important thing to remember when harvesting your pumpkins and gourds is to cut through the stem with a knife rather than trying to twist or tear it from the vine. If the stem is damaged during harvest (or after), it will lead to a rapid decline in the post-harvest life of the fruit. Gourds and pumpkins with long intact stems are easier to handle and last much longer. Now, for the fun part: What varieties can you grow? There is a tremendous amount of variation in the color, shape, and size of pumpkins and gourds, much too many to list, but that diversity lends itself to their decorative uses. If you’re picking a pumpkin to turn into a Jack-o-Lantern, you will likely want one that is large, orange, and relatively smooth. If you’re using pumpkins or gourds for other decorative purposes, however, a good rule of thumb seems to be that the uglier and more unusual they are, the better they work as decorations. Many varieties are odd shaped, have weird growths on them, or come in random combinations of colors that look like an artist has splattered paint on the flesh of the fruit. Some of the most interesting ones I’ve come across are ‘Red Warty Thing,’ a large pumpkin that looks exactly like the name, and ‘Porcelain Doll,’ a creamy-pink, flat pumpkin that is wider than it is tall. Comb through your favorite seed catalogs and find the ones that appeal to you. Grow a few favorites for next year!
Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. It seems like every year, in late summer or fall, after a wet period, the same thing happens: Mushrooms start to pop up in lawns and gardens. Without fail, the phone calls start, with caller after caller wondering why the mushrooms have shown up and what can be done about them. The simple answers to those questions are that the mushrooms appear because it’s wet and there’s nothing that you can really do about it, but there’s, of course, a little more to it than just that. Mushrooms usually arise in the lawn or garden when there is a type of fungus present in the soil and moisture conditions are high. Even though we don’t see it, there are always things happening inside the soil, and one of those things is decomposing of plant tissue, whether it be roots, stems, or fallen leaves that have incorporated into the soil surface. As this plant tissue breaks down, it becomes a food source on which mushrooms can grow and thrive. They are particularly prone to develop in areas where trees have been cut down, as the rotting roots underground contribute to mushroom growth. This can happen even several years after a tree has been removed.
Although there are many different types of mushrooms that show up in lawns, there are a few that are particularly distinctive. One is the stinkhorn, a foul smelling orange-mushroom. It is often long and slender and may have a dark tip. As with most mushrooms, much of its body is underground, so just removing the part that’s visible above ground won’t accomplish much. The mushrooms that result from fairy rings, a specific fungus that causes mushrooms to appear in circular patterns, are also distinctive. This disease is often particularly worrisome to those who have it, because of the unique pattern; however, it’s really no different than what I’ve already described. Decaying material in the soil feeds the mushrooms and they grow when there is a lot of moisture present. The growth just happens to be in a recognizable shape rather than random or scattered throughout the lawn. Above: A fairy ring, the name given to mushrooms growing in a circle in grass.
Though not a mushroom, slime molds are fungi that also grow on decaying organic material under wet conditions. These often show up in flower beds where hardwood mulch is used. Slime molds can be quite unpleasant to look at. One slime mold is called dog vomit fungus, because that is exactly what it looks like. Although unsightly, this fungus won’t harm plants and can be eliminated by removing the mulch it grows on. Many mushrooms are nothing more than a nuisance in the lawn and garden. They can be mowed or picked, but will return as long as conditions stay wet. You may notice them in low-lying areas or others in poorly drained spots where extra water seems to collect. Improving the drainage or diverting water away from these locations might help with long-term mushroom control. Digging them out and replacing the soil in areas of heavy infestation is also an option, but probably one that would only be practical in very small areas. Herbicides such as roundup are not effective on mushrooms. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. Boxwoods are one of the most popular landscape plants in North Carolina. Well-maintained boxwoods can provide a landscape with a formal, elegant look. However, boxwoods are not immune to insect and disease problems. In fact, one might argue that they have more than their fair share. Above: Create a formal, elegant look by shaping boxwoods into a circular profile. Below: Boxwoods sculpted into topiary forms. Those of you who grow boxwoods, particularly the American type (although the English and Japanese are susceptible as well), may have seen damage caused by an insect called boxwood leafminer. The symptoms of boxwood leafminer injury include smaller than normal leaves with yellow blotches covering the top part of the leaf. The bottom of the leaf will be bumpy and blistery, as the leafminer has laid its eggs inside the leaf. Gradually the insects will hatch from the eggs and chew their way out of the leaf. The adult insects then puncture the underside of the leaf and lay eggs back into it. In addition to making a healthy boxwood quite unattractive , these insects are difficult to kill. Adult leafminers are active in mid-April, searching for new leaves to lay eggs in. If needed, this is the best time to treat with a contact insecticide, though they can also be treated with preventative systemic insecticides throughout the year. As always, follow the label directions if using an insecticide. Above left: Yellow blotches, caused by the boxwood leafminer insect, form on the top part of the leaf. Above right: The bottom of a leaf infected by boxwood leafminers is bumpy and blistery. light brown color. Once this happens, there is nothing you can do to save the plant, and you should not replant boxwoods in the same area, as they will be likely to develop the same disease, as it is permanently in the soil. Phytophthora is worse in poorly drained soils, so taking steps to improve drainage, such as adding compost or sand to clay soil, may be helpful as a preventative measure.
One of the most common problems of boxwoods is neither an insect nor disease but rather a physiological problem. Many types of boxwoods, particularly the Japanese types, tend to turn a bronze, orange, or reddish color during the winter. Not all leaves will turn this color, perhaps just a few on the tips of branches. This is normal and is caused by winter winds and may be worse when the soil is dry, the pH is too acidic, or if the temperatures vary drastically during the winter. This will generally not kill the plant, but will definitely make it less attractive. In the spring the new foliage often returns to a normal green color. Keeping the plants moist and adjusting the pH to about 7 by adding lime will lessen this type of winter damage. Boxwoods of all types tend to perform best in soils that stay on the dryer side, and in areas of partial to even full shade. As is often the case with landscape plants, planting the right plant in the right place is perhaps the most effective way to limit future problems. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. |
Matt Stevens
Pitt County Extension Director & Horticulture Agent Archives
November 2024
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