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The Culver’s Root Fan Club
Why are certain plants popular with gardeners and others not? It is a pattern that I have always found interesting. Currently, one of the popular trends that will hopefully become the norm is adding native plants to the garden. These plants are beneficial for sustaining both the adult and the larval forms of our local insect populations. In addition, plants that provide color, height and texture during the summer months have also become very popular. Culver’s Root, botanically known as Veronicastrum virginicum has all of these virtues, yet for some mysterious reason, it has yet to gain recognition within the gardening community.
Culver’s Root is one of approximately 20 species of Veronicastrum found throughout North America, Europe and Asia. A member of the Plantain Family or Plantaginaeae, this species is native to open forests, meadows, grassy mountain slopes and prairies from Ontario south to Georgia and Louisiana. It was originally collected by the Reverend and Naturalist John Banister (1654-1692) soon after he moved to Virginia in 1679 and was initially named Veronica virginica in 1753 by the Swedish botanist Carl Linnaeus (1707-1778). It was not until 1917 that the Herbarium curator and drug inspector for Park, Davis and Company, Oliver Atkins Farwell (1867-1944) assigned the proper genus name. Interestingly, the name Veronicastrum was not new to the world of plants, as it was originally penned in 1759 by the German botanist and surgeon Philipp Conrad Fabricius (1714-1774). Obviously, it incorporates the genus name of Veronica, which was initially crafted by Linnaeus in 1753. According to Christian faith, St. Veronica gave her veil to Jesus to wipe the sweat from his face as he carried the cross to Calvary. Evidently, some species of Veronica have markings on the leaf that resemble St. Veronica’s veil. Astrum is Latin for Star, indicating that Veronicastrum resembles or shines like Veronica! The species epithet honors the location of its discovery by John Banister. The common name pays tribute to Dr. Culver, a physician in the early Eighteenth Century who supposedly recommended the root for medicinal uses. Interestingly, there does not appear to be a record of Dr. Culver’s life, indicating the use of the root by the doctor may be more of a myth than fact!
The apparent absence of Veronicastrum in many Gardens is by no means due to its lack of physical stature, since the plant typically reaches 5-7’ tall with a spread of 2-3’. The stout stems have whorls of 5, 6 or 7 leaves at nodes every 6-8” along the stem. Each leaf is upwards of 7” long! This leaf arrangement provides numerous horizontal lines in the Garden (as seen above right with Veronicastrum virginicum ‘Roseum’), which can be successfully used to pull the horizontal lines of architecture out into the Garden. If the plants are massed in a meadow-like setting, the whirls of foliage creates an almost psychedelic effect on the eyes! Come late June and throughout July, the tips of the stems yield 6-12” long spike-like racemes of white or bluish white flowers. The central spike typically has one to several whirls of smaller, subtending flower spikes that appear from the lower leaf nodes, as seen at left. These lower spikes help to enhance the display while providing a royal ‘crown-like’ appearance. The individual flowers appear in vertical rows along the stems. Each outwardly oriented flower is cup shaped, consisting of 4 fused petals. They are approximately ⅛” in diameter by ¼” long. The brown tipped anthers extend an additional ¼” beyond the flower, resulting in an airy or lacey effect for the flower spikes as seen below. The stems can be pinched back in mid to late May if a more compact plant is desired. Pinching the plants also delays flowering time by several weeks, but otherwise does not alter the overall appearance. If a light lavender flowered form is desired, consider ‘Lavender Towers’ (pictured above) or ‘Fascination’. ‘Cupid’ is a new selection whose flowers are a much darker lavender with blue highlights. Certainly one to look for in the years to come!
Culver’s Root needs full sun and soils that do not dry out in order for it to thrive its best. With its tall stature, it is traditionally placed towards the back of a border. However, since it possesses a very upright or columnar habit, it can also be placed towards the front of a border, where it enhances the visual depth to a border; the act of having to look past or around the plant to view the balance of the border makes the garden appear larger. It also looks fantastic worked in with some of the mid-sized ornamental grasses, such as Karl Foerster Feather Reed Grass (Calamagrostis x acutiflora ‘Karl Foerster’), since the flowers appear to float above the top of the grasses. Plus, the upright, spiky composition of the Culver’s Root is repeated with the Feather Reed Grass, creating a very dynamic, vertical composition. You might consider working Culver’s Root with Rodger’s Bottlebrush Buckeye (Aesculus parviflora var. serotina ‘Rodgers’) or Summersweet (Clethra alnifolia). The image at left features the straight species of Bottlebrush Buckeye in the backdrop, which blooms several weeks earlier. Rodger’s Buckeye and Summersweet are July blooming shrubs with long upright racemes of white flowers, echoing those of Veronicastrum. The repetition of the flower shape and color brings great unity and cohesion to the Garden! Culver’s Root remains attractive well into winter, since the frosted stems add attractive forms to the fall and winter Garden composition, as seen below in October with Agastache ‘Purple Haze’ and Calamagrostis. I have yet to see the plant self-sow when left standing through winter and subsequently cut the plants back in early to mid-March.
For a plant that has a long history with gardeners, starting with John Banister in the late 1600’s, it seems odd for this plant to not be a garden favorite. With the regal crown-like floral display combined with its many other attributes, it only seems natural for this plant to have far better recognition in the gardening community. Perhaps it’s time to start the Culver’s Root fan club?
State Program Leader for Home and Public Horticulture (NJAES)
Finally, the hazy, lazy days of summer have arrived – something many of us longed for during the cold snowy months of last winter! The temperatures are warm, the days are long and the rain has unfortunately been scarce! The heat and humidity have certainly returned too, so try to garden during the cooler temperatures of the early mornings and evenings. Keep records on daily temperatures and rainfall, since summers’ heat and nighttime temperatures impact a plant as much as winters’ cold. Always remember to wear a big hat, apply ample sunscreen to exposed skin and drink plenty of water while you garden!
Things to do:
- Weed and fertilize your containers.Water as needed, which is usually once per day. The plants are now beginning to approach their mature size and it is important to keep them well fed and hydrated. If you used slow release fertilizer pellets in your containers, you may wish to consider a reapplication near months end. Most fertilizer pellets only last 2 or 3 months and the rate of release increases as the temperatures soar above 85°F. For heavy feeders, like Brugmansia (picture above right) you should supplement slow release feed with liquid fertilizer – the slow release granules do not release the nutrients at a sufficient rate to support blooming.
- Some annuals, such as Coleus, Plectranthus and Persian Shield (Strobilanthes) would benefit from an occasional pinching of the tip, allowing lower buds to break dormancy and grow (as seen at right, 2nd picture, for Persian Shield). This allows the plants to become denser and prevents them from getting straggly or becoming excessively large and ‘eating’ the neighboring plants.
- Hanging baskets should receive a serious cutback in order to renew the plants for a late July through September display.
- Irrigate perennial and annual gardens for long periods ensuring a deep penetration of water into the soil should rainfall become scant.
- It is now ok to remove the old foliage of Narcissus as it is now turning yellow and next year’s bulbs have fully developed.
- Reapply mulch to retain moisture should it have become thin or disturbed through replanting of annuals or perennials or from weeding. Mulch only needs to be a total of 2-3” thick including older mulch and newly applies.
- For turf grass, raise the cutting height to 3” during these hotter and drier months to reduce plant stress. If you irrigate, do so for extended periods during the early morning to encourage deeper root growth. Try not to water in the evening, since that will promote various fungal problems. Avoid fertilizing turf during July and early August as that will necessitate more irrigation.
- For Roses, deadhead or remove the old flower blossoms, give them a light feeding and remove any leaves from the plant or on the ground that have blackspot, as this will help to reduce future outbreaks.
- Any Japanese Beetles on roses or other plants can be destroyed by flicking them into soapy water.
- Some perennials can be lightly trimmed such as the early blooming Salvias (Salvia nemorosa) or more heavily cut back such as Catnip (Nepeta faassenii) and Ribbon Canary Grass (Phalaris arundinacea var. picta) to initiate prolonged blooming or attractive foliage into the fall. Nepeta ‘Walkers Low’ is photographed at right 2 weeks after being cut back, with an unpruned specimen behind. Make certain you provide adequate irrigation if you cut the plants back hard. I leave the dried flowers of Yarrow (Achillea) and Astilbe on the plant, as they look attractive in the fall and winter. Early July is the latest time to pinch back unruly Asters and Chrysanthemums, since pinching any later will delay the bloom time too late into the fall.
- Weed! Even with the limited rainfall and heat, there is an endless growth of weeds. It is best to get them young before they become too noticeable and the root systems become too established. Worse yet, try not to let them seed, as the average lifespan of a seed is 7 years which equates to 7 more years of weeding! Mulching heavy does not equate to less weeds either, and will lead to more issues in the future since excessive mulch is not healthy for plants.
- Peas, radishes, lettuce, spinach and other cool season crops need to be removed, composted and replaced by beans, beets or any 80 day to maturity crop. Thin carrots to roughly 1” apart and beets to 2” to allow room for proper root development.
- At this point summer squash and cucumbers are beginning to come of size; harvest them small (4-6”) and frequently to ensure continued yields and tenderness. If you planted potatoes, they can also be harvested starting in mid-July. A second crop of cucumbers can be planted now to replace those planted earlier that will begin to loose vigor come late August and September.
- Check parsley for Black Swallowtail Butterfly eggs or caterpillars.
- If your Zucchini Squash gets the borer early in the season and collapse, and you still wish to grow squash in that location for this year, consider planting some of the Scallop Squash, often called Patty Pan Squash for an autumn harvest. They mature in about 50-54 days from seed and come in solid White, Golden, and a combination of White and Green Striped. Not only are they delicious, they will add color to the Thanksgiving Table as well!
- When watering tomatoes, make certain that the fruit remains dry in order to reduce the occurrence of blossom end rot. Keep the tomatoes staked (as seen at right). By positioning poles along a row of tomatoes and holding the tomatoes upright between two strings, the fruits can be kept off the ground, air can circulate through the plant (reducing disease risks) and ripening fruit is better seen. A close-up of how the plants are supported is pictured below, with the green arrows pointing to the twin strung on either side that was installed as the plants were growing in June and July.
- Maintain even moisture in the soil around tomatoes to reduce the risk of the tomatoes splitting. This is particularly true of Heirloom tomatoes and using a straw mulch will help maintain consistent moisture.
- Yellowing of the lowest leaves on the stems of tomatoes is an indication of Early Blight. It is best to remove these lower leaves, such that there is no contact with the soil and reducing the threat of future outbreaks. Also, wash your hands after removing the leaves before touching other plants to reduce the chance of spreading the disease.
- Provide a light pruning and training of rampant growing Wisteria stems, stray stems of Clematis, and other vines. A heavy pruning will invigorate excessive vegetative growth and less flower bud development.
- Prune water sprouts and suckers on small trees and large shrubs before they become too large and begin to deform the plant.
- With young ornamental and shade trees, you may wish to prune off or thin the lowest hanging branches if you have not already done so, as they will continue to droop lower until growth ceases towards mid-month. These low hanging branches shade out any plantings beneath, blocking important views of the garden and make walking about difficult. Remember, to cut branches back to – but not into – the branch collar at the base of the branch. Continue to visit local garden centers as new materials are continuing to arrive and there may even be a couple of mid-summer sales beginning!
State Program Leader in Home and Public Horticulture (NJAES)
Summer has arrived! The days are wonderfully long, rain has proven to be ample to S date, and the temperatures promise to become more summer-like as the month progresses. June is filled with chores that linger from spring, as well as preparations necessary for the garden to continue to thrive well into late fall. As the temperatures rise, enjoy the coolness of the early morning and evenings for those tasks requiring the most exertion, with the heat of the day reserved for light duties. Try to water in the early morning as well, since evening watering tends to promote diseases and evaporation is most extreme during the mid-day hours. Also, don’t forget your hat and sunscreen. Finally, remember to sit down with your favorite cold beverage to write in your journal and to enjoy the fruits of your efforts!
Things to do:
- Finish decorating containers and mixed borders with annuals and tropicals. The rather chilly weather of May has pushed back much of the planting of tender plants to this month. Do not be bashful about using larger and bolder plants such as Banana, Canna, Alocasia, Colocasia or even some of the larger Bromeliads such as Aechmea ‘Harvey’s Pride’ as pictured at right. The bolder foliage adds a wonderful textural impact as well as foliage color.
- Fertilize annuals with a liquid feed once per week through June to give them a good start. If you used slow release fertilizer in your containers, use a 50% dilute solution of liquid feed. During hot periods, containers may need to be watered twice per day, especially if they are in the sun and the pots are smaller than 12”.
- If you have deer, apply a deer spray weekly or after a heavy rain. It is best to rotate weekly between three different types of sprays for best effects.
- Deadhead May blooming Iris to reduce the occurrence of the Iris borer as pictured at right. Cut the flower stalks as close to the rhizome as possible. Study the blooms of your Iris; if the blooms are few and the foliage is limp or overly dense, the plant either needs division or to be moved to a more sunny location. If it needs division, August is the best time.
- Weed! All of the rain and cool weather from May has created abundant growth and the spring blooming weeds are about to go to seed. Remember, weed seeds last an average of 7 years! Also, do not be afraid or feel bad about removing seedlings of the more aggressive perennials. Brunnera macrophylla is a beautiful spring blooming plant, but can monopolize a garden!
- Deadhead the Peonies as they finish blooming.
- Lightly fertilize repeat blooming daylilies and Roses at the end of the month for a good August/September bloom.
- Resist the urge to remove the yellowing foliage of Daffodils and other bulbs until it has totally turned brown. The foliage is producing the carbohydrates and storing them to ensure a good floral display for next year.
- Plant native plants! Help feed out butterflies, moths, native bees and caterpillars. We need our insects to thrive so that we can too!
Shrubs and Trees
- For small trees and shade trees, pinch off most of the water sprouts that you see growing from branches or stems – typically they appear at points where water sprouts or a branch was pruned off this past winter! Removing them as they start to grow discourages future dormant bud break.
- Many low branched trees may need to have portions of the lowest branches removed, as the new growth from May and early June adds weight to the branch, causing it to droop ever lower. This is a chore that often needs to be done each year until the tree is at least 15-20 years of age and the stems are of significant size to support the added weight.
- Selectively prune 2-3 stems of leggy multi-stemmed shrubs such as Fothergilla that may be growing in too much shade back to 6-8” tall too promote new growth from the base. Early June is also a great time to prune Azaleas and Rhododendrons as they finish blooming, since it will not impact next year’s bloom!
- Cut turf weekly. During periods of drought, irrigate the turf for extended periods in the early morning, promoting deep root growth. As the summer heat begins, raise the cutting height to 3” to reduce the stress on the turf.
- Harvest spinach, lettuce, radishes and arugula daily. As the days become hotter, the lettuce will become increasingly bitter and less tasty. These plants will also produce flowers or ‘bolt’, after which the foliage becomes extremely bitter, so it is important to harvest while the plants are smaller. Once the plants begin to bolt, remove them and plant summer squash, okra, cucumbers, pole beans, or other vegetables that will provide a yield in 65-70 days (September into October).
- Early June is time to thin your beets to 3” apart should you wish to harvest baby beets or 5-6” should you wish them to grow larger. Either pull out or cut off the Harvest spinach, lettuce, radishes and arugula daily. As the days become hotter, the lettuce will become increasingly bitter and less tasty. These plants will also produce flowers or ‘bolt’, after which the foliage becomes extremely bitter, so it is important to harvest while the plants are smaller. Once the plants begin to bolt, remove them and plant summer squash, okra, cucumbers, pole beans, or other vegetables that will provide a yield in 65-70 days (September into October).
- Early June is time to thin your beets to 3” apart should you wish to harvest baby beets or 5-6” should you wish them to grow larger. Either pull out or cut off the baby foliage, should you not wish to disturb the soil. Don’t throw away the leaves either, since they are a great addition to salads!
- It is not too late to plant tomatoes. Planting in June often avoids the problems with early blight as well! If the plants are leggy, bury the stem up to the first true leaf, as the stem will produce roots and yield a sturdier plant. As the tomatoes grow, make certain that they are staked, lifting the fruit to come off the ground and reducing the chance of decay.
- For tomatoes, it is ideal to pinch off the lower shoots up to the point of the first flower cluster (pictured at right). This will allow for a more manageable plant and a more sustainable crop of fruit.
- Plant Eggplant, Peppers, Okra, Basil and other plants that prefer heat of summer early in the month.
- Mulch vegetables with newsprint or cardboard covered with straw, reducing weeds and water loss. This is ideal for Heirloom tomatoes since they need consistent soil moisture in order to discourage splitting of the fruit. You can also mulch with lawn clippings provided that herbicides or insecticides were not applied to the turf.
- Stop harvesting asparagus and rhubarb. They need to produce stalks and leaves of sufficient size in order to develop the energy reserves for next year’s harvest (the same reason that you do not remove bulb foliage until it has turned totally brown).
- Compost! If you have yet to set up a composting bin, this is a good time to start. Not only can most weeds (without seeds) go into the bin, but so can bolted lettuce plants and greens left from the dinner table. It is a great way to do our part to help reduce landfill waste.
State Program Leader in Home and Public Horticulture, NJAES
Mountain Mint – Truly, a Gardeners Mint
Mint is a plant that conjures up a multitude of thoughts and emotions among gardeners. Typically, our first thought is of a plant with wonderfully fragrant foliage that happens to combine well with Ice Tea and Mint Juleps! Unfortunately, this is matched with an equally unsettling vision of a plant that knows no boundaries and will rapidly spread throughout your garden! True mints are found within the genus Mentha, and their aggressively spreading nature makes them problematic in an ornamental garden. However, there are other plants in the mint family or Lamiaceae that display a far greater degree of garden refinement and manners. Mountain Mint, botanically known as Pycnanthemum muticum, is one such member of the Lamiaceae and it defies my imagination as to why this plant is not more popular among gardeners.
Mountain Mint is certainly not a new plant to the world of horticulture. It was first discovered by the French botanist Andre Michaux (1746-1802) in 1790, when he found masses of the plant growing in Pennsylvania! Michaux initially named and described the plant as Brachystemum muticum, which was published posthumously in 1803 in his work Flora Boreali-Americana. Interestingly, in the same book he described a new genus named Pycnanthemum! Both names are from the Greek to describe the flower structure; Brachys means short and Stelma means column while Pyknos means dense and Anthos means flower. It only took a few years for the French botanist and mycologist Christiaan Hendrik Persoon (1761-1836) to assign the proper genus name in 1806. The species epithet comes from the Latin Muticus for blunt, perhaps a reference to the dome-shaped or blunt appearance of the apical flowers. Although the common name is Mountain Mint, it actually does not grow in alpine regions, but rather in open, moist fields and forest edges, which can be located along the lower elevations of a mountain.
Personally, I was not introduced to this plant until 2010 while touring Central Park. It appeared periodically throughout the park as a 2-3’ tall mass of shimmering silver along the edge of woodlands and ponds. Although the day was cloudy and it was mostly growing beneath a canopy of tall trees, the plant gave the impression of sunlight cutting through openings in the branches and illuminating the forest floor beneath. The gentleman leading the tour mentioned how these masses of Mountain Mint had been installed in an effort to reduce weeds. Naturally, I thought it was another invasive mint and was about to dismiss the plant when he noted it was merely a dense, ‘weed-suppressing’ plant and not invasive. A weed suppressing, non-invasive mint – my interest in this plant began to grow!
The shimmering, silvery effect of the plant was not the result of a true flower petal, but rather a pair of silver colored bracts or modified leaves that subtend the terminal boss of small white to light pink flowers, as seen in the image above. Much like Poinsettias and our native Flowering Dogwood, the actual flowers are very small and the primary impact is created by these bracts. For Pycnanthemum, they provide a beautiful ornamental effect for over 3 months! The flowers themselves are roughly ⅛” long, white with pink markings and are densely arranged in a ½” diameter compressed flower structure called a cyme. It is this dense arrangement of flowers that sparked the crafting of the two initial genus names. The flowers open over a 3 month period beginning in June and are a great source of nectar for bees, beneficial wasps, moths and butterflies! In fact, it is rare that the plants are not a flurry of activity when in bloom. Come winter, the clusters of dried seed capsules atop the stems have a nice winter presence, especially with a heavy December frost as pictured at the end. My interest in this plant grew even further!
The lance-shaped, dark green foliage, measures 2-2 ½ inches long and is much like a typical mint, the foliage is very aromatic when rubbed. Tightly clad to the square stems by only a short petiole, the foliage contains pulegone, an oil with an aroma reminiscent of spearmint that is very effective at repelling mosquitoes when rubbed on the skin. This aroma is also effective at eliminating deer browse!
Mountain Mint is a great plant for working into the Garden. It looks great paired with the silver foliage of Lamb’s Ear (Stachys lanata) and it is great at brightening the darker foliage of deep purple leaved plants like Purple Leaved Smoketree (such as Cotinus coggygria ‘Velvet Cloak’). I have found that the plants and stems have a very vertical appearance that can make a design look awkward when planted along the edge of a planting (as pictured at left) since the transition to the ground plane is very abrupt. It is best to have a lower growing plant or a mounding plant placed at the front of Mountain Mint to provide a more gentle transition to turf, a walkway or simply the ground plain. Plants grow well in full sun as well as light shade, providing that the soil does not become excessively dry for prolonged periods. The plants are adaptable to various soil types and pH; they are typically found growing on alkaline soils in the wild, but are tolerant of acidic soils and are surprisingly tolerant of moister soils along pond edges. The soils simply cannot remain waterlogged with ponding water for extended periods of time. The rhizomes do spread about 4-6” per year, but they are easily cut with a garden spade and the shallow stems are easily extracted, even if they have started to grow into a neighboring plant. This is a practice that should typically be done every other year.
If more of a clump forming species is of interest consider Pycnanthemum flexuosum or Appalachian Mint. Originally named Origanum flexuosum in 1788 by the American botanist Thomas Walter (1740-1789), its name was altered a century later in 1888 by Nathaniel Lord Britton (1859-1934). Britton was the American botanist who went on to cofound the New York Botanical Garden! The species epithet means pliant and is probably a reference to the flexible stems. Growing 2-3’ tall and roughly as wide, the dense root system is great for soil stabilization and since the foliage is also aromatic, it too is resistant to deer browse. The flower clusters or cymes lack the silvery bracts of its cousin, but they are much larger, typically around 1 ½” in diameter (as pictured at right). The purple flecked, white flowers remain rather diminutive, with the ¼” long tubular flowers appearing for nearly 2 months throughout the summer. Like its cousin, they are also exceptionally attractive to pollinators. Unlike its cousin, each flower has a more pronounced calyx or leafy base that initially serves to protect the flower bud and then physically support the tubular flower. Once the flower fades and drops away, each of the 5 off-white sepals that compose the calyx have a long bristly spur at the tip, giving the flower head a Sputnik or fuzzy appearance. The ultimate effect produces a bit more drama to the flower and the Garden, which I found very ornamental! This species has similar cultural requirements as its cousin and both are hardy throughout NJ, easily enduring a zone 5 winter and the summer’s heat.
Interestingly, both species began their affiliation with horticulture under different and distantly related genera within the mint family, only to find out they were in fact closely related cousins. My interest and admiration for what these plants can provide for the Garden only continues to grow as I continue to find new ways to incorporate these plants in designs! Granted, no plant is perfect, since neither of these Mints should be eaten or used as a garnish in a glass of Ice Tea or a Mint Julep! However, if you have been searching for a deer resistant native plant that is friendly to pollinators, suppresses weeds and works well others, here are 2 mints that you surely want to add to your list of great garden worthy plants!
State Program Leader in Home and Public Horticulture, NJAES