What Grows There :: Hugh Conlon, Horticulturalist, Garden Advisor, and Photographer

Some Summer Perennials Reach New Heights

Posted by Hugh on July 7th, 2024

Celebrate this 4th of July with three giant flowering perennials: Giant coneflower, Joe Pye weed and Queen Of The Prairie Filpendula.

Giant / Large coneflower (Rudbeckia maxima) is an herbaceous perennial that is grows in average, moist, well-drained soils in mostly full-day sun (USDA hardiness zones 4-9). Also called “Dumbo’s Ears”, it tolerates light shade, heat, some drought, and a wide range of soils. It can be grown from seed, but under ideal growing conditions, it will self-seed. It also propagates itself through rhizomes. Plant it in along a border, in a cutting, pollinator, or cottage garden or in a meadow or naturalized area.

Tall flower stalks rise to 5-7 feet (3-4 feet wide), bearing bright yellow-rayed 3-inch-wide flowers with drooping ray petals and each with a 2 to 6-inch dark brown central cone. Flowers attract butterflies. After blooms go to seed, do not cutoff the flowers stalks. Instead, allow goldfinches and other small birds to feed on the seedheads. According to the NC Extension, large coneflower serves as a food source for the larvae of the Wavy-lined Emerald butterfly.

Joe Pye weed (Eutrochium dubium) is a tall and wide native perennial that blooms in gardens where space is not an issue. (USDA hardiness zones 3-10). Joe Pye wild seedlings grow 8-10 feet, especially if soil moisture is plentiful. Floral heads age from purple, pink, and red petals. Blooms are pollinator magnets and are an important nectar source for Monarchs and other butterflies.

Joe Pye is a tough-as-nails perennial that will quickly spring up in late spring garden. In late summer, this tall perennial flower produces waves of nectar-rich pink blossoms that butterflies and other pollinators love. Horticultural varieties grow more compact such as E. maculatum ‘Gateway’, E. dubium ‘Little Joe’, and E. dubium ‘Baby Joe’.

Queen Of The Prairie at Kingwood Center, Mansfield, Ohio

Queen Of The Prairie (Filipendula rubra) is a U.S. native perennial that is valued for both its bold foliage and mid-summer flowers. It prefers calcareous soils in several swampy meadows. It is a very tall, typically grows 6-8 feet high with upright, clump-forming branches. Terminal, astilbe-like, 6-9 inches wide panicles of tiny, fragrant, pale pink flowers are a glorious sight in early to mid-summer meadow garden. Deeply cut, compound-pinnate, bright green leaves have 7-9 lance-shaped leaflets, each with an unusually large, 7-9 lobed, terminal leaflet (4-8″ long). Leaves are fragrant.

Maintenance of these giants: All 3 appreciate part shade in hot southerly climes. Foliage may scorch in full sun if soils are allowed to dry out. Propagate by dividing clumps in spring. Freely self-seeds and can form large colonies in optimum growing conditions. Usually, foliage declines and cut back hard to promote new growth and avoid seedlings in next season’s garden.

Insects, Diseases, and Other Plant Problems: Fairly trouble-free perennials including moderately deer resistant. Snails and slugs can injure young plants. Powdery mildew may be troublesome for a short time, but healthy plants usually recover.

‘Sun King’ Aralia Glows In the Summer Heat

Posted by Hugh on July 1st, 2024

Plants with golden foliage can brighten up almost any drab garden patch. Sun King golden aralia (Aralia cordata ‘Sun King’) is no exception, hardy in USDA hardiness zones 3-9. It is also known as Japanese spikenard and mountain asparagus. Under ideal conditions this thornless, rhizomatous, herbaceous perennial grows rapidly to 3-5 feet tall and as wide in a single season.

The golden compound foliage emerges in mid-spring and retains its bright color throughout the summer. Growth rate is rapid and dies back to the ground in late autumn. In mid-summer numerous small clusters of tiny white flowers shoot up, borne on 2 feet tall racemes. Lustrous purplish-black berries follow in the fall.

Sun King makes a bold almost tropical statement in a semi-shade garden. Grow it in a compost-rich moist soil and in ½-day sunlight (morning hours preferred). The foliage will retain the golden color if given at least 2-3 hours of sun each day. More shade will result in lime-green or chartreuse foliage; 4 or more hours will likely burn the foliage. In Southern USDA zones 8 and 9, grow only in dappled sunlight to avoid leaf burn. Golden aralia should be mulched and watered over dry spells lasting 10 or more days.

Summer seed heads develop (Longwood Gardens, Kennett Square, PA)

Sun King aralia mixes well in large containers planted with green and other brightly colored foliage plants. It combines with the following perennials: coral bells (Heuchera spp.), and astilbes. Golden aralia is deer resistant. Tiny white flowers in early summer attract numerous honeybees. After a few years plant may colonize from its own germinated seedlings.

No pruning is necessary as golden aralia usually dies back to the ground in cold winter. Dead stems and plant debris can be removed once new spring growth emerges.

No serious insect or disease problems trouble this reliable perennial. Aphids, mealybugs, spider mites, slugs and snails are occasional pests. Leaf spots may be a problem under overhead irrigation.

‘Sun King’ golden aralia was selected the 2020 Perennial Plant of The Year by the Perennial Plant Association. It is an excellent complement to hostas and woodland perennials.

‘Sun King’ golden aralia is not easily found in garden center commerce. However, several online nursery companies do list it

Bletilla – Hardy Garden Orchid

Posted by Hugh on June 26th, 2024

Chinese ground orchid (Bletilla striata), aka “Hardy Garden Orchid”, is a terrestrial orchid which produces small, cattleya-like, downward-facing purple flowers. It is indigenous to moist grassy slopes of central China and southern Japan.

Ground orchids produce attractive foliage and showy flowers, that bloom from mid-spring and early summer. The flowering racemes stand approximately 12-18 inches high atop naked scapes (stems). Foliage dies to the ground at the start of winter. White to purple flowers emerge in spring into early summer. Ground Orchids are not classified as invasive. (USDA hardiness zones 5-9).

Bletilla’s corm-like pseudo-bulbs usually sit at ground level and serve as nutrient storage for overwintering. Each pseudobulb typically produces 3-5, linear, pleated, forms clumps of pleated, pale green, sword-shaped, pale green leaves (to 12 inches long).

Ground Orchids are best grown in organic-rich, medium moist, well-drained soil and in partial shade or early morning sunlight. In southerly zones 6 -9 summers, plants belong in afternoon shade. Plant pseudobulbs 4 inches deep in spring. After flowering, continue to irrigate plants during the growing season. Plants will naturalize over time under ideal growing conditions.

Clumps are not reliably winter hardy in northerly climes (north of USDA Zone 5). Instead, grow Ground Orchids in containers. Dig up garden clumps in late autumn plus container plants and store them in a dry frost-free location for re-planting next spring. Plus, continue to provide moderate moisture to plants for the remainder of the growing season. Propagate by dividing pseudo-bulbs in the fall.

Ground Orchid should be fertilized in early spring at a low rate. No serious insect or disease problems trouble this plant. Slugs and snails are occasional pests. Uneasy about winter hardiness in your area? — pile 2-3 inches of loosely packed leaves over bletillas to protect from cold injury.

Red Hot Pokers /Exceptional Summer Performers

Posted by Hugh on June 21st, 2024

‘Gold Rush’ (photo from Walters Gardens)

Red-hot Pokers (Kniphofia spp.) are easy to grow long-lived perennials from South Africa. (USDA hardiness zones 5b-9). They go by a number of common names including torch lilies and tritoma. Colorful floral spikes (with a little imagination) resemble sizzling pokers or fiery torches, visited often by hummingbirds, bees and butterflies.

Modern day cultivars are mostly hybrids and vary in plant height and flower color. One or more floral spikes arise 1.5 to 4 feet in height, depending on cultivar. Color choices include off-whites, yellows, oranges, reds, and blends of two or more tints. From late May thru October additional re-blooming occasionally follows if the spent flower scapes are rapidly deadheaded and clump(s) are irrigated.

Red-hot Poker excels when planted in average well-drained soil. Full to partial (6 hours minimum) sunlight is ideal. Most, but not all, cultivars are cold hardy in the Southern Appalachian region (USDA zones 6b-7a). Newer cultivars demonstrate improved cold hardiness. The sharp-edged grass-like foliage appears mostly evergreen and may be ravaged by rough winters. Prune back the old pokers to 3-4 inches above the soil line in late winter for a fresh re-start.

Many modern varieties are bred to grow shorter (under 20 inches) compared to the species, K. uvaria, which grows 3 feet and higher. Terra Nova Nurseries, an Oregon wholesale nursery, sells two series of dwarf red-hot pokers, bred for the both the container and garden market. The Poco® series has 5 color variations and the Popsicle® series comes in 6 hues. Late blooming ‘Fire Glow’ is a lovely 14-inch dwarf cultivar with large bi-color orange and red flower spikes. The Echo® Series, offered by Itsaul Nursery in Atlanta Georgia, grow 30-48 inches high, depending on cultivar. Echo Duo (reddish-orange), Echo Mango (apricot), and Echo Rojo (orange-creme) are popular choices.

‘Lady Luck’ Red-Hot Poker (photo from Walters Gardens)

The August 2024 issue of Fine Gardening magazine the Chicago Botanical Garden lists Red Hot Poker Test Results. Dr. Richard Hawke has been evaluating 28 red-hot poker varieties since 2020. The varieties that earned highest ratings include: K. ‘Gold Rush’ (48” yellow), K. ‘Joker’s Wild’ (36” deep orange), K. ‘Lady Luck’ (52” green, chartreuse), K. ‘Orange Blush’ (28” bright orange), K. ‘Rocket’s Red Glare’ (39” red, open yellow), K. ‘Sunset’ 27”, red-orange, open orange).

A 2-year and older plant clump is both heat and drought tolerant. Every 3-4 years, rhizomes should be dug and divided either in early fall or late winter. Red-hot pokers have few serious disease and insect issues. Root rot may become a significant problem if soil is poorly drained.

‘Joker’s Wild’ Red-Hot Poker (photo from Walters Gardens)

Perennial Salvias Getting Better

Posted by Hugh on June 14th, 2024

Perennial salvias (Salvia × sylvestris) represent a number of hybrid crosses between S. nemorosa and S. pratensis but may include S. × alpestris, S. × asperula, S. × collina, and S. × superba. Most cultivars are branched, upright, clump-forming, perennials with opposite, oblong to lanceolate, medium green leaves and showy spikes of tiny, tubular, two-lipped flowers (each to 1/2” long). Flower color choices range from blue to lavender to purple, depending on cultivars. Most S. nemorosa and hybrids are hardy in USDA Zones 3-8.

Perennial salvias bloom from late spring to early summer, but sporadic additional bloom may continue to appear throughout much of the remaining summer. Flowers rise well-above the basal leaves on square stems to as much as 30” tall. Following initial spring bloom, plants will rebloom much of the remaining summer.
Cultivars:

S. nemorosa ‘May Night’ (Mainacht) produces dense spikes of deep violet purple flowers over a long period of spring and summer if the old spent flowers are clipped off. Plant grows 18-24” high x 15-18” wide. Chosen Perennial Plant Association Plant of the Year (1997).

S. nemorosa ‘Pink Profusion’ bears darker pink calyxes on an almost perfect dense plant habit (14-16” high x 16-20” wide).

S. nemorosa ‘Caradonna’ produces violet blue floral spikes and has an upright plant habit (24-30” high x 15” wide.

S. nemorosa ‘East Friesland’ – a compact form with a long bloom period, purple stems and dense violet-purple flowers that rise above aromatic foliage to 18” high from late spring to early summer.

Salvia ‘East Friesland’ -deadhead to force continuous blooming through spring and summer

S. nemorosa ‘April Night’ blooms a month earlier than the iconic Salvia ‘May Night’; plant blooms on thick stronger stems.

S. hybrida ‘Blue By You’ has beautiful Salvia with excellent winter hardiness and summer heat tolerance. Sterile hybrid for longer floral shelf life; blooms up to 2 weeks earlier than other varieties. (S. nemorosa x S. pratensis) (zones 4b-9a). All-America Selections Winner 2023.

General Care: Perennial salvias grow in average, dry to medium, well-drained soils in full sun. Plants excel in moist, humus-rich soils with good drainage. Plants repeat bloom throughout the summer, but regular moisture is essential for reblooming. Liquid fertilizer 4-6 weeks until late August with Miracle-Gro™ or similar product. Salvias are moderately drought tolerant. Plants excel where summer night temperatures are cool (north of USDA Zone 7). In hot climes, plants become somewhat floppy and open up. Some hybrid salvias are sterile; few come true from seed.

Garden Performance: Attract Bees, Deer Resistant, Attracts Hummingbirds, Heat Tolerant, Frost Tolerant.

Indian Pinks

Posted by Hugh on June 7th, 2024

Indian Pinks (Spigelia marilandica) is a strikingly beautiful native wildflower throughout central and southeastern U.S. It is sometimes called “woodland pinkroot”. This perennial grows well in many parts of the U.S. (Zones (5b-9). Plants emerge in mid-spring. Sometime in June, depending on locality, their bright red tubular flowers flare open, crowned by five sharply pointed pale yellow reflexed lobes. By the 4^th of July flowers will provide floral fireworks in your garden.

Indian pinks prosper around a rich moist open woodlands or shade garden. They grow equally well in mixed containers. Plant in a well-drained, mildly acidic soil that is generously amended with compost or humus. A partially sunny site in full morning to dappled sunlight is ideal. Irrigate plantings during summer dry periods and avoid wet soggy soils.

In older plantings vigorous plants will grow 2 – 2.5 feet tall. Leaves are arranged opposite on the stem, attached directly to the main stem (no petioles), as well as an entire (toothless) margin. Plants stand erect and are rarely branched.

New plantings of Indian pink often start off slowly, taking 2-3 years to reach maximum flowering. Create a dazzling display by setting five or more plants en masse. Over the years in good humus-rich soil, Indian pinks often naturalize and look stunning. Flowering time may be extended over several months by swift removal of the old spent flowers (deadheading).

The brightly colored flowers attract numerous pollinating insects and provides food for hummingbirds. No disease and pest problems cause Indian pink any troubles.

The popularity of Indian pinks continues to increase. In recent years, the U.S. native plant industry have been adding new clones of Indian pinks to their catalogs and many more garden centers, not box stores, are selling them. Tissue culture labs are also producing them. Relatively new in stores is a vegetatively propagated clone ‘Little Redhead’ which demonstrates high vigor and plant uniformity. (24-28 inches high and 20-24 inches wide).

Another Indian Pinks selection, ‘Ragin Cajin’, has orange red flowers on a rounded plant form (20-24 inches high and wide). This selection from Plant Delights Nursery in Raleigh is highly floriferous and performs well in either sun or shade. (20-24 inches high and wide).

Mini-Oakleaf Hydrangeas

Posted by Hugh on May 26th, 2024

Oakleaf hydrangea (Hydrangea quercifolia) is a U.S. native and it offers four seasons of landscape beauty. (USDA hardiness zones 5-9). Typically, oakleafs grow 10-12 feet tall deciduous shrubs that are broad-rounded, suckering, and multi-stemmed. In the wild, if left unpruned, shrubs reach over 20 feet in height and spread.

I have selected five compact growers in the 3-6 feet range. They’re an ideal size for large 15+ gallon containers and planting in small gardens. The large leaves mimic those of oak trees. Cone-shaped white flowers are cone-shaped and comprised of showy sterile flowers that protect the mass of fertile flowers beneath.

Oakleafs are easily grown in humus-rich, moist, well-drained soils in full sun to part shade. Provide adequate shade in the southern U.S. zones so that plants are never over-stressed in droughty soils. Annual summer mulching in pine needle or ground / bark-based aids retain soil moisture and weed maanagement.

Bloom occurs on old wood (last year’s growth). Pruning, if needed, should be done immediately after flowering in early August to rein in shrub size, despite removal of many spent flowers that still look attractive. An added attribute is that inner branch wood and stems exfoliate to reveal a rich brown inner wood.

Dwarf (Compact-growing) Cultivars:

‘Little Honey’ is a petite grower (3-4 feet tall and 4-5 feet wide) with snow-white cone-shaped flowers. Flowers are secondary to its glorious chartreuse foliage. Shrub grows best in full sun in the north and in partial sun to partial shade in the mid-South. The aging flowers turn crimson at the start of autumn.

‘Pee Wee’ grows 4 feet high and 3 feet wide white spring flowers that fade to pink in the fall. Its oak-leaf like foliage stays deep green through summer and turns bright red in autumn.

‘Sike’s Dwarf’ has a dwarf mound habit that matures 2-3 feet in height and 3-4 feet in width. Elongated, conical white, mostly sterile flower panicles, each 3-4 inches long, gradually fade to light pink and eventually brown in fall. Deep green 3-5 inch long leaves turn autumnal shades of bronze, maroon and purple.

‘Ruby Slippers’ is a U.S. National Arboretum introduction that grows 3 to 4 feet tall and slightly greater in spread. ‘Pee Wee’ is one of its parents. Large flower clusters emerge white, age to light pink and mature to ruby red. Its leaves turn deep mahogany red in fall.

‘Munchkin’, another National Arboretum release, is a compact grower that matures to 3 to 4 ½ feet tall and wide with a rounded shrub form and dark green leaves that turn deep burgundy in fall. Large clusters of white flowers stand upright age to pink.

‘Gatsby Girl’ (photo from PW. thank you!)

Gatsby Gal® is a semi-dwarf oakleaf hydrangea from Proven Winners (PW) that grows 5- 7 feet tall and wide. Its green, oak-shaped foliage and large fragrant blooms in summer finishes with an outstanding fall color.

No serious insect or disease issues trouble oakleaf hydrangeas. Some susceptibility to leaf blight and powdery mildew. Aphids and spider mites are occasional visitors.

Attention Blog Readers: Interested in “larger growing oakleaf hydrangeas”? Look for a blog titled as such.

MT. Cuba Evaluates BlueStars (Amsonia)

Posted by Hugh on May 21st, 2024

New Amsonia ‘Starstruck’ Planting in Parking Lot of Mt Cuba Center

MT. Cuba Center is located near Hockessin Delaware, near Wilmington (USDA hardiness zone 7a.). It has recently published a new trial report on bluestars (Amsonia spp.) for the mid-Atlantic region. BlueStars are a genus of popular, long-lived herbaceous perennials. Most are native to the U.S. and Mexico in addition to one Asian species (A. elliptica) and (A. orientalis) in Greece and Turkey.

Mt. Cuba Center conducted over 10 years that evaluated several varieties, cultivars, and hybrids of three U.S. native species – A. ciliata, A. hubrichtii, and A. tabernaemontana. The trial focused on garden performance and ornamental qualities. It evaluated 20 different Amsonia varieties.

Amsonia species and cultivars vary in overall size and ornamental qualities such as foliage texture and bloom time, but all provide multiple seasons of ornamental interest. Sprays of blue flowers arrive in mid-spring followed by blemish-free summer foliage. Many varieties close the year with outstanding gold or orange fall color, especially when grown in full sun.

Cold hardiness will vary with species. Most bluestars are hardy in USDA hardiness zones 3-11. In harsh northerly areas, bluestars may be overwintered by covering them in a heavy frost blanket, or overwinter container plants in an unheated garage that stays just above freezing.

The Amsonia trial was grown in part-to-full sun in “average” soil, best described as clay-loam with a pH near 6.5. Throughout the trial, plants were given minimal care. Supplemental water was provided only during the first year after planting to encourage establishment.

BlueStars support early-season pollinators including native bees and hummingbirds and are the host plant for several species of butterflies and moths. Amsonias are botanical members of the Apocynaceae family, which includes milkweed (Asclepias); plant stems produce a milky sap that discourages browsing by deer and other mammals.

Most BlueStar varieties grow about 2-3 feet tall, and 2-3 feet wide. small, tidy, shrub-like clumps. Leaves are 3-4 inches, narrow and lance-shaped, with a pronounced mid-rib. Species size will depend on the variety grown and garden conditions.

*Amsonia ciliata tenuifolium* (white form)

Garden notes: Amsonia species prefer from full sun to part shade and a moist soil with a pH between 6.2-7.0 but adapt to most soils. They do not like prolonged dry conditions but once established. BlueStar plants can handle brief periods of drought. BlueStars thrive in a hot and humid climate.

Bluestar requires very little maintenance. Bloom clusters can get floppy when heavy with flowers and the seed pods that follow. To prevent this, either stake them with a hoop or trim them back by one third after flowering. Trimming will mean losing the attractive seed pods.

BlueStar can be grown from seeds harvested when the pods dry. You can start seeds in the fall or overwinter them in a cold frame or protected area, then transplant in the spring. Simply cover them lightly with soil and keep the soil moist until plants germinate.

Minor chlorosis and rust symptoms occur in high pH above 7.0. Otherwise, BlueStar plants are virtually problem free, and pests or diseases regularly bother them.

In late winter or early spring, cutback (cleanup) the previous year’s foliage. BlueStar stems are hollow, leaving 12 –18 inches of stem and provide a habitat for native bees.

Diseases were infrequently observed in this trial, and aside from the plants were virtually pest and disease free. BlueStar may be started from seed or purchase plants from nurseries and garden centers.

*A. tabernaemontana* ‘Montana’ – deeper blue flower & slightly wider leaves

Successful Gaura Growing Tips

Posted by Hugh on May 3rd, 2024

*Oenothera* lindheimeri ‘Whirling Butterflies’

Gaura (Oenothera lindheimeri) is a low-maintenance perennial native to the southern U.S. (Zones 5-9) and is a durable plant for gardeners. Its waving wands are dotted with dozens of whitish to pinkish flowers don’t stop blooming until summer temps climb above the 90°F range. Gaura is often called “whirling butterflies” because the flowers appear to dance in the breeze.

Gaura blooms all summer long producing graceful wands of nectar-rich white, pink, or bi-colored flowers that butterflies love. The deer-resistant plants grow 2-3 feet tall. Although whitish flowering forms have small, mostly non-distinctive green leaves, the foliage develops reddish tones in the dark pink flowering varieties.

Gauras are not long-lived perennials; wet winter soil will kill these drought-tolerant natives. Thus, site selection and ground prep are very important components in growing gauras. Plants have a long deep taproot and can be difficult to transplant. It is heat and drought tolerant and can handle high humidity with ease. It’s at its best in full sun but tolerates some afternoon shade in warm Southern climes. Excellent drainage is the key to success. Amend the soil with a mix of compost and gritty sand (not beach sand) or in raised beds.

Plant 3-5 gaura plants for maximum impact and space them at least 12-15 inches apart. Dwarf varieties are also an excellent container plant. Irrigate gaura sparingly to encourage this taproot plant to dig deep. Generally, gaura thrives in poor lean soil and does not require fertilizing. Too much fertilizer can make plant(s) floppy.

Gaura (Wandflower) Varieties- Four beautiful varieties include:

‘Corrie’s Gold’: Flowers are white tinged with pink and gold variegated foliage.
‘Passionate Rainbow’: pink flower wands and pink-edged foliage.
‘Siskiyou Pink’: showy rose-pink flowers on its notably wispy stems.
‘Sparkle White’: dainty white flowers are tinged with pink.

Overall, gauras may be affected by certain pests like aphids, whitefly and flea beetles. Root rot may occur in heavy and/or poorly drained soils. Rust and powdery mildew may also occur. Applications of insecticidal soap should resolve most pest issues. Gauras are also deer and rabbit resistant.

Gaura plants may flop over in the garden, and staking may be an option. Rigid, upright flowers like hyssop (Agastache), ‘Autumn Joy’ sedum, globe thistle (Echinops), or blazing star (Liatris) have similar growing conditions and blooming periods in a dry garden. Flowers invite pollinators by the score. Dwarf varieties make also excellent container plants.

Rethink Before Planting These Five Groundcovers

Posted by Hugh on April 26th, 2024

Initially, these 5 groundcovers were alluringly beautiful. But, over time, each grow very aggressively and become a major chore to restrained in the garden. Several states have declared one or more species as invasive and ban them for sale and interstate transportation.

English Ivy under tree growing up trunk and on ground

Purple Wintercreeper (Euonymus fortunei ‘Coloratus’, also known as Euonymus fortunei var. radicans, Euonymus radicans, Euonymus japonicus var. coloratus) and others. Purple Wintercreeper, is a very well-known ground cover. This trailing vine grows 12-18 inches tall and 24-36 inches in spread. The two-inch long leaves are glossy, ovate to elliptic, dark green (above) and purplish-red beneath). Leaves turn purplish red in fall and winter. Euonymus prefers moist, well-drained soil conditions in partial shade. (Zones 5 to 9).
Bishop’s Weed, Goutweed (Aegopodium podagraria variegatum) is an aggressive plant that forms dense patches via long, white, and spreading rhizomes. Goutweed grows in many areas of the U.S. and becomes a high maintenance weed. Growth-wise, the cultivar ‘Variegatum’ has basal light green foliage with creamy white margins. While rated as less aggressive than the species, plants may revert back to the green leaves with greater vigor. Foliage of variegated goutweed will burn in full sun. (Zones 3-10).
Evening primrose (Oenothera speciosa), aka Mexican primrose or Showy Ladies, blooms in the evening hours. Most garden shops do not sell it and have become a pass-a long between other green hobbiests. Flowers usually remain open thru late morning. The 1.5 – 2-inch-long seed capsules follow. By late summer the plant(s) have disappeared from their garden spots. Some seeds and underground runners return the next spring. (Zones 4-9). NOTE- As a North American native species, does not qualify as an invasive plant.
English Ivy (Hedera helix) is a high-climbing, evergreen vine available in many varieties at garden centers. English ivy is a common house plant. It has become an invasive garden plant in many areas of the U.S. Most varieties are aggressive groundcovers that grow in a wide range of sun or shade conditions. Some are meek and don’t attempt to take over. Ivy vines invade and spread into native forests and smothers tall trees and low growing native plants on the forest floor. Similarly, they rapidly cover trellises, walls, fences, trees, or any structure that they encounter. (Zones 4-13)
Creeping myrtle (Vinca minor), aka common periwinkle, is an aggressive low maintenance ground cover that excels in shady landscape areas. This low-spreading plant. grows vigorously in woodsy areas and into shady lawns. (Zones 4-9). Equally invasive is its large leaf cousin, Vinca major, but not as winter hardy in zones 7-9.

The most effective way to eliminate these aggressive groundcovers is to cut plants to the ground after they have fully leaved out in the spring, and next blanket the ground with black plastic or heavy cardboard. This will prevent photosynthesizing, essentially depleting their carbohydrate reserves. An alternative method is to overspray young foliage or cut stems/vines containing the ingredient glyphosate (Roundup™ and other labels) or Triclopyr (Garlon™).