All posts by hudelson

Ageratum

What is ageratum?  The genus Ageratum includes approximately 60 species of annual and perennial herbs and shrubs in the aster family (Asteraceae) that are all native to Central and South America.  One species that is commonly used as a bedding plant, Ageratum houstonianum, is from Mexico, and is named after William Houston (1695-1733), a Scottish physician who collected the first ageratum plants.  The name ageratum is derived from the Greek “a geras”, meaning non-aging and refers to the long-lasting nature of ageratum flowers.

Ageratum plants have soft, fuzzy flowers that can be blue, pink, lavendar or white.
Ageratum plants have soft, fuzzy flowers that can be blue, pink, lavendar or white.

Wild species of ageratum can grow to over two feet in height and typically reseed themselves liberally.  Varieties offered by nurseries and garden centers however are almost all hybrids that are more compact and better behaved.  Commercially available ageratum cultivars grow in neat mounds, flowering from late spring through fall.  They are one of the more dependable flowering annuals. Ageratum plants have oval to heart-shaped leaves that are up to two inches long.  Flowers of ageratum are typically some shade of blue, but can be pink, lavender or white.  The soft, fuzzy flowers are dainty and feathery, often delightfully fragrant, and usually cover plants completely.  Each flower cluster consists of five to 15 tubular florets. There are many different cultivars of ageratum, including attractive dwarf, tufted plants as well as tall, upright types that can be used as cut flowers.  Most cultivars are propagated from seed, and are predominantly F1 hybrids (i.e., offspring from crosses of two plants of closely related species or strains of a single species).

  • ‘Blue Blazer’ was the first commercial F1 ageratum hybrid.  This cultivar has better plant uniformity and vigor, and blooms earlier than open-pollinated cultivars.
  • ‘Blue Danube’ has compact six to eight-inch-tall plants covered with mid-blue flowers.  This cultivar is one of the best varieties for uniformity, earliness and general performance.
  • ‘Blue Horizon’ is an F1 hybrid that grows 30 inches tall and produces three-inch clusters of purplish-blue flowers on long stems.  This cultivar is great as a cut flower.
  • ‘Blue Mink’ is an open-pollinated cultivar that grows 12 inches tall and has powder-blue flowers.
  • ‘Hawaii’ is a series of F1 hybrids, each of which is dwarf (up to eight inches tall) and compact, with soft pink, royal blue or pure white flowers.  Members in this series flower earlier and longer than other varieties.
  • ‘Pinky’ produces salmon pink flowers on bushy and compact eight-inch-tall plants.
  • ‘Purple Fields’ is an F1 hybrid that produces compact, mounded plants that spread up to 12 inches across.  This cultivar is covered with unusual, purple flowers.
  • ‘Summer Snow’ is an F1 hybrid with fluffy white flowers;
  • ‘Trinidad’ has a unique, early-blooming blend of white, blue, violet and pink flowers on six-inch-tall plants.

Where do I get ageratum?  Ageratum transplants can be purchased at local garden centers.  However, ageratum can also be grown very easily from seed.  Start ageratum seeds eight to 10 weeks before you would like to transplant them into your garden.  Surface sow the seeds, barely covering them with vermiculite or potting mix.  Be sure that the seeds receive light to stimulate germination.  Germination usually takes seven to 21 days.  Transplant the seedlings into trays or pots when they are large enough to handle.  Move potted plants outside to harden off and transplant them into the garden when all risk of frost has passed.

Blue-flowered ageratum pairs well in the garden with yellow-flowered ornamentals.
Blue-flowered ageratum pairs well in the garden with yellow-flowered ornamentals.

How do I grow ageratum?  Transplant ageratum plants six to eight inches apart in a sunny spot.  Ageratum prefers a moist, well drained soil, but will also tolerate dry conditions.  Ageratum plants generally do not have insect or disease problems, although spider mites can be an issue, especially in hot, dry weather.  On most cultivars, old flowerheads turn brown and remain on the plants.  Deadhead regularly to improve the appearance of plants and prolong blooming.  Some cultivars are self-cleaning (i.e., the flowers fall off naturally).  Ageratum plants are sensitive to cold temperatures, so be sure to cover plants on cold nights in the fall to extend their survival.

How do I use ageratum most effectively in my garden?  Because of their short stature, most varieties of ageratum are best used for edging or borders of flowerbeds, in rock gardens, or in containers.  Blue varieties are particularly attractive when combined in the garden with pink-flowering plants.  Combine soft blue-flowering varieties of ageratum with pink begonias (Begonia spp.) for a low, pastel ground cover, or mass them with short yellow marigolds (Tagetes spp.) or cockscomb (Celosia spp.) for greater contrast.  Taller blue varieties of ageratum go well with yellow cosmos (Cosmos sulphureus).  Also try mixing the powder blue varieties with white petunias (Petunia spp.), lamb’s ear (Stachys spp.) or dark blue lobelia (Lobelia spp.).

For more information on ageratum:  Contact your county Extension agent.

Rusty Root

What is rusty root?  Rusty root is slow-developing root rot of ginseng that typically attacks older ginseng plants (two-year-old ginseng or older).  While the disease can destroy the plant’s entire root system and kill the plant, often rusty root is more important because it leads to roots that are unmarketable due to low quality.

Rusty-brown, corky, dry tap-root decay typical of rusty root
Rusty-brown, corky, dry tap-root decay typical of rusty root

What does rusty root look like?  Ginseng plants with rusty root often do not exhibit aboveground symptoms of the disease, although foliage of infected plants can exhibit a red, orange or yellow discoloration.  Roots of infected plants are often only partially decayed.  Decayed areas are rusty-brown and remain firm with a dry, corky, but never mushy texture.  While rusty root can occur anywhere on a ginseng root, it often occurs at the tip of the root and progresses upward.

Where does rusty root come from?  The most commonly cited cause of rusty root is Cylindrocarpon destructans, a soil-borne fungus that appears to survive readily in soils where ginseng has been grown.  Other fungi, such as Fusarium spp. may also be involved.  In addition, some researchers suggest that a boron deficiency may also contribute to rusty root development.

How do I save ginseng with rusty root?  Once a ginseng plant has been affected by rusty root, little can be done.  There are currently no fungicide treatments available to control this disease.

How do I avoid problems with rusty root?  Avoidance of rusty root fungi is the only current means of disease control.  Select a site not previously used for ginseng production.  Be sure not to track soil or plant material from infested gardens into non-infested gardens.  Clean equipment, hand tools and footwear after working in infested gardens.  Use high-pressure water or a detergent solution to clean large equipment, and a 10% bleach solution or alcohol to clean hand tools and shoes.  Soil fumigation has been used by some growers to successfully manage rusty root, even in areas where ginseng has been produced in the past.  However, other growers have found this technique ineffective.

For more information on rusty root: Contact your county Extension agent.

Phytophthora Root Rot – Ginseng

What is Phytophthora root rot?  Phytophthora root rot is the most serious root disease of American ginseng (Panax quinquefolium) in Wisconsin.  Left untreated, this disease can totally destroy a ginseng crop during a typical three to four year production cycle.

Healthy (left) and Phytophthora cactorum-infected (right) ginseng roots.
Healthy (left) and Phytophthora cactorum-infected (right) ginseng roots.

What does Phytophthora root rot look like?  Ginseng plants with Phytophthora root rot show signs of wilting, often combined with a reddish discoloration in their foliage.  Roots of affected plants are tan and watery, and often disintegrate when handled.  Infected roots often also have a pungent, bitter, earthy odor. Where does Phytophthora root rot come from?  Phytophthora root rot is caused by Phytophthora cactorum, a common soil fungus.  This fungus is most active during wet periods, particularly during May and early June in Wisconsin.  However Phytophthora root rot can occur anytime during the growing season. How do I save ginseng with Phytophthora root rot?  Once a ginseng plant has been infected by Phytophthora cactorum, little can be done to save the plant.  If infected plants occur in patches, attempt to localize the area by carefully removing a 1 to 2 ft. wide swath of healthy plants, about 5 ft from the edges of the affected area. How do I avoid problems with Phytophthora root rot?  Site selection and maintenance are critical for control of this disease.  Select a site with topography and a soil type that ensures good drainage, and plan gardens so that older gardens DO NOT drain into younger gardens.  In wetter sites, dig trenches to drain standing water.  Also, DO NOT move soil or plant material from an infested garden into a non-infested garden.  Disinfect tools, boots and spray equipment with a 10% bleach or detergent solution when moving from garden to garden.  Fungicide treatments are also important for management of Phytophthora root rot.  A combination of Ridomil Gold GR and Aliette WDG provides the best control and should help prevent the development of fungicide-insensitive strains of Phytophthora cactorum. For more information on Phytophthora root rot: Contact your county Extension agent.

Mystery Seedling Disease

What is mystery seedling disease?  Mystery seedling disease (MSD) is a root disease that affects young (i.e., seedling) ginseng leading to plant death, or sparse, unthrifty stands.  MSD is similar to rusty root (see University of Wisconsin Garden Facts X1061) and may be a seedling phase of this disease.  Like rusty root, MSD is most important because it leads to roots that are unmarketable due to low quality.

Healthy ginseng seedlings (left) and those affected by MSD (right).
Healthy ginseng seedlings (left) and those affected by MSD (right).

What does mystery seedling disease look like?  Initial symptoms of MSD may simply be a lack of germination of ginseng seeds in seedling ginseng gardens.  Plants that do emerge often have foliage with a red tinge.  Roots of infected plants are often stunted and bulbous, with an intact crown and decayed taproot tip.  Older infected plants (e.g., two-year-olds) are typically severely stunted. Where does mystery seedling disease come from?  Current research indicates that several fungi (either alone or in combination) may be involved in MSD.  These include Septonema, Cylindrocarpon destructans, Rhizoctonia, Pythium and Fusarium.  Because of the similarity of MSD and rusty root, nutrient deficiencies (e.g., a boron deficiency) might also be involved in the disease.

How do I save ginseng with mystery seedling disease?  Once a ginseng plant has been affected by MSD, little can be done.  There are currently no fungicide treatments available to control this disease.

How do I avoid problems with mystery seedling disease?  Avoidance of MSD fungi is the only current means of disease control.  Select a site not previously used for ginseng production.  Be sure not to track soil or plant material from infested gardens into non-infested gardens.  Clean equipment, hand tools and footwear after working in infested gardens.  Use high-pressure water or a detergent solution to clean large equipment, and a 10% bleach solution or alcohol to clean hand tools and shoes.  Soil fumigation has been used by some growers to successfully manage MSD, even in areas where ginseng has been produced in the past.  However, other growers have found this technique ineffective.

For more information on mystery seedling disease: Contact your county Extension agent.

Foliar Phytophthora

What is foliar Phytophthora?  Foliar Phytophthora is the above ground phase of Phytophthora root rot (see University of Wisconsin Garden Facts XHT1018).  Left untreated, this disease, along with Phytophthora root rot, can destroy large sections of a ginseng garden.

Typical symptoms of foliar Phytophthora on a three-year-old ginseng leaf.
Typical symptoms of foliar Phytophthora on a three-year-old ginseng leaf.

What does foliar Phytophthora look like?  Watch for ginseng leaves with a papery, transparent appearance, the typical symptom of foliar Phytophthora.  Often papery leaf areas are separated from healthy tissue by watery, blackish-green tissue.  Infected leaves and stems disintegrate rapidly and often Phytophthora root rot follows as the pathogen moves from the leaves and stems into the roots.

Where does foliar Phytophthora come from?  Foliar Phytophthora is caused by Phytophthora cactorum, the same fungus that causes Phytophthora root rot.  This fungus is common in soil and can be splashed onto ginseng leaves during rains.  In Wisconsin, foliar Phytophthora is most common during May and early June.

How do I save ginseng with foliar Phytophthora?  Once Phytophthora cactorum infects the foliage of a ginseng plant, it often moves into the root system and little can be done to save the plant.  If infected plants occur in patches, attempt to localize the area by carefully removing a 1 to 2 ft. wide swath of healthy plants, about 5 ft. from the edges of the affected area.

How do I avoid problems with foliar Phytophthora?  Cultural methods that are useful for controlling Phytophthora root rot can also be useful for controlling foliar Phytophthora (see University of Wisconsin Garden Facts XHT1018).  Any activity that reduces soil moisture is important for control because Phytophthora cactorum tends to be less active in drier soils.  In addition, adequate mulching of ginseng beds is very important.  Mulch appears to provide a physical barrier that helps prevent splashing of the fungus from the soil onto leaves and stems.  Finally, during wet periods, fungicide treatments can be critical for management of foliar Phytophthora.  Alternating applications of Aliette WDG and Dithane DF (when available) provides the best control of this disease.

For more information on foliar Phytophthora:  Contact your county Extension agent.

Alternaria Leaf and Stem Blight – Ginseng Stem

What is Alternaria leaf and stem blight?  Alternaria leaf and stem blight is the most serious foliar disease of American ginseng (Panax quinquefolium) in Wisconsin.  Left untreated, this disease can totally defoliate a ginseng garden in a few weeks.

Alternaria stem blight on three-year-old ginseng.
Alternaria stem blight on three-year-old ginseng.

What does Alternaria leaf and stem blight look like?  Ginseng leaflets with leaf blight have irregularly-shaped necrotic (dead) areas, often surrounded by a yellow halo.  Necrotic areas expand to destroy the entire leaflet.  Ginseng stems with stem blight collapse and are brownish-orange, with a layer of black soot (spores of the causal fungus) that can be rubbed away.

Where does Alternaria leaf and stem blight come from?  Alternaria leaf and stem blight is caused by the fungus Alternaria panax.  This fungus first enters ginseng gardens as wind-borne spores.  Once in a garden, the fungus can survive in diseased ginseng debris, and there produce spores that cause new infections.  Warm, humid Wisconsin summers favor the development of this disease.

How do I save ginseng with Alternaria leaf and stem blight?  Preventative fungicide treatments are critical for control of leaf and stem blight.  If available and legal to use, Dithane DF is the preferred fungicide for Alternaria leaf and stem blight control.  Other, less effective fungicides such as a combination of Rovral and copper hydroxide, or Aliette may also be used.  Whenever possible, use these products in combination with Dithane DF.  Check with your county Extension agent about current product availability, as well as for information on appropriate rates, timings and methods of application.

How do I avoid problems with Alternaria leaf and stem blight in the future?  You can reduce the severity of Alternaria leaf and stem blight by reducing the humidity in your ginseng garden.  This can be accomplished by planting smaller gardens, orienting gardens in the direction of prevailing winds, planting less dense ginseng stands, using side and end curtains sparingly, and trenching to remove standing water.  In larger gardens, leaving 1 ft. gaps in the shade every 100 ft. will help increase airflow and reduce humidity.

For more information on Alternaria leaf and stem blight:  Contact your county Extension agent:

Alternaria Leaf and Stem Blight – Ginseng Leaf

What is Alternaria leaf and stem blight?  Alternaria leaf and stem blight is the most serious foliar disease of American ginseng (Panax quinquefolium) in Wisconsin.  Left untreated, this disease can totally defoliate a ginseng garden in a few weeks.

Alternaria leaf blight lesions on three-year-old ginseng leaves.
Alternaria leaf blight lesions on three-year-old ginseng leaves.

What does Alternaria leaf and stem blight look like?  Ginseng leaflets with leaf blight have irregularly-shaped necrotic (dead) areas, often surrounded by a yellow halo.  Necrotic areas expand to destroy the entire leaflet.  Ginseng stems with stem blight collapse and are brownish-orange, with a layer of black soot (spores of the causal fungus) that can be rubbed away.

Where does Alternaria leaf and stem blight come from?  Alternaria leaf and stem blight is caused by the fungus Alternaria panax.  This fungus first enters ginseng gardens as wind-borne spores.  Once in a garden, the fungus can survive in diseased ginseng debris, and there produce spores that cause new infections.  Warm, humid Wisconsin summers favor the development of this disease.

How do I save ginseng with Alternaria leaf and stem blight?  Preventative fungicide treatments are critical for control of leaf and stem blight.  If available and legal to use, Dithane DF is the preferred fungicide for Alternaria leaf and stem blight control.  Other, less effective fungicides such as a combination of Rovral and copper hydroxide, or Aliette may also be used.  Whenever possible, use these products in combination with Dithane DF.  Check with your county Extension agent about current product availability, as well as for information on appropriate rates, timings and methods of application.

How do I avoid problems with Alternaria leaf and stem blight in the future?  You can reduce the severity of Alternaria leaf and stem blight by reducing the humidity in your ginseng garden.  This can be accomplished by planting smaller gardens, orienting gardens in the direction of prevailing winds, planting less dense ginseng stands, using side and end curtains sparingly, and trenching to remove standing water.  In larger gardens, leaving 1 ft. gaps in the shade every 100 ft. will help increase airflow and reduce humidity.

For more information on Alternaria leaf and stem blight:  Contact your county Extension agent.

African Violets

What are African violets? African violets (Saintpaulia spp.) are popular flowering houseplants in the Gesneriad family (Gesneriaceae), native to Tanzania in East Africa. Their compact forms make them ideal for use on tabletops, windowsills, and hanging baskets.

The blossoms of African violets can provide year-round color for your home.
The blossoms of African violets can provide year-round
color for your home.

There are many varieties of African violets, including trailing and miniature varieties. African violets usually form rosettes of rounded, velvety leaves with scalloped edges on short fleshy leaf stems. Leaves are often dark green with red-tinted undersides, and sometimes are variegated. Small clusters of flowers surround the foliage in shades of pink, red, white, violet, purple, blue and bicolor. Flowers can be single, double, semi-double, fringed, star-shaped, and Geneva (edged in white). African violets have a reputation for being difficult to grow, but under suitable conditions they will thrive, producing long blooming flowers throughout much of the year.

How do I care for African violets? African violets prefer locations with bright, indirect light.  In a south or west exposure, plants need to be protected from direct sunlight during peak hours, or foliage will burn.  If African violets do not form flower buds, they are likely not receiving enough light and should be moved to a sunnier location, or placed under artificial light.  In particular, supplemental fluorescent or full spectrum lighting may be necessary in winter months to encourage year-round flowering.  Position lights eight to 12 inches above plants, allowing 14 to 16 hours of light per day.  African violets prefer 70-75°F days and 60-65°F nights.  Place plants in a location with good air circulation, but keep them away from cold windows and cool drafts as sudden changes in temperature can harm the plants. African violets should be watered moderately from spring until fall, allowing soil to dry slightly between waterings.  Reduce water slightly in winter months.  Bottom water plants to avoid water splash on foliage, as cold water can damage leaves causing brown spots.  Fill saucers with warm water, allow plants to soak up water for approximately 30 minutes, and drain off excess water once the soil is sufficiently moist.  African violets are extremely susceptible to crown rots, which can rapidly kill the plants.  To prevent crown rots, avoid overwatering, avoid watering directly into the crown, and avoid watering at night. African violets grow best when potted in a well-drained, soilless potting mix or pre-packaged African violet mix.  Keep plants slightly pot-bound to encourage flowering.  Use a pot that is approximately one half the width of the plant’s spread.  When plants are in flower, apply a specially formulated African violet fertilizer once a month, following the label instructions of whatever fertilizer you select.  Remove older flowers and leaves as they begin to wither to improve the aesthetics of the plant, and to prevent problems with Botrytis cinerea, the gray mold fungus (see University of Wisconsin Garden Facts X1122).

For more information on African violets:  Contact your county Extension agent.