Morningglories

Images above: Upper left: Ivyleaf morningglory climbing on a fence (Antonio DiTommaso, Cornell University). Upper right: Ivyleaf morningglory seedling (Scott Morris, Cornell University). Bottom: Ivyleaf morningglory flower (Scott Morris, Cornell University).

Images above: Left: Pitted morningglory seedling (Scott Morris, Cornell University). Right: Pitted morningglory foliage (Antonio DiTommaso, Cornell University).

Images above: Left: Tall morningglory seedling (Antonio DiTommaso, Cornell University). Right: Tall morningglory flower and leaves (Antonio DiTommaso, Cornell University).

Images above: Left Three Images: Blade portion of one cotyledon of (from left to right) ivyleaf, pitted and tall morningglory (Antonio DiTommaso, Cornell University). Right Three Images: (from left to right) Ivyleaf, pitted and tall morningglory leaf shape (Antonio DiTommaso, Cornell University).

Identification

Other common names:

• Ivyleaf morningglory:  common morningglory, ivy-leafed morning-glory, ivy-leaved morning-glory, morning-glory, entireleaf morningglory
• Pitted morningglory:  pitted morningglory, small white morningglory, small white-flowered morningglory, white morningglory
• Tall morningglory:  common morningglory, morning-glory, purple morning-glory

Family:  morningglory family, Convolvulaceae

Habit:  Twining summer annual herbs.

Description:  Seedling stems are green to maroon and ridged.  Cotyledons are two-lobed, hairless, symmetrical, and green. 

• Ivyleaf morningglory:  Cotyledons are deeply notched at the tip and slightly notched at the base, forming a butterfly shape.  Each 0.6-1.75” (1.5-4.4 cm) long by 0.6-1.5” (1.5-3.8 cm) wide cotyledon fits within a square to rectangular or trapezoidal outline.  The first true leaf is unlobed, heart shaped, and hairless.  All other true leaves are three-lobed, with upright hairs on both blade surfaces, stems, and leaf stalks.                                                                            
• Pitted morningglory:  Cotyledons are split more than 75% of their length into a V and have narrower and pointier lobes than tall and ivyleaf morningglories.  Fully expanded cotyledons are 1.9” (4.9 cm) long by 2.6” (6.6 cm) wide at the broadest point.  All young leaves are heart shaped and tapered to the tip.  Leaves are nearly or completely hairless.
• Tall morningglory:  Cotyledons are green, 0.6-1” (1.5-2.5 cm) long by 0.6-1” (1.5-2.5 cm) wide, butterfly shaped, and fit into a square outline.  All young leaves are heart shaped and covered in small hairs that lie parallel to the leaf surface.

Mature plants trail and climb by twining, branching stems that can reach 12 ft (3.7 m), although 6.5 ft (2 m) is more common.  Leaves are alternate.  Roots are coarsely branched.

• Ivyleaf morningglory:  Stems are hairy.  Leaves are 2-5” (5-13 cm) long by 2-5” (5-13 cm) wide, tri-lobed, and covered in upright hairs; leaves generally have a heart shaped base and tapered lobes.
• Pitted morningglory:  Stems are smooth.  Leaves are nearly hairless, up to 3.7” (9.4 cm) long by 3.1” (8 cm) wide, heart shaped, and tapered to a narrow, pointy tip.  A small taproot is present.
• Tall morningglory:  Stems are hairy.  Leaves are heart shaped with a blunt tip and basal lobes that may overlap slightly.  Leaves are 2-5” (7-13 cm) long and nearly that wide and are covered with appressed hairs. 

Flower petals are fused into a funnel shaped flower with many stamens and three pistils.  Clusters of flowers form in leaf axils. 

• Ivyleaf morningglory:  Petals are 1.1-2” (2.7-5 cm) long, initially off-white to light blue but turning pink-purple after opening.  Clusters of 1-3 form in each leaf axil.  Thin, hairy or bristly, green, 0.5-1” (1.3-2.5 cm) long sepals curve backwards at the tip. 
• Pitted morningglory:  Petals are 0.6-1.2” (1.5-3 cm) long and characteristically white to pinkish.  Otherwise the flowers resemble those of ivyleaf morningglory.
• Tall morningglory:  Petals are 1.75-2.75” (4.5-6.9 cm) long and light colored when young, turning purple-pink or blue as they open and mature.  Clusters of 3 or more form in each leaf axil.  Narrow, lance-shaped sepals are 0.5” (1.3 cm) long and clasp the base of the fused petals.  Otherwise the flowers resemble those of ivyleaf morningglory.

Fruit and seeds:  Flowers produce egg shaped capsules that remain partially concealed by the remaining sepals.  Capsules contain 2-4 (usually 3) compartments.  Seeds are dark brown to black and wedge shaped.  Seeds have two flat and one round side.

• Ivyleaf morningglory:  Each capsule produces 4-6 seeds.  Seeds are large, almost 0.25” (0.6 cm) wide, and covered in minute hairs.
• Pitted morningglory:  Each capsule produces four, 0.2” (0.5 cm) wide, smooth seeds.
• Tall morningglory:  Each capsule produces four to six 0.2” (0.5 cm) diameter seeds, similar to those of ivyleaf morningglory.

Similar species:  Several other morningglory species exist, with smallflower morningglory [Jacquemontia tamnifolia (L.) Griseb.] being of great importance in the southern U.S.A.  It can be distinguished from the morningglories described above by the densely pressed hairs on the foliage and by its tight clusters of small, bright blue flowers.  Bindweeds, such as field bindweed (Convolvulus arvensis L.), are often confused for true morningglories.  Bindweeds are perennials whereas the weedy morningglories discussed here all arise from seeds.  Wild buckwheat (Polygonum convolvulus L.) is a twining annual that has leaves resembling pitted morningglory, but wild buckwheat has small green flowers and sheaths extending up the stem from the base of leaves.

Management

Morningglories are difficult weeds to control, and their vining habit makes them aggressive competitors.  Early planting dates for corn, soybean and cotton allow the crop to become competitive before most of the morningglories emerge.  If morningglories emerge and vine before the crop canopy closes, substantial crop yield losses can result (Keeley et al. 1986).  Tine weed aggressively to break or bury newly emerged seedlings.  You may need to do this more frequently than for smaller seeded and therefore slower growing weeds.  Because many emerge from deep layers of the soil, relatively few can be uprooted, and rotary hoeing is likely to be less effective than tine weeding.  To avoid crop damage, cultivate frequently enough to kill morningglories before inter-row plants have attached to crops.  If possible, use a belly mounted cultivator or accurate guidance system with shallow pitched half sweeps to get close to the rows.   Shorter season crop varieties may allow harvest before the vines interfere severely with harvesting equipment.  Consider setting the combine to capture morningglory seeds with the grain, and then clean them out later or use equipment to capture or destroy seeds in the chaff. Flame weed in well-established cotton while morningglory seedlings are still small.

Winter wheat suppresses morningglory establishment by keeping the soil cool and undisturbed during the peak germination period.  Seedlings that do emerge are suppressed by shade.  A dense, vigorous stand of spring grain has a similar effect provided the grain is planted early.  Morningglories are favored by rotations of short annual crops like alternating peanut and cotton (Leon et al. 2015), so diversifying rotations to include an established sod during the warm periods of the year will suppress morningglory populations.

Although some seeds will likely survive solarization, even a few days at 140-158° F (60-70° C) in moist soil eliminates a large proportion of pitted morningglory seeds (Egley 1990).  Despite being more tolerant of heat than other weed species tested, pitted morningglory seeds were rendered unviable by narrow-windrow burning of soybean residue (Norsworthy et al. 2020). 

Both plastic and straw mulch are ineffective for controlling morningglories.  The vines find their way through the planting holes in plastic – they are essentially led to the crop by light.  Large seed reserves allow the seedlings to emerge through 6” (15 cm) or more of straw (Mohler, personal observation).  Cover crop residue only suppressed pitted morningglory early in the season, but had little effect by mid-season (Pittman et al. 2020).

Ecology

Origin and distribution:  Ivyleaf morningglory probably originated in tropical America (Fernald 1950, Whigham 1984).  Authorities disagree about whether tall and pitted are native to the Southeast and southern Midwest (Correll and Johnston 1970, Stephenson et al. 2006) or were introduced from the American tropics (Fernald 1950, Whigham 1984).  Ivyleaf morningglory is now widely established east of the Rocky Mountains and in the Southwest (USDA Plants).  Pitted morningglory occurs from Massachussetts to Iowa and south to Florida and Texas, and also in California.  Tall morningglory is native to tropical America but is now established in most of the U.S.A. (USDA Plants).  All three species are most problematic in warm, humid regions, and their occurrence tends to be scattered in the northern and western states.

Seed weight: Ivyleaf morningglory, 27-35 mg; pitted morningglory, 19-25 mg; tall morningglory, 19-25 mg (Stoller and Wax 1973, Crowley and Buchanan 1982, Shergill et al. 2020, Mohler unpublished). 

Dormancy and germination:  Usually, a high percentage of morningglory seeds have a hard seed coat that prevents them from absorbing water and thereby maintains dormancy (Elmore et al. 1990, Jayasuiya et al. 2007).  A substantial proportion of recently matured seeds of all three species will germinate, but germination declines after the seed coat hardens (Holm 1972, Norsworthy and Oliviera 2007, Stoller and Wax 1974).  Seeds require exposure to moist conditions or high relative humidity (as occurs in spring) to become sensitized, followed by high temperatures (as occurs in early summer) to break dormancy (Jayasuiya et al. 2008).  However, dry conditions (as occurs in late summer) will desensitize seeds so dormancy is not broken by high temperatures. Seeds germinate best at warm temperatures from 59 to 95 °F (15 to 35 °C) (Elmore et al. 1990, Gomes et al. 1978, Norsworthy and Oliveira 2007, Oliveira and Norsworthy 2006, Singh et al. 2012, Thullen and Keeley 1983).  Moistened seeds of pitted morningglory germinated best at these warmer temperatures, but seeds with broken seed coats germinated equally well at day/night temperatures from 59/43 to 95/68 °F (15/6 to 35/20 °C) (Jayasuiya et al. 2007, 2008).  Pitted morningglory germination was more tolerant of drought than several other weed species including ivyleaf morningglory (Hoveland and Buchanan 1973).  Pitted morningglory germinated best at pH 6 to 8 whereas tall morningglory germinated well at a pH between 5 and 7 (Oliveira and Norsworthy 2006, Singh et al. 2012).  Light generally has little effect on germination of morningglory species, but it did promote germination of tall morningglory seeds that had been buried in the soil (Holm 1972, Jayasuiya et al. 2007, 2008, Norsworthy and Oliveira 2007, Singh et al. 2012).   Seeds of tall morningglory germinate poorly in soil with low oxygen.  This is not directly due to excess CO2 or a lack of oxygen, but occurs because seeds in a low oxygen environment produce volatile organic compounds that enforce dormancy (Holm 1972).  Venting of volatiles during tillage would promote germination.  Flooding also greatly reduced germination of tall morningglory (Singh et al. 2012).

Seed longevity:  Morningglory seeds can persist in soil because of their hard seed coats (Elmore et al. 1990, Stoller and Wax 1974).  Ivyleaf mornigglory seeds remained viable for up to 17 years (Burnside et al. 1996).  However, more typically, 36% and 70% of ivyleaf seeds disappear between late autumn and the following August, and mortality is little affected by depth of burial (Stoller and Wax 1973).  Pitted morningglory seeds buried at 22” (56 cm) had 31% survival after 39 years (Toole and Brown 1946).  In contrast, in another experiment, only 13% of pitted morningglory seeds remained viable after burial for 5.5 years (Egley and Chandler 1983).  When a sowing of pitted morningglory was tilled annually to 6” (15 cm) and no seed return was allowed, the number of seedlings emerging declined by 58% per year (computed from Egley and Williams 1990).

Season of emergence:  All three species have some emergence throughout the warm months of the year, but peak emergence tends to occur in early summer (Elmore et al. 1990).  Studies in Illinois showed flushes of ivyleaf emergence primarily in June and July following rainfall (Stoller and Wax 1973).  Out of 23 summer annual weeds tested, ivyleaf morningglory was the latest emerging species in spring, but had the longest emergence duration once it began emerging (Werle et al. 2014). 

Emergence depth:  Generally, all three species emerge best from the top 1-2” (2.5-5 cm) of soil, but substantial numbers can emerge from 4” (10 cm) (Elmore et al. 1990, Singh et al. 2012).  A few individuals can even emerge from 6” (15 cm) (Cole 1976, Gomes et al. 1978, Mohler unpublished, Oliveira and Norsworthy 2006, Wilson and Cole 1966).  Tall morningglory seeds at 0.5” (1.3 cm) emerged faster and plants became more competitive with crops than seeds emerging from 2” (5 cm) (Cole 1976).  

Photosynthetic pathway:  C3

Sensitivity to frost: The first frost usually kills morningglory plants (Stinchcombe and Rausher 2001, Tiffin and Rausher 1999).

Drought tolerance:  Ivyleaf morningglory does not compete effectively for soil moisture (Elmore et al. 1990).  Tall morningglory is more susceptible to drought than cotton (Elmore et al. 1990).  Tall morningglory responds to drought by allocating more resources to leaves; thus it maintains overall biomass, but reproduction is reduced (Mason et al. 2015). 

Mycorrhiza:  Tall morningglory is mycorrhizal (Fracchia et al. 2009).

Response to fertility:  Ivyleaf is a poor competitor for N, but grows poorly without N fertilization (Whigham 1984).  Tall morningglory responds to low N by allocating more resources to roots, but overall growth and reproduction are severely reduced (Mason et al. 2015).  Tall morningglory is more responsive to soil P and K than corn or soybean, but less responsive than forage grasses (Hoveland et al. 1976).  It grows poorly on soils with a pH below about 5.3 (Buchanan et al. 1975).

Soil physical requirements:  Pitted morningglory tolerates poor soil drainage (USDA Plants).

Response to shade:  Large seeds and a twining growth habit often allow morningglories to escape competition for light by climbing up competing plants (Oliver et al. 1976, Whigham 1984).  Light interception by the crop leaf canopy must exceed 90% for suppression of ivyleaf morningglory (Cordes and Bauman 1984, Keeley et al. 1986).  Cotton competitively suppressed newly emerging ivyleaf once the crop leaf canopy closed, but plants still produced a few seeds (Keeley et al. 1986).  Rapid canopy closure in narrow-row soybeans suppressed pitted morningglory growth (Murdock et al.1986).  Tall morningglory has longer internodes, longer stems, thinner stems and larger leaves when growing in shade (Gianoli 2002).  These shade-responsive traits are enhanced when support is available (Gianoli 2002), allowing the species to climb and access light within a crop canopy, even when it emerges after the crop.  Tall morningglory, however, is unable to flower in shade (Gianoli 2002).

Sensitivity to disturbance:  Ivyleaf morningglory has a high potential to recover from removal of the growing tip when vines are greater than 4” (10 cm) long (Mager et al. 2006).

Time from emergence to reproduction:  Ivyleaf morningglory flowers 4 to 7 weeks after emergence (Crowley and Buchanan 1982, Keeley et al. 1986, Stinchcombe and Rausher 2001, Thullen and Kelley 1983).  Tall morningglory flowers 6 to 8 weeks after emergence (Tiffin and Rousher 1999, Crowley and Buchanan 1982).  Seeds of both species mature about 4 weeks after flowers open, and plants continue to flower and set seeds until they are killed by frost (Stinchcombe and Rausher 2001, Tiffin and Rousher 1999).  Pitted morningglory tends to flower as days shorten to 13 hours in late August, regardless of whether they emerge in May or late June (Crowley and Buchanan 1982, Senseman and Oliver 1993).

Pollination:  Ivyleaf morningglory is primarily self-pollinated and flower structure indicates that pitted morningglory is likely self-pollinated as well (Elmore et al. 1990).  Tall morningglory has a high rate of cross pollination (70%) (Ennos 1981), mostly by bumblebees and small butterflies (Elmore et al. 1990, Stucky 1984).  The prevalence of self-pollination in ivyleaf morningglory flowers is explained by the close proximity of anthers and stigma, whereas this distance is highly variable in the outcrossing tall morningglory (Ennos 1981).  Also, the larger and more conspicuous flowers of tall morningglory attract more bumblebees and provide greater potential pollinator energy gain than do ivyleaf flowers (Stucky 1984).  Self-pollination incurs no penalty; outcrossed and self-pollinated populations of tall morningglory perform similarly in response to drought or nitrogen stress (Mason et al. 2015).

Reproduction: Plants emerging mid-summer and growing without competition often produce about 5,000-7,000 seeds, but under good conditions, plants can produce as many as 11,000 (ivyleaf), 16,000 (pitted), and 26,000 (tall) seeds (Crowley and Buchanan 1982, Gomes et al. 1978, Keeley et al. 1986, Senseman and Oliver 1993, Stephenson et al. 2006, Thullen and Keeley 1983).  Crop competition, however, greatly decreases seed production.  For example, pitted morningglory competing with soybean produced only 5% and 0.4% as many seeds as plants growing without competition in two successive years (Senseman and Oliver 1993).  A study of ivyleaf morningglory showed that plants emerging in early July produced the most seeds, with earlier and later emerging individuals producing substantially fewer seeds (Thullen and Keeley 1983). 

Dispersal:  Given the similarity of morningglory seeds to those of field bindweed and their hard, impermeable coat, the seeds probably pass through livestock and are spread with manure (Harmon and Keim 1934).  Since deer frequently feed on morningglory, they may spread the seeds as well (Stichcombe and Rausher 2001).  These species probably also disperse when seeds in contaminated feed grain pass through livestock.

Common natural enemies:  Ivyleaf morningglory can be heavily damaged by white rust (Albugo ipomoeae-panduratae) and orange rust (Coleosporium ipomoea) but produce thousands of seeds per plant anyway (Crowley and Buchanan 1982, Stinchcombe and Rousher 2001).  Tall and pitted morningglory are less damaged by rusts.  Tall morningglory (and probably other species) can be heavily attacked by tortoise beetles (Deloyala guttata and Metriona bicolor), the sweet potato flea beetle (Chaetocnema confine), and the corn earworm (Heliothis zea) (Fineblum and Rausher 1997, Simms and Rausher 1989, Tiffin and Rausher 1999).

Palatability:  Ivyleaf and tall morningglory have better digestibility and higher crude protein than warm season forage grasses, but they are deficient in P (Bosworth et al. 1980).

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