Perennial rhizomatous begonias add bold texture and color to north Florida gardens

Perennial rhizomatous begonias add bold texture and color to north Florida gardens

Article by Dr. Gary Knox, Professor of Environmental Horticulture at the UF/IFAS NFREC Quincy

Introduction

Rhizomatous begonias are a large group of Begonia species, hybrids and selections characterized by large, sometimes-colorful leaves arising from thick rhizomes that grow along the soil surface. White or pink flower clusters that appear in late winter and spring are an extra bonus with these plants. Some types can be used in north Florida as herbaceous perennials that add bold leaf texture and color as well as flowers to shady gardens.

Begonia mass planting

Common rhizomatous begonias such as Begonia nelumbiifolia, ‘Erythrophylla’ (“Beefsteak”), and ‘Ricinifolia’ have long been grown outdoors in south and central Florida gardens as herbaceous perennials. North of these areas, rhizomatous begonias were considered cold sensitive and thus used strictly as pot-grown plants grown indoors or protected over winter. Nonetheless, north Florida trials testing the performance of outdoor, in-ground plantings started in Tallahassee and Gainesville as long ago as the late 1980s and early 1990s. With the proven success of some rhizomatous begonias in north Florida, interest in these plants increased rapidly in the early 2000s. Since then, savvy north Florida gardeners have been delighted by the possibility of using rhizomatous begonias as interesting herbaceous perennials for the shade garden. While temperatures below freezing can damage or kill leaves, these plants will usually produce new leaves from the rhizomes once warmer temperatures return in spring.

Plant Description Under North Florida Conditions

Leaves of rhizomatous begonias are this plant’s most distinctive feature and are why this group is so appealing to gardeners. Leaves often are large, from a few inches wide to almost 3 ft. in diameter (as reported for the cultivar ‘Freddie’ under the right conditions). Leaf shape may be rounded, star-shaped or irregularly edged, and leaf colors include burgundy, red, bronze, chartreuse, silver, and various shades of green including one so dark as to be almost black. Many types have leaves displaying patterns of one or more colors and some have silver or red markings. Undersides of leaves are often burgundy-colored, and leaf stems (petioles) also may exhibit colors other than or in addition to green. Leaves may be smooth, textured, or fuzzy-appearing due to large numbers of sometimes conspicuous hairs. Some types have leaves with an interesting three-dimensional spiral located on top of the leaf where the leaf blade attaches to the stem.

Begonia ‘Big Mac’ foliage

Rhizomatous begonia rhizomes are thickened, fleshy stems 1 to 2 in. or more in diameter that grow, branch and spread horizontally at or just below the soil surface, often in the mulch or leaf duff. Adventitious roots develop along the rhizome, and dormant buds embedded in the horizontal stem can be stimulated to grow new leaves after damage, stress or when divided. With age, as rhizomes grow outward, the oldest part of the rhizome will stop producing leaves and eventually die.

The rhizomes contain water and food reserves that allow this type of begonia to survive environmental stresses like drought as well as leaf loss or damage from cold temperatures. Shoots and roots can grow from the rhizome even if leaves and roots are killed or damaged.

Flowers occur in late winter to spring, depending on the species, cultivar and weather, and are quite showy on some selections. Flowers typically are white to various shades of pink and occur in a cluster (technically called a cyme) held above the foliage, in some cases dramatically high above the foliage. Individual flowers may range in size from 3/8-inch to over 2 inches at their widest point and a flower cluster may contain a few to over 120 individual flowers, depending on selection and growing conditions. A mature rhizomatous begonia may have an extended period of flowering, providing weeks of color. This long floral display results from large numbers of flowers developing sequentially on an individual flower cluster such that new flowers are still forming long after the first flowers have opened. Furthermore, multiple flower clusters appear over an extended time period. Flowers occasionally are pollinated and form winged seed capsules, though seed production and viability are variable. After flowering, the leaves remain a point of interest in the garden due to their size, lush appearance, interesting shapes and colorful patterns.

Cultural Requirements, Use and Maintenance

Rhizomatous begonias grow best in light shade or indirect light but can tolerate morning sun. Plants thrive in rich, organic, well-drained soil that is moist but not wet. A layer of organic mulch or leaf litter often is enough to provide basic conditions for growth in most soils if they are well-drained. Accordingly, organic mulches or leaf litter should be applied regularly around plants. Fertilizer stimulates growth but decomposing organic mulches can provide adequate nutrients, except perhaps with poor or sandy soils.

Newly planted begonias should be watered regularly. After establishment, most rhizomatous begonias benefit from regular watering but only require irrigation during periods of drought or extended dry weather.

An individual plant makes an attractive specimen plant in a container or in the garden. With time, a rhizomatous begonia can spread and, in the garden, develop into a patch. Alternatively, planting large numbers of the same rhizomatous begonia can create a very dramatic garden border, mass planting, or groundcover, especially in spring when all plants are flowering. To achieve this effect more rapidly and with smaller numbers of plants, tips of rhizomes can be pruned to stimulate rhizome branching and result in a denser plant or patch. Rhizome tip pruning should be done after plants finish flowering. Plants can be divided and moved easily since only the rhizome is needed to establish a new plant, but this should occur after flowering and early in the growing season so plants have long enough to establish before cold weather.

For aesthetic purposes, dead or damaged leaves may be removed as needed but especially after frosts and hard freezes. Similarly, leaves that overwinter often become “ratty” in appearance with time and may be removed without affecting plant growth.

Potential Problems

Rhizomatous begonias have few pests or other problems. Mealy bugs can occasionally infest plants. As with other large-leaved plants, wind or physical contact can tear and damage leaves. In north Florida, winter frosts and freezes can damage and disfigure leaves or kill leaves entirely, causing them to lose structural integrity and collapse, appearing mushy. Foliage may be protected during cold weather by frost cloth, sheets or other typical cold protection strategies, though heavy coverings could themselves damage leaves.

Rhizomes themselves usually survive cold weather because they are insulated from low temperatures by being half-buried in the ground and/or being covered by mulch. Adding mulch regularly to rhizomatous begonia plants will provide increased freeze-protection. Also, their typical planting location under tree canopies protects plants from a radiation freeze. Soil drainage is a more important factor for rhizomes since wet soil conditions could lead to rot, particularly in winter.

Common Types and their Descriptions Under North Florida Conditions

With hundreds of species and thousands of cultivars and hybrids, rhizomatous begonias can be overwhelming. Many rhizomatous begonias look alike and even experts have difficulty distinguishing species and cultivars. Many grown in north Florida have their origins in Mexico, Central and South America, though the Begonia Family is huge and species are found nearly world-wide.

Begonia heracleifolia

Technically rhizomatous begonias include Rex begonias, a group derived from Asian native, Begonia rex, and known for their especially colorful leaves. However, most Rex begonias do not grow well in Florida’s heat, high rainfall and high humidity, and so these begonias are excluded here.

Begonias listed below represent types that have proven resilient and usually cold hardy in north Florida USDA Cold Hardiness Zone 8b.

Species:

Begonia heracleifolia: The species boasts star-shaped leaves up to 6 in. across on stiff, hairy, thick leaf stems (petioles) up to 5 in. long. Each of the pointed leaf lobes is edged in dark green and has a chartreuse stripe along the central midrib, adding contrast. Spectacular sprays of pale pink flowers appear in late winter in clusters measuring 3 ½ in. by 4 ½ in. on 6-in. flower stalks (pedicels). Each cluster contains about 30 or more flowers, each about 1 in. across. As the season goes on, foliage gets showier and showier. It often dies down after winter freezes but re-emerges in late spring.

Begonia nelumbiifolia

  1. nelumbiifolia: This cold hardy begonia is known for its exceptionally large, water lotus-shaped leaves, creating a stunning specimen. Individual leaves can grow as large as 18 in. by 14 in. on leaf stems as long as 36 in. but 12 in. by 9 in. leaves are more typical. As temperatures warm, new developing foliage continues to get bigger, growing into very large leaves by fall. There also is a form in which the medium green leaves have red veining. White flowers are displayed above the foliage in mid to late spring in airy clusters measuring 7 ½ in. to more than 12 in. across on stems up to 48 in. tall. Clusters may contain as many as an astounding 120 flowers, each about ¾ in. across at its widest point.

2. popenoei: Huge rounded leaves with red veins and undersides make this a specimen plant which can grow to 3 ½ ft. tall and wide. Hardy with protection, it throws up tall stalks with clusters of white flowers in late winter.

Cultivars:

“Beefsteak”: This catch-all name refers to the original beefsteak begonia, ‘Erythrophylla’, as well as many derivatives that look similar. Beefsteak begonias characteristically have rounded leaves with a glossy green to bronze top surface and reddish undersides. Leaves range in size from 4 to 7 in. in diameter, and flower clusters are on stems up to 18 in. tall. ‘Erythrophylla’ was developed in 1847 and is considered a tough, vigorous plant, hence the common name, “beefsteak”. Given the long history and vigor, ‘Erythrophylla’ and derivative beefsteak begonias have long been shared as pass-along plants, world-wide as potted plants and later as an in-ground Florida garden plant. One type has ruddy, evergreen leaves and long-lasting, bold pink flower clusters. The scalloped 4-in leaves are on short 5 ½ in. reddish leaf stems but are most notable for remaining undamaged by temperatures down to the mid 20s °F, long after all other begonias’ leaves have turned to mush. Mid spring finds this plant topped by numerous clusters of dark pink flowers, with the display lasting 6 weeks or more. Individual clusters are about 8 in. by 5 in. on flower stems about 12 in. tall. Each cluster contains about 20 flowers each about ¾ in. wide at its widest point.

Begonia ‘Big Mac’ in flower

‘Big Mac’: This is a large, vigorous plant with enormous star-shaped leaves having reddish undertones and red leaf stems. The plant grows about 3 ft. tall and 2 ft. wide. Individual leaves may grow up to 18 in. wide on 16-in. leaf stems but typical leaves on younger plants are 10 in. to 12 in. wide. Individual white flowers are an amazing 2 in. wide at their widest point in clusters measuring 7 in. by 12 in. and containing about 75 flowers. Cold winters will knock it to the ground, but this begonia re-emerges again in late spring. This plant was hybridized in 1982 by Paul P. Lowe in Lake Park, Florida.

‘Joe Hayden’: This begonia features dramatic, dark, lobed leaves with burgundy undersides. Leaves are up to 8 in. long supported by leaf stems up to 9 in. long. In spring, the plant is topped by light pink flowers held high above the foliage. Each cluster measures about 5 in. by 7 in. on flower stems up to 26 in. tall. Each cluster contains more than 100 individual flowers, each about ¾ in. across at its widest point. This selection was hybridized in California in 1953 by Rudolf Ziesenhenne, but many similar selections have been made and are often confused with ‘Joe Hayden’.

Begonia ‘Joe Hayden’

Many other cultivars are common, but other cold hardy types suitable for north Florida include ‘Caribbean King’, ‘Caribbean Queen’, ‘Washington State’ and the catch-all ‘Ricinifolia’ types (with large, castor bean-shaped leaves). New breeding by scientists and enthusiasts promises to deliver many more types of rhizomatous begonias with increased foliage cold hardiness and an expanded range of foliage types and colors. A major Texas nursery introduced a series of rhizomatous begonia hybrids marketed as Crown Jewel Begonia™. The series currently features five patent-pending cultivars that are promoted as landscape plants for Zone 8. Additional breeding work is ongoing in north Florida.

Availability and Propagation

Rhizomatous begonias are available from Internet/mail order nurseries, some American Begonia Society members, other gardening groups, and plant societies. The introduction of trademarked rhizomatous begonias like Crown Jewel Begonia™ show promise for wider availability of rhizomatous begonias from nurseries.

Rhizomatous begonias are easily propagated by division, separation of rhizomes, or by rhizome pieces. When planting, place the rhizome or pieces (as small as 2 in. long) horizontally and half buried in a new in-ground location or in a container with potting soil. As with other begonia species, leaves may be used for propagation, though this method usually takes longer to achieve a size suitable for planting in the garden. Plants can be grown from seeds but production time is similarly long.

References:

American Begonia Society. (2020) https://www.begonias.org/index.htm. Accessed 15 April 2020.

Ginori, Julian, Heqiang Huo, and Caroline R. Warwick. (2020) A Beginner’s Guide to Begonias: Classification and Diversity, ENH1317. Environmental Horticulture Department, UF/IFAS Extension. January 2020. https://edis.ifas.ufl.edu/ep581.

Lowe, Paul. (1991) Growing Rhizomatous Begonias in the Ground in Southern Florida. Begonian 58:89. May/June 1991. https://www.begonias.org/Articles/Vol58/GrowingRhizomatousBegoniasFlorida.htm.

Schoellhorn, R. (2020) Personal communication, Alachua, FL.

Sharp, Peter G. (2011) Down to Earth – with begonias. 111 pp. http://ibegonias.filemakerstudio.com.au/PeterSharp/DownToEarthWithBegonias.pdf.

The International Database of the BEGONIACEAE. (2020) http://ibegonias.filemakerstudio.com.au/index.php?-link=Home. Accessed 16 April 2020.

UF/IFAS Gardening Solutions. (2019) Begonias. http://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/begonias.html.

Watkins, Sue. (2020) Personal communication, Tallahassee, FL.

For One Insect, Pine Needles are the Preferred Menu Item

For One Insect, Pine Needles are the Preferred Menu Item

Spring has arrived and so have the insects. Caterpillars are crawling around and one possesses a unique appetite.

Neodiprion spp. is the most common defoliating insect group affecting pine trees. In all, there are 35 species that are native to the U.S. and Canada.  The redheaded pine sawfly, Neodiprion lecontei, is the primary species found in the Florida Panhandle.

Adult sawflies can be as large as 1/3 of an inch in length. The female can be two-thirds larger than the male and are mostly black with a reddish-brown head, with occasional white coloration on the sides of the abdomen.

Mature larvae of the redheaded pine sawfly. Credit: Patty Dunlap, Gulf County Master Gardener.

The ovipositor, the tube-like organ used for laying eggs, is saw-like, hence the common name. During the fall, females make slits in pine needles and deposit individual eggs, up to 120 eggs at a time. The eggs are shiny, translucent and white-hued. Mature larvae (caterpillars), as seen in the accompanying photo, are yellow-green, emerge in the spring and feast on pine needles. After weeks of feeding on needles, the mature larvae drop to the ground. The cocoon, a reddish-brown, thin walled cylinder, is spun in the upper layer of the soil horizon or in the leaf litter; this is called the pupae stage.  The pupae overwinter, and adults emerge from the cocoon in the spring of the following year.

Mature larvae are attracted to young, open growing pine stands. Pine is the preferred host, but cedar and fir, where native, are secondary food sources. Neodiprion lecontei is an important defoliator of commercially grown pine, as the preferred feeding conditions for sawfly larvae are enhanced in monocultures of shortleaf, loblolly, and slash pine, all of which are commonly cultivated in the southern United States. Defoliation can kill or slow the growth of pine trees as well as predispose trees to other insects or disease.

Are there control methods? Yes, biological control is a major factor, as natural enemies are numerous. Disease, viruses and predators help regulate population control. For small scale control, physically removing eggs or larvae is key. Again, most infestations occur on younger tree plantings, so they’ll be in reach. Be sure to scout young pines for signs of infestation. Horticultural soaps and oils are effective chemical controls, if needed.

For more information, contact your local county extension office.

Supporting information for this article can be found in the UF/IFAS Extension EDIS publication, “Redheaded Pine Sawfly Neodiprion lecontei” by Sara DeBerry: https://edis.ifas.ufl.edu/pdffiles/IN/IN88200.pdf

 

 

UF/IFAS Extension is an Equal Opportunity Institution.

Pomegranates in the Panhandle

Pomegranates in the Panhandle

Last week at the Panhandle Fruit and Vegetable Conference, Dr. Ali Sarkhosh presented on growing pomegranate in Florida.  The pomegranate (Punica granatum) is native to central Asia.  The fruit made its way to North America in the 16th century.  Given their origin, it makes sense that fruit quality is best in regions with cool winters and hot, dry summers (Mediterranean climate).  In the United States, the majority of pomegranates are grown in California.  However, the University of Florida, with the help of Dr. Sarkhosh, is conducting research trials to find out which varieties do best in our state.

In the wild, pomegranate plants are dense, bushy shrubs growing between 6-12 feet tall with thorny branches.  In the garden, they can be trained as small single trunk trees from 12-20 feet tall or as slightly shorter multi-trunk (3 to 5 trunks) trees.  Pomegranate plants have beautiful flowers and can be utilized as ornamentals that also bear fruit.  In fact, there are a number of varieties on the market for their aesthetics alone.  Pomegranate leaves are glossy, dark green, and small.  Blooms range from orange to red (about 2 inches in diameter) with crinkled petals and lots of stamens.  The fruit can be yellow, deep red, or any color in between depending on variety.  The fruit are round with a diameter from 2 to 5 inches.

 Fruit, aril, and juice characteristics of four pomegranate cultivars grown in Florida; fruit harvested in August 2018. a) ‘Vkusnyi’, b) ‘Crab’, c) ‘Mack Glass’, d) ‘Ever Sweet’.

Fruit, aril, and juice characteristics of four pomegranate cultivars grown in Florida; fruit harvested in August 2018. a) ‘Vkusnyi’, b) ‘Crab’, c) ‘Mack Glass’, d) ‘Ever Sweet’. Photo Credit: Ali Sarkhosh, University of Florida/IFAS

A common commercial variety, ‘Wonderful’, is widely grown in California but does not perform well in Florida’s hot and humid climate.  Cultivars that have performed well in Florida include: ‘Vkusnyi’; ‘Crab’; ‘Mack Glass’; and ‘Ever Sweet’.  Pomegranates are adapted to many soil types from sands to clays, however yields are lower on sandy soils and fruit color is poor on clay soils.  They produce best on well-drained soils with a pH range from 5.5 to 7.0.  The plants should be irrigated every 7 to 10 days if a significant rain event doesn’t occur.  Flavor and fruit quality are increased when irrigation is gradually reduced during fruit maturation.  Pomegranates are tolerant of some flooding, but sudden changes to irrigation amounts or timing may cause fruit to split.

Two pomegranate training systems: single trunk on the left and multi-trunk on the right.

Two pomegranate training systems: single trunk on the left and multi-trunk on the right. Photo Credit: Ali Sarkhosh, University of Florida/IFAS

Pomegranates establish best when planted in late winter or early spring (February – March).  If you plan to grow them as a hedge (shrub form), space plants 6 to 9 feet apart to allow for suckers to fill the void between plants.  If you plan to plant a single tree or a few trees then space the plants at least 15 feet apart.  If a tree form is desired, then suckers will need to be removed frequently.  Some fruit will need to be thinned each year to reduce the chances of branches breaking from heavy fruit weight.

Pomegranate fruit affected by anthracnose.

Anthracnose caused by Colletotrichum sp. to pomegranate fruit. Photo Credit: Gary Vallad, University of Florida/IFAS

Anthracnose is the most common disease of pomegranates.  Symptoms include small, circular, reddish-brown spots (0.25 inch diameter) on leaves, stems, flowers, and fruit.  Copper fungicide applications can greatly reduce disease damage.  Common insects include scales and mites.  Sulfur dust can be used for mite control and horticultural oil can be used to control scales.

What are those scales on my palm tree?

What are those scales on my palm tree?

A couple weeks ago, I was on a site visit to check out some issues on Canary Island Date Palms.  The account manager on the property requested a site visit because he thought the palms were infested with scale insects.  He noticed the issue on a number of the properties he manages and he was concerned it was an epidemic.  From a distance, lower fronds were yellowing from the outside in and the tips were necrotic.  These are signs of potassium deficiency with possible magnesium deficiency mixed in.

Potassium and magnesium deficiencies in a canary island date palm.

Transitional leaf showing potassium deficiency (tip) and magnesium deficiency (base) symptoms. Photo Credit: T.K. Broschat, University of Florida/IFAS Extension

Nutrient deficiencies are slow to correct in palm trees.  It’s much easier to prevent deficiencies from occurring by using a palm fertilizer that has the analysis 8N-2P2O5-12K2O+4Mg with micronutrients.  Even if the palms are part of a landscape which includes turf and other plants that require additional nitrogen, it is best to use a palm fertilizer with the analysis previously listed over a radius at least 25 feet out from the palms.  However, poor nutrition wasn’t the only problem with these palms.

Upon closer look, the leaflets were speckled with little bumps.  Each bump had a little white tail.  These are the fruiting structures of graphiola leaf spot also known as false smut.

Graphiola leaf spot (false smut) on a Canary Island Date Palm

Graphiola leaf spot (false smut) on a Canary Island Date Palm. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County

Graphiola leaf spot is a fungal leaf disease caused by Graphiola phoenicis.  Canary Island Date Palms are especially susceptible to this disease.  Graphiola leaf spot is primarily an aesthetic issue and doesn’t cause much harm to the palms infected.  In fact, the nutrient deficiencies observed in these palms are much more detrimental to their health.

Graphiola leaf spot affects the lower fronds first.  If the diseased, lower fronds are not showing signs of nutrient deficiencies then they can be pruned off and removed from the site.  All naturally fallen fronds should be removed from the site to reduce the likelihood of fungal spores being splashed onto the healthy, living fronds.  A fungicide containing copper can be applied to help prevent the spread of the disease, but it will not cure the infected fronds.  Palms can be a beautiful addition to the landscape and most diseases and abiotic disorders can be managed and prevented with proper pruning, correct fertilizer rates, and precise irrigation.

Not Your Typical Coneflower – Cutleaf Coneflower Rudbeckia lacineata

Not Your Typical Coneflower – Cutleaf Coneflower Rudbeckia lacineata

Until plans were underway for our UF/IFAS Demonstration Butterfly Garden, I had never heard of Cutleaf Coneflower, Rudbeckia lacineata. Master Gardener Volunteer Jody Wood-Putnam included this gem in her garden design and introduced me and many of our visitors to a new garden favorite.
Although in the same genus as your common Black-eyed Susan’s (Rudbeckia fulgida or R. hirta) this perennial has very distinct differences. Rather than the low growing, hairy, oblong leaves of Black-eyed Susan, Cutleaf Coneflower has smooth pinnately lobed leaves with serrated edges. The leaves are still clump forming but form an almost bush-like shape. By mid to late summer, tall flower spikes emerge and are covered in bright yellow flowers bringing the overall height of the plant over 5 feet tall!
Cutleaf Coneflower is native to North America with several variations adapted to different regions including the Southeast and Florida. This perennial performs well in full sun to part shade and needs a lot of space. Mature plants can reach 3’ wide by 10’ tall and may require staking. The plant can spread through underground runners, so be sure to give it lots of space. In North Florida leaves may be evergreen if winter is mild. Cutleaf Coneflower is a good wildlife attractant providing nectar and pollen for many insects and if you leave the flowers on to mature the seed the is eaten by songbirds, including goldfinch.
To see this plant in person, stop by the UF/IFAS Demonstration Garden at 2728 E. 14th Street, Panama City, FL. If during normal business hours, check in for available seeds from our Pollinator Garden. 850-784-6105
More information about Cutleaf Coneflower see https://plants.ces.ncsu.edu/plants/rudbeckia-laciniata-var-humilis/
Japanese Plum Yews for the Landscape

Japanese Plum Yews for the Landscape

We are always on the lookout for an attractive plant for our landscape.  At the nursery, some plants have a more difficult time gaining our attention. They may not be as showy, possessing neither colorful flowers nor bold foliage.  In these cases, we could be missing out on low maintenance plant that offers its own form of beauty in the right landscape spot.
One plant that I love is the Japanese plum yew (Cephalotaxus harringtonia), especially the spreading form ‘Prostrata’.  In the nursery container, this plant is nothing special but once established in the landscape it performs well.  The conifer type leaves are an attractive dark green and the ‘Prostrata’ selection is low growing to about 2 to 3 feet.  An advantage too is that growth is slow so it won’t take over or require routine pruning.
Japanese plum yews grow best in partial shade and once established will be fine with rainfall.  For a shadier side of the home, the spreading plum yew has a place as an evergreen foundation plant too.

Japanese plum yew in a shaded garden. Photo by Beth Bolles, UF IFAS Extension Escambia County

If the ‘Prostrata’ selection is too low growing for you, consider the ‘Fastigiata’ cultivar that will grow upright to about 8 feet with a 5 foot spread.

A year old planting of upright Japanese plum yew in filtered light. Photo by Beth Bolles, UF IFAS Extension Escambia County