Land Use and Forages

What do honey bees eat?

Honey bees must collect nectar and pollen from flowers to feed the colony.  Nectar, which they convert into honey, is the primary source of carbohydrates and some minerals.  Pollen is the primary source of protein, which is critical to developing larvae.  Typically animal pollinated plants provide nectar to entice pollinators to visit, but even wind pollinated plants which supply no nectar can be important pollen sources for honey bees. 

Honey bees are generalists. They feed on a wide array of plant species which makes them adaptable and capable of living in most of South Carolina. Honey bees are also very efficient at locating the most productive and highest quality food sources.  This broad diet and foraging efficiency enable them to adapt to a wide array of ecosystems.

Plant diversity is critical to honey bee health. Certain plants are known to be superior nectar producers and are important for making surplus honey, but a diet on these plants alone may not supply the complete spectrum of nutrients that honey bee colonies need to thrive.  Each plant species supplies unique nutrients and other compounds that contribute to the diet of the colony.  Often honey bees will forage on secondary nectar sources in order to gather critical nutrients. 

Plants bloom at different times of the year.  Honey bees will forage throughout the year in most of South Carolina.  They cluster inside of the hive on cold winter days, but they will forage on warm days even in winter.  Maintaining plant diversity ensures that nectar and pollen are available throughout the year.  The primary nectar flows occur in spring and fall in South Carolina, but many native plants bloom in summer and winter, providing nutrition throughout the year. 

What are the most productive nectar plants in South Carolina?

Most often people think of meadows of wildflowers as being the most productive systems for bees, but this is not the case in most of South Carolina.  The state is dominated by forest.  About 60% of the land is forested (private, state and federal land), 20% is managed farmland, and 18% is developed or disturbed.  This means that forest plant communities cover most of the land and that native trees often are the most important nectar sources for honey bees in the state.  Beekeepers should learn to identify these trees and shrubs to determine what food is available nearby.

Figure 1

Land Use Statistics according to the 2015 USDA National Resources Inventory
https://www.nrcs.usda.gov/Internet/NRCS_RCA/reports/nri_sc.html

Forest plant communities in South Carolina change from the mountains to the coast.  There are four distinct ecoregions: the Blue Ridge mountains, the piedmont, the sandhills, and the coastal plain.  Each ecoregion contains unique plant communities because of differences in slope, temperature, precipitation, and soil types.  From the beekeeper’s perspective, South Carolina can be divided in two, the upstate (mountains and piedmont) and the lowcountry (sandhills and coastal plain).  The division between the two, sometimes referred to as “the fall line,” follows the sandhills from Cheraw through Columbia to Aiken (Figure 2).  Certain plants grow well above the fall line, other plants grow well below the fall line, and some plants can be found statewide. 

Figure 2
 

Statewide

There are many nectar producing trees that thrive all across the state.  The most widespread and prolific nectar trees are red maple (Acer rubrum), tulip poplar (Liriodendron tulipifera), dogwood (Cornus florida), southern magnolia (Magnolia grandiflora), eastern redbud (Cercis canadensis), southern catalpa (Catalpa bignonioides), willows (Salix spp.), red mulberry (Morus rubra), black cherry (Prunus serotina), American holly (Ilex opaca), persimmon (Diospyros virginiana), black gum (Nyssa sylvatica) and southern crabapple (Malus angustifolia).  These trees are common throughout the state and readily available at garden centers. 

There are also a variety of nectar producing shrubs and vines that grow throughout most of South Carolina.  Blackberries (Rubus spp.), blueberries (Vaccinium spp.), devil’s walkingstick (Aralia spinosa), elderberry (Sambucus canadensis), sumac (Rhus spp.), virginia sweetspire (Itea virginiana), beautyberry (Callicarpa americana), carolina rose (Rosa carolina), trumpet vine (Campsis radicans), virginia creeper (Parthenocissus quiquefolia), and passionflower (Passiflora incarnata) are some of the most productive.  Poison ivy (Toxicodendron radicans) also is an exceptional nectar producer.  Poison ivy nectar is healthy for honey bees and does not contain urishiol, the poison in the leaves and stems that responsible for rashes and irritation.

Natural and human caused disturbances in the forms of mowing, grazing, tillage, selective herbicides, fire, timber harvests and wind storms create openings in the forest and allow sunlight to reach the ground. Numerous species of wildflowers take advantages of these openings and provide additional forage for honey bees, especially during the summer months when most trees are not blooming.  Areas such as roadsides, utility rights-of-way, field edges, yards and forest clearings provide meadow-like conditions for wildflowers to colonize.  The most productive nectar producing wildflowers found in these disturbed areas are goldenrods (Solidago spp.), asters (Symphiotrichum spp.), tickseeds (Coreopsis spp.), sunflowers (Helianthus spp.), bush clovers (Lespedeza spp.), milkweeds (Aesclepias spp.), thistles (Circium spp.), salvias (Salvia spp.), spiderworts (Tradescantia spp.)

Above the Fall Line

The landscape of South Carolina above the fall line is characterized by rolling hills and steep slopes.  The rocky soils and slopes limit agriculture to the more level valleys, so most of the land is forested.  Pines dominate the lower piedmont close to the fall line, but forests transition to hardwoods closer to the mountains. In general, hardwood forests produce more nectar than pine dominated forests, so nectar supplies also tend to increase closer to the mountains.  There are several nectar producing trees that are much more common above the fall line than below it.  These include black locust (Robinia pseudoacacia), honeylocust (Gleditsia triacanthos), basswood (Tilia americana), and sourwood (Oxydendron arboretum).  Basswood, an exceptional nectar producer, was once prolific across the eastern US, but heavy forest harvesting has greatly reduced its prevalence in the southeast. Sourwood is the most coveted nectar tree in the region, producing a light, sweet and flavorful honey. A number of understory trees and shrubs also are important in this region, including American plum (Prunus americana), serviceberry (Amelanchier spp.), winterberry (Ilex verticilata), buckeye (Aesculus sylvatica), chokeberry (Aronia spp.), and pawpaw (Asimina triloba).

Agriculture in the upstate has some row crop and vegetable production but is largely managed as pasture or hay fields to support livestock. Pastures and hay fields consist of grasses which provide no nectar, although some operations do include clover and alfalfa, which are excellent nectar producers. The upstate also has some fruit orchard production.  The counties along the mountains (Oconee, Pickens, Greenville) produce apples, which rely heavily on honey bees and are good nectar trees.  Also, the western counties in an area called “the ridge” (Edgefield, Saluda, Aiken, Greenwood) are the heart of peach production and make South Carolina the second largest peach producer in the nation.  While peaches do not require bee pollination, they do supply nectar and pollen. 

Historically, the piedmont was home to a unique ecosystem called the piedmont prairie.  These prairies formed when bison roamed and natural fire was common.  Grazing and frequent fire limit woody vegetation and select for meadowland plants, many of which support pollinators.  Elimination of bison from South Carolina and changes in land use have greatly reduced the once expansive piedmont prairies, but efforts are underway to restore this unique ecosystem. You can learn more about efforts to restore piedmont prairies at https://www.segrasslands.org/piedmont. Many of the wildflowers once common in these prairies can still be found in utility rights-of-way, along roadsides and in well-thinned forests where prescribed-fire is used.

Below the Fall Line

South Carolina below the fall line is mostly flat or low rolling terrain with sandy or loamy soils that make for prime farmland.  For this reason most row crop agriculture in South Carolina occurs in this region, and cultivated fields are almost as common as forestland.  Where soils are not suitable for agriculture, pine forests dominate.  Many of these pine forests are intensively managed for pulp and timber production, South Carolina’s largest industry.  Intensive pine management reduces tree diversity to maximize pine tree growth, so commercial pine stands tend to produce less nectar than natural pine stands. Unmanaged forestland tends to be mixed pines and hardwoods. In the coastal plain, hardwoods are dominant only in the wetlands and river flood plains where conditions are too wet for pines. 

The uplands of the coastal plain were once vast pine savannahs with widely spaced longleaf pines.  The forest floor in these pine savannahs was a meadow of grasses and wildflowers that was extremely diverse.  Like the piedmont prairies, these pine savannahs have largely vanished from the landscape, replaced by managed loblolly pines and agricultural fields.  Several important nectar producing plants still thrive in the remaining upland pine forests of the low country.  These include gallberry (Ilex glabra), Carolina laurelcherry (Prunus caroliniana), yaupon holly (Ilex vomitorium), sweetbay magnolia (Magnolia virginiana), and fetterbush (Lyonia lucida), along with an array of wildflowers that once called the pine savannahs home.

Lowcoutntry beekeepers benefit from being located near wetlands. The expansive wetlands and river flood plains in the coastal plain are home to many exceptional nectar producers.  The most notable is the swamp tupelo (Nyssa aquatica), a dominant tree in permanently flooded freshwater wetlands. It is the source for tupelo honey, one of the most highly prized honeys in all of North America.  The wetlands are also home to Dwarf palms (Sabal minor) which are prolific in the forested floodplains. The iconic palmetto tree (Sabal palmetto) is another nectar source unique to the region, and groundsel trees (Baccharis halimifolia) and button bushes (Cephalanthus occidentalis) are abundant at wetland edges.  Closer to the coast and river deltas, the remnants of rice plantations left vast freshwater marshes and tidal meadows that harbor an array of wetland wildflowers such as swamp milkweed (Asclepias incarnata) and pickerelweed (Pontederia cordata).

Agriculture in the coastal plain also provides nectar sources for honey bees.  Several of the row crops such as cotton, soybeans, peanuts, flax, and canola cover thousands of acres across the region and are nectar sources for honey bees.  There also are many fruit and vegetable operations growing cucurbits (squash, cucumbers, watermelons, cantaloupe, etc.), berries (blueberries, blackberries, elderberry, etc.), and brassicas (turnips, radishes, collards, cabbage, broccoli, etc.) which provide nectar to bees if they are allowed to flower.  The other way agriculture helps bees is by disturbing and increasing fertility of the land which encourages many annual flowering plants to colonize field after the crops have been harvested.  Plants such as wild mustard, henbit, thistle, buttercups, plantains, dandelions and a host of other “weeds” provide nectar sources for bees in and around agricultural fields.  Also, field margins which provide superior forage habitat are home to blackberries, pokeweed, sicklepods, and a variety of other early successional wildflowers.

Where is the best place to keep bees in SC?

There are nectar producing plants all across South Carolina, which means that honey bee colonies can thrive just about anywhere in the state.  Because honey bees tend to forage within a 2 mile radius of the hive, localized land uses and plant communities have a much greater effect on nectar availability than regional influences.  For this reason it is most productive to locate bees where there are a mixture of land uses including agriculture, forest land (preferably mixed hardwood and pine), and wetlands. Even urban and residential areas can provide suitable forage for bees. Honey bees are generalists that are very effective at finding the best resources around them, which makes them adaptable to most of South Carolina, but having a diversity of land uses ensures a diversity of plants that provide resources throughout the entire year and supply a nutritional diet for honey bees.

Areas that restrict forage range and plant diversity are less productive for honey bees.  Bees that are kept at the immediate coast, along beaches and on barrier islands have areas of open water and salt marshes within their foraging range.  Open water and brackish marshes are not productive foraging habitat. Colonies that have large percentages of their foraging areas covered in open water and salt marshes may experience limitations in food resources.

Areas that are intensively managed in monocultural crops also restrict forage availability to bees.  Bee hives located where there are large expanses of industrial pine production, hay/pastures managed in single grasses, and row crops, sometimes experience nutritional deficiencies and extended periods without adequate nectar. Some cultivated crops such as cotton and soybeans can serve as nectar sources, but they provide resources to bees for a short period of time during the year, which can lead to a boom or bust scenario if other food sources are not present. Beekeepers may find that colonies placed in large monocultural fields experience periods of very limited food resources when crops are not in flower and may need to be moved to areas with more plant diversity while the crops are not in flower.  When crops are in flower, these same agricultural areas may be some of the most productive foraging areas in the state, especially during the natural nectar dearth that occurs between the spring and fall nectar flows. Also, monocultural crops may not satisfy the complete nutritional needs of honey bee colonies. In general, most of South Carolina has mixed land uses within the normal foraging range of bees, even in the most intensively farmed parts of the state.

Are there any plants that are bad for bees?

YES.  Two plants are worth discussing, and these are Swamp Cyrilla (Cyrilla racemiflora) and Yellow Jessamine (Gelsemium sempervirens).  

Swamp Cyrilla (also known as the Titi tree, Cyrilla racemiflora) is a compact tree that grows in flooded wetlands.  It grows statewide but is more common in the coastal plain.  Pollinators are highly attracted to this tree when it blooms in the summer, but it can produce a condition called "purple brood" in honey bees.  Purple brood appears to be related to toxins in the nectar which cause death in honey bee larvae.  While the condition may limit colony growth while the plant is blooming, it does not appear to cause colony death because it does not affect adult workers.

Yellow Jessamine (Gelsemium sempervirens) is a vine that grows on forest edges and is the state flower of South Carolina because it is common statewide.  It also happens to be toxic to honey bees.  Beekeepers sometimes report dead bees piled at the hive entrance early in the spring which appears to coincide blooming yellow jessamine. Yellow jessamine blooms before most other plants begin blooming and may be one of the only early nectar and pollen sources in some locations. Bee kills related to yellow jessamine seems to be most pronounced in areas of the state dominated by pine forests where alternative food sources may be limited.

While swamp cyrilla and yellow jessamine cause bee mortality, the affects seem to be temporary and can be overcome with supplemental feeding and moving colonies away from areas with high densities of these plants while they are blooming.

What about exotic plants and invasive species?

Beekeepers in South Carolina have long touted the benefits of several exotic species to honey bees.  It is understandable that bees would use these plants because many of them originate in Asia and Europe where honey bees first called home.  Unfortunately the negative impacts of many of these exotic plants greatly outweigh the benefits they provide to beekeepers. Remember, honey bees are generalists that need plant diversity.  While many of these invasive species are exceptional nectar producers, their behavior of displacing native species and reducing plant diversity actually detracts from honey bee health in the long run and also causes even more damage to native pollinators and invertebrate biodiversity. The most prolific nectar producing invasives in South Carolinsa are chinese tallow (Triadica sebifera), chinese privet (Ligustrum cinese), japanese privet (Ligustrum japonica), chinese wisteria (Wisteria sinensis), kudzu (Puereria mirifica), chinaberry (Melia azederach), tree-of-heaven (Ailanthus altissima), callery pear (Pyrus calleryana), mimosa tree (Albizia julibrissin), japanese honeysuckle (Lonicera japonica) and thorny olive (Eleagnus pungens).

While beekeepers may find their bees using these plants heavily, it is not advised to plant or spread these plants because of damage they cause to native ecosystems.  Proliferation of invasive plants may reduce plant diversity and ultimately harm bees and native pollinators.