Mycorrhizal fungi develop mutually beneficial symbiotic relationships with plant roots. Photo by Edward L. Barnard, Florida Department of Agriculture and Consumer Services, Bugwood.org.
If you have taken an elementary school science class, you have probably learned the basics of photosynthesis. In case you are a bit rusty, photosynthesis is the process by which plants capture sunlight to manufacture their food. They absorb carbon dioxide from the atmosphere and water from the soil. With these ingredients, they create carbohydrates, or sugars, that supply the energy to grow and develop.
As you can imagine, this energy is vital to the health of the plant. But fascinatingly, plants expel between 20 and 40 percent of these sugars from their roots into the surrounding area around the roots. The sugars that the plant releases, along with amino acids, organic acids, enzymes, and other substances, are called root exudates. The area just inside the root where the sugars are released, and the area just outside the root where the sugars end up, is called the rhizosphere.
But why would a plant waste this energy? This is because they derive benefits from the unique microbial population that inhabits the rhizosphere. Plant roots are limited by the amount of nutrients they can take up in the soil. By feeding microorganisms their sugars, they are essentially recruiting workers to help them scavenge for nutrients in areas that they cannot access on their own.
A microscopic image of mycorrhizal fungi in black walnut. Photo by Robert L. Anderson, USDA Forest Service, Bugwood.org.
Bacterial colonies, which are types of microorganisms, establish themselves within the rhizosphere and feed on the root exudates, allowing the bacteria to multiply. Along with the sugars they take in from the root exudates, they also take in nutrients from the soil. The waste that is produced by the bacteria is rich in bioavailable plant nutrients, which the plant then uses, creating a plant-microbe symbiotic relationship where everyone wins.
Another type of specialized microorganism, mycorrhizal fungi, also develops a symbiotic relationship with plants. Its meaning is within its name, as “myco” literally means fungus and “rhiza” literally means root. There are an estimated 50,000 fungal species that form these beneficial relationships with approximately 95 percent of plant families.
The mycorrhizal fungal hyphae, which are tiny fungal filaments one cell thick, do not have chlorophyll and are therefore not able to photosynthesize. Instead, the fungal networks have a large surface area that allows them to be particularly good at extracting nutrients from the soil. This enables them to access nutrients that plant roots would not be able to access on their own. The fungi drill into the plant root and trade these nutrients, along with water, with the plant in exchange for the sugary root exudates. In this way, both the fungi and the plant benefit from the relationship. Interestingly, these types of relationships will only develop once the plant releases particular root exudates that attract the microorganisms they are seeking. In essence, the mycorrhizal fungal hyphae will not associate with the root until they are invited.
Along with root exudates, root hairs and other plant cells accumulate within the rhizosphere as they grow and die throughout the plant’s life cycle. The combination of the root exudates, dead root hairs, and dead plant cells creates essentially a compost pile within the rhizosphere. This combination of substances establishes an environment where beneficial microorganisms can thrive, and a plant can maximize its nutrient uptake capacity.
Amazingly, there can be up to a billion bacteria and several yards of fungal hyphae living in just one teaspoon of soil! Of course, not all microorganisms are beneficial to the plant. But remarkably, plants have developed many ways in which they benefit, and ultimately thrive, in this diverse soil ecosystem.
As humans, we continue to learn more and more about these complicated and interesting interactions taking place in the soil beneath us. And the more we learn, the more we discover just how important these diverse ecosystems are to the health of the food web, and therefore, to the health of our planet as a whole.
If you are looking for an interesting native plant that attracts wildlife and makes a statement, look no further than Weeping Yaupon Holly Ilex vomitoria ‘Pendula’. The weeping growth habit with olive green leaves and white bark are attractive year-round. A bonus are the showy bright red berries that attract birds in the fall and winter. It is a cultivar of Yaupon Holly Ilex vomitoria which is tolerant of variable light and soil conditions making it a very adaptable plant.
Weeping Yaupon is a small evergreen tree that grows 15-30 feet tall with a mature width of 6-12 feet. Once established it has a high tolerance to drought conditions and is also able to sustain salt spray making it a good fit for coastal landscapes.
Applying the right amount of water to the lawn when the turf actually needs water is not always the easiest task for busy homeowners. UF IFAS Extension Escambia County Master Gardener Volunteer Greg Leach shares information about a soil moisture monitoring system that attaches to a home sprinkler system. This can help you apply water to the turf when it is actually needed by measuring soil moisture availability.
Our Gardening in the Panhandle blogs cover many horticultural topics concerning yards, however let us not forget about properties that contain a body of water (pond, lake, retention or detention basin, stream, river or Gulf of Mexico). Out of the nine Florida-Friendly Landscaping™ principles, five directly deal with water quality. Those principles are #2 Water Efficiently, #3 Fertilize Appropriately, #6 Manage Yard Pests Responsibly, #8 Prevent Stormwater Runoff, and #9 Protect the Waterfront. An easy argument can be made that the remaining four principles (#1 Right Plant, Right Place, #4 Mulch, #5 Attract Wildlife, and #7 Recycle) can also impact water quality on your properties.
Photo Credit: University of Florida/IFAS Extension
The quickest and easiest way to start improving water quality is setting up a maintenance-free zone along your shore. At minimum, you should keep all chemicals 10′ away from the water’s edge and increase that distance as your slope becomes steeper. Chemicals include all fertilizers (#3) and any pesticides/herbicides (#6) meant for the landscape (there are times when situations arise where treatment of the water is warranted). If you must fertilize up slope, make sure to reduce irrigation (#2) to about 25% of normal the first time which keeps the fertilizer from dissolving and running down your slope’s surface (#9).
Cascades Park in Tallahassee, FL.
If possible replace turfgrass with a no mow zone containing plants adapted for shorelines to prevent applications of fertilizer and chemicals. Plants (#1) other than turfgrass will have deeper roots, stabilize the bank better and absorb more chemicals before entering the water. These taller plants in turn can become habitats (#5) for birds and other specimens which can increase your ecosystem’s biodiversity. Some properties have collection swales or low lying areas where water pools and then flows into the water. It is best to understand how water flows through the property and reduce chemicals in those areas too (#8).
Heavy rains caused water levels to raise around this pond and decomposing leaf litter added a film over the pond.
As gardeners, we tend to compost our leaves and yard debris (#7) plus use mulch (#4) to reduce water loss from our soils. Keep mulches and compost piles away from flood zones and when possible keep leaves from washing into your water as they can create films on the surface. Never allow grass clippings to land on water surfaces as they will add nutrients when tissue decays.
As Florida continues to grow, we all must play an important role in keeping our water clean and safe for us, animals, birds, and aquatic life. If you have questions on improving your water quality, please contact your local county Extension Agent or Water Regional Specialized Agent (RSA). For additional information visit these other sites.
Urban Fertilizer Ordinances in the Context of Environmental Horticulture and Water Quality Extension Programs: Frequently Asked Questions: https://edis.ifas.ufl.edu/publication/AE534
Beach vitex in bloom is an attractive plant, which can make it more difficult to convince property owners of its harmful potential. Photo credit: Rick O’Connor, Florida Sea Grant
One of the biggest problems with beach vitex (Vitex rotundifolia) is its beauty. It has rounded, deep green leaves (with a silvery gray cast) and a beautiful little lavender-purple bloom. Like most weedy invasive plants, the plant was imported and sold as an ornamental groundcover for many years. Homeowners and landscapers planted it in coastal areas where it is well adapted to the salt and heat, and no one realized it would be so problematic. Ever since, beach vitex took root and has continued growing, unchecked, throughout the coastal south.
In this photo, beach vitex has overrun all native dune vegetation to form a monoculture. Photo credit: Randy Westbrook, Invasive Plant Control, Inc. bugwood.org
North and South Carolina started having big issues first, when beach vitex was planted deliberately to stabilize sand dunes after hurricanes. Soon after, a coastal restoration specialist with the Army Corps of Engineers realized the mistake. The vines run along the ground in such thick mats that native vegetation like sea oats can be choked out. The wide-spreading fibrous roots and tall profile of sea oats hold sand in place better than the beach vitex’s low growth and taproot, which have long term consequences for maintaining dune stability. The thick tangle of vitex growth is yet another obstacle for hatchling sea turtles in a long list of man-made problems that has made nesting and reproduction difficult.
The invasive vine beach vitex has taken over a stretch of sand on Pensacola Beach. Photo credit: Rick O’Connor, Florida Sea Grant
Eradication of the noxious weed has proved difficult. When a plant gets the nickname, “beach kudzu,” you know something went seriously wrong. Beach vitex produces millions of seeds in late summer and early fall, which are dispersed by wind, birds, and float over water. Unless removed before going to seed, even a small patch of the vine can expand rapidly. While not as prevalent in Florida, over 80 sites have been identified in the western panhandle with beach vitex. Due to these problematic issues, the plant was recently added to the Florida Noxious Weed and Invasive Species List, making it illegal to sell, grow, move, or release the plant.
