Barbara Faurot

WSU Extension Master Gardeners recently gathered online for their state-wide Advanced Education Conference. Experts shared the latest research in horticulture, forestry, entomology, soil science, and more. 

Three talks on the tiniest subjects in the garden—chemical signals, microbes, and insects—offer insights for home gardeners.  

DO PLANTS TALK?

Dr. David William Crowder, WSU associate professor of entomology, shared research on plant communication — how plants detect signals and respond to defend themselves and their neighbors against pests, pathogens, and environmental stress.

Plant communication occurs through volatile chemicals above ground, root secretions, or fungal and microbial networks. Plants use these chemicals and hormone signals to allocate their resources between growth and defense needs. 

Plants can “eavesdrop” by detecting when a plant neighbor is attacked and producing defensive chemicals, even if they are not being attacked themselves. They also use colors, scents, and nectar or pollen rewards to attract pollinators and ensure plant reproduction. Bees mark certain flowers, leaving a trail of volatiles so other members of the hive can find high quality resources. 

Knowledge of these interactions can be helpful to home gardeners. For instance, plant varieties matter. Select local organic seeds and plants to ensure high quality genetic material that will be better able to withstand environmental stresses and deter pathogens. Organic plants produce more salicylic acid, helping defend against herbivore pests like aphids and weevils. 

Soil rich in organic matter and microbes will help plants produce defensive compounds. Promote rhizobia — keystone microbes — by planting legumes to take advantage of their ability to form nodules and fix atmospheric nitrogen.

Avoid broadcasting pesticides, herbicides, or fungicides. They can actually interfere with the plant’s ability to defend itself! 

Crowder concludes by suggesting we spend time in the garden observing the interactions among plants, insects, and pathogens. “Know your system” to help make sure plants are healthy and able to produce the defenses they need to grow and thrive.

SOIL! WHAT IT IS AND HOW IT WORKS

Dr. James Cassidy, OSU senior instructor of soil science, explained that a single pinch of garden soil has more than 1 billion living organisms, including bacteria, mycorrhizae, fungi, nematodes, protozoa, and mites. He cited research indicating that one reason we love gardening so much is the antidepressant compounds released from these soil microbes. It’s science!

Healthy soil contains 20 to 30 percent air, 20 to 30 percent water, 5 percent organic matter, and 45 percent dissolved minerals (sand, silt, and clay). When soil drains, it is “breathing,” pulling in oxygen for all those microbes. The microbes create enzymes that help release mineral nutrients from organic matter. This is why it’s critical to have well-drained, uncompacted soil. 

Plants need air and water at their roots. Deep, infrequent watering is best to stimulate deep root growth and avoid over-watering. “Minimally disturbed soil self-organizes, resulting in a variety of different pore sizes allowing for the flow of nutrients, air, and water,” says Cassidy. “Gardening is managing this space.”

Help feed the microbes by layering compost, leaves, or wood chips on top of the soil, or planting cover crops. Leave roots in place from finished crops, as the roots and root hairs will decompose and leave organic matter behind. If your soil is heavy on clay or sand, add organic matter to help break apart clumps or improve drainage. Cassidy concludes that “No matter what the question, the answer is add organic matter!”

IF BUGS COULD TALK

Retired WSU Extension educators Sharon Collman and Dave Pehling offered an engaging look at the grievances the insect world has against humans, and ways we can work together for mutual benefit. 

Insects would like us to know that they are producers of honey, scavengers, decomposers, pollinators, predators, distributors of seeds, and the subjects of art, poetry, and film. They are a food source for birds, bats, fish, amphibians, and mammals. 

Beneficial insects are declining in number and diversity due to pesticides, habitat loss, invasive species, and other perils. Speaking for the insects, Collman says, “They would like our help in three main areas — available food, protection from insecticides, and undisturbed soil for nesting.” 

Here are their suggestions:

Provide a variety of plants with diverse flowers and blooming times. Increase foraging opportunities by planting in clusters and adding flowering plants or herbs to small spaces like parking strips. 

Avoid unnecessary use of fertilizers and pesticides. For a specific issue, target only that pest using research-based information on the lifecycle of the pest and the least toxic approach. “Targeting a small area makes it easier for beneficial insects and pollinators to return,” advises Pehling. 

Offer nesting sites like bug hotels, pithy stems, and holes in wood to create homes for cavity nesters. Bare or sparsely graveled soil provides nesting sites for solitary ground nesting bees and other beneficial species. Leaves and organic matter are broken down by microbes and returned to the soil for the plants. 

Reduce light pollution by shading bright outdoor white or bluish lights. Better yet, use yellow, pink, or orange lights that are less attractive to insects. Avoid using bug zappers, which zap 1 billion insects each year in the U.S., most of which are benign and beneficial. 

“The insects will be very grateful,” concludes Collman. 

WSU Extension’s Hortsense website offers strategies to target specific pest problems: 

http://hortsense.cahnrs.wsu.edu/Search/MainMenuWithFactSheet.aspx.

Master Gardeners are available to address your gardening questions at the online plant vlinic: http://jefferson.wsu.edu/plant-clinic.

(Barbara Faurot is a Jefferson County Master Gardener and Master Pruner, working with other volunteers who serve as community educators in gardening and environmental stewardship.)