{"id":410,"date":"2019-10-01T09:20:00","date_gmt":"2019-10-01T13:20:00","guid":{"rendered":"https:\/\/site.extension.uga.edu\/forsyth\/?p=410"},"modified":"2025-12-01T10:42:32","modified_gmt":"2025-12-01T15:42:32","slug":"how-plants-fight-back","status":"publish","type":"post","link":"https:\/\/site.extension.uga.edu\/forsyth\/how-plants-fight-back\/","title":{"rendered":"How Plants Fight Back<\/strong>"},"content":{"rendered":"\n

By Heather N. Kolich, ANR Agent, UGA Extension Forsyth County<\/p>\n\n\n\n

Gardening is a healthy hobby. It gets us outside where, in addition to getting physical exercise, we can soak up the mental and physiological benefits of nature. Food gardeners also reap the nutritional benefits of just-picked produce and the satisfaction of self-sufficiency.<\/p>\n\n\n\n

We need to remember, however, that all-natural isn\u2019t necessarily harmless. My daughter once volunteered to pick wild blackberries so we could make jam. Along with the berries, she collected the pain of thorn pokes, ant bites, and sunburn. Even for those of us who\u2019d rather do taxes than eat a salad, plants are the basis of our food chain. Most of us have experienced the truism that if we plant it, something will show up that wants to eat it. Because plants can\u2019t run away from hungry herbivores, they employ a variety of strategies to deter total digestion.<\/p>\n\n\n\n

Mechanical defenses<\/strong><\/p>\n\n\n\n

\"A
Thorns, spines, and prickles help defend plants from hungry herbivores.<\/figcaption><\/figure>\n\n\n\n

Painful experiences are powerful deterrents for some animals. That\u2019s why plants grow a variety of sharp accessories. In the natural form, some trees, shrubs, and herbaceous plants sport thorns, prickles, or spines. These modification of branches (thorns), epidermis (prickles), and leaves (spines) are efforts to stop or at least slow down animals that want to eat the plant.<\/p>\n\n\n\n

Through selective breeding, horticulturalists have developed thornless key lime trees, nearly spineless hollies, and roses and blackberries without prickles. While this improvement makes harvesting and pruning easier on us, breeding for a desirable trait can breed out other desirable traits, such as fragrance or productivity. And when a modified plant escapes cultivation, its progeny can revert to the thorny form, as Bradford pear trees have done.<\/p>\n\n\n\n

\"A
The tiny hairs (trichomes) on stinging nettle use a chemical to deliver a painful sting when touched.<\/figcaption><\/figure>\n\n\n\n

Trichomes are tiny hairs on plants that can create a barrier to leaf-eating insects. Some trichomes are tipped with glands that combine the hairy mechanical defense with a chemical. The chemicals may produce fragrance or odor, actively prevent insect attack, or, in the case of stinging nettles (Urtica dioica<\/em>), deliver a painful warning.<\/p>\n\n\n\n

Chemical defenses<\/strong><\/p>\n\n\n\n

Odors, bitter taste, and toxins are other defenses plants use.Some plants, such as poison ivy (Toxicondendron radicans<\/em>), carry a warning in their names, but not every toxin is harmful to every species. Urushiol, the toxin in poison ivy, poison oak (Toxicodendron toxicarium<\/em>), and poison sumac (Toxicodendron vernix<\/em>), causes skin irritation, itching, and blisters at the contact points in sensitive humans. It rarely affects animals, however, and the berries, leaves, and stems of poison ivy are a sought-after food source for many birds and woodland mammals.<\/p>\n\n\n\n

\"a
Monarch caterpillars sequester the toxins found in all parts of milkweed plants to make themselves toxic to predators.<\/figcaption><\/figure>\n\n\n\n

All parts of milkweed plants (Asclepias sp.<\/em>) contain resinoid, alkaloid, and\/or glycoside toxins. If ingested, these compounds cause a succession of symptoms potentially terminating in coma and death. The larvae of Monarch butterflies, however, feed exclusively on common milkweed. Rather than succumbing to the toxins, the larvae isolate them inside certain tissues, effectively making themselves poisonous to predators.<\/p>\n\n\n\n

\"A
Nandinas are popular landscape plants, but their berries contain cyanide, a toxic compound that can kill birds that eat the fruit.<\/figcaption><\/figure>\n\n\n\n

<\/p>\n\n\n\n

Nandina shrubs, a popular landscape plant, are among some 2,000 plant species that harbor cyanide in their tissues. Heavy feeding on nandina berries caused a mass kill of cedar waxwing birds in South Georgia ten years ago.<\/p>\n\n\n\n

While some plants are inherently poisonous, others are completely innocuous until an animal begins to eat them. Damage to leaves or stems stimulates the plant to produce a chemical that may taste bad or make the feasting beast sick. When my Labrador Retriever was a puppy exploring her backyard world, she sampled some azalea leaves. Fortunately, they just made her sick, but the negative association helped her learn not to nibble. Both she and the landscape plants peacefully co-existed for many years.<\/p>\n","protected":false},"excerpt":{"rendered":"

Gardening is a healthy hobby. It gets us outside where, in addition to getting physical exercise, we can soak up the mental and physiological benefits of nature. Food gardeners also reap the nutritional benefits of just-picked produce and the satisfaction of self-sufficiency.<\/p>\n

We need to remember, however, that all-natural isn\u2019t necessarily harmless.<\/p>\n","protected":false},"author":192,"featured_media":420,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[145],"class_list":["post-410","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-anr","tag-plant-defenses"],"_links":{"self":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts\/410","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/users\/192"}],"replies":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/comments?post=410"}],"version-history":[{"count":2,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts\/410\/revisions"}],"predecessor-version":[{"id":2318,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts\/410\/revisions\/2318"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/media\/420"}],"wp:attachment":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/media?parent=410"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/categories?post=410"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/tags?post=410"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}