Regional Gardening Reports :: National Gardening Association

In the Garden:
Pacific Northwest
May, 2011
Regional Report

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Trilliums are one of my all-time favorite woodland plants. I love their delicate flowers. My only complaint is that their bloom time is much too short!

Ants Can Be Beneficial

Ants are some of nature's most proficient recyclers, removing plant debris, dead insects, and even certain fungal spores from plant leaves. Their tunneling mixes and aerates the soil, as well if not better than a population of earthworms. Many species of ants feed on caterpillars and small insects, which in turn reduces damage to vegetable crops.

Members of some species eat honeydew, the sticky substance excreted by aphids. These ants, sometimes called herding ants, feed and protect the aphids, milking the honeydew by stroking the aphids. Ants can even transport aphids from plant to plant to ensure a continuous supply of honeydew. These ants are always on guard and will protect the aphids from predators. One species of ants, called harvester ants, eats and stores seeds, which sometimes sprout around the nest, leading to the misconception that harvester ants cultivate their own food. It's just a myth, but it's an interesting thought.

Ants can pollinate flowers during their investigative trips through the garden. The sweet sticky substances that attract bees and hummingbirds can also attract ants. If there is a way for the ants to climb up and into the stamen and style of the flowers, they can effectively transfer pollen.

Ants do the Planting
Because the chances of a seedling's survival increases the farther it gets from the competition of its parent, plants have evolved ingenious ways of dispersing their seeds far and wide. The parachute of a dandelion or milkweed seed, or the wing of a maple seed can carry the next generation away on a breeze. Other seeds have brightly colored fruits that are attractive to birds and mammals or burrs that attach temporarily to feathers and fur. Trillium and bloodroot, along with many other woodland wildflowers, are unusual in that they rely primarily on ants to disperse their seeds.

Seed-dispersing ants are voracious scavengers, and leave a chemical trail to attract other ants once a food source is found. The seeds they find most attractive contain oily, protein-rich projections that rival juicy grubs or caterpillars in taste. For example, trillium seeds have a fleshy structure called elaiosome. The elaiosome is rich in lipids and proteins, making it a desirable food for their offspring. It's not uncommon for hoards of ants to haul these types of seeds 10 to 30 feet back to their nest to feed their young. Any seeds not eaten are moved onto the colony waste pile along with the indigestible exoskeletons of insect prey, excretions, and other waste.

These piles of waste, which are high in organic matter and essential nutrients like phosphorous and nitrogen, are perfect places for these seeds to end up. Many woodland wildflowers have relatively large and nutritious endosperms (the food-storage tissue surrounding the seedling embryo) that, like the yolk of a hen's egg, gives them the energy to become established in heavy leaf litter and shade. When deposited by ants into their waste piles, the seeds are effectively protected from competition from parent plants, and from predatory mammals, birds, and insects. Once planted in these little compost-rich gardens, the seeds have a much better chance of survival than seeds planted by you or me.

Not-So-Beneficial Behavior
On the downside, ants can bite and certain species can destroy wood with their tunneling. Most annoying of all, I think, are ants that find their way indoors!

If you have ant colonies close to the house that you need to control, there are several things you can do. A good, least-toxic method is the use of boric acid baits. Boric acid baits can eliminate some ant colonies in about a week. The trick is not to kill the ants at the bait station, but to get the ants to carry the boric acid back to the nest, where it will be shared with members of the colony that never leave the nest.

Most ants feed either on sugars or on protein, fats, or oils. To see which type you have, place a small dab of jelly and a small dab of peanut butter where the ants are seen and watch which food they are attracted to. Once you've determined their preference, you can make a boric acid bait by mixing either one-half cup jelly, such as apple jelly, with one rounded teaspoon of boric acid powder, or one half-cup of peanut butter with one rounded teaspoon of boric acid powder. Make a bait station by placing the boric acid mixture into a glass or plastic jar with a lid. Punch several holes in the lid of a jar and screw the lid on tightly. The holes should be large enough for the ants to pass through to reach the bait. Place the bait jar on its side where the ants will come in contact with it. If the ants are unable to gain footing on the jar lid, you might want to scratch the surface with sandpaper. If you find many dead ants around the bait station, whichever bait you use, lower the amount of boric acid in the mixture. If you are still finding live ants after a week to ten days, increase the amount of boric acid. Although boric acid is of very low toxicity, it is best to place bait jars where children and pets cannot reach them.

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