A weed may be defined as any plant growing in the wrong place. Perhaps an even better definition is, “A weed is a plant for which we haven’t found value.”
Just like there is no such thing as a bad child, only bad behavior, there is no such thing as a bad plant. It is just that we haven’t yet figured out its use. Perhaps a better word to describe what we call weeds would be “pioneer species,” trying to heal the wounds created by man or natural events like lava flows and hurricanes.
We have many plants that have been introduced to the islands by accident or on purpose. Some have found an ideal niche and became either established, or what we may consider invasive. One hundred years ago there were very few restrictions on what plants could be introduced. The primary limitations were ones that could affect our two major agricultural crops: pineapple and sugarcane.
Now there are severe restrictions and penalties for new plant and animal species imported without proper permits and inspection by the Department of Agriculture. With all that said, we have many alien plants that have been here a long time. Then it becomes a matter of management. When non-native species become established in our forests, we blame the plant, but forget that wild pig activity makes it ideal for non-native plant species to flourish.
A banyan tree in the park is great, but when one sprouts up on your roof, it’s a pioneer species. What we call weeds in lawns are usually the result of poor management. Lawns injured by insects, fungus or nematodes will readily become infested with plants we don’t like. Improper mowing, watering and fertilization will lead to a weedy lawn. So, don’t blame what we call weeds for a poor lawn. They are often just a symptom of improper maintenance practices. Besides, dandelion leaves make a great addition to salads or cooked as greens.
When it comes to turf, high quality, weed free cuttings or seed, properly established is important. Soil that is not infested with perennial weeds like wainaku grass is also a basis for preventing weeds in a new lawn. After that, proper management practices that result in a dense, vigorous turf will aid in preventing weeds. Once weeds get established in lawns, it is difficult to get control. If you ultimately decide you must use an herbicide, then here are some things to consider.
Product availability is changing so fast with the pesticide concerns that it is difficult to make general recommendations. Check with your local garden shop or call the Master Gardener Helpline for specific problems.
Just like the “three Rs” of learning, we find some very important “Rs” related to the application of herbicides. These “Rs” are to the RIGHT material, at the RIGHT time, in the RIGHT amount, applied in the RIGHT way. Understanding all the instructions of an herbicide label to be sure it will control your specific problem without injuring your desirable plants is as vital as using the right amounts. Safety margins may be smaller than you think. To apply pesticides in the right way, you must choose equipment that will give proper coverage. Spray jars that attach to your garden hose are good where you need to apply nutritional sprays, fungicides or insecticides to the lawn. However, with herbicides, it’s a better idea to use a small 2-3 gallon tank sprayer. A tank sprayer is vital since hose attachments are not accurate enough.
If you end up having to pull weeds by hand, smile. Let’s take a positive approach to “weeds.” Did you know that many of those seemingly pesky fellows are actually edible or medicinal?
Plants we often consider as weeds are usually types that appear wherever we have disturbed the soil. They grow rapidly and often compete with more desirable species. They mature large quantities of seed, and they are often difficult to control. Weeds are often described as undesired plants, plants growing out of place, or plants that are considered a nuisance. Both the characteristics and the definitions of weed emphasize that these plants are closely connected to humans. They come and go as people disturb the soil. Just as people have traveled and dominated the land, so have these species benefited from their activities.
Because of their origin so close to the activities of man, many plants we call weeds have been discovered to be edible or medicinal, and indeed may be used as beneficial herbs throughout the world.
So when you go out to pull what we call weeds, it’s easier if you know they could be for dinner or to help heal a cut or settle an upset stomach. For example, one of our most common weeds is the Spanish needle (Bidens pilosa). The young shoots may be boiled and used as a vegetable dish, used cooked in salads or stews. The leaves may also be dried and cooked later. Many grasses are edible, especially the rapidly-growing sprout or shoot of larger growing types. Bamboo is an example.
The common purslane, or Portulaca, has leaves and tender shoots that can be eaten raw. They are often used in salads or cooked as a spinach dish.
The familiar cattails of swampy areas are a source of several kinds of food. The starchy tubers are edible as young flower spikes. Young leaves are also eaten.
There are more than a hundred edible plants referred to weeds. If you are interested in these and other useful plants, check at the local library or do a computer search for Edible Leaves of the Tropics by Franklin Martin and Ruth M. Ruberte.
And don’t forget, when we refer to plants as weeds, we have automatically labeled them as being worthless. Better we call them a kinder more neutral term like “pioneer species”! That way we can contemplate the concept that everything and perhaps everyone has value.
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Norman Bezona is professor emeritus, University of Hawaii College of Tropical Agriculture and Human Resources.