KCFS Banner

By Norman Bezona Prof emeritus University of Hawaii College of Tropical Agriculture

By Norman Bezona
Prof emeritus
University of Hawaii
College of Tropical Agriculture


A weed is sometimes defined as any plant growing in the wrong place. Perhaps an even better definition is that a weed is a plant for which we have not found a use. Just like there is no such thing as a bad baby, there is no such thing as a bad plant. It is just that we haven’t yet figured out for what it is good.

Unfortunately, we sometimes find the plants are used in an inappropriate manner. Then they may be referred to as weeds. Examples of this are the tobacco plant, digitalis and even certain mushrooms. These plants can be used as medicines or poisons.. So it is not that the plant is intrinsically bad, it is that we have misused it. The digitalis plant may be used to poison someone or in the proper amount, it may be used to saves lives.

My grandmother often used to say that God created all, and it was good. I think she must have read that somewhere. A banyan tree in the park is great, but when one sprouts up in your roof

banyan tree ta prohm angkor wat cambodia

A poorly placed Banyan Tree. A weed is in the eye of the beholder.

gutter, it’s a weed. Weeds in lawns are usually the result of poor management. Lawns injured by insects, fungus or nematodes will readily become infested with weeds. Improper mowing, watering and fertilization will lead to a weedy lawn. So, don’t blame the weeds for a poor lawn. They are often just a symptom of improper maintenance practices.

When it comes to turf, high quality, weed-free cuttings or seed, properly established is important. Purchasing and using soil that is not infested with perennial weeds like nut sedge or torpedo 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, they are difficult to control. Product availability is changing so fast with pesticide misuse concerns that it is difficult to make general recommendations. Check with your local garden shop or call the Master Gardener Hotline on Thursday mornings at (808) 322-4892 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: 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 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 or garden.

However, with weed killers, 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.” Again remember that many of those pesky fellows are actually edible or medicinal? Plants we often label as weeds are usually types that appear wherever the soil has been disturbed. It is nature’s way to heal wounds caused by landslides, fire and humans or their “misadventurous” activities.

These pioneer species grow rapidly and often compete with what we may consider more desirable species. They mature large quantities of seed, and are often difficult to control. Weeds are often described as undesired plants, plants growing out of place, or plants that are a nuisance. Both the characteristics and the definitions of weeds emphasize that they are plants closely related to man.

A tasty salad - all from "weeds"

A tasty salad – all from “weeds”

They come and go as man or his animals disturb the soil. Just as man has traveled and dominated the land, so have these species benefited from his activities. Because of their origin so close to the activities of man, many weeds have been discovered to be edible, or medicinal and indeed are used locally by diverse cultures throughout the world. So when you go out to pull weeds, don’t forget they could be for dinner. 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. A close relative is the kookoolau which was used by Hawaiians as a healing tea. It is again gaining popularity and may be found at some health food stores. 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. Dandelions and nasturtiums also add to tasty salads. 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 100 edible plants we refer to as weeds.

If you are interested in these and other useful plants, check at the local library for “Edible Leaves of the Tropics “by Franklin Martin and Ruth M. Ruberte, Mayaguez Institute of Tropical Agriculture, P.O. Box 70, Mayaguez, Puerto Rico, 00708. Local kahunas, kupunas and some folks who have recently migrated from Asia and Mexico really know a lot about edibles and medicinals that we think of as weeds, so tap their knowledge where possible. The ‘Rs’ of herbicides

  • Right material
  • Right time
  • Right amount
  • Applied in the right way.