Pump up your plant knowledge by learning family relationships

gardening image
Five petals help identify apples as belonging in the rose family. Photo from Flickr by Matthias Bachmann, CC BY-SA 2.0.
Last Updated: 
March 24, 2017

CORVALLIS, Ore. – Learning to recognize 400,000 species of plants is more than daunting; it’s impossible. But making a start by learning how to identify family characteristics can help you manage a healthier garden.

“It’s important for gardeners to be aware of how to ID plants,” said Karen Pleasant, Oregon State University Extension Service master gardener coordinator in Josephine County. “It will tell you what the correct cultural needs are, what kind of problems they may have. Knowing which plants you have will really help you know how to take care of them.”

Identification can be especially crucial for people who want to know which wild plants are edible and to learn about the medicinal aspects of plants, she said. Both are popular hobbies that require the correct information to keep safe.

Just as human families exhibit resemblances, so do plants. Each of the 620 plant families share characteristics such as the shape and composition of flowers. For instance, the huge aster family (Asteraceae) – which includes sunflowers, asters, daisies and dandelions – is recognized by the daisy-shape of the flowers.

“If you’re looking at a daisy or a sunflower, the center where the seeds form is the disc flower,” Pleasant said. “It’s composed of lots of little flowers fused together. What look like petals around the disc are the ray flowers.”

The third-largest family is the pea family (Fabaceae), which is easily recognized by people who have grown peas or sweet peas. The flowers include a large curved “banner” petal in the middle with two little wing petals on either side. Right in the center are two fused petals called keels. Plants in this family – lupine, wisteria, beans, locust, alfalfa and more -- also bear pea-like pods.

Number four in the lineup of plant families is the mustard family (Brassicaceae). The flowers have four petals and six stamens (four tall, two short), which surround the pistil in the center.

“There are a lot of garden plants in this family, broccoli, mustard, wall flowers, candytuft,” Pleasant said. “They’re easy to identify because of the four petals.”

About to make an appearance in the garden are early-blooming fruit trees, which are part of the rose family (Rosaceae). They sport five free (not fused) petals. If you see petal confetti raining on the ground soon, you can just about be sure the plant is in the rose family.

A good place to start the identification process is by determining if the plant is a monocot or dicot. The vast majority of plants are dicots with typical flowers and two seed leaves when they sprout; monocots only have one. They also have hollow flower stems, kneelike nodes or joints, and are pollinated by wind. In addition to lawn, this group includes lilies, orchids, bamboo, ornamental grasses, sedges and rushes.

“It’s like becoming a plant detective,” Pleasant said. “Study the plants in your garden. Once you get used to the patterns, you can narrow it down to genus and species. Then you know how to grow and take care of them.”

You can learn more by joining garden clubs, study groups, the Extension master gardener group or grab a plant key, which takes you through a series of steps to make identifications.

“It’s true, it’s like learning a new language,” Pleasant said. “It can be intimidating at first. One idea is to plant several plants in the same family together so that you can see the similarities. It’s really fun.”

Author: Kym Pokorny
Source: Karen Pleasant