By Cynthia B. Lauer, Master Gardener, SCMG
In this article, we explore three taxonomic families of plants. Common names are used along with their botanical names based on the binomial system described in Part I. The wild crab apple, for example, is Malus coronaria; the first word denotes the genus, the second the species. On the taxonomic hierarchy, family is one category above the level of genus and it can include dozens, even hundreds, of individual genera. Genera can include dozens, even hundreds, of species. Learning about taxonomy reveals the close relationship between turnips and nasturtiums or hollyhocks and cacao to give just two examples.
First the Crunch: The Apiaceae Family
Breaking down into over 400 genera and 3,700 species, this plant family includes a few vegetables found in every kitchen. It also includes many popular culinary herbs. The distinctive characteristic of this family are the tiny flowers made up of five petals, sepals, and stamens arranged like an umbrella (or to use the scientific word, an umbel). All the stems of the flower cluster radiate from a single point at the end of the stalk. The flowers secrete nectar attracting pollinators like flies, beetles, moths, and bees. Celeries are hosts to the Black Swallowtail butterfly. Parsley and carrot are the larval hosts for other species of Black Swallowtail butterflies. In most species, seeds are dispersed by wind but a few species like those in the Daucus (carrots) genus are distributed when their bristles are caught in animal fur.
Plants in this family are put to many culinary uses. The tap root of carrots (Daucus carota) and parsnips (Pastinaca sativa) are harvested as food while in celery (Apium graveolens), it’s the stalks of the plant that are eaten. Seeds, leaves or fruit can contain aromatic oils giving flavour to food cooked with anise (Pimpinella anisum), chervil (Anthriscus cerefolium), cumin (Cuminum cyminum), cilantro/coriander (Coriandrum sativum), parsley (Petroselinum crispum), and dill (Anethum graveolens). Seeds of fennel (Foeniculum vulgare), cumin, and caraway (Carum carvi) are also used in cooking.
Almost every member of this group is considered useful as a companion plant. Ladybugs, parasitic wasps and predatory flies are strongly attracted to the nectar found in the umbellate flowers. These are the beneficial insects that gardeners like to host because they prey on insect pests on nearby plants.
As wildflowers, diligent plant identification is crucial since some members of the Apiaceae family are very dangerous. The deadliest plants in North America are poison hemlock (Conium maculatum), water hemlock (Cicuta maculata), and cow parsley (Aethusa cynapium) because they contain compounds that cause convulsions. (Despite their common name, these plants are completely unrelated to the hemlock tree). Wild parsnip (Pastinaca sativa), chervil (Anthriscus sylvestris), and Queen Anne’s lace/wild carrot (Daucus carota) can be phototoxic, irritating skin when exposed to sunlight. Giant hogweed (Heracleum mantegazzianum) is a problem plant from Maine to British Columbia; visitors to public parks may see warning signs posted. Wild parsnip (Pastinaca sativa) and spreading hedge parsley (Torilis arvensis) are invasive in some areas. Goutweed (Aegopodium podagraria) is sold in plant nurseries even though it is well-known for its invasiveness in many gardens.
Giant Hogweed (Herracleum mantegazzianum), antefixus21, Flickr, Creative Commons
Then the Chunks: The Brassicaceae Family
This family contains well over 300 genera and 4,000 species. Often referred to as mustards, it is the vegetables that are well known: broccoli, cabbage, cauliflower, brussels sprouts, kale, turnips, radish, bok choy, rapini, and arugula as well as Brassica napus, the plant that is processed as canola oil. Brassicaceae also includes ornamentals such as stonecress (Aethionema), alyssum (Alyssum), rock cress (Arabis), basket-of-gold (Aurinia), wallflower (Erysimum), dame’s rocket (Hesperis), candytuft (Iberis), sweet alyssum (Lobularia), honesty (Lunaria), stock (Matthiola), and nasturtium(Nasturceum). Garlic mustard (Alliaria petiolata) is a serious invasive plant known to many gardeners.
Brassicaceae species are characterized by four-petalled cross-shaped flowers (hence its description as cruciferous or crucifix) featuring two long and two short stamens. It produces pod-like fruits known as siliques. This family are important providers of vitamins A, B1, B2, B6, C, E, K, and calcium, iron, and magnesium.
Members of this family have been long studied in the field of plant genetics and molecular biology. One small and unassuming species, Arabidopsis thaliana or mouse-ear cress, has served as one of the earliest model organisms worldwide. Scientists discovered that brassicas have one of the best-studied plant chemical defense systems. Known as the glucosinolate-myrosinase system, it targets different insect herbivores. Unfortunately, many insects have adapted and are able to overcome the chemical leading to significant losses in agricultural crops. Brassicas continue to be widely used in plant science where gains have been made into the mechanisms used by insects that use these plants as hosts.
Finally the Herbs: The Lamiaceae Family
Researchers have been sorting out the taxonomy of Lamiaceae for three decades using both morphological and molecular phylogenetic methods. As a result, the family has expanded. It now comprises more than 230 genera and over 7000 species but, as a 2021 report claims, Lamiaceae “has remained one of the greatest challenges due to limited availability of genetic data.”
Known as the mint family, Lamiaceae includes all of the mints (peppermint, pennyroyal, catnip), but also sage (Salviaspp.), basil (Ocimum basilicum), oregano (Origanum vulgare), marjoram (Origanum majorana), lemon balm (Melissa officinalis), and thyme (Thymus vulgaris). In addition to their use in the kitchen, Lamiaceae provides us with aromatic oil (eg. lavender, Lavandula; patchouli, Pogostemon cablin), wood (eg. teak, Tectona grandis), ornamentals (eg. salvia, bee balm, coleus, lamb’s ears), and medicinal herbs like Korean mint (Agastache rugosa), hyssop (Hyssopus officinalis), and heal-all (Prunella vulgaris), making it an important group ecologically and horticulturally.
Rosemary, waferboard Flickr, Creative Commons
Plants in Lamiaceae have readily recognizable features. They are all herbaceous, have square stems, four stamens, and four nutlets or seeds. Flower clusters are arranged as a tube with five lobes and two lips held by five fused sepals. Flowers have two to four stamens. Many North American genera support bees and other pollinators. The Hermit sphinx moth, for example, is hosted by mints. A few specialist bees are hosted by Monarda. In addition to bees, these plants may also attract beneficial insects to the garden.
Quite a few introduced members of Lamiaceae spread aggressively. Catnip (Nepeta cataria), shisho (Perilla frutescens), all-heal (Prunella vulgaris), the mints (Mentha spp.), lamiums (Lamia spp.) and creeping Charlie (Glechoma hederacea) all require vigorous control.
