Sunday, March 29, 2015

Pass the Mustard

I’m always impressed when I’m with an experienced plantsman and he/she is able to confidently announce that a plant we’re examining is part of a certain plant family: “Well, clearly this is in the Heath family, Ericaceae.” Details are not always given so I just nod appreciatively and write it down. When it comes to the Mustard family, however, the family resemblance is a bit more obvious and spring time is a great time to recognize it.

Brassicaceae is the scientific name for the mustard family.  It contains approximately 375 genera worldwide, about 55 of which are found in North America. The plants in this family are mostly herbaceous plants that are annual, biennial or perennial. Of course you know many of the plants from the edible world: mustard (Sinapis and Brassica), radish (Raphanus), cabbage/broccoli/ cauliflower/turnip (Brassica), horseradish (Armoracia),  wasabi (Eutrema), cress (Lepidium) and watercress (Nasturtium).

Four petals
Flowers of the Brassicaceae family are recognized by having 4 petals arranged crosswise, as in the shape of a cross (hence an older name - Cruciferae - for the family). 

They also have 4 sepals (the green leafy parts that enclose the flower bud and later surround the flower at the base when it is open). They have 6 stamens, 4 of which are long and 2 of which are short.  The flowers are often held in elongated clusters.

Sepals on Cardamine diphylla
Some of the more familiar ornamental members of the mustard family include Alyssum, wallflower (Erysimum), dame’s rocket (Hesperis matronalis), candytuft (Iberis), moneyplant (Lunaria), stock (Matthiola), and Nasturtium. The ornamental forms of these plants are not native to the US, although there are some species of them that are.

There are some exceptionally weedy, and in two cases invasive, members of the mustard family. Garlic mustard (Alliaria petiolata) is the worst, but certainly many of us have fought against the annual hairy bittercress (Cardamine hirsuta) in our own yards. 

Pepperweed (Lepidium latifolium) is an invasive plant in the western US.

Slender toothwort, Cardamine angustata

Notable among the springtime native plants that you will find are the toothworts. Formerly known as Dentaria, they are now considered part of the Cardamine genus. Four species of toothwort are found in Georgia: slender toothwort (Cardamine angustata), forkleaf toothwort (Cardamine dissecta, formerly Dentaria multifida), cutleaf toothwort (Cardamine concatenata), and two-leaved toothwort (Cardamine diphylla). All of them are found in north Georgia only and they are perennial.

Cardamine bulbosa

The native bittercress have a more statewide distribution. These include species like Cardamine bulbosa, Cardamine pensylvanica, and Cardamine parviflora. Only C. bulbosa is reliably perennial.

There are native species of rockcress (Arabis) and Draba in Georgia as well, two other family members.

A late summer blooming member of the mustard family in Georgia is pinelandcress (Warea). I was fortunate to see it in bloom on a field trip to the Fall Line Sandhills with the Georgia Botanical Society.

Seed pods forming

Once the plant sets seed, the seed pods can be long and thin (known as a silique) or short and broad (a silicle). Long thin pods can be seen on toothworts and bittercress. 

One source indicates that all members of the mustard family are edible (but they don’t always taste good). I can’t vouch for that, so please use caution. This same source says that crushed leaves have a similar smell for all members.

Mustard family members in general are rather weedy and short-lived. [As far as I’m concerned, toothworts are not nearly weedy enough but at least they are perennial.] Research on the abilities of mustard family plants to perform phytoremediation has shown some promise. Phytoremediation is a process of decontaminating soil or water by using plants to absorb or break down pollutants. Now perhaps I can finally feel good about those hairy bittercress weeds in my yard!

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