Wednesday, August 12, 2009

Family Affair

I know, it’s been a long time since that last Biology class for most of us, but I ran across an interesting article on upcoming changes to a lot of plant families, and thought I would tell a bit about it here. For everyone who’s forgotten, not only do plants have common names that we use in everyday conversation (tomato!), but they also have two part genus and species names, in Latin (tomato’s two part name is Solanum lycopersicum).

In addition, plants are grouped into families of related genera. It’s that family level of organization that is addressed in Ellen Dean’s article Upcoming Changes in Flowering Plant Family Names: Those Pesky Taxonomists are at it Again!.

When I took a class in plant taxonomy (1979?), some of the easiest plant family names to remember were descriptive of some feature of plants in that family. For example, plants in the family Cruciferae had four-petaled flowers in the shape of a cross, and plants in the family Umbelliferae had flowers in specialized clusters called umbels that looked a bit like umbrellas. Since we had to learn the plant families, these clues were welcome.

Taxonomists, though, have been busy in the last several decades, reworking some plant family names and even entire families. Some family names were changed partly to regularize the word endings, so that all family names end with “aceae.” Some have been changed because an older type specimen, with a different name, has been found in a herbarium someplace. These are reasons for name changes of the Umbelliferae and the Cruciferae.

In addition, closer examination of plant characteristics using a method called Cladistics, added to DNA evidence, has led to the reworking of some groups of plants. This week, I came across Ellen Dean’s article that explains that even more family names, and the groups of plants within some families, are changing.

Plant families are important to gardeners because plants within one family may be more likely to have similar disease and/or pest problems than plants in different families. This is one reason why we are told to rotate plants within a family through the garden in such a way that they don’t follow each other in the same location for several years.

Another reason for crop rotation in the garden is that plants within a family tend to make similar nutrient demands on the soil. Tomatoes are likely to use up exactly the nutrients that peppers also need, so planting peppers after tomatoes would make soil preparation for the peppers more difficult than if peas were following those tomatoes.

Being familiar with the plant families is useful in managing crop rotations, and knowing both the old and the new names can help avoid any confusion. For gardeners, the number of plant families to keep up with is fairly limited (thank goodness!). However, anyone working with older books will likely see the older family names and lists, and could become confused when faced with an unfamiliar, new (!), plant family name.

These are the ones I try to be aware of:

Brassicaceae (used to be Cruciferae): broccoli, cabbage, collards, kale, turnips, radish

Apiaceae (used to be Umbelliferae): carrots, parsley, parsnips, cilantro, fennel, dill

Amaranthaceae (now includes the Chenopodiaceae): amaranth, beets, spinach, chard

Fabaceae (used to be Leguminaceae): green beans, English peas, sugar snap peas, southern peas, runner beans

Solanaceae: tomatoes, peppers, eggplants, potatoes

Cucurbitaceae: cucumbers, melons, squashes, pumpkins

Asteraceae (used to be Compositae): dandelion, sunflower, chicory, radicchio, lettuce (surprise!)

Liliaceae: onions, garlic, shallots

These families are less likely to pose a problem for me in planning rotations, because I don’t use them as abundantly in the veggie garden:

Lamiaceae (the mint family): basil, mints of all kinds, anise hyssop, rosemary, sage, oregano, thyme

Poaceae: corn, wheat, rice

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