Lachenalia is a genus of small bulbs mostly found in the western part of South Africa, where the rainfall is concentrated in the winter months. Like other species in the genus, Lachenalia namaquensis is dormant during the dry summer months, and it comes to life in the fall with the arrival of the rains. The small but strikingly beautiful spires of flowers arrive in late winter to early spring. While formerly placed in the Hyacinth Family, this family grouping has now been folded into the Asparagus Family.
Panax quinquefolius - Ginseng. What happens for pollination in wild populations in forests appears murky. Interestingly it blooms in June/July well after almost every other plant has finished blooming. The literature indicates that its likely to be getting some cross pollination from Lasioglossums and Flies. I am voting more for the flies. Photo and specimen by Helen Lowe Metzman.
The mustard family, Brassicaceae, is one of the most economically significant families of plants today, containing a large portion of cultivated vegetables and oil crops, particularly those that originated in Europe and the Mediterranean. The genus Brassica alone yields cabbage, broccoli, brussels sprouts, cauliflower, bok choy, kohlrabi, turnip, rapeseed, and many more. This family also contains some of the most invasive species of plants that disrupt and devastate habitats across the globe, particularly following European colonization events. I plan on making this a series where I explore this group of plants’ presence and role throughout human history. But first, what are the evolutionary advantages that allow for this plant family’s success?
The key feature for identifying members of this family is the flowers with four distinct petals of the same size arranged in a cross shape, usually yellow, white, or purple. Almost all members of this family are pollinated by insects.
The tissue of all plants in this family contains glucosinolates, a group of sulfur compounds that acts as a defense against herbivory and are toxic to many herbivores, including most insects. In humans, this group of compounds can taste bitter, and the degree to which the bitterness is experienced is strongly influenced by genetics and varies across different ethnic groups. In fact, the heritability of this gene is so well established that before DNA testing became available, this genetic factor was used as a paternity test.
The success of this family is also attributed to their ability to outcompete other plants through different means. For example, some members of this family have the ability to release allelopathic chemicals into the soil that prevent the germination of other seeds nearby and kill beneficial bacteria. In the cases where members of this family have become invasive, they permanently alter the composition of the soil and form monocultures that disrupt native flora, and controlling them becomes extremely difficult.
The seed production in this family is another factor in their potential for weediness. The seeds tend to be very small, as they lack endosperm (food reserve for the embryo) and therefore they can travel far. The fruit produced by this family, called a silique, opens on two sides, and as the seeds dehisce they can be catapulted quite far from the origin plant. The numerous seeds can also remain dormant in the soil for a long time, and have a high germination rate. All of these evolutionary advantages have made it possible for this family to become cosmopolitan, present in every continent except Antarctica. The same evolutionary advantages, however, can be devastating when introduced out of their evolutionary contexts where the biological controls they coevolved with are not present.
I plan on exploring more detailed examples from this family to outline what makes them adaptable to human cultivation, what makes them successful invasives, and the ecological, cultural and political role they have played throughout human history.
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