By: Chris Friesen, Manitoba Conservation Data Centre
When we think of plants, we tend to think green. This is because the vast majority of plants produce chlorophyll in their above-ground parts which they use to harvest sunlight to produce their ‘food’, with water and additional nutrients obtained from the soil through the roots. However, some species have evolved ways of obtaining these resources by ‘stealing’ them from other plants!
Most members of the Orobanche family of plants are at least partially parasitic on neighbouring plants – they have specialized roots called haustoria that ‘invade’ the roots of neighboring plants to obtain water and/or nutrients. In Manitoba, species in the genus Aphyllon (Broom-rapes) obtain all their resources this way and don’t bother producing any chlorophyll (so are not green at all!). Others, such as Manitoba’s Agalinis species, have chlorophyll to produce some of their own nutrients but parasitize other plants to ‘steal’ the rest.
Manitoba is home to three species of the genus Agalinis (sometimes called the False Foxgloves): Rough Agalinis (Agalinis aspera), Gattinger’s Agalinis (Agalinis gattingeri), and Slender Agalinis (Agalinis tenuifolia). Slender Agalinis parasitizes a wide variety of other plants, but host associations of Rough Agalinis and Gattinger’s Agalinis are unknown. All three are herbaceous annuals that grow in sparsely vegetated dry to moist prairie meadows on gravelly calcareous soils. Manitoba is at the extreme northwestern edge of the range of all three species. Distinguishing between them can be tricky, but a few characteristics can help.
Above: Rough Agalinis (Figure 1)
Rough Agalinis (Figure 1) can grow to 35 cm tall but is often shorter. Leaves are narrow and linear, 0.8-1.5 cm wide, have an opposite arrangement on the stem, and are rough to the touch – hence its common name. The somewhat tubular flowers, with petals flaring outward at the end, are usually pink though pure white ones can occur. The interior of the flowers are dotted with purple and have two yellow lines radiating from the centre (Figure 2).
Above: Rough Agalinis Flower (Figure 2)
In Canada, Rough Agalinis is found only in Manitoba, just to the south of Birds Hill Provincial Park, with scattered occurrences in the southwest Interlake, and a couple of occurrences between Brandon and Wawanesa. Some sites are large and have hundreds or even thousands of plants, but most are small in both area and number. A number of sites are confined to remnant prairie habitat in roadside ditches. Because of its limited distribution and threats to its habitat, Rough Agalinis is designated as both provincially and federally Endangered.
Slender Agalinis can be distinguished from Rough Agalinis by its leaves, which are not rough to the touch, and by its (usually) smaller flowers. The stems of Slender Agalinis are sometimes distinctly reddish. It is found in southeastern Manitoba and the south Interlake, and is considered uncommon though it can be locally abundant.
Gattinger’s Agalinis was first discovered in Manitoba in 2007 and only five occurrences are known, all in the southwest corner of the Interlake. Gattinger’s Agalinis plants are usually smaller and finer than the other two species, and produce fewer and smaller flowers (Figure 3). Like those of Rough Agalinis, the flowers have two yellow lines radiating from the centre, but the interior is white with purple spots (Figure 4) rather than pink with purple spots. Gattinger’s Agalinis is also both provincially and federally Endangered.
Above: Gattinger’s Agalinis (Figure 3)
Above: Gattinger’s Agalinis Flower (Figure 4)
Manitoba’s Agalinis species bloom in early to mid-August. Individual flowers are short-lived – they open early in the morning and often fall off by the end of the day. Because the plants are inconspicuous, the fallen flowers are often seen before the plant itself.
The Manitoba Conservation Data Centre tracks all occurrences of these species in order to protect them from disturbance, so please send in your observations. You can do this via our website (http://www.manitoba.ca/sd/environment_and_biodiversity/cdc/report.html) or by including the observation in the ‘All Manitoba Nature’ project on www.iNaturalist.ca.
If you have any questions about these or other rare species in Manitoba, please contact me at firstname.lastname@example.org or 204-945-7747.