Friday, June 13, 2014

Nuttall's Thistle - Cirsium nuttallii




Although there are nearly a half-dozen thistles sporadically present in a few north Florida counties, only two are found within the peninsula.  I have previously written about purple thistle (C. horridulum) which is common in open disturbed sites statewide. Nuttall's thistle (Cirsium nuttallii) is the second species, found throughout Florida, except much of the western panhandle, in sunny, open disturbed habitats.  Nuttall's thistle also occurs in much of the Southeastern Coastal Plain. It is not uncommon to see this and purple thistle growing in the same location, but they are distinctly different from each other.
Thistles are biennials; they do not flower in their first year, but develop a deep taproot and a basal rosette of leaves. Flowering occurs in the second year, they go to seed, and then the plants die. The large number of seeds produced by their parents, however, ensures that more plants will emerge next spring.
Nuttall's thistle is a robust, lanky species that reaches a mature height of 5 feet or more. The basal leaves are more narrow than in purple thistle, but they are equally armed with numerous sharp spines.  In fact, the entire plant is exceedingly spiny.
A great many flower heads are produced atop the stems in summer.  These too are much narrower than in purple thistle. The flowers vary in color from nearly white to a more common light pink.  Plants remain in flower for many weeks, and as with other thistles, they are exceedingly attractive to pollinating insects.
Though thistles are wonderful plants for pollinators, they are extremely difficult to control in a landscape garden.  Their thorniness makes working with them a challenge and the fact that they need to reseed to persist means that they need to be left alone until the seeds are dispersed. By then, you may have hundreds of seedlings germinating in every corner of your landscape (and in those of your neighbors).  In many Midwestern states that I have lived in, growing thistles in a landscape is prohibited because they can be invasive.
If you have a more naturalistic setting and wish to add this species, despite its drawbacks, it is easy to propagate from seed collected when mature ("fuzzy"). This species is not currently available from commercial sources. Use it in out-of-the-way locations, away from pathways and trails and be prepared to weed out seedlings that appear in locations where they are not desired. Weed them when very small, when they are less well armed by thorns. Nuttall's thistle does well in partly sunny areas, but also can be grown in full sun.

4 comments:

  1. When should we germinate the seeds in South Florida?

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  2. I'd sow the seed immediately. That is what it does in nature.

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  3. I just posted a picture of this thistle on my facebook page because I didn't know what the name of it was. My sister gave me the name, so I looked it up on Google, and your blog popped up! Thank you for the information. I live in Salt Springs, in the Ocala National Forest, and these are pretty prolific right now. Really pretty, but I don't want it in my yard. I can enjoy it on my walks alongside the road.

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