Today when I was in the nursery at McClendon’s Hardware in Belfair buying trellis plants, I was reminded of the old joke about the guy who wasn’t sure of the plural form of mongoose but needed two of them. Mongooses didn’t sound right and neither did mongeese. So he asked the pet-store owner to sell him one mongoose and while doing so to sell him another. Since I wasn’t sure if the plural of clematis is clematises, clemati, or possibly clematum, I played it safe and asked for two clematis plants (see photo). K will like them. The pink one is called Clematis montana (her mom is from the Treasure State), while the one with purple flowers goes by Clematis alpina.
Last summer I built a trellis at Treasure Island. The structure was supposed to add color to the front yard. A secondary purpose was to provide a bit of privacy. K bought three ornamental climbing plants for it: wisteria, honeysuckle, and jasmine. But we planted them during the hottest part of the summer, and despite abundant watering, so far they have acted like they need crampons and a rope team to reach the top of the trellis. So this spring they are getting a bit of help in the form of these two new recruits. That makes 5 plants in all for a 21-foot-long trellis. Overkill probably, but still cheaper than building a solid fence.

Good question, Rod; however, as is often the case with such questions, the answer is not simple: “Plural is clematises but its awkwardness has led to its being discarded. Therefore ‘clematis’ is used for one or more than one plant.” (Source: http://www.howellsonclematis.co.uk/Pages/Pronouncing.html )
Don’t be too sure about “Overkill.” That’s what I thought once about a Passion Fruit vine I gave Satchi for a birthday present and set one small vine to work on an extensive trellis; however, it eventually smothered the trellis, a tree, the side of our house and an Kyushu Electric Co. pole to the point where they had to send a worker to remove 90% of the prolific growth.
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