Variety vs Cultivar vs Sport - Gardening Parlance - February 2023

I'm nothing if not a gardener who keeps learning with every shovelful of dirt and every keystroke digging around the Web. And, I'm also guilty of calling things the wrong name from time-to-time. Part of what I've tried to do is to learn the actual plant names (genus species) vs. the trade names. But, I've also thrown around the terms 'variety' and 'cultivar' and 'sport' all over the place and NOT really learned when/where to use each one.

What prompted me to think about the terms was an email from Gardeners Supply where they showed some 'common gardening terms' including Variety and Cultivar. Here's a landing page they have of those and other gardening terms like hybrid, heirloom and open-pollinated. A couple of nuggets from that page:

• Many commonly available plants are varieties or cultivars, with interesting features that make them more desirable than the straight species. 

• Some cultivars are patented, making it illegal to propagate them yourself. The plant name may bear a trademark symbol, and you may see a warning that propagation is prohibited.

The extension office from Iowa State has a byline penned by Cindy Haynes from their Department of Horticulture that shows that the difference between cultivars and varieties shows up in the names.  From Dr. Haynes:

Varieties often occur in nature and most varieties are true to type. That means the seedlings grown from a variety will also have the same unique characteristic of the parent plant. For example, there is a white flowering redbud that was found in nature. Its scientific name is Cercis canadensis var. alba. The varietal term "alba" means white.

...Varieties and cultivars also have differently naming conventions. A variety is always written in lower case and italicized. It also often has the abbreviation "var." for variety preceding it. The first letter of a cultivar is capitalized and the term is never italicized. Cultivars are also surrounded by single quotation marks (never double quotation marks) or preceded by the abbreviation "cv.".

I mentioned 'sport' as another term.  The West Virginia Botanic Garden has a post up that tries to unpack all of the terms - including sport.  Which...I've used in totally wrong ways.  From their story, they use the Yew as an example:

Growers hoping to combine ornamental merit with hardiness have crossed English and Japanese yews and dubbed the results Taxus x media. The roman “x” after the genus name indicates a hybrid of species within that genus. Taxus x media plants grown from seed vary considerably. Growers propagate interesting plants by rooting cuttings. If the resulting plants display desirable traits, growers may append cultivar names. For example, a favorite yew from my nursery days was the Hatfield yew, Taxus x media ‘Hatfieldii,’ a cultivar that arose from a hybrid.

Sometimes a plant produces a branch that looks very different from the rest of the plant, perhaps because of a mutation affecting gene expression. The unusual branch is called a “sport,” and the parent plant is said to have “thrown a sport.” If rooted successfully, sports may result in new cultivars.

(emphasis, mine)

Hybrids can, sometimes throw off 'sports', which...if successfully rooted may become a new cultivar.  Got it.  (Kinda).

Let's use the tree form Doublefile Viburnum that we planted last year as an example.  Here, below, is the product label:

It reads: Viburnum plicatum var. tomentosum.  

The .var is the 'tell' that this is a particular variety is the tomentosum variety.  

Now, look at this product listing from Hinsdale Nursery for a similar Doublefile Viburnum (from that same blog post) below:

Viburnum plicatum var. tomentosum 'Mariesii'.  

That 'Mariesii' is added to the end and included in single quotations.  That signals that this is a cultivar.  A cultivar named 'Mariesii'.  

So, neither of those use the word 'Doublefile'.  What the heck?  

The Missouri Botanical Garden has a listing up that provides even more details.  That...aren't straight-forward (to me).  They explain:

Two different forms of this shrub are commonly sold in commerce: (1) Japanese snowball bush (f. plicatum) .... and (2) doublefile viburnum (f. tomentosum)...

...The sterile snowball form (f. plicatum) is known from cultivation only (first observed as a garden plant in Japan). It was discovered prior in time to the discovery of the wild fertile doublefile form (f. tomentosum) from which it was actually developed. As a result of this inverted schedule of discovery, the sterile form was mistakenly given a species name (Viburnum plicatum) and the subsequently discovered fertile form (f. tomentosum) was named as if it were a variety of the species. The wild form (f. tomentosum) is native to forests and thickets in China and Japan.

Doublefile is actually a problem child as it has a problematic (as the kids say these days) naming convention.   

Another one to think about - to understand cultivars and varieties - is the newly planted Triumph Elm Tree.  That tree has a specific name:  Ulmus ‘Morton Glossy’.  Those single quotes mean that 'Morton Glossy' is a specific cultivar.  And...that makes sense, as Chicagoland Grows created this tree as a cross between the Accolade Elm and the Vanguard Elm. 

Lesson learned (sort of).  I'll stop (now) using the term 'sport'.  And, be sure that I'm using cultivar vs. variety at the right time with the right plant.  Or, at least I'll try.