September 2010

2010 Spring Trials: Comparing Ipomoea By Ryan Hall

Ipomoea, better known as sweet potato vine, has become an important mainstream crop for growers across the United States. Ipomoea has become one of the accent plants that growers reach for when designing mixed containers and baskets. Notable for their striking foliage colors of chartreuse, dark purple and burgundy, ipomoea make excellent trailing companions with other spring annuals. Ipomoea has a long history as a food crop but had only recently gained ground as an ornamental plant. Some of the first cultivars are still grown today, each admired for different, unique attributes. ‘Marguerite’ is the giant of the bunch, with striking, heart-shaped chartreuse leaves. ‘Blackie’ and ‘Ace of Spades’ have dark-purple foliage, ‘Ace of Spades’ with heart-shaped leaves and ‘Blackie’ with dissected leaves. A number of years ago, North Carolina State University made efforts to improve upon these popular cultivars. Their results were the aptly named Sweet Caroline and Sweet Caroline Sweetheart series. This series garnered much press and admiration from growers and the gardening public. As with most successful plant introductions, other breeding companies were eager to get a piece of the action and started to develop their own series.

These breeding developments and the availability of multiple series is always the preface to our comparative trials. We like to focus on genera with new breeding development and a lot of confusing choices for the grower. Ipomoea fit these criteria perfectly, and this trial was our first that focused on a plant grown for its foliage.

When we start a comparative trial, we hope to see some distinctive winners and losers, but often the case is a trial of relatively similar and un-exciting “me-too” introductions. This was clearly the case with our lobelia and scaevola trials in 2009. Ipomoea proved to be a bit more interesting, especially when the subject of royalties and distribution came up. Often, when we have a very close comparison from a breeding-quality standpoint, cost is the next natural comparison.

What’s in a Series?
A clear trend from the beginning was the lack of series uniformity. I think most growers consider series to be well-matched groups of plants in a range of colors, but with similar habits and growth characteristics. Often, though, series simply package a group of plants marketed by one breeder or distributor. Often these series are really more of a collection. There is nothing wrong with collections, but growers should be forewarned that if they order a series of ipomoea, they’ll most likely get a nice collection of varieties. Of all the series we compared, the original Sweet Carolines proved to have the nicest range of colors on compact habits, all with dissected leaves.

The black-leafed heart types were my least favorite of the trial; they all had a bad habit of being floppy in the pot and having a lollipop-type habit. Alternately, the chartreuse dissected-leaf varieties all had very nice container habits and were well suited for gallon pots.

Best Performers
“So, what varieties were the best?”

I struggle with this question because “the best” is so often subjective to a grower’s market and the perception of what’s valuable for customers, but here are some of our favorites.

Bright Ideas (Floranova). One of the smaller but better series, and one of the few series to include nice rust color. ‘Bright Ideas Lime’ is one of the most compact and densely branched selections, making it ideal for smaller containers, and as a less aggressive accent plant in mixed combinations.

Desana (Suntory). Another collection of good varieties. We especially liked ‘Desana Bronze’, a larger heart-leafed form with dark-chocolate leaves that sat nicely in its pot. ‘Desana Bronze’ seemed to be a clear improvement over ‘Ace of Spades’.

‘Goldfinger’ (GroLink). This selection was the surprise hit of the trial with a nicely compact habit and dissected leaf. I was impressed with the quality growth and overall very clean look of this variety. This can be a testament to genetics and most likely excellent stock management. Outside of its quality look, it also proved to a low-cost option available to growers.

‘Sweet Caroline Bewitched’. This variety screams Halloween combos. Bewitched is unique in the Sweet Caroline family, but it really stood out in our trial with a vigorous but well-behaved habit, making a presentable gallon and great-looking basket. The leaf is heart shaped with deep serration at the leaf tip. We hope North Carolina State can bring more foliage colors into the Bewitched line.

Sweet Caroline (Proven Winners). Lime, Red and Black all were nicely compact and, as mentioned before, probably the truest series of the lot. Now, with their new home as a Proven Winners plant, they should see continued success in this upscale brand.

The Bottom Line
Almost all of the series had attributes that will work for growers’ programs; again, it comes down to application. Growers who need something a bit more robust for, say, municipal baskets may opt for something like ‘Marguerite’; growers looking for something to complement their petunias and verbena in a 10-inch patio combination pot may opt for one of the less-vigorous, more-compact varieties like ‘Bright Ideas Lime’. Growers should look to trial-garden programs for indicators of landscape performance and tolerance of weather conditions near them, such as harsh summer weather.

Growers now have a nice range of selections to select from for their programs. However, breeders can still contribute to this genus with more compact habits, better natural branching, unique leaf shapes and colors, and possibly even complementary flowers that are programmable. Usually, once ipomoea flowers, it’s a tangled mess. What about breeding for flowering on a compact plant that can be used as a traditional bedding plant. Combine flowers with the striking foliage colors already present, and this genus will turn into a garden classic.

Pacific Plug & Liner is always interested in feedback on its trials, and we are eager to hear what people would like to see next year.

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