In 1999, year three of our perennial trial garden, we again bid farewell to a "graduating class" of perennials while welcoming some incoming freshmen. Among our graduates, a select few performed with true distinction and will be missed a great deal. Others in turn dropped out early, proving susceptible to the vagaries of our Michigan winters (and summers).
Whatever the results, the information gathered in our trials and in comparable trials throughout the country could not come at a better time. Breeders and nursery professionals are scrambling to meet the consumer demand for perennials, both the new and the familiar. The need is obvious for objective information from trial garden evaluators trained in horticulture.
This information benefits professionals by enabling them to select, grow and market the perennials most appropriate for their regions and customers. More importantly, this information (assuming professionals avail themselves of it!) enables consumers to enjoy success in their gardens.
As for the MSU trial data, we are currently distributing reports to the companies whose varieties we trial. Copies of each year’s report also are available for a nominal fee to anyone who requests it. (Ordering information appears at the conclusion of this article.)
One recurring observation I have made since the trials began in 1996 is that the first-year performance of a plant is not necessarily indicative of its merit as a perennial. The old adage about perennials – "The first year they sleep, the second year they creep, the third year they leap" – has been borne out repeatedly in our trials.
I might add that although many plants "leap" in their second year, almost all "sleep" the first year (building up root systems, one would assume). I have trialed numerous perennials that really impressed me in their first year, and this is certainly an attribute (providing they perform as well or better in subsequent years). However, I have learned not to prejudge anything.
My report for the 1999 trial results will again feature the plants that merit placement in the top "fifth" of the class. Our rating system is set up on a scale of 1-5; a rating of 1 is not acceptable, 2 is below average, 3 is average, 4 is above average and 5 is exceptional. The overall score is based on the cumulative score from four rating criteria:
1. Leaf color and quality (Were the leaves a nice healthy green? Did the leaf quality hold up throughout the summer?)
2. Plant vigor (Did the plant grow, or just sit there all summer?)
3. Bloom/stalk strength (Were flowers held straight? Were flowers held above the foliage? How did flowers fare after a heavy thunderstorm with typical winds?)
4. Bloom display (Did plant provide a good strong floral display, or only partial flower cover?)
Granted, this is a fairly demanding list of requirements to meet, but a number of plants earn high ratings each year despite what the weather and the bugs throw at them.
The perennial trials – with beds located between the MI 4-H Children’s Garden and the DeLapa Perennial Garden (and also newly expanded beds to the west of the Frank’s Nursery and Crafts Rose Garden) – are becoming a regular stop for many garden visitors as well as for landscape professionals. The performance of the plants speaks for itself; these plants generate a lot of interest. We are now often asked, "Where can I purchase one of these?" Each entry is labeled with a tag that states:
1. It is a trial item
2. The year it began its testing
3. Species and cultivar
4. Sponsoring company (Of course, we hope this is good advertising for our sponsors.)
Once again, the spring of 1999 seemed to start early; some of our items were already in bloom the first week of April, which was prior to the official start of the ratings period. Also notable was the relative dryness of the summer. It was the second year in a row with rainfall totals significantly lower than normal (both for the short-term and for the 30-year average). Coupled with a typically warm and muggy Michigan summer, the rainfall deficit proved quite a challenge for many varieties.
Needless to say, insects relish the sort of conditions that plants find stressful. Our chief insect pests this year were columbine skipper moths, lace bugs and spider mites. In our neck of the woods, meadow voles are also a grim reality; I note the plants they found especially tasty.
Although no plant received a perfect score of 5, several came very close. These are true star performers for the Midwest garden. Many of these should perform equally well in other parts of the country, in some cases by providing a bit of shade, by providing supplemental irrigation, or both.
For each of the following 15 top-of-the-class "graduates," I include the 1999 score as well as the score or scores for previous years in the garden. Each year’s score should be interpreted separately; in other words, 1999 is not the overall score but merely the rating for that particular year.
(1997: 4.5, 1998: 4.0, 1999: 4.2)
This is a tough little ground cover with really charming, finely dissected, gray-green foliage. At times plants struggle a bit with boggy winter conditions (and hot, humid summers), but they respond well to emphatic shearing. The flowers, small, white daisies with a red reverse on the petals, are an added bonus to the handsome foliage. Gardengnome would probably do splendidly as a rock garden plant where the drainage would be better.
Aquilegia ‘Cameo Mix’
(1997: 3.6, 1998: 4.1, 1999: 4.5)
Cameo Mix puts on a spring show of profuse tiny flowers that lasts quite a while. The appeal of these plants is only slightly mitigated by two drawbacks: the foliage declined a bit after flowering, and plants were bothered by columbine skipper moths to the extent that we had to treat them periodically with Bt. I dislike having to spray, but these plants were worth it.
Aquilegia ‘Cameo Rose’
(1997: 3.4, 1998: 4.1, 1999: 4.4)
This is a sister selection to Cameo Mix with equally charming flowers – hues of rose and white. This plant evoked a lot of "oohs and ahs" from visitors who toured the garden early enough to catch its bloom period. Interestingly, the bloom peak of Cameo Rose was one week later than Cameo Mix, although both selections finished blooming almost simultaneously.
Astilbe ‘Elizabeth Bloom’
(1997: 3.0, 1998: 3.8, 1999: 4.4)
I was impressed with the foliage quality of this astilbe. It had very nice deep-green leathery leaves that held up almost all summer before showing signs of drought stress. It was nibbled in passing by the voles, but they actually preferred neighboring Heuchera ‘Bressingham Bronze’, so damage was not as bad as it could have been.
Campanula ‘Chettle Charm’
(1998: 3.8, 1999: 4.6)
This selection spent the first year building up strength for a truly amazing floral explosion in its second season. Stems were thick and numerous, and crowded with blossoms. The only fault to be found might be that once the first flowers passed their peak, they detracted a bit from the waves of bloom that followed. (Because of floral structure, deadheading was somewhat of a challenge.) Nonetheless, for two weeks this charmer provided a glorious floral display. Foliage remained a handsome deep green throughout the summer as well. Voles found this plant delicious.
Dicentra ‘Adrian Bloom’
(1997: 4.0, 1998: 3.9, 1999: 4.1)
After spending some time with this pink-flowered selection I started calling it "The Energizer Bunny." Once it started to bloom, it kept going, and going, and going. The plot was in flower (with some lulls in flower number) from April until the end of the assessment period in October. The foliage yellowed somewhat during the most humid spells of our summer – perhaps the consequence of plants’ resting briefly after expanding energy on blooming. Clipping the damaged foliage stimulated a nice flush of new healthy leaves, and more flowers....and yet more flowers.
(1998: 4.1, 1999: 4.1)
This plant produced amazing numbers of deep-lavender flowers with yellow centers over a very long bloom time. The plant habit, which we considered somewhat lax, may have been induced by the rather rich soil of the plot; perhaps a leaner diet would have resulted in a more upright growth habit. Nonetheless, the overall effect was a rather charming blowsiness; plants leaned up against their neighbors and "got comfortable," so to speak. This led to a nice association with the adjoining Helenium ‘Coppelia’ – a color juxtaposition perhaps not to everyone’s taste, but we proclaimed it a serendipitous combination that worked well.
Hemerocallis ‘Miss Mary Mary’
( 1998: 3.1, 1999: 4.0)
This was another selection that spent its first year gathering strength. While it did bloom the first year, I was not prepared for the strength of the floral display the following year. This was an amazingly floriferous daylily, which bloomed intermittently through the summer after the first main bloom. Miss Mary Mary did not score high in floral uniformity, but no one could behold a block in bloom and not be impressed.
Hemerocallis ‘Miss Victoria’
(1998: 3.5, 1999: 4.0)
Miss Victoria has dainty pale-yellow flowers with a light bronze reverse. The flowers are borne on fairly tall and slender stems. The overall effect of this daylily is one of refinement; in fact, I love this selection! Its score was lowered to a standing of 4.0 because its foliage yellowed for a spell in midsummer, which detracted from the appearance of the block (and gave the evaluator palpitations!). Like Miss Mary Mary, it rebloomed lightly after the main bloom period.
(1998: 4.1, 1999: 4.5)
For the second year in a row, this plant cut loose with a "four-alarm" flower display. The flowers – a very attractive burnt orange – were so dense they completely obscured the foliage. If I had to find a fault with this selection, it would be an increased post-bloom susceptibility to powdery mildew. (Of course, this is not the only perennial with this trait.) We also found a lot of vole damage late in the summer; our response was a premature shearing back of the plants.
(1997: 4.7, 1998: 4.9, 1999: 4.9)
I am really going to miss Annabel. The foliage of this selection was always a luscious deep-green. It grew vigorously (never more so than after enduring one of the periodic, savage maulings by the voles). The gorgeous flowers, which reminded me of little tea roses in bud, were a lovely shade of pink – not too pale and not too hot. A top performer all three years in the trials, Annabel was a real triple-crown winner.
Heuchera ‘Bressingham Bronze’
(1997: 4.1, 1998: 4.5, 1999: 4.2)
Also in its last year, this is another selection whose absence will be mourned. Its foliage was a very nice deep-wine color, decorative in its own right as well as serving as a nice foil for the late flowers. Foliage margins suffered a bit in our hot, dry summers, but this would not be a problem in a shadier site. The voles will also miss Bressingham Bronze. I had to prune and reset damaged plants every fall in the trials, which kept them from reaching their full potential.
Kniphofia ‘Bressingham Comet’
(1998: 4.1, 1999: 4.5)
This Kniphofia has not proven reliably hardy for us here in Michigan. Only about 40 percent of the plants survived the winter of 1998-1999. Those that survived started out slowly but continued to gain strength through the summer. Once plants started blooming in August they continued non-stop until severe frosts froze the buds that were continuing to form. Based on this observation, I would speculate that the plants did not enter the dormant state necessary to successfully overwinter. Instead, they continued to grow and push flowers without responding to decreasing day length and cooler temperatures. Be that as it may, the profusion and uniformity of the flowers were real attention-getters, particularly in the autumn.
Lavandula ‘Blue Cushion’
(1997: 3.4, 1998: 4.7, 1999: 4.5)
This compact, little lavender was a stunning item in our trials. Its vigor and floriferous nature never wavered. This led to a problem in the final year of testing; in midsummer the foliage on about three-fourths of the plants took on a decidedly yellowish cast. I did not unduly penalize the plants because I felt the cause was cultural – plants were closely spaced in the plot. Indeed, when I sheared them back hard, they all sprouted healthy new growth. The problem did not reoccur.
(1997: 4.4, 1998: 4.5, 1999: 4.9)
In its final year, this selection approached perfection. All that stood in its way were two scores of 4.6 for leaf color/quality and for vigor. With that in mind, the leaf color was outstanding (one of our best varieties), while the vigor was such that plants were actually overcrowded in their final year of testing. Flower coverage was wonderful; hardly any foliage was visible during bloom. The one drawback pertained to maintenance. Once bloom was over, the plants needed an intense deadheading to make them look presentable. Considering the profusion of flowers, this was no small task. Nonetheless, uniformity, excellent foliage and sheer profusion of blooms more than compensated for the extra maintenance demanded.