Veronica spp.

Features - New Varieties

Spiky flowers rise like sentinels in the sunny garden.

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January 21, 2011


Left to right: Veronica ‘Heraud’, Veronica ‘Giles Van Hees’, Veronica gentianoides ‘Pallida’, V. pinnata ‘Blue Eyes’.


Speedwells (Veronica spp.) are notable for their graceful and bountiful flowers, as well as their reliable nature. These long-blooming, easy-care perennials offer a range of plant types with a disQtinct verticality prized by gardeners. Whether at the front, middle, or back of the border, their slender wands enliven the garden with color and the busyness of butterflies and bees throughout spring and summer. Their popularity has only increased in recent years due to the introduction of many hybrid cultivars with new flower colors and improved plant forms.


Many colors, foliage
There are approximately 250 herbaceous species of Veronica native to temperate regions of the Northern Hemisphere, found in such diverse habitats as alpine meadows, grasslands, oak forests, and riverbanks. The taxonomy of Veronica is currently under revision. Although speedwell flowers may be white, pink, violet or purple, the sumptuous shades of blue are particularly coveted by gardeners. Foliar characteristics are variable among Veronica species — from lanceolate to almost round, glossy to pubescent, with smooth, lobed or toothed margins. Basal leaves are often opposite, while leaves on flowering stems are alternately arranged.

For comparison and distinction, speedwells are usually grouped by habit, either prostrate spreading or upright clump-forming. Among the prostrate species familiar to gardeners are alpine speedwell (V. alpina), harebell speedwell (V. prostrata), creeping speedwell (V. repens), comb speedwell (V. pectinata), and gentian speedwell (V. gentianoides). Popular upright species include long-leaved speedwell (V. longifolia), spiked speedwell (V. spicata), and Hungarian speedwell (V. austriaca).


In the landscape
Speedwells are generally easy to grow and prefer sunny locations in moist, well-drained soils. Plants grown in less light will not bloom as profusely and may become lax or open in habit. Speedwells can be long-lived provided that garden soils drain freely, which is especially important during winter months. Many speedwells drop their lower leaves in summer, resulting in bare stems and a spindly habit. A midsummer shearing after the first bloom promotes healthy new basal foliage and encourages late summer flowering. Deadheading throughout the bloom cycle produces many new, albeit shorter, floriferous spikes later in the season. Taller speedwells may require staking, especially in overly moist or fertile soils. Dividing crowns in early spring is beneficial for plants that have lost vigor with age. A number of foliar diseases may affect plant health, including powdery mildew, downy mildew, leaf spots and foliar rust.
Prostrate speedwells are suitable for the front of the border, as edging along walkways, as ground covers, in rock gardens or on low walls. These low-growing species begin to bloom in mid-April, making them delightful companions to spring bulbs. In borders and wildflower gardens, upright speedwells mix nicely with many summer perennials such as yarrows (Achillea spp.), coneflowers (Echinacea spp.), cranesbills (Geranium spp.) and catmints (Nepeta spp.). Their telltale spikes are frantically alight with butterflies and abuzz with bees from mid-June onward.
 

The evaluation study
The Chicago Botanic Garden (USDA Hardiness Zone 5b) evaluated 64 taxa of Veronica in full-sun trials between 1999 and 2009. The goal of the comparative trial was to recommend outstanding speedwells for northern gardens. Sixty-one taxa completed a minimum four-year trial, with more than half of the taxa evaluated for six years.

The evaluation garden was openly exposed to wind in all directions and received approximately 10 hours of full sun daily during the growing season, an average of 165 days per year. The clay-loam soil was amended with composted leaves and had a pH of 7.4 throughout the evaluation term. The site was normally well drained, but at times the soil retained moisture for short periods in summer and winter.

Maintenance practices were kept to a minimum to simulate home-garden culture, thereby allowing plants to thrive or fail under natural conditions. Water was provided as needed and mulch consisting of shredded leaves and wood chips helped with water conservation and weed suppression. Moreover, plants were not fertilized, winter mulched or chemically treated for insect or disease problems.


Performance report
Plants were regularly monitored during the evaluation period for ornamental traits such as flower color, bloom period, plant size and plant habit. In addition, data were collected on disease and pest problems, winter injury and habit quality and plant health issues related to and/or affected by cultural and environmental conditions. Final performance ratings are based on flower production, plant health, habit quality and winter hardiness.

Seven speedwells received good-excellent ratings for their overall performance, including Veronica ‘Fairytale,’ V. ‘Giles Van Hees,’ V. austriaca ‘Ionian Skies,’ V. longifolia ‘Blue John,’ V. spicata ‘Baby Doll,’ V. spicata ‘Ulster Blue Dwarf’ and V. wormskjoldii.

These top-rated speedwells exhibited strong habits and excellent flower production throughout the evaluation period. The lack of any serious pest or disease problems, along with good winter survivability, contributed to their high ratings.


Flower production evaluation
Many of the speedwells received four-star good ratings or higher for heavy flower production, robust plant habits, disease and pest resistance, and winter hardiness.
Among the top-rated plants were outstanding ground-hugging speedwells such as:

Veronica ‘Blue Reflection,’ V. gentianoides ‘Pallida,’ and V. prostrata ‘Mrs. Holt’; as well as exceptional upright clumpers such as V. austriaca ‘Ionian Skies,’ V. longifolia ‘Blue John’ and V. spicata ‘Baby Doll.’

Regardless of their stature or habit, they all featured spiky inflorescences rising from several inches to a foot or more above the foliage. Speedwells were generally long-blooming plants, often flowering from June into September, although not continually during that time.


Some drawbacks
Seasonal stem decline was a prevalent condition that affected the upright speedwells each summer. Despite leaf drop and/or stem death, most plants recovered quickly after being sheared to the ground at the end of the first bloom period. Cold hardiness was not an issue, but crown loss or plant death due to wet soil conditions in winter was a fairly significant problem for the speedwell trial. Powdery mildew and leaf spot were observed in multiple years but were neither widespread nor severe in most cases.

A complete report of all varieties trialed is available at www.chicagobotanic.org/downloads/planteval_notes/no33_veronica.pdf.


Richard G. Hawke is plant evaluation manager at the Chicago Botanic Garden,
www.chicagobotanic.org/plantevaluation.