The Ornamental Dwarf Speedwells
(Editor's Note: This article was originally published on March 22, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
In last week's article, I described those speedwells (Veronica spp.) which are ideally suited to the perennial border. However, the vast majority of ornamental speedwells are creeping, mat-like or otherwise dwarf in habit, often with evergreen foliage. These species are better suited to the rock garden, grown as a groundcover, cascading over retaining walls or grown along the front of the border. As with the tall species, blue shades are by far the most common colour although white and lavender-pink do exist. While most of the tall species produce narrow, spike-like flowers, the low types typically produce solitary flowers or short racemes from the upper leaf axils. These low species are generally sun-lovers requiring well-drained soil. Several are quite drought-tolerant. Self-seeding may be a problem with some but a shearing after blooming will help curb this activity. The blooming season can be variable from late spring to mid-summer, depending on the species.
First I'll start with the more-or-less clumping species. Veronica allionii is much like a miniature version of the spiked speedwell, V. spicata. Plants produce low rosettes of semi-evergreen leaves and 10 to 15 cm narrow spikes of mid-blue flowers. Hardy to zone 4, this native of the Alps blooms in early summer and oftentimes repeat-bloom if promptly deadheaded.
Details of Veronica allionii
From Japan comes V. schmidtiana. This zone 5 species has evergreen, crinkly, heavily-toothed leaves which are held close to the ground. In early summer, loose spikes of lavender-blue flowers are produced on 15 to 20 cm stems. This species is short-lived so be sure to collect seeds. It dislikes hot temperatures which explains why it does so well in my area!
Details of V. schmidtiana
Among the most easy and popular species is V. prostrata. This one forms quite large mats of evergreen foliage and small axillary spikes reaching 15 to 25 cm in late spring-early summer. Hardy to zone 4, this species is available in a number of named selections including ‘Heavenly Blue' (dark blue), ‘Silver Queen' (silvery-blue), ‘Rosea' (light pink), ‘Alba' (white), 'Nestor' (light blue) and the striking ‘Trehane' (yellow foliage with dark blue flowers).
Details of V. prostrata including the cultivars 'Heavenly Blue' (top right), 'Nestor' (lower left) and 'Trehane' (lower right)
Veronica peduncularis has a mounding, almost subshrub-like habit 15 to 20 cm tall. Semi-evergreen, they are perhaps best trimmed back close to the ground in spring to maintain a denser plant. The relatively large, sky-blue flowers are prolifically produced in small axillary clusters in mid-late spring. In cool-summer regions like my own growing area in Newfoundland, Canada, this species blooms prolifically all summer! This species is both heat and drought-tolerant. An additional feature of this species is the glossy purplish-red winter and spring foliage. ‘Georgia Blue' (mid-blue) is a popular selection. Not named after the State, ‘Georgia Blue' is named after the country Georgia, an area once included in the former USSR. ‘Waterperry Blue' has lavender-blue flowers and even richer purple-red winter foliage. In fact, in my area, the leaves remain purple-tinted all summer. This species is rated hardy to zone 5.
Veronica peduncularis 'Georgia Blue' and 'Waterperry Blue' (rightmost)
From Europe come two similar species called V. fruticans and V. fruticulosa. Both form evergreen subshrubs with small, glossy leaves and upper axillary clusters of mid-blue (V. fruticans) or lavender-pink (V. fruticulosa) in late-spring-early summer. Both are rated for zone 4. These are apt to be self-seeding if not promptly deadheaded.
Veronica fruticans and V. fruticulosa
As an alternative to growing creeping thyme between stepping stones or patio blocks, you can try V. repens, which, in my opinion, actually does a better job. The plant habit is completely prostrate with rounded, evergreen foliage. The relatively large flowers are ice-blue and produced individually from spring through summer. The cultivar ‘Sunshine' has yellow-foliage. This species, rated to zone 4, has quite good tolerance to foot-traffic. Also used between stepping stones is V. liwanensis. This species has gentian-blue flowers and smooth foliage but reaches 5 to 10 cm so is not particularly tolerant to foot-traffic. It is also better suited to dry-winter climates.
Details of V. repens, the cultivar 'Sunshine' and V. liwanensis
There are a host of mat-like, fuzzy-leaved species from Greece through Asia Minor. All prefer xeric, scree conditions in winter-wet climates and even then, may prove challenging. They do far better in the drier winter Rocky Mountain States, especially Colorado and Utah. In my winter-wet region I have fair success with V. whitleyi and V. aphylla. Both have masses of gentian-blue, solitary flowers in late spring-early summer then sporadically until fall. The foliage is grey-green. Of similar habit are V. caespitosa and V. thymoides. For really silvery foliage try V. tauricola, V. bombycina or V. macrostachya. These have wonderful contrasting blue flowers. They are especially nice cascading over the edges of alpine troughs. These are all rated for zone 5.
Some of the scree species include V. aphylla, V. whitleyi and V. tauricola
There are several more ornamental low to creeping speedwells available on the market and new species, especially from southern regions of the former USSR, are being introduced on a regular basis. Check out the seed exchange of the North American Rock Garden Society or Alpine Garden Society to obtain some of these choice, alpine speedwells.
There are several people I wish to thank for the use of their pictures: plantaholic186 ('Trehane'), Gabrielle ('Sunshine'), lincolnitess ('Nestor'), rebecca101 ('Heavenly Blue'), Ally_UT (V. tauricola), poppysue (V. prostrata), clareb (V. liwanensis) and JamesCO (V. repens).