There are so many beautiful plants when Spring finally arrives. Clear, bright colours and the incredibly delicate scents awaken the imagination and bring back the primary child. The time is right to strip away all those years of cultural learning and conformity - do something bold. Why not "wallflowers" - everyone disparages the lowly cabbage family, yet many worthy species of draba and erysimum give an early boost to the rock garden.
Browsing through Jurasek's seed list, I came upon some Turkish collections of matthiola, "stocks". These three matthiola spp. anchoniifolia, montana, and trojana are diminutive plants from higher elevations on three different Turkish mountains. First thoughts were that they must have fragrance like the familiar garden cultivars and reasonable though likely unexciting flowers. They also have the advantage of being perennial. M. anchoniifolia forms tufts of linear leaves, covered with white tomentum, just enough to mute the colour to an aqua/green. Flowering begins in early May and the floral display can best be described as understated, but alluring. Four thin petals unfurl like dark, chocolate wafers.
The flowers are held close to the stem in a short raceme; and, though the colour fades to a medium coffee, they remain for 3 weeks or more and are set off quite well against the aqua of the leaves. m. montana has spathulate leaves and brown flowers also. The leaves of m. trojana are basal and pinnatisect in shape. Flowers are described as being pale violet/purple flowers; but, it has not yet bloomed here. All three species are small (under 15cm. in flower). They grow on different mountains in Turkey above 1500m amongst rocks. Not surprisingly, they are very heat and drought tolerant. I also think that they will be of easy culture given a hot, dry position in the rock garden. Alas, though some fragrance is present, it is sweet but faint. So much for suppositions.
Plants of odd form and colour can be used to draw attention. Josef Halda did this in a tufa garden by putting rosettes of a dark violet/maroon Jovibarba heuff. 'Violet' on the surface of the stones. No pattern is evident, but it does draw the eye in for a closer inspection of the other smaller plants in the crevices. As this jovibarba does not produce offsets, it will remain relatively small and not smother the whole surface.
Oncocyclus iris have made a career of flaunting weird colour combinations to draw attention; and indeed, if in flower, they are guaranteed to fell a garden writer who chances to see them. There is but a brief window of opportunity for this, as the flowering period is usually over in a week or two for all the species we have in the garden.
The most brilliant one is i. iberica ssp. lycotis - huge flowers that are 6cm-7cm across. Standards are translucent with dark purple/brown veins; falls are black/brown. Sitting atop short (~20cm) stems, and waving lightly in the wind, the flowers are both elegant and voluptuous.
Of leaner nature is i. acutiloba ssp.lineolata. Aptly named with its rather narrow, pointed falls which are light gray, marked with maroon veins, and a dark maroon signal patch in the middle. Standards are like the falls, lacking the dark patch. Very floriferous, it grows easily in our garden. Both species are from higher elevations in Turkey and Iran - i. acutiloba has the broader distribution.
Various forms of i. paradoxa are also growable in the garden. Flowers are dark blue and purple combinations; understated, but exotic looking. Less available, but worth searching for are i.barnumae and i.meda. Sometimes seed is available - bear in mind that colours vary a lot. Selecting forms is slow as so few are available.
All the hardy species grow well in a straight gravel/sand that is without organic content and remains dry. They do withstand summer moisture better than I expected and really have presented no problems. I have found the hardy onco's to be easier to grow than many of the smaller juno iris. The only caveat is that they should not be moved in the Spring when they are very actively growing and producing flowers - this can kill them. Later in July the leaves start to dry up and they go into a dormancy if conditions are dry. By September, growth stops and then you can dig, divide and replant. This state continues until ~ November, so there is ample time to deal with them. They do winter-grow somewhat, and prefer not to be disturbed then. Iris acutiloba is particularly easy to grow, and I really don't understand why it is only rarely offered in specialist lists.
There you have it. Three rather different ideas to add interest to the rock garden. The choice is personal.