Svante Malmgren Henric Nyström
Dactylorhiza, species and hybrids
There is an immense number of species and subspecies within the genus, Dactylorhiza. The systematics of Dactylorhiza provide a perfect hobby for a botanist with time on his hands. In this genus, morphological studies alone are inadequate to delineate species and their relationships and almost no hypothesis can be rejected. Plants that have been allocated to different subspecies can be found growing in adjacent sites, not to mention the next county or country.
F1 Dactylorhiza hybrids, at least those “containing” D. incarnata /ochroleuca/ cruenta and sphagnicola, produce healthy, viable seedlings in our own experiments (research studies, Malmgren). The morphology of these hybrids is so variable that it is completely impossible to deduce the parent plants of origin. F2 hybrids frequently do not resemble either the parent or grandparent plants.
Crossing and breeding experiments in combination with DNA research will provide more definite conclusions. In common with Ophrys, sowing the seed of a single capsule from a self-pollinated plant will reveal the great variability within a single species.
It seems that all Dactylorhizas are very easy to propagate asymbiotically. Further growth in soil usually poses no problems and the plants generally flower after four years. Any two species may be hybridised, sometimes producing plants of great vigour and beauty. Many Dactylorhizas deserve to be evaluated as potential garden plants.
Sowing medium: “Standard medium” with amino acids plus 20 ml
pine-apple juice/liter medium. 0,5-1 cm3 potato in each flask à 20 ml
medium is not neccessary but possibly beneficial also for Dacts (?).
Several “new” Dactylorhizas, of uncertain legal status, from Asia and elsewhere are now appearing on the market and time will tell which of these are appropriate for the garden and large scale propagation.
Dactylorhiza fuchsii with all its variations is not uncommon in Sweden and may be found growing wild in many different biotopes. This explains why it can be grown easily as a garden plant. The species is extremely variable ranging from small plants with pale lilac flowers to grand, 70cm tall, specimens that exhibit dark purple blooms.
Dactylorhiza O´Kellyi is (probably still) considered to be a subspecies of Dact
Fuchsii, from Ireland and northern parts of Scotland. An interesting fact is that approx 10% of the plants have pink flowers, 90% pure white. Easily propagated as the otherDacts.
Dactylorhiza purpurella is another species from coastal regions of the northwest Atlantic. We have propagated a charming little form from the Faroe Islands. It flowers very late and reaches just 20-25cm in height.
Dactylorhiza sambucina is very difficult to grow in gardens. In Sweden, at least, it is restricted in the wild to specific habitats in warm, sunny, dry locations. As a result, its leaves remain above ground for only a short period in the spring and early summer and the species will not tolerate other conditions. In a suitable natural site, though, it will grow well and increase over time. Its hybrids, however, are not so fussy and D. sambucina makes a good hybrid partner (see below).
It is very easy to propagate . The plant grows slowly from year to year and often takes five or six years until flowering for the first time. A large proportion of the D. sambucina on the market is probably made up of illegally collected plants.
Plants with yellow flowers produce yellow flowered offspring; those with red produce red offspring. Only by cross-pollinating the two can intermediate colours be produced.
Dactylorhiza majalis, in contrast, is very easy to grow in gardens. Easily propagated too, it grows strongly and flowers four years after sowing. White flowered forms of this species exist and they propagate true to form. (White flowered forms of various orchid species may occasionally be found in the wild. In most cases, and even after carefully controlled self-pollination, these plants produce offspring with flowers of a normal colour.) D. majalis is an exception to this generalisation.
Dactylorhiza foliosa is a very beautiful species with large flowers and it seems to be completely resistant to fungal attack. It has been adopted widely as a garden plant and is thoroughly deserving of this status. When we propagated a white flowered specimen there was not even a single plant amongst its offspring that had white flowers. All sported a variety of purple shades.
D. foliosa is also very good as a hybrid partner and its crosses have improved hardiness when grown in areas with a cold spring climate. Hybrids with D. fuchsii are commonly offered for sale but our favourite is the cross with Gymnadenia conopsea (see under Gymnadenia).
Dactylorhiza hybrids can be strongly recommended for garden use. Almost any tuberous European orchid can be hybridised with D. fuchsia and many other dacts will produce intergeneric hybrids too. Some of these lack vitality and good looks but experimentally almost any cross can be produced.
D. fuchsii x Gymnadenia conopsea is a “perfect” garden orchid, which grows to 65cm in height and quickly increases by division. We have propagated it on several occasions (see under Gymnadenia… we usually use Gymnadenia as the maternal parent).
D. fuchsii x purpurella (the latter from the Faroe Islands) is a very cute hybrid, which flowers late. It carries a very compact spike of dark flowers.
D. fuchsii x sambucina is a much stronger hybrid and some plants flower three years after sowing. It is very reminiscent of D. sambucina but has a quite different and much greater vitality and speed of growth. It is an early flowering hybrid that we have raised several times and it is our intention to do so again.
As we have never discovered a “true-breeding” white D. fuchsii, we have never managed to create a yellow flowering hybrid with D. sambucina… they all bear red flowers.
D. fuchsii x Coeloglossum viride and D. fuchsii x Leucorchis albida are not very beautiful but have been grown experimentally out of interest. They are easily raised from seed, in common with all Dactylorhiza hybrids and species.
The plan behind the production of the cross, D. fuchsii x Platanthera bifolia was to create a tall orchid with the form and scent of the Platanthera parent… potentially a perfect garden plant. A white D. fuchsii was used as the mother plant and hybrids were raised over two sequential years. Disappointingly, the result was a small plant, only 15cm high, and although white flowered, bore not a hint of a scent! All the offspring were the same, illustrating the problems that are faced when plant improvement is attempted!
D. fuchsii x Orchis mascula and D. fuchsii x O. militaris can be raised from seed easily but the latter is poorly viable in the long term. The O. mascula hybrid blooms very early and has flowers of a dark purple colour. We have propagated this on several occasions.