Rhizomatous Alliums

One of the largest and most important sections of the genus Allium is section Rhizirideum, or the rhizomatous onions. This group is characterized by species having poorly-developed or vestigial bulbs attached to distinct rhizomes. Generally speaking, rhizomatous onions are summer growing with season-long foliage, prefer more moist habitats than the summer-dormant bulbous species, and contain some of the most attractive and desirable species for gardens.


Allium albidum ssp. caucasicum is a nice compact form of this European mat-forming onion. The small white flowers in July and August are particularly large, showy, or plentiful, but it's a pleasant enough little species that makes carpets of fine green strap-shaped foliage. It's small enough to grow in a trough, as shown in the image. Photos by Mark McDonough.

Allium albidum ssp. caucasicum, Mark McDonoughAllium albidum ssp. caucasicum, Mark McDonough

Allium carolinianum is not from Carolina at all, but a Himalayan species. It can be a difficult plant to please, and in most years the buds abort for some reason. The foliage is quite remarkable, being very thick and waxy, particularly when first emerging. The first photo is early in the spring; the second was taken June 2002, when at least one of the buds was spared and condescended to flower. The plant is variable. I have grown better performing forms in the past, but alas over the years the others have perished. Photos by Mark McDonough.

Allium carolinianum, Mark McDonoughAllium carolinianum, Mark McDonough

Allium hookeri var. muliense - A Chinese species, the variety muliense has bright yellow flowers instead of white. The foliage is very broad, with 8-9 leaves, looking more like a hemerocallis than an allium. The flowering stems reaches over 2' (60-70 cm), with a hemispherical head of flowers in June and early July. Three photos by Mark McDonough, June 2004.

Allium hookeri var. muliense, Mark McDonoughAllium hookeri var. muliense, inflorescence from a top view, Mark McDonoughAllium hookeri var. muliense, inflorescence from below shows the 2 bracts, Mark McDonough

Allium hymenorrhizum "robust form" - I've grown several forms of this species, but this one from Jerry Flintoff is by far the most robust and distinctive. It grows 3' to 3-1/2' tall (90-105 cm) and has lollipop balls of lilac-pink blooms in early summer. The first photo shows a flower head with buds ready to open, the second shows flowers at full anthesis, and the third shows the succulent sprouting shoots in late March to early April, the leaf bases stained beet red and the emerging leaves strongly falcate. Photos by Mark McDonough.

Allium hymenorrhizum, Mark McDonoughAllium hymenorrhizum, Mark McDonoughAllium hymenorrhizum, Mark McDonough

Allium incensiodorum was collected in Istria, northern Croatia, where it grows with Cyclamen purpurascens, Paeonia officinalis, Helleborus multifidus subsp. istriacus and other fine Mediterranean plants among limestone boulders. Leaves are strap-like. Flowers in mid August in cultivation in the UK. Photos by Tom Mitchell.

Allium incensiodorum, Tom MitchellAllium incensiodorum, Tom Mitchell

Allium insubricum - From the Alps, this is considered to be among the most desirable of Allium species. It is closely akin to the equally beautiful Allium narcissiflorum. It can be difficult to grow and flower well. Photo by Mark McDonough, taken in the garden of a nearby friend.

Allium insubricum, Mark McDonough

Allium lineare - There's much confusion over the status of the two names "strictum" and "lineare", but I'll go with the majority of thought on this one and use "lineare". A pleasant easy to grow species that makes a bright show in shades of pink in early summer (June). Seeds around a little too readily. Photo by Mark McDonough.

Allium lineare, Mark McDonough

Allium nutans "extra-wide leaf form" - This Siberian species is a terrific plant. But it's a highly variable entity, and there are inferior forms as well as truly superior forms. The one shown here is remarkable on account of the extra wide and thick gray leaves that spirally twist into impressive mounds. The first photo shows the plant in spring with the pirouetting rosettes of foliage, the second shows the massive muscular leaf rosettes in June, the third shows the nodding and twisting flower stems, and the last shows the typical flower form, dense floral globes that look fuzzy on account of the protruding stamens. Flower color can be found in all shades of rose, lilac, pink, to white. Photos by Mark McDonough.

Allium nutans, Mark McDonoughAllium nutans, Mark McDonoughAllium nutans, Mark McDonoughAllium nutans, Mark McDonough

Allium przewalskianum is a delightful small species from Central Asia to China, with very fine terete foliage, good-sized balls of rose-purple flowers, and distinctive fibrous orange-colored bulb bases. The second photo is a clear close-up up the cinnamon orange bulb bases and white roots. Photos by Mark McDonough.

Allium przewalskianum, Mark McDonoughAllium przewalskianum, Mark McDonough

Allium ramosum is an early summer blooming species that is unnecessarily confused with Allium tuberosum. Flowering in June, stems can reach 3' (90 cm), with ample heads of nice white flowers, each tepal touched with a fine red nerves on the outside. This species has not been weedy nor aggressive like A. tuberosum. Photo by Mark McDonough.

Allium ramosum, Mark McDonough

Allium rubens is a quiet, unassuming species from Central Asia. It has very narrow foliage, and little, few-flowered semi-nodding clusters of light pink bells. The roots and bulb base are also reddish pink color. It is one of the few "ever blooming" species, throwing up modest blooms all summer long. Drawing by Mark McDonough.

Allium rubens, Mark McDonough

Allium senescens ssp. glaucum is a small, late flowering rhizomatous onion. The "cowlick onion" or the "spiral onion" is well known in cultivation... or is it? The horticultural entity known under the "glaucum" name is represented in cultivation by a whole range of grey-leafed, spiraling dwarf plants that flower in late summer to early autumn. Photo by Arnold Trachtenberg.

Allium senescens ssp. glaucum, Arnold Trachtenberg

'Blue Eddy' is a seedling selected, named and photographed by Mark McDonough. The name is a fanciful allusion to the extra dwarf blue-gray swirls of foliage, like small swirling eddies of water. The plant is very effective as a ground-cover. Depending on the season and light from the time of day, the foliage appears grayish green to grayish-blue. Autumn flowers are pale pink on 6"-8" (15-20 cm) stems.

Allium senescens ssp. glaucum 'Blue Eddy', Mark McDonoughAllium senescens ssp. glaucum 'Blue Eddy', Mark McDonough

Allium togasii is one of the very best and most useful little onions. It's a Japanese species that flowers in late summer to early autumn, depending on the form grown. It prefers a sunny position in very sandy soil. The first photo shows the grassy clumps of thread-thin foliage in spring. The second photo shows the plant in bloom, with spheres of palest pink in August on 4-6" (10-15 cm) stems. The foliage has most disappeared by the time the flowers arrive. Sometimes spelled A. togashii. Photos by Mark McDonough.

Allium togasii, Mark McDonoughAllium togasii, Mark McDonough

Allium tuberosum is a late-summer blooming species that's attractive in the garden or perennial border. Be forewarned, it can be very weedy by overly aggressive self seeding, as reported by some growers, whereas other growers say it is well behaved. Possibly the climate and garden conditions affect its propensity for weediness. Photos by Arnold Trachtenberg.

Allium tuberosum, Arnold TrachtenbergAllium tuberosum, Arnold Trachtenberg

Allium tuvinicum - Named for the Tuva region of Russia, this is a small turf-forming species with narrow leaves and a long season of small creamy white flowers just clear of the foliage. The species has a wide distribution into Mongolia. Not exciting, but pleasant enough. Photo by Mark McDonough.

Allium tuvinicum, Mark McDonough

Allium index - Allium flavum Relatives - Allium hybrids - American alliums A-B - American alliums C - American alliums D-F - American alliums G-H - American alliums I-M - American alliums N-R - American alliums S-Z - Big Ball alliums - Blue alliums - chives - Domed alliums - Drumstick alliums - Miscellaneous alliums A-E - Miscellaneous alliums F-M - Miscellaneous alliums N-R - Miscellaneous alliums S-Z


Return to the PBS wiki Photographs And Information page
Page last modified on August 15, 2012, at 07:38 AM