'Silver Mound'
Common name: Wormwood
Family: Asteraceae, Aster
Height x width: 6-48" x 12-48" depending on species
Growth rate: fast
Foliage: all except lactiflora have small, alternate; often finely divided and aromatic when bruised
Flowers: dioecious (male and female flowers on separate plants) except for lactiflora, white or yellow in early to mid summer
Hardiness: 3-5 to 8-9 varying with species
Soil: most except wet, often tolerate poor; lactiflora prefers moist
Light: sun
Pests and Problems: powdery mildew or rust on some species (seldom serious or even seen)
Landscape habit, uses: colored foliage contrasts in borders, rock gardens for clump species, cut and dried foliage, herb gardens, slopes for invasive species; stellerana tolerates salty air and water
Other interest: common name from use by Romans of this plant to treat intestinal worms, santonin from some Asiatic species still used for this purpose; Mugwort common name from use of this species in mugs to flavor beer prior to hops; various species used for many ailments include liver and kidney problems prior to 19th century; absinthium originally used to prepare absinthe--a dry bitter beverage ingredient (now produced artificially without this species)-- which was found in 19th century to contain thujone causing absinthism-- delirium and eventually death; some use of fragrance fingerprinting to differentiate cultivars by their chemical fragrance properties
Other culture: some species are invasive by roots so proper placement is crucial; some species fall over and open in centers with hot, humid weather as in the South (ludoviciana doesn't)
Propagation: division, stem or root cuttings, seeds
Species:
The following are the most common perennial species in the U.S., cold
hardy to at least zone 6, and do not include ones grown primarily for herbs
(dracunculus, Tarragon; vulgaris, Mugwort) or native vegetation
(tridentata, now Seriphidium--sagebrush). Mugwort is an aggressive
to invasive spreader, especially the variegated A. vulgaris 'Oriental
Limelight'.
| Species | zones | height | woody | foliage | habit | native |
| *abrotanum | 5-8 | 3-4' | yes | gray, very fragrant | upright | So. Europe |
| *absinthium | 3-9 | 2-3' | yes | silvery-gray, fragrant | upright | Europe |
| alba | 6-9 | 2-3' | yes | gray, lobed, fragrant | upright | Europe, N. Africa |
| armeniaca | 5-9 | 2-3' | no | gray, wooly below | upright | Asia Minor |
| douglasiana | 3-9 | 6-9' | no | green, gray below | upright | W. U.S. |
| filifolia | 3-9 | 2-3' | yes | silvery | upright | Mexico |
| frigida | 4-9 | 8-12" | yes | silver | upright | N. temperate |
| *lactiflora | 3-8 | 4-6' | no | green | upright | China, India |
| *ludoviciana | 4-9 | 2-4' | no | silvery gray beneath | invasive | N. America |
| pontica | 4-9 | 1-2' | yes | light green, fragrant | self sows | Europe |
| pycnocephala | 3-9 | 1-2' | yes | gray silky | upright | W. U.S. |
| schmidtiana | 3-8 | 1-2' | yes | silver, finely cut | mounded | Japan |
| stelleriana | 4-8 | 1-2' | yes | silver, lobed, divided | spreads | E. U.S., Asia |
Cultivars:
The following are the most often found in U.S. commerce, with those
marked * the most popular.
| Cultivar | species | foliage | other |
| 'Guizho' | lactiflora | very dark green | creamy flowers, from Blooms |
| 'Huntington' | x absinthium | silver, deeply cut | zones 5-7, 2-4', heat-tolerant |
| *'Lambrook Silver' | absinthium | grayish, finely cut | 2-3' tall, tends to flop |
| *'Nana' | schmidtiana | silver, finely cut | most popular in genus |
| *'Powis Castle' | hybrid | silver, finely cut | zones 6-8, 2' tall |
| 'Silver Bouquet' | stelleriana | silver | low mat-forming, from UBC |
| *'Silver Brocade' | stelleriana | grayish-silver | low mat-forming, from UBC |
| 'Silver Frost' | ludoviciana | silver, finely cut | |
| *'Silver King' | ludoviciana | silver, cut | |
| *'Silver Mound': 'Nana' | schmidtiana | ||
| *'Silver Queen' | ludoviciana | silver, cut | shorter than 'Silver King' |
| *'Valerie Finnis' | ludoviciana | silver, entire | 1-2' tall, non-invasive |
(cultivar photos, except 'Nana', courtesy Missouri botanical gardens plantfinder)
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