Achillea

502 SOLIDAGO HYBRIDS, ×SOLIDASTER
‘Praecox’, a selection of Solidago virgaurea, bears bright yellow flowers. Early
summer and fall flowering occur. Popular in Europe.
‘Strahlenkrone’, an exceptional yellow cultivar, grows about 2–2½' (60–75
cm) tall.
‘Super’ has lemon-yellow flowers on 2–3' (60–90 cm) stems. This is one of the
most handsome goldenrods we have seen, but, unfortunately, is highly susceptible
to rust and intolerant of poor drainage. Losses in our trials were close to
100%.
‘Tara’ has mid-yellow plume-shaped flowers and robust habit.
‘Tara Gold’ has golden-yellow flowers.
‘Toto’ produces deep yellow flowers.
‘Yellow Submarine’ bears lemon-yellow, open, spreading blooms. Excellent
performer.
Additional Species
Solidago caesia (wreath goldenrod) has dark yellow flowers with 3' (90 cm)
tall bluish wiry stems. Flowers occur in the fall and may be used to extend goldenrod
flowering time. This unusual goldenrod may find a niche in the cut flower
market.
Solidago odora (sweet goldenrod) has yellow flowers on 3' (90 cm) stems. The
benefit of this species is its fragrant foliage, which smells like anise when crushed.
Solidago rugosa ‘Fireworks’ and S. sphacelata ‘Golden Fleece’ are exceptional yet
underused goldenrods. ‘Fireworks’ performed very well in trials as a garden plant
(Hawke 2000).
Pests and Diseases
Powdery mildew (Erysiphe polygoni) is a white fungus on the undersides of the
leaves and the stems. Downy mildew can also be a severe problem. Work done by
Hawke (2000) at the Chicago Botanic Garden with different goldenrod taxa suggested
that Solidago caesia, S. flexicaulis, S. graminifolia, S. sphacelata ‘Golden Fleece’,
and S. ‘Peter Pan’ were less susceptible to powdery mildew than others tested.
These data may be useful for breeding some disease resistance into the hybrid cut
flower forms.
Rust (Coleosporium asterum) is the most serious disease of goldenrod. Rustcolored
pustules cover the foliage and stems in late summer. Because pine trees
act as an intermediate host, plant well away from stands of pine trees. No effective
control is known, although spraying with zinc-based fungicides appears to
provide some control.
Leafminers, whiteflies, and spider mites are pests of Solidago.
Leaf yellowing is not uncommon and may be related to high pH, low soil temperatures,
or mineral imbalance. An application of 1.8–2.0% zinc sprayed every
10 days has been shown to reduce leaf yellowing (Bartels 2001).