Achillea

44 ACHILLEA MILLEFOLIUM AND HYBRIDS
Stem length: Stem lengths are short the first year of planting, but as plants
mature, the percentage of saleable stems greater than 20" (50 cm) increases as
shown in the following table.
Stem length distribution of Achillea millefolium ‘Rose Beauty’ over
time. Spacing 1' (30 cm).
Stem length (%)
Year 20"
1 7 17 76
2 4 9 87
3 0 0 100
z = multiply (in) by 2.54 to obtain (cm)
Spacing: Common yarrow spreads aggressively and forms a dense mat. Any
semblance of spacing in our trials disappeared by the third year; even those
spaced 3' (90 cm) apart were a solid mat at that time. As the following table
shows, flowering stems/plant increased as spacing distance increased, but
stems/ft 2 declined. A 1' (30 cm) spacing is recommended.
The effect of spacing on yield and stem quality of Achillea
millefolium. Second-year data.
Spacing (in) z Stems/plant Stems/ft 2y Stems >20" (%)
‘Rose Beauty’
12 42 42 90
24 91 23 83
36 107 12 91
‘Cerise Queen’
12 94 94 68
24 143 36 42
36 185 21 58
z = multiply (in) by 2.54 to obtain (cm)
y = multiply (stems/ft 2 ) by 10.8 to obtain (stems/m 2 )
Work in Italy also found up to 12 stems/ft 2 (130 stems/m 2 ) in the second year
when planted at a little less than 1' (30 cm) spacing (Zizzo et al. 1994).
Fertilization: Plants need little additional fertilizer if planted in organic soils.
High rates of nitrogen result in rapid vegetative growth at the expense of flower