- Herbaceous plants, usually rather tall (11/2 feet to 3 feet), in some cases dwarf and neat alpine plants with blue flowers in various shades ; are among the hardiest of plants, and will grow in any soil. All the taller kinds are admirably suited for naturalisation among long grass and other herbaceous vegetation. A great number that are in cultivation in borders are only fit for this purpose. The dwarf kinds are equally suitable for bare places, or among other dwarf plants.