Maximilian sunflowers are perennial wildflowers native to the North American prairies. The many-branched plants grow up to 8 feet tall and produce scores of medium size yellow blossoms that resemble sunflowers. They are hardy and vigorous growers, seldom needing much help from the gardener once established. Plant them in a row to screen an unsightly view or as a privacy fence. They begin blooming in mid- to late summer and continue blooming until killed by frost.
Pick a spot that is in full sun with well-drained soil. It is adaptable to all soil types but does not like soggy soil that stays wet after rainfall. They prefer average soil and amending or improving the soil prior to planting is not necessary.
Plant seeds of maximilian sunflowers in late fall. The seeds will overwinter and germinate the following spring. Plant seeds about 3/8 inch to ½ inch deep. Space the seeds an inch apart. Firm the soil over the seeds but do not water. Do not lay down a protective winter mulch. The seeds need to be exposed to cold winter temperatures in order to germinate.
Thin seedlings the following spring when they are about 2-inches tall. Thin them so they stand about eight inches apart in rows at least three feet apart. If planting near a fence or other structure, allow three feet of space between the seedlings and the structure.
Water seedlings regularly until the plants become established by midsummer. After that, supplemental watering is not required.
Mulch the planting area to conserve soil moisture and discourage the growth of weeds.
Remove dead top growth in late fall and discard or compost. Protective winter mulch is not necessary.
Side dress with compost in early spring to maintain vigorous growth, especially if planting Maximilian sunflower as a hedge or privacy screen. Pull back mulch, spread an inch of compost around the base of the plants and replace the mulch.