Missouri Ironweed

Description:  Missouri ironweed has a relatively large number of florets per flowerhead; also, it usually has hairy stems and leaf undersides. Like other ironweeds, Missouri ironweed is an upright perennial that bears branching, rounded clusters of fuzzy-looking magenta or purple flowerheads in late summer and fall. The foliage is often grayish due to a covering of fine hairs on the leaves and stalks. The stems of Missouri ironweed are hairy, with longer, spreading or often bent to tangled hairs toward the tip, sometimes minutely hairy toward the base.

Flowerheads have 32–60 florets per head. The involucral bracts (overlapping, scalelike structures at the base of the flowerhead) are neither curly and threadlike, nor are they narrowly pointed and curling back. Instead, they are rounded or broadly angled to a bluntly pointed tip, the innermost (top) ones often abruptly tapered to a minute, sharp point, appressed (pressed snug against the flowerhead base), glabrous (smooth) or minutely hairy, glandless or with sparse, minute, impressed resin glands toward the tip, the midvein not keeled or only slightly keeled toward the tip. The margins are usually cobwebby-hairy. For more information see: mdc.mo.gov/discover-nature/field-guide/missouri-ironweed

Care and Growing Tips:  Like many native wildflowers, ironweed is quite easy to grow. It prefers rich, moist soil that is slightly acidic, but it will readily survive in less favorable conditions. These are large plants, so space them at least 28 inches apart as they will quickly fill in. Ironweed plants prefer full sun, but can thrive in partial sun as well. This plant needs at least four hours of direct sunlight each day, but six to eight hours is better.

Ironweed prefers moist soil, it will need at least 1 inch of water per week, and will readily tolerate even more. It will also do quite well in boggy, poorly draining soils where many other plants struggle. It readily tolerates the heat and humidity patterns throughout its hardiness range, zones 5 to 9. Where the climate is naturally arid, it may require more ground watering. This plant requires no pruning, but deadheading spent flowers is a good idea if you want to limit its self-seeding habit, which can cause the plant to quickly spread. At the end of the growing season, garden plants can be cut down to near ground level.