Helianthus maximiliani Seeds | Maximilian Sunflower
LATIN NAME: Helianthus maximiliani
COMMON NAME: Maximilian Sunflower
Plant Profile
Heinrich Adolph Schrader described the species and named it for Prince Maximilian of Wied-Neuwied, the naturalist who travelled up the Missouri river. The honour was a patron’s, not a collector’s, and the naming has caused a small flood of misspellings ever since: the original epithet is maximiliani, yet maximilianii is so common that both turn up in the same catalogue.
A creeping rhizome runs outward each season, and the fibrous roots that follow it hold prairie soil against rain. Rather than trusting a single stem to survive a dry summer, the plant spreads a network underground and puts up stems wherever it reaches; in a garden that produces a colony which widens every year.
The leaves are the diagnostic feature: alternate, lanceolate and long, ten to twenty centimetres, folded lengthwise along the midrib into a shallow trough, with a rough sandpapery surface. Flower heads are six to nine centimetres across with yellow rays and a darker disc, borne in a long raceme, twenty or more on a strong stem, opening in late summer and continuing until frost.
The late flowering is a prairie adaptation. By mid-August the tall grasses have set seed and soil moisture is falling, and a plant flowering then has the pollinators to itself. Helianthus maximiliani is diploid with 2n = 34, and it crosses readily with relatives such as Helianthus grosseserratus. Those hybrid swarms make the genus a model for the study of plant speciation.
Rust, caused by Puccinia helianthi, is one of the diseases that costs sunflower growers most, and resistance found in wild perennial species has been introgressed into cultivated lines by repeated backcrossing. The same is true of resistance to white mould and downy mildew.
The seed heads are small but abundant, and goldfinches work them through the autumn. Leave the stems standing through winter rather than cutting them early: the hollow stalks shelter overwintering insects, and the seed heads keep feeding birds when the ground is frozen. Cut the stand back to the base in early spring, before the new shoots are tall enough to be damaged.
Science & Biotechnology
Wild perennial sunflowers including this one are donors of resistance to downy mildew, rust and white mould in the annual oilseed sunflower, and the species has been screened in programmes seeking a perennial oilseed crop. Rhizome architecture, drought tolerance and late flowering are the traits of interest, and the genome has been assembled to speed the search.
The bitterness that keeps livestock off young stems comes from sesquiterpene lactones, a family that includes costunolide and its derivatives. The plant also bleeds a milky latex when a stem is cut, and that latex has been examined in the search for alternative sources of natural rubber, since several Helianthus species produce hydrocarbon of usable molecular weight.
Uses & Benefits
On a farm the species earns its place as forage. Cut before the stems harden, it makes palatable hay or silage, and it regrows from the rhizome afterwards. It is also favoured cover for pheasant and quail, and its late flowers are one of the few nectar sources still open to bees once the season has turned.
Quality is best at the first cut, so mow or graze early and let the stand recover before autumn. The stand thickens rather than thins with age, and a field left alone for several seasons will need its edges controlled. Cutting in late summer removes the flowering stems and reduces the seed left for birds, so many growers keep a strip uncut along a hedge.
Growing from Seed
Sow two centimetres deep in late autumn, or in early spring after holding the seed damp and cold through the winter, and barely cover it. Direct sowing into a weed-free bed gives the strongest plants; raising them in deep pots and planting out once the rosette has four or five true leaves is tidier for a small garden. Space plants 60 to 90 cm apart, and thin to 45 cm for a solid block.
Give the plant poor to moderately fertile soil in full sun and it will stand up by itself. Give it manure and it grows taller, flops in the first gale and flowers later and less. Water new plantings through their first season and then only in real drought. A root barrier sunk 30 cm into the ground keeps a border clump within bounds.
The stalk borer hollows the stems and its damage shows as a wilting tip; cut the affected stems below the entry hole and destroy them, because the larvae pupate in the stubble. Aphids cluster on new growth unless the plants are fed too well, powdery mildew appears on stressed foliage, and rust shows as orange pustules in a humid summer. Pinching the tips in early summer keeps the stems to a useful height.
Our Take
This is a plant for the back of a big border or the edge of a meadow, and it is worth the space for the way it holds the garden’s colour into the last weeks of the year. If the annual form suits your scale better, the common sunflower will do the job in one season, the cup plant gives the same prairie presence on taller stems, and the New England aster carries the purple-and-gold combination to the first hard frost.
Related Reading
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