Broom corn, scientifically known as Sorghum vulgare var. technicum, is a unique plant cultivated primarily for its utility rather than its grain. It is a tall, annual grass whose long, stiff seed heads are harvested, dried, and bound together to create natural brooms and whiskbrooms. It is also frequently grown in gardens as a dramatic ornamental for its height and colorful seed plumes. Gardeners often question its ecological behavior and whether it poses a threat to native ecosystems.
Defining Broom Corn and Its Identity
Broom corn is a cultivated variety of Sorghum bicolor, commonly known as grain sorghum or milo. It is a domesticated, warm-season annual grass, bred for its long, fibrous panicles used in broom-making, and completes its life cycle within a single season. The confusion about its invasive nature stems from its close genetic relationship to Johnson Grass (Sorghum halepense). While both belong to the genus Sorghum, Johnson Grass is an aggressive perennial that spreads using thick, underground rhizomes. Broom corn lacks this perennial root structure, which is the primary reason their growth habits differ significantly.
Is Broom Corn Classified as Invasive?
Broom corn is generally not classified as an officially invasive species by federal or state regulatory agencies. A plant is designated as truly invasive when it is non-native, capable of spreading widely, and causes significant ecological or economic harm. While broom corn is non-native to North America, it rarely meets the criteria for this destructive designation.
The difference lies in its annual life cycle and lack of rhizomes, which prevents it from forming the dense, hard-to-remove colonies characteristic of true invasive grasses. Its primary method of spread is by seed, which is far easier to manage than the deep root systems of a rhizomatous perennial like Johnson Grass.
Broom corn is best categorized as a prolific self-seeder or a “volunteer plant.” It can become a garden nuisance because it produces a large quantity of viable seeds that readily sprout the following season. This aggressive self-seeding is a localized problem for gardeners, but it does not equate to the broad, ecologically damaging spread of a regulated invasive species.
Controlling Prolific Self-Seeding
Since broom corn’s spread depends entirely on abundant seed production, management involves preventing those seeds from maturing and dropping.
Deadheading and Disposal
The most effective control strategy is deadheading, which involves removing the seed heads as soon as they are fully formed but before the seeds dry out and scatter. Removing the panicles while they are still green ensures that viable seeds are contained. Birds are highly attracted to mature seeds and can inadvertently spread them, making timely removal essential.
Removed stalks and seed heads should not be placed in a home compost pile. The seeds are hardy and can survive the composting process, leading to unexpected sprouting. Instead, the material should be bagged and disposed of as yard waste or allowed to dry completely in a controlled area away from garden beds.
Cultural Practices
For gardeners growing broom corn in large quantities, rotating the crop’s location each year helps mitigate the volunteer problem. Moving the planting area prevents a buildup of seeds in one spot. Consistent, shallow cultivation of the soil surface in the autumn and early spring can also disrupt and destroy newly germinating seedlings before they become established.