Is It a Weed?

Green Antelope Horn Milkweed (Asclepias viridis) is an important plant for the Monarch Butterfly.  The Monarchs reproduce in the southern U.S. in late summer when the plant is tough.  The problem is that they prefer tender leaves which provide food for the caterpillar stage.

Many ranchers see the Milkweed as just that -- a weed.  It is often targeted along with other weeds that compete with the grasses for grazing.  In many areas, although the Antelope Horn is a perennial, their presence is declining due to the use of herbicides for the control of all non-grass species growing in pastures.

For those ranchers who utilize mechanical means, such as mowing to control pasture weeds, the Antelope Horn and Monarchs can benefit.  Mow in July so that there will be new, fresh growth of the Antelope Horn in August when the Monarchs arrive and are looking for places to reproduce.

Any plant can be considered a weed.  The definition of a weed is any plant growing where it is not wanted.  Competition between plants for limited resources is a critical issue for ranches -- especially during drought conditions.

The way ranchers choose to control weeds is generally an economic decision.  Often, chemical means are the most effective and the most cost effective.  Many weeds are a sign of overgrazing.  They colonize where the grasses have died due to drought and inadequate leaf cover -- not enough left standing.  Without the standing forage, the heat and drought conditions can kill the roots, creating bare areas.  When the rains come, forbs -- weeds mostly -- are the first plants to return.  Reducing weeds allows more grass to be produced.  It is something of a balancing act that requires careful attention to maintain soil health and a healthy balance of the plants growing.  Those factors then determine the level of grazing that can be healthily maintained.

When you add the desire to retain habitat for species such as the Monarch Butterflies, the equation becomes more complex.  Despite the bad reputation they often receive, most ranchers wish to see nature thrive and work to maintain healthy land and pastures.  For those who have areas where the Antelope Horn is established, they can use mechanical means only for weed control while utilizing the more effective chemical means in places that don't contain critical species.  Summer mowing would open the canopy for late season growth while stimulating re-growth of the milkweed prior to the needs of the butterflies.