Cool-season perennial grasses like tall fescue, orchardgrass and bluegrass are very important in many pasture systems. Each of these grasses only produces seedheads during the spring, and managing to prevent those seedheads from reaching maturity will improve the quality of the pasture during late spring and summer, and will be a critical first step in toxic tall fescue pasture renovation.
When cool-season perennial pastures green up in spring there are two populations of tillers present. (A tiller is the individual part of each plant that comes from the crown and contains a growing point that pushes up leaf growth.) The older tillers will be destined to make a seedhead (called reproductive tillers), while younger tillers will not make a seedhead until the following year (called vegetative tillers). Vegetative tillers continuously develop from the crown. The flowering tillers start to elongate as the seedhead develops (the boot stage), and eventually the heads emerge. Once the head starts to flower and set seed, the nutritive value of the seedhead declines rapidly. During this stage the vegetative tillers are suppressed by shade and also by hormones released by the flowering tillers.
Removing the flowering tillers early will release the vegetative tillers to make additional growth. It will also favor lower growing species like white clover. The collective effect will provide much better quality grazing during the rest of the year. Removing the seedheads will also prevent mature seed from developing which can be an irritant to the eyes of grazing cattle, and also will result in potential reseeding which is undesirable in some situations. In the case of infected tall fescue, toxins are concentrated in the seedheads, so removing seedheads is one of the most important practices to reduce fescue toxicosis.
There are several ways we can control the development of the seedheads in cool season perennial grasses. Clipping pasture is the most common approach. While clipping is effective if done early, often the seedheads are allowed to mature too long, resulting in mature seed. Also, the resulting cut stems are sharp and can impede grazing if clipping is too high. Often clipping is done at about 12 inches to avoid cutting “available forage”. Unfortunately, this leaves a lot of low quality forage and is the perfect height for those sharp stems to poke a cow in the eye, potentially leading to pinkeye. If you control seedheads by clipping then do it before seeds mature and at a short enough height to remove much of the stems. Subsequent grazing cycles will tend to be to that clipper height, which ideally would be 4 to 6 inches.
Cutting hay at the boot or early flower stage is a good way to remove seedheads. Hay should be cut early enough such that vegetative tillers and other species have plenty of time to grow before hot summer weather develops. The traditional practice of allowing hay to “ripen” is still too common, and when weather turns hot and dry these late cut stands provide little regrowth because vegetative tillers will be small and inactive and easily dried out, and other plants present are accustomed to heavy shade that is abruptly removed..
Sun curing for hay will also reduce toxin levels in toxic tall fescue, so that is another advantage of hay on farms dominated by Kentucky-31 toxic tall fescue. Be aware that baleage/haylage from toxic tall fescue will be more toxic than hay made from the same forage due to limited exposure to UV light. Also, if you make your own hay, cutting before mature seed is present will help you prevent moving toxic tall fescue into novel endophyte stands, or stands of other non-toxic forages.
In the case of tall fescue the herbicide metsulfuron suppresses seedheads when applied in the boot stage. Metsulfuron is an active ingredient in Chaparral and Cimarron, and both will control seedheads. The herbicides kills the reproductive tillers, while vegetative tillers are only slightly suppressed. We did demonstration with this approach several years ago, and when application was during the boot stage or earlier seedheads were effectively suppressed, forage quality was higher, and toxin levels were reduced. Suppressing fescue seedheads also releases other cool-season forages like orchardgrass and bluegrass that may be in the stand and which are not impacted by metsulfuron.
Traditionally, cattle have been turned out to pasture once plants are about 6 inches or higher. Whether in a rotational or continuous grazing system this practice means that most of the pasture is grazed later than optimal, resulting in a lot of seedheads and need to clip. Turning cattle out earlier, as soon as tillers start to elongate and moving fast the first cycle in a rotational system can effectively control seedheads. When in the boot stage animals very readily graze them off, resulting in effective seedhead control. The key to this practice is to move animals fast enough to prevent close grazing of vegetative tillers. This practice has a “sweet spot” of about 2 weeks when most of the growing points are elevated, but seedheads are still palatable enough to be readily consumed.
Another traditional practice is to allow cool season pastures to mature so they can reseed themselves. While it may be desirable to do this (rarely) when pastures are thin and most plants are desirable, it often also allows weeds, toxic tall fescue, and other undesirable plants to make seed and build up in the pasture. At some point a complete pasture renovation (removing the old stand and replacing with improved forages) is beneficial when pastures are thin.
If you do plan to renovate pasture this season you should make effort to reduce all kinds of mature seeds produced on the pasture in the year prior to renovation. This is critical when converting from toxic tall fescue to novel endophyte tall fescue, but is also a good policy to reduce weeds and other non-seeded species in any new stand.
Completely preventing mature seed for renovation of toxic fescue pastures will likely require two clippings, or a combination of hay and clipping, metsulfuron and clipping, or early grazing and clipping. In most cases a single one of these practices will improve quality of pasture as described earlier, but none will be by itself control seed production adequately in preparation for renovation projects.
Doing your best to control seedheads through combining the tools of rapid rotational grazing, early hay production and herbicide suppression will improve forage quality. Preventing mature seedheads will also reduce symptoms of fescue toxicosis and is a critical step in preparing pasture for pasture renovation with non-toxic forages. How will you control seedheads this year?
~ Matt Poore for Amazing Grazing, Carolina Cattle Connection. This is a preview of an article written for the Amazing Grazing Column in the Carolina Cattle Connection and appears here with permission of the Carolina Cattle Connection
The Alliance for Grassland Renewal is a national organization focused on enhancing the appropriate adoption of novel endophyte tall fescue technology through education, incentives, self-regulation and promotion. For more resources or to learn more about the Alliance for Grassland Renewal, go to www.grasslandrenewal.org