From Idaho to the Dakotas, sprawling over rolling hills and stretching across the flat lands, creeping through timber and dispersed amongst cropland, a sea of lemon yellow laps at the horizons. Since mid-June, the prevalence of sweet clover has been the subject of old timers and youngsters, ranchers and townspeople. Conversations range from questioning haying quality to myths about being a precursor to a tough winter. Montana State University Extension Range Specialist Dr. Jeff Mosley concurred, this is the most abundant the plant has been in over three decades.
“For a good sweet clover year like this, it typically happens when you have a late spring with good moisture and especially if the preceding fall also had good moisture. It takes two years in a row of good late spring moisture,” Dr. Mosley explained.
The legume is a biennial, which means the first year it is in the leaf stage while the flowers and stems come in the second year. Hefty stands like those in the region this year benefit the soil by adding high amounts of nitrogen – as much as 70 pounds of nitrogen can be added to one acre of soil per stand of clover.
“It has a taproot and the taproot and other roots decay rapidly after the plant dies, thus adding organic matter to the soil,” Dr. Mosley said.
Additionally, Dr. Mosley said wildlife benefits greatly from the plant. Mule deer, antelope and elk all find it to be palatable. He said sage grouse, sharp-tailed grouse, Hungarian partridge and pheasants all eat the seeds.
“Sweet clover flowers are attractive to bees and butterflies. Good sweet clover years often result in bumper honey production,” Dr. Mosley added.
Sweet clover can make good feed for cattle as well. Forage quality is comparable to alfalfa, crude protein is at 15 percent in sweet clover versus 18 percent in alfalfa. There are precautions to be aware of when harvesting the crop. Dr. Mosley said while it used to be grown and baled for hay, it’s not very common anymore and said it is particularly important to note the moisture content before baling.
“It is similar in nutritive value to alfalfa, but it can be toxic. There’s a substance in the clover called Coumarin and if it’s in the hay and gets moldy, it converts to a toxic substance called dicoumarin. If you’re putting it up for hay you want to make sure that it’s not too moist; that it’s dry, which is hard because there’s a lot of moisture in that stem,” he explained.
If baling sweet clover into small squares, Dr. Mosley said the moisture should not be greater than 12 percent. Large bales should not be higher than 13-14 percent moisture. Sweet clover typically takes longer to cure than alfalfa since the stems hold so much moisture.
“When cut for hay, prolonged exposure to sunlight causes most of the coumarin to volatilize, consequently cured hay is more palatable than sweet clover for grazing. Because of the woody stems, sweet clover is best cut for hay at the 10 percent bloom stage. Cutting it later results in stemmy, low-quality hay,” he said.
If the hay is stored outside or stacked, the moisture can accumulate in the bottom bales which creates a perfect recipe for dicoumarin. Dr. Mosley warned that this toxic substance can prevent blood clotting inside the animal which causes them to bleed to death internally.
If it is moldy, he said watch the amount fed to cattle. It takes a large amount to be lethal, so rotating it with good hay every other week, or mixing it with good hay, can help prevent toxicity. For bred cows, Dr. Mosley said to quit feeding a month before calving to lower the risk of hemorrhage.
There aren’t typically issues when grazing a stand of sweet clover. The plant is most palatable to livestock during the leaf stage. At this stage, it is possible for animals to bloat, according to Dr. Mosley. On very rare occasions a stand of sweet clover can develop dicourmarin.
“After hail or frost, sometimes, that disturbance can cause the coumarin to turn into dicourmarin. It’s really rare that you can see the affect in terms of mortality, but what can happen is the cows can abort or stillbirth the calves,” he said.
Sweet clover was introduced in the 1800’s from Europe and Asia, so while the plant is technically not native, it has evolved to a naturalized species in many regions. The plant produces seeds that can stay viable in the soil for up to 80 years.
“There’s going to be enough seed produced this year to keep it going for a while,” Dr. Mosley said adding that growth years of this caliber may continue to occur relatively often.
Dr. Mosley quipped that we could see major snowfall in the winter based on a myth he heard about sweet clover.
“Folklore wisdom says that in a good sweet clover year, you can tell the depth of the snow in the coming winter by the height of the sweet clover in the preceding summer. If this is true we better be getting the snow plows ready, because the sweet clover is four feet tall this summer!”BACK