– Mark VanGessel, Extension Weed Specialist; firstname.lastname@example.org
I have gotten a few phone calls about both Grape hyacinth and Star of Bethlehem. For those not familiar with these species, they are both perennial weeds that have long, narrow, fleshy leaves. They both form numerous underground bulbs. Star of Bethlehem is in the lily plant family while grape hyacinth is in the asparagus family. While both are present in fields this time of year, Star of Bethlehem emerges in the spring and then produces white flowers. Star of Bethlehem leaves have a faint white stripe that runs the length of the leaf. Grape hyacinth emerges in the fall, over winters and then produces purple flowers in the spring. Both species flower in the spring and then die back quickly but they can impact planting of summer crops if they have high infestation levels. They can also interfere with the growth of small grains and forages. Grape hyacinth will also interfere with soybean harvest in the fall because the leaves can get up to 8 to 10 inches tall and if the infestation is severe, the waxy succulent leaves will interfere with the cutter bar.
Management of these two species is very different.
Star of Bethlehem leaf with faint white stripe
Star of Bethlehem flowers
Flowering grape hyacinth
Star of Bethlehem Control. In a field study, Star of Bethlehem was sprayed in the early spring and both Aim at 1.5 fl oz and Gramoxone at 2 qts were excellent for “burning down” emerged Star of Bethlehem. Glyphosate teatments at rates of 1.5 or 1.9 lbs ae/A [48 or 57 fl oz of Touchdown Total] were not effective. When rated the following spring (one year after treatment), Gramoxone treated plots had 93% Star of Bethlehem control, whereas two applications of glyphosate at 1.9 lbs ae each application provided 77% control and Aim did not reduce spring emergence the following year.
Grape Hyacinth Control. We conducted a trial a few years ago with funding from the Delaware Soybean Board. Glyphosate was applied at two rates (1.0 and 1.5 lb ae/A or sequential applications of 1.5 lb ae of glyphosate. Treatments were made either April 10 or May 2, 2014. When evaluated shortly after soybean planting, treatments applied April 10 showed better control than treatments applied May 2. However, with later ratings these differences were not observed. When rated in the fall and one year after treatments, no treatment was highly effective. The best treatment was two applications of glyphosate at a rate of 1.5 lb ae/A.
In a separate trial conducted by Dr. Flessner at Virginia Tech, they examined a single application of glyphosate, paraquat, and glyphosate plus dicamba. However, they did not include sequential treatments of glyphosate. The found similar levels of control with all three treatments, when rated at soybean planting and in the fall.
Management of this weed is going to require diligent efforts to achieve long-term control. While a single application of glyphosate or paraquat can burn down grape hyacinth prior to soybean planting, it had limited impact in the fall or one year after application.
There is on-going research on management of this species.