Bur Clover/Burclover (Medicago minima) Also known as
So what is the difference between the above two, M. minima and M. lupulina, when Medicago polymorpha is also referred to as a Bur Clover? M. polymorpha is more specifically referred to as California Burclover. It also has a different looking hop, or seed pod.
- Medicago minima -------- Medicago lupulina ------ Medicago polymorpha
These weeds are cool season annuals, biennial, and a short lived perennials. Stems are sprawling, flexible branches that eventually grow upward. There are three oblong leaflets on the stem. The center leaflet is born of a short branch, or pediole, of the stem. Attached to the center leaflet are two outside leaflets.
This weed has a roundish flower head, about a 1/2 inch in size, consisting of cluster (up to 50 small yellow flowers) on a separate branch about 1/8 inch long.
This weed gets it's name from the bur that houses one seed only. The bur is a little pod that turns black when mature. Because the pod is sticky it adheres easily to anything, including us. This way the seed can transfer and re-seed.
Bur clover can be found in meadows, roadsides and other poorly maintained soils. It is considered non-competitive and taller vegetation can crowd it out. If this weed has a strong presence it is indicative that soil has fertility problems (see below).
Bur Clover sprouts by seed and creates a shallow taproot that spreads. Because much the weed runs low to the ground grass cutting is usually ineffective. The weed usually grows outward in lengths up to 2 feet wide. If left unmowed this flowering weed is capable of growing upward up to 2 feet tall as well.
Manual removal, whether pulling or hoeing, is possible but usually creates more weeds. Using a propane torch to heat soil and burn weed seeds can be effective and also applying a preemergent in the fall to kill weed seeds before germination helps. If using post-emergents, try a non-selective glyphosate.
Probably the most effective method of extermination would be to understand soil testing methods and check your soil pH. Nitrogen is the biggest factor here. If it is lacking in soil, along with a percentage of phosphorus weeds are highly likely to grow.