2026 June 7 Yellow and White Sweet Clover Control

I have tremendous respect for Yellow Sweet Clover and White Sweet Clover (Melilotus officinalis and Melilotus alba) which I first met in 2020 after a new street tree was planted in my tree lawn by the city. Even though they are not native, I typically leave clovers that appear in my garden. They usually stay low to the ground, have pretty blooms for pollinators and they fix nitrogen in the soil. I see them as a living mulch. Even when they are cut back, they continue to help soil structure and prevent erosion. 

The Yellow Sweet Clover is front and center in this photo. You can see the common Red (pink) Clover Trifolium pratense is much shorter in the foreground and background. This is likely a first year plant that will not bloom until next year. I’m going to cut it back to the ground both this year and next year to prevent blooming and seed production.

At first, I left the plants be, but their growth habit was much different than the small white and pink (red) clovers I was used to. The stems grew tall and woody fast. These clovers were my height by June and had many pretty bright flowers. Looking back, I wish I had cut them back that first year. 

Typically, I don’t worry about annual or biennial plants like these because they live out their life cycle in a couple of years. However, Yellow and White Sweet Clovers produce between 35,000 and 100,000 per plant and the hard seeds are viable for 20 to 40 years. Their height and strong stems easily outcompete native plants. My tree lawn was just a patch of  sweetclover after one growing season. 

It is hard to decipher this dense patch of Sweet Clover in the photo because it has not bloomed yet. This was a good time to cut the clover back, but it would have been even better a week or two ago when the stems had not become woody yet.

Timing is everything if you any to control the population of White and Yellow Sweet Clover. Some farmers have found that they make good grazing for livestock, but that must be done early before the stems become woody and the plant becomes bitter. Attempts to eradicate this invasive species must always be done before flowering. Pulling or cutting before they flower is definitely an option. Controlled burns can also keep the population in check. Here is some more information on controlling the plant.

At work, a newly planted native site was becoming covered in Sweet Clover. This makes sense because the soil was disturbed in construction. This week we attacked it with machetes and shears. Unfortunately, some of the stems had already become too woody for machetes, so cutting it back with shears seemed to be the best move. We decided to leave the cut plants on site as mulch. Mechanical control is important in this case because the plant is still beneficial to the soil when it is cut. The nitrogen stays fixed in the soil and the soil structure is not impacted. Chemical control might work too, but why waste the opportunity to improve the soil?

As sweet clover is cut, a strong vainilla smell comes forth. At home, I harvest this plant, bundle it and dry it. It makes a wonderful incense similar to Sweetgrass Hierochloe odorata. To me, it’s a special plant that helps heal disturbed soils, so I consider the cutback a “harvest” not an eradication. 

Also, just for the record, I believe Ohio does have two species of native clover: Round Headed Bush Clover Lezpedeza capitata and Buffalo Clover Trifolium reflexum. I’m thinking if the space wants clover…maybe we should be planting those varieties here.