Question: I’ve been trying to get rid of some grape hyacinths in my shrub bed. I used a weed killer, but they didn’t all die. Then I dug them out, but they came back up this year. I want to try something besides chemicals this time. What can I do?
Grape hyacinths can be challenge. They look lovely in bulb catalogs, and they are, but as many gardeners can tell you, you plant grape hyacinths, you might have them forever. They’re tougher than most weed killers and will show up again and again when you’re sure you’ve dug them all out. The bulbs multiply quickly with tiny bulblets, and those bulblets can break away from their mother bulbs very easily.
Repeated pulling of the grape hyacinths can be effective, but it takes time and persistence. Begin pulling out clumps of grape hyacinth after they appear in the spring. The green tops are still firmly attached to the bulbs while they are fresh and young, but as they age, they will break away easily, leaving the bulbs behind in the soil. Even though you’ll feel you’ve gotten all of them, there will be some bulblets left behind. They’ll sprout, grow and reproduce and you’ll pull some of them the following year.
Have a bucket or other container with you when you pull the plant out and put everything you pull directly into the bucket so that nothing gets dropped back onto the ground on the way to your garbage can. Don’t throw the grape hyacinths into your compost pile.
It can take years of diligent effort, but if you’ll keep pulling them out, you’ll eventually see very few grape hyacinths in your shrub bed.
If you want to try using an herbicide again, the active ingredient glyphosate (Ultra-Kill, Killzall, Roundup) can be effective with repeated application, but just like controlling grape hyacinths by repeated pulling, using an herbicide will take more than one year to see results. Glyphosate isn’t a good choice for grape hyacinth in lawns because it also will kill the grass. You can try a lawn weed killer with multiple active ingredients to control grape hyacinth if they show up in your lawn, but you’ll need to repeat the applications every spring to see new some control. You should not spray lawn weed killers during the heat of summer.
If you don’t want to pull the grape hyacinth or use a conventional herbicide, you can also use a strong vinegar-based spray to repeatedly burn back the foliage. Over time, if you’re persistent you’ll reduce the vigor of the bulbs.