I want to use a weed killer in my big flower bed. What do you recommend, how much and when do I apply it, before I sow seeds? How long before I can sow my seeds?
The Gardener’s Answer
Hi, Betty: Since you want to sow seeds in your flower bed, using any type of pre-emergent is not an option. These products cannot differentiate between weed seeds and seeds that were intentionally planted. So, this leaves a couple other options for getting rid of existing weeds: you can either spot spray or hand pull. Roundup or any nonselective herbicide with the active ingredient glyphosate will kill the plants, but will also kill existing shrubs/perennials you have in the flower bed. Avoid using this on a windy day and use a piece of cardboard to help block any potential drift. If you want to go the more labor-intensive but earth-friendly route, you can hand pull and then apply corn gluten as a pre-emergent to prevent seeds from germinating. This of course means you cannot plant seeds, but if your goal is to eliminate the weeds in this bed you may have to skip a season of planting seeds to get the weeds under control. If you spot spray with a synthetic herbicide, you take the chance of damaging existing plants and you would still have to dig up the weeds, but you can plant flower seeds one day after you spray according the label on the bottle. If these are vegetable seeds some can be planted three days after, but others, like tomatoes, have a 30-day wait time. As with any chemical, it is important to follow recommended application rates. After you get these weeds under control, make sure to apply a layer of mulch. This will help prevent future weeds from popping up.