Answer: There are several approaches to controlling weeds in a flower garden. Your biggest defense is to remove larger weeds by pulling or digging them root and all, hoeing off smaller weeds just below the soil level, and then mulching.
Use an organic mulch layer several inches thick. This helps keep down weeds, reduces the need for watering, and also helps feed the soil gradually as it breaks down. The mulch should be raked or fluffed periodically to disturb any weed seeds that may blow in and prevent them from growing in the mulch.
If you have constant trouble with weeds coming up thorugh the mulch, you could cover the soil surface with sheets of newspaper (dampen it and overlap the edges), and then top that with the mulch. This excludes light and helps smother the weeds.
Keep in mind that every time you dig or till the soil you are bringing more weed seeds to the surface. If you added organic matter at the start and then use organic mulch every year you should be able to plant without excessive digging or re-tilling.
If you have perennial weeds that return time after time from the root, you need to either grub out the root better or you could use a spot treatment of herbicide containing glyphosate. Read and follow label directions. This is a nonselective herbicide so you may find that the wipe on application method works better than spray in an established flower bed.
If you have any weeds that do come up, cut them off short immediately to weaken their roots. If you have weeds that are about to bloom, deadhead to prevent them setting seed and spreading. Keep in mind also that some weeds will grow quickly in the cool weather of fall, so you may need to take steps in fall as well as spring and summer.
I hope this helps.
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