How can I control weeds?
Although weeds grow throughout the year, the ones that are most attention-grabbing are those that pop up quickly, usually in late winter/early spring and later summer/early fall.
Most of these are annual weeds, whose seeds germinate in response to environmental conditions. These types of weeds would be very easy to control with a pre-emergent herbicide, except that it’s so hard to time the application with unpredictable weather.
As the name implies, these products keep seeds from germinating, so by the time you see the weed, it’s much too late. Even an organic pre-emergent such as corn gluten meal just ends up fertilizing the weeds and making them stronger, if not timed appropriately.
No need to use products: annual weeds are best pulled, or just mowed over, before they flower and produce the next generation. If the weeds are in your lawn, you’ll need to encourage the lawn to grow more densely into the spots where the weeds were, which will limit errant seeds from sprouting when they blow in from around the neighborhood.
You might have also heard about using horticultural grade vinegar as an organic herbicide, but that only kills the top, not the roots, so still, it’s much better to pull weeds, if at all possible.
Be careful when purchasing bulk top soil, which will invariably contain weed seeds. If tilling an area, you may turn up a bank of old weed seeds that would then germinate, but also, that nice, soft soil makes it very easy for newly-blown-in seeds to sprout. Just keep an eye out on newly tilled areas, and run the hoe across any weed seeds that sprout. When young and tender, all you need to do is disturb them slightly to keep them from continuing to grow.
Note: many gardeners and urban farmers no longer till to avoid bringing up a weed seed bank or harming earthworms.