How Fast do Weeds Grow?

My garden is living proof that plants need food, water and sunshine to grow. I provided water and fertilizer but the backyard was sunny for only a part of the day. This year, we moved the garden to the side of the house and WOW! It turns out a lot more sun spurs a lot more growth. Our plants are doing well. Unfortunately, so are the weeds. Which makes me wonder, why do weeks seem to grow so quickly?

“Actually weeds don’t grow faster than other plants, weeds just time things a lot better,” said Steve Bowe, a group leader in Biology Research and Development at BASF told me.

Consider the carrot, which we tried to grow in our garden. The seed package says carrots will germinate in around 20 days. You can assume if growing conditions are perfect it may be a few days faster. If conditions are less than ideal, germination may take a few additional days. Whatever the case, weeds such as chickweed and pigweed take advantage of that.

The weeds sprout in a few days and by the time the last carrot has sprouted, the weeds will have bloomed and seeded. It can happen so quickly that the initially slow growing carrot has no chance and it completely smothered. There’s one more challenge for the carrot. The weeds produce enormous amounts of seeds, which sprout on the surface and can grow in a wider range of conditions. It’s another reason the carrot doesn’t stand a chance.

So what is a poor gardener to do? Farmers rely on herbicides, which doesn’t make sense for a home garden. BASF’s Steve Bowe advises hoeing the top one to two centimeters of soil. There’s no reason to go deeper and risk damaging the roots of your crop. Hoeing the very top of the soil means what has sprouted already will dry out, and the loose and dry top layer will stop other seeds from sprouting. It also should slow the evaporation of water from the soil. Less evaporation means higher soil temperature, and thus faster growth of your favorite vegetables.

—Frank Graff 

Frank Graff is a producer/reporter with UNC-TV, focusing on Sci NC, a weekly science series. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!

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