“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.
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.
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.
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.
Very true. Also, local plants that you haven't planted have an advantage over anything you bring in, because they are already adapted to the soil conditions and other environmental factors, and they may have established rhizomatic root structures that you might miss while weeding.
The plants we want to grow have usually been bred for traits other than growing fast & in harsh conditions. We want big flowers or big fruit – things that distract the plant from growing and spreading. This means we have to create really good place for them to grow, with lots of water & rich soil – an environment that our rabbit plants will grow twice as well in.
With that out of the way, there's just some plants that grow faster than others. They have deep roots than can pull lots of water out of the ground, they have big leaves to capture lots of sun & they flower quickly, allowing them to spread their seeds far & wide and they're hardy, growing in all sorts of light & soil conditions. They're basically the rabbits of the plant kingdom.
Corn would be a weed if it ended up in a field of soybeans or your rose garden.