Weeds by nature are very resourceful.

Weeds by nature are very resourceful.  This resourcefulness is the reason we call them weeds.  Agronomically, a weed is defined as a plant out of place.  My definition of a weed is any plant you don’t want and is darned hard to kill.  Now that is a weed.
I got on to this topic this morning when I noticed the dandelions that had been blooming out in front of our office last week had gone to seed.  Those fluffy white heads were shedding their little seeds on their parachutes which  were being distributed  down wind to infest some other lawn next spring.  It has been below freezing for much of the last two weeks and yet, here were these dandelions doing there thing just like it was May.  Now that is tough.
Mother Nature has prepared these weeds for their survival under very harsh conditions.  This is why farmers must battle constantly to control the weeds that show up in their crops.  Farmers are fortunate to have herbicides that make it possible to kill weeds without damaging the crop and so is the average consumer.  Without this technology, there would be much less food produced and we would be paying a much larger share of our annual income on food.
However, before we start thinking we have the weed problem whipped, we need to look at some of the things that mother nature has thrown into the mix that makes us vulnerable to attack from the pesky weeds of the world.
First of all, it is just plain expensive to control weeds.  A farmer typically would spend $30 $40 per acre to control all the weeds that need to be controlled and even then may not get the kind of weed control needed.  Most failures are due to weather conditions that rendered a herbicide helpless to control the weeds.  Those factors would include wet weather, dry weather, cold weather, windy weather and other weather affects are the most likely reason for herbicide failure.
One other factor that really isn’t a weather affect is a weed’s ability to develop resistance to a herbicide.  Now this really is one of Mother Nature’s tricks.  Weed populations have a lot of variability in genetics within a species.  This variability means that there is always the possibility that certain individual weeds may have inherited a trait that allows it to get around the control mechanism of any given herbicide.  In the beginning there may be only one or two weeds in the whole field that survives.  However, they are the only two that manages to reproduce and in a few years these weeds could produce a lot of seed so that this resistant weed has taken over the whole field.  This does happen!
Weeds have all kinds of survival strategies and the farmer must be aware of all of these in order to keep them at bay.  So the cold hardy dandelions in front of our office are only the tip of the iceberg, so to speak.  It takes a lot of work and research to stay a step or two ahead of these weed pests.