When Invasives are susceptible

Let's think about how plants grow in general terms:

While in the soil, the roots store energy and keep the plant alive through winter.  Then it starts off slowly, coming up from the soil when it warms.  Then it grows at a steady pace, assuming conditions are not extreme (drought/excessive rain, temps not dramatically cold/hot).
Then the plant begins to produce flowers, and eventually goes on to produce seeds.  This part of the plants life is pretty dramatic.  It takes a lot of energy to complete this.  The root system for this plant is also very structured and strong.

Before I ask the inevitable question of when is the correct time to apply herbicide, let me tell you this:  If the plant is close to seeding out (full mature plant/seeds are almost viable) some plants have the ability to force their seeds out under pressure.  So most of the time, the best time to apply herbicide is when the plant is young and beginning to develop.

Here's an example of the other side of the spectrum:

Specific biennial plants produce a base the first year of roots, stems, and leaves.  The second year this plant flowers and seeds out.  

The mechanical treatment approach to this gets down to the nitty gritty.  In order for a successful kill, you wait until the plant is just about to seed out before you mow/brushcut/weed-whack it down.  You want to take advantage of the expending energy of the plant.  But the timing of this is very crucial.  

If you cut too early, the plant will reemerge smaller, and still produce seeds only a week after you cut it!  This is especially true with white sweet clover.  One mature white sweet clover can produce up to 350,000 seeds!!  So you can imagine what even a tiny plant could still produce.  

Below is an example...

Randy Quaid - Independence Day

Let me explain:

If Randy Quaid flies up to the laser a little too early before the ship gathers up all of its energy to deliver the blow, there wouldn't be much of an explosion, and the ship threat is still there (cut too early, and the plant will reemerge).  

Likewise, and a little more obvious, had he been a little bit late, the laser would have been sent off (350,000 seeds are dropped) and the movie doesn't end on a good note. 

Good thing the timing was perfect!!!!!