"Shade out weeds" with black plastic. True or False?

Taming the Blackberries

My vision was to cover the "weeds" with cardboard, then add wood chips.  This is what I tell people to do.
​I have done it a hundred times on large and small properties. 

Year 1  These vines were 6 feet deep, that's taller than me! They grow fast! ​ And it wasn't just blackberries, it was ivy too!!  Attempted weed whacking & looking for the ground.   ​**insert laughing emoji here**   Exhausting hand-clearing!

Year 2   Snow suppresses growth, and we get back on the project early in the new year.   

​LOOK, I uncovered some ferns!!
  YAY, Forward Movement!!  

We worked hard to put in some logs for terracing and planted a few shrubs. 

​And then the rains came,
​And the blackberries got a BIG boost.

Year 3   ​One (popular) idea is to use a dark plastic tarp, to prevent photosynthesis which kills the weeds. SO, in the fall we put a giant tarp at the bottom of the slope and it stayed on from October until the next June.  
​My father built greenhouses for a living, so I was skeptical of the tarp idea, ​(plastic with heat=greenhouse).  So, I kept up with the cardboard on the top part of the slope.  Then the leaves fell and the winter came. 

Then early in the year cardboard again, then wood chips to hold the cardboard down. 

Be sure to remove the tape!!

And now to check on the weed suppression tarp method!

Tarp has been on for 8 months.
​

LOOK greenhouse.....
Weeds Exploding!

Many believe that using weed barrier or black plastic will prevent photosynthesis and kill weeds. SO, I tested it.   ​FALSE!

Here's where I covered the ivy in the early spring with cardboard. 

Still fighting all the invasives, but we are also implementing more trees & shrubs.   Progress! 

 Year 4   Every year we start in the early spring with more cardboard - a truckload of it!! Otherwise, all the work from the previous seasons gets nullified, and all the plants & shrubs will get overtaken.  LOOK how it's thriving in year 4!! ​