Pros and Cons of Weed Barrier

Please excuse me if there is a posting or series of posting on this topic.  

I have put together 3 each, 4 ft X 6 ft raised boxes comprised of 7.25" cedar that I have treated with cedar oil.  They are spaced out on my former corn plot.  I put them there after 3 years of battling weeds and, this year, not getting enough corn seeds to germinate.  Normally the corn would sprout just fine but not this year, the weeds sure did like it this year.  Not sure why the corn did such a poor job of sprouting this year but we did have a very wet and cold spring/early summer in the Denver, CO area.  I put the best quality weed barrier I could get from Lowes over the soil after removing the weeds/corn and leveling the plot.  I then put the raised box frames on top of this.  My plan is to have three succession plantings of corn where I can put something over the top to give a greenhouse effect and be able to plant early in May. Plus have a much more weed control situation.

I am ready to start making my Mel's Mix.  I have the vermiculite, peat moss and 5 different kinds of compost, enough for three boxes, 6 in deep.  Before I do this my question is about using the weed barrier in case the advice I get is to not have the weed barrier and I can still cut it out in the bottom of the boxes.  

Questions are:
1) Is 6 inches  of Mel's Mix enough to plant corn in?  Does it matter if it is early or late corn?  Early doesn't get as tall but late can get pretty tall.  I've seen where people put chicken wire or netting around the corn plot to give it some stability when the plants are tall.  Comments?

2) Will the roots of corn be stunted by the weed barrier?  I don't think so, it seems that in the past when I pulled the corn plants up at the end of the season the roots I saw were about 4 inches deep.

3) Should I just remove the weed barrier under the boxes?  The soil under the boxes is really good and if the weed barrier is a problem and weeds won't grow up through the 6 inches of Mel's Mix I can remove the weed barrier in this area and allow any roots that need to go deeper to do that.  

My research has turned up conflicting answers on all of the above so if there is advice from the official SFG website I will listen or read whatever anybody has to say.

Thanks in advance.
Mark

I agree with Ohio Gardner.  I always start new beds with cardboard between the soil and mel's mix.  After 1 season it will have decomposed mostly.  This will not work if you have invasive weeds that will come back no matter what you do.

Hi, Mark,  As a Certified Instructor I have to encourage you to use weed fabric as outlined in the 3rd Edition of ALL NEW Square Foot Gardening, pages 61, 81 and 142.  Page 81 deals with using weed barrier topped with wood chips to keep the weeds at bay from the surrounding area.  If there are common weed seeds in your soil, it will help prevent them from germinating and coming up into the bed.  However, the roots from your garden plants can go through the weed fabric, as it is weed barrier, not root barrier.  Conversely, roots from neighboring plants can come up through the weed fabric as they love the Mel's Mix.  That happened to me, so all of my beds are now off the ground with plywood bottoms and filled with 6-7" of Mel's Mix.

1.  Yes, corn will grow in 6" of MM.  I find that the level drops rather quickly in the summer (microbes breaking down the composts) so I would recommend top dressing with more compost as needed to keep the level up.  Yes, some folks do add something around the bed to help keep the corn upright.  I have used both nylon trellis mesh and chicken wire with posts.

2.  No, the roots will not be stunted.  Roots grow in order to access nutrients and water, which are provided in the 6" of MM.

3.  I have to vote no.  Leave the barrier so that when you pull out your garden, deeper seeds will NOT be pulled up into the MM.  Some folks use cardboard under the beds and / or in the isles.

PS  We love photos!  Hint.

Thanks, Sanderson, for answering my questions. I will take photos as I go and post them. What part of the US are you located?

Regarding corn, any comments or advice on corn varieties? I’ve had good success with 70ish day corn but wanted to try 90ish day corn this year.

Sanderson, I see you are in a warmer climate than me once I access the forum on my laptop.  The next question I have is regarding the details of corn planting in a square foot box.  The questions are as follows:

1) Mel's book (I have the book with a publish date of 2018, pages you reference are slightly different) states most corn is planted 4 per square foot.  Question I have is this in general for the shorter or early maturing varieties that don't grow as tall?  Some of the research I have done indicates if you plant a later maturing or taller stalk variety you may want to plant as few as threw oe two or one per square foot.

2) He also states (on page 224 in my book) to plant presoaked seeds.  Can you expand on this?  How long do you presoak the seeds?

BTW, all my corn planting will happen late spring of 2020, we are too far into the summer in the Denver area .

Thanks again!
Mark

Trying to grow longer season corn in our climate is going to require a few tricks.  I would use weed barrier, but not under the beds. Perennial weeds grow right through it and you are not worried about annual weeds down there. In early spring cover your corn beds with black weed cloth, that will keep weeds from sprouting and warm the soil for the corn.  Cut holes in the cloth to plant your corn seed through.  Use row covers to cover the beds at night and for those late cold snaps that always happen.  I would ask Yolo about spacing with longer season varieties, she seems to have the highest success rate growing corn year after year on this forum.

Good luck.
Turan

Mark, Turan is in your area and Yolos is the corn queen. Between the 2 you should be able to get a handle on your corn growing next year.

1. I have only planted Silver Queen and Gem and those at 4/sq ft. I've never soaked the corn seeds. I do soak bean seeds for 30 minutes while I prep the beds.

Okay, so..... the advice I got recently is exactly what I was talking about in regards to confusion on weed barrier advice.  Some people say yes on the weed barrier, others say no.  I already have the weed barrier laid down underneath the raised box frame so I am going to leave it if it is not problem for rooting of the corn.  Can anyone definitively say that weed barrier is a problem for underlaying corn beds?  

Turan, I like the idea of laying it down on top of the MM in the spring to warm the soil up and prevent wind blown seeds from germinating then poking holes to put the corn seed in to the soil.  I have extra weed barrier left over I can use for that.

Turan, the perennial weeds are a problem but the biggest problem was a wind blown seed, purslane, that is still sprouting, even in my gravel bed surrounding my earth boxes and three other conventional raised beds.  This weed just exploded this year so it is a battle to keep it under control.

OhioGardner, thanks for the thread. That gives me food for thought.