The Mulch Chronicles- Part 1

I’ve said it before and I’m sure I’ll say it again but part of why I farm is the desire to experiment!

Weed pressure is very high on my farm so I have to have a solid system for controlling weeds. And preferably one that doesn’t require a ton of time either!

I began planting my dahlias the same old way this year but I knew in my gut that I wasn’t happy with it. I began researching, talking to other farmers, and just generally thinking about the process. The longer I farm, the more I question everything I do. There’s so much labor that goes into growing that I’m constantly looking for innovations and refinement.

So today begins a multi-part series on mulch! (Didn’t think I’d find enough to say about mulch for several posts but with everything that’s been on my mind- I don’t think it’ll be a problem)

So before we get to what I’m experimenting with- let’s take a look at where I started.

I wish I had a picture from the summer of 2018. But maybe I can describe it: mid July, 90+ degrees everyday, full sun, sweat dripping everywhere. I’m staring at a bed of weeds so high that you wouldn’t know there were dahlias growing in there unless I told you. This is what my dahlia field looked like!

I’m pretty sure I lost it several times that year. This is when I began thinking about planting in black fabric mulch. (I did have the dahlias mulched with wood chips— but as you see above- it didn’t work) Over the winter, I began burning holes into black fabric mulch for each dahlia bed. I had resisted the black fabric growing trend for years because I had a lot of reservations about it. But I was desperate!

These raised beds are 4x16 and each bed holds 64 plants at 1’ spacing. And up until this past week- this is the system I’ve used. And it worked reasonably well —until last year.

Last year’s weather showed a lot of the downsides to black fabric mulch. The things I feared began to come true! The extreme heat and drought we faced didn’t interface well with the black fabric. I lost hundreds of tubers that basically just burnt up in the ground.

I had to pull out all my tricks to cool the field down- overhead watering during the day. We also used Surround crop protectant (this is a kaolin clay based spray that is used by a lot of organic fruit farmers). The Surround spray is white so it not only protects your crop but also reflects light. We sprayed the fabric and the plants.

This picture is from late June of 2022. As you can see, you have to keep spraying as the plants grow. Also a lot of rain will wash it off (but it will last through some rain- just depends on how much). Also once your plants begin to bud you have to discontinue use because nobody wants a white chalky stem! But it helped get me to the point where the plants where big enough to shade the fabric.

Now do I think black fabric is a bad idea for hot climate growers? Well— it all depends. If you are a more extreme hot climate (zone 8 plus), then it’s probably not going to be the right thing for you. But I’m a zone 7b and I run this kind of weird borderline. Things that work for cool climates can sometimes work here as well as the really hot climate methods too.

I do think that if you plant early enough in spring to get a thick plant canopy over your fabric that this system could work well for a hot climate grower. But I don’t like planting super early because I don’t want blooms in July. I will say that the black fabric does a fantastic job at keeping the weeds down. We usually make one weeding pass through the field when the plants are around 18” tall and that’s about it for the season.

But after last years extreme heat and drought, I knew I had to find another way.

I’m experimenting with 2 methods this year: straw mulch and cover crop mulch. We’ll talk about straw first (cover crop mulch is part 2)

So why haven’t I tried straw before? It does seem like the obvious choice. Well I did try it - many years ago and not long after laying it down, I had a nice crop of green grass growing under my plants. I soon discovered there wasn’t a clean weed free source of straw locally to me.

I mentioned this to my grower friend, Lori (of Broad River Blooms). She, being the generous person that she is, shared with me her straw source.

For my local friends, you can order this through Tractor Supply stores, possibly Lowe’s too. It’s an extremely fine milled straw. It makes a very dense mat over the soil. It also has a tackifier that keeps the straw together and helps prevent washing away.

I decided at first I would try it on one bed. I put it down about 2 weeks ago and began keeping tabs on that bed. Watching for weeds (too soon to tell on that part) but also checking moisture levels. The black fabric tended to get so hot that the soil was drying out underneath it. After a few days (with no rain and only 1 run of the irrigation system), I did a moisture check. It was still moist underneath the mulch. The bed next to it with black fabric was bone dry!

Since this picture was taken, the dahlias have begun to poke through. We have also had a heavy rain— the straw stayed in place! Now we wait to see if it keeps the weeds down after all that rain.
(BTW- I’ve figured that one bale will cover at least 2 4x16 beds).

Another thing to think about when using any type of mulch while growing dahlias is removal. If you dig your tubers in the fall, you must think about how the mulch will affect that process. The straw seems easy to handle. If it’s too thick, we will rake it off the bed. With the fabric mulch, we had to be very careful pulling it off to make sure we didn’t knock the labeling tags off our plants.

Another bonus to using a natural mulch is that it will break down and add organic matter to the soil over time.

The only cons I’ve thought of for the straw mulch so far are — expense. The black fabric is reusable so it’s a one time expense. But I’ve done the math and the straw is still affordable within my crop projections. Second, there is always a risk of residual herbicide when bringing something like this into your farm. I do feel better about buying this brand rather than sourcing straight bales. I know that straw bales are often purchased from many sources and therefore there is less control over what gets sprayed on the grass before it’s cut.

Over the next week, I am going to be removing the fabric from the beds we’ve already planted and adding the straw mulch. The tubers are just beginning to sprout so if I do it now, I won’t damage the plants.

I really hope the straw keeps the weeds down because if not, it’s going to be a lot to keep weeded!

Next time— using cover crops as mulch. Let’s just say this is where it gets interesting (and a bit creative)!