I'll be planting several hundred iris rhizomes in 2021 as I plan to launch a commercial iris business in the next two or three years. One of my greatest concerns is weed and grass control in my iris rows. Mostly, the time required to stay ahead of annual and perennial weeds.

I have planted winter rye as a winter cover crop on the ground I'll be planting this year. I'll turn that in later this Spring, then plant a follow up cover crop of brassica (mustard). I'll turn the mustard under before it goes to seed.

At that point I intend to build slightly raised beds, 30" wide by 50' long. I'll install drip irrigation on those raised beds and cover them with 2 mil. clear plastic to solarize the soil for six to eight weeks before the rhizomes begin to arrive for planting. This drip irrigation, under the plastic, should allow me to keep the soil sufficiently moist for the solarization to work and the brassica should provide a bit of fumigation as well.

I hope this will reduce the viable weed bank but I still want to find a way to minimize hand weeding. That means either a pre-emergent, applied immediately after planting the rhizomes, or some kind of over-the-top post-emergent herbicide.

My soil is a loamy sand. Excellent for irises. I'm located on 40 acres in a very isolated area. Nearest neighbors are five miles or more away. Also, a very dry climate. No risk of contamination by run-off.

What pre-emergents or post emergents have you used on your irises? What kind of results have you experienced?

Thank you for your time!

Sincerely,

Randy Smith
Southwest Kansas
Zone 5

Ronstar and Snapshot seem to be popular among commercial iris growers, however nothing keeps all of the weeds from growing, so they are used in combination with hand weeding.

We just have trouble with pasture grass so use Grass Be Gon. But then we don't have commercial beds. Talk to people in your area about weeds in general & perhaps write to other commercial gardeners.

Tom, Lucy,

Thank you both!

The ground I'll be planting in has been in native grasses for at least 30 years, probably much longer. So, weedy grasses are a concern along with Russian thistle and ragweed. I'm hoping the solarization will help.

And I do realize some hand weeding will be required. Just hoping to minimize that as much as possible.

Thanks again!

Randy

If I remember right, somewhere on one of these threads someone wrote what Superstition Iris Gardens does with there cover crops. I think this was a few years ago. You might try contacting Superstition also.

I use Preen on my iris beds. It has to be re-applied every three months, but really does a good job keeping down the weeds. A little hand weeding is still required, but not much.

You must read the label on pre-emergents with special note to make sure read what weeds that particular brand "gets". If a weed you particular want to get isn't on the list, in all likelihood that brand probably will be of little use. Please note these are pre-emergents. They work on killing weeds as they start germinating and useless against weeds that are already growing.

Also after a few years of using the same brand which "worked" but new varieties of weeds start taking over which are not being "killed" by the brand you have been using. Now without competion the "new" weeds take over. That is why every few years you have to change brands to get your new enemy weed (s).

We used Ronstar that worked to get perlwart (a moss like grower, which is strangely a member of the carnation family). And then a few years ago a new weed began taking over. It was identified as mossy pygmyweed, (strangely a member of the jade plant family which allows it to multiply quick both by the leaves rooting and the plentiful seed it produces). We have turned to Freehand which has been effective against the pgymyweed and every other weed that has been a problem here (for now).

iciris, Thank you! I will contact Superstition.

AndreaD and JosephGhio, Thank you for your input!

This first year's bed will be 50' x 65' so might be good to experiment with a couple of different options, each on 1/2 of the planting. Also, good advice about rotating choices to catch 'new' weeds or avoid developing 'resistant' weeds.

I did find this about weeds:

Boxergirl said:I finally got my new weed preventer!! thanks to Rick at superstition for this suggestion of product. I'm praying this is going to work miracles like he says it does for him! Does anyone else use this?

Here is the post I was talking about above:

Moiris said:Since I wanted to know I re-read Rick & Roger's posts on Facebook about Superstition's iris culture practices, which are very unique. Carl gave the basics...here is more detail, with thanks to Roger Duncan who answered my questions with detailed information.

They transplant all their irises in September/early October into newly prepared beds.
The bed preparation begins with breaking the old bed down (after moving the irises to the new bed) via rototilling, then planting a cover crop in late October/early November. The cover crop mix is about 40% oats, 40% wheat, 10% vetch, and 10% other grains (barley, rye, etc) that becomes the 'green manure' when cut down and tilled in.

They plant the cover crop in late October or early November and irrigate it with sprinklers. They found that if they waited for the rainy season to start there was too much competition with the local migrating birds (redwing blackbirds and meadowlarks) who like to eat the seeds. The cover crop germinates in a couple of weeks and the grains grow slowly over the winter, then in late winter, the vetch germinates and twines up the grain stalks. Early next Spring when the soil is dry enough for the big tractor to get into the field, they get it cut with a flail mower and tilled in. At that time, the cover crop can be anywhere from 3 to 4 feet high. That is usually mid to late March or early April but has been as late as May in wet seasons. Makes no difference if the grains have formed seed heads because the solarizing will kill the seeds.

After the cover crop has been tilled in, they occasionally water the area to help it break down in the soil, then after a month or so they form the beds which are slightly raised with drainage ditches on both sides and down the middle of each 2-bed set-up so the rain flows away from the beds without causing damage. Then in late May or early June they put the plastic down to solarize. The plastic is actually greenhouse film with UV-inhibitors built in and is somewhat costly. Regular construction grade plastic would break down in a few weeks under the intense unrelenting blazing wall-to-wall every day California sun and 100-degree plus summer temps. In our climate Roger says solarizing gives the full effect in only 2 weeks if DONE RIGHT, but they leave the plastic on through the busy summer order filling season and then uncover the beds when they are ready to transplant in September and early October.

And so goes the cycle...transplant irises, till, plant cover crop , till, solarize, uncover, plant irises. In this way they use half of the ground for growing the current year's iris crop while the other half of the ground is being rejuvenated by the cover crop and solarizing for the following year.

BTW, only the commercial beds get solarized, the seedling beds get the cover crop, but no solarizing. They say it isn't fair to properly evaluate seedlings grown under totally perfect conditions, thus those beds don't get solarized. They started this cover cropping/solarization method about 20 years or so ago and they originally followed a University of California study, but have added some minor tweaks along the way. Not organic, but much better for the environment using mainly the sun and water and hardly any chemicals.

Warning label: this process works wonderfully in our Central California climate, but may not work as well or even at all in other climates.

Excellent! Thank you iciris! That saves me from bothering them at Superstition.

I did a bit of research on Weed Impede. Found it on domyown.com website.

It's the same active ingredient as Surflan.

Based on what I've learned here I'm going to test two products, Weed Impede (Surflan) and Snapshot.

Preen is 1.47% Trifluralin. Snapshot is 2% Trifluralin plus Isoxaben.

I'll see if one is more effective in my soil, on my specific weeds, than the other. If they both perform comparably I'll be able to use them in rotation.

Thank you Everyone!

Randy

iciris, it appears you posted the full Superstition "story" just before I posted my last reply.

Thank you for that! I actually planted winter rye last year and plan to follow up with mustard (brassica) before roto-tilling the mustard in. I then planned to build slightly raised beds, install drip irrigation and plastic to solarize. My understanding is that the mustard will provide a "natural fumigant" under the plastic.

This is incredibly helpful. It confirms my plans aren't too "radical" and just might work.

Can't tell you how much I appreciate you tracking that down! Thank you, thank you!!

Randy

You're more than welcome, best of luck with your business.

iciris (and moiris): Thanks for posting the details about the cover crops. I would guess the vetch is included because it fixes nitrogen, which the previous iris crop would have depleted from the soil. Randy, you might want to consider including some type of legume in your cover crop.

Laurie,

That's a good idea. Irises don't need a lot of nitrogen but my sandy soil is likely deficient and it's difficult to get an accurate nitrogen value when you send in a soil sample.

I've looked at Sunn Hemp in the past. It's a good cover crop for sandy soil and is a nitrogen fixer.

Thank you Laurie!

Randy

I just weed a lot. Nothing else. I like Superstition's procedure.

urania1 said:I just weed a lot.

Good one! You and me both!

IrisLilli said: Good one! You and me both!

Me 3!

me too, but I don't always weed as often as required.

Robin, I'm shocked and horrified!