Hi Trant - that surprises me because I have used the same stuff extensively with no problem. I also use grass clippings as they are available. Maybe you got a bad cube?

You could try solarizing it, spread it out 2 inches thick under some black plastic and let it sun for a week and cook the seeds. Or try a different brand.

You don't use black plastic to solarize. You use clear plastic, 6 mill to 8 mill thickness. Black plastic does not raise temperatures nearly as much as clear does.

While I'm sure it's annoying, it shouldn't be too difficult to pull the grass which should come right up, then place it on top of the existing straw.

All straw i not created equal. It also needs to be applied properly by fluffing and then lightly sprinkling, it should never be packed down when you add it to your garden. There can be an issue where there are straw are seeds which might sprout but they're usually very easy to pull and add to your compost pile. It's good to know your source so you know what you're getting.

Hay and Straw Glossary

A popular organic mulch, hay is commonly used to protect soil and plants from the elements, to line pathways, and to address various needs in the garden. What many people don't realize, however, is that various products are often labeled as "hay" at garden centers, but there are many different types of hay and straw that are commonly sold in bales. While they are easily confused, it's important for gardeners to become familiar with the differences.

Salt hay
Salt hay, or Spartina patens, is a grassy plant that grows in salt marshes and wetlands. It is useful for keeping weeds from growing in paths, preventing runoff, and keeping soil from turning into mud whenever it rains or the garden is watered. A layer of salt hay will keep soil moist and encourage worms to come to the surface, which will help to aerate the soil. It also makes an attractive path to walk on between garden rows. Salt hay is an ideal all-purpose mulch because its seeds won't grow away from salt water so it won't germinate in your garden.

Golden straw
What is commonly termed "Golden straw" is either oat straw, Avena, or wheat straw, Triticum. This straw is a by-product of the process of separating oat or wheat seeds from their stalks. Golden straw is often used as bedding in horse stalls; because there are no seeds, the horses won't eat it. This straw spreads nicely, and the lack of seeds means there is no risk of it germinating in your garden. It can be used in the same way as salt hay.

Wheat straw
An excellent choice for straw for use in the vegetable garden. Lay down six inches in height in the fall then direct sow seeds in the spring. No need to dig. There will be a handful of weak sprouts from seeds, just pull them out.

Feed hay
Just as its name implies, feed hay is used to feed livestock. Though inexpensive and plentiful, it is not a good choice for use in gardens because it is full of seeds. The main ingredient of feed hay is alfalfa, Medicago sativa. It also frequently contains flowers and seeds from many other plants and weeds such as clover and golden rod. These seeds are likely to germinate, resulting in a garden full of weeds rather than flowers and vegetables.

Sorry to hear about the weeds, trant, but the mulch IS still helping with other things like soil moisture control and will be a great soil improver for next year's garden. ;)

It's unusual, in my experience, to find weed seeds in straw - hay yes, but straw usually tends to be pretty weed/seed free. Any chance you added some manure to the garden before the straw? It is my main source of weed seeds here.

But like Violet said, once mulched, it is usually much easier to remove the weeds that do pop up - especially if you water first. I just pull back a handful of the mulch, yank out the weeds, and shove the mulch back in place.

Good luck. ;)

Dave

Your "grass seedlings" are more likely oats, barley or wheat.....
I use regular straw from local farmers, but normally it's laid thick enough that they any seeds usually don't even get to germ until fall when the temps are cooler and the straw is breaking down. You can hoe them in then for added OM.

Vera

I've nothing to add, except that I bought a bail of the main(e)ly mulch and have the grass growing in it too! I could've sworn the lady at the nursery said it was treated somehow and was weed/seed free. Maybe just weed free I guess. The ones I've pulled up indeed look like they're sprouting from wheat or oat seeds, they're tan, oval shaped and bisected down the middle.

This is the first garden I've done and figured I gotta mulch with something, and this stuff does seem much better than the options I could find at HD and other nurseries. I was starting to see a real weed problem starting before I mulched, so I figure I'd rather deal with the grass popping up here and there than all the various weeds.

My garden is small though, about 14.5' x 3.5' and at my mother's house since I don't have a yard. I haven't been over in a week so I'm guessing there will be plenty of grass to pull. I've found it's easier to locate the blades by looking across the garden at ground level than it is from above.

I talked to mom the other night, and she said something's eaten my pepper plants, so I guess the grass is now the least of my worries.

I use hay for mulch and have for all the years I've been gardening--over 40. I do make sure when I buy the hay that it's not heavily seeded, but only once have I had any real problems with seeds (the seller lied about the quality).

Yes it's exactly like oat or barley or one of those cereals.

Wow this severe thunderstorm just passed through and even dropped some hail, I am really anxious to see what it did to my garden ! :(