By Kathleen Harvey, Owner, Plant Artistry, LLC

It’s time to prepare the flower beds for winter. What materials are best for the soil to prepare it for new plants in the spring? A debate is currently trending about which is better mulch: straw or hay? They may look similar, but they’re actually quite different.

Straw is the stalk of a cereal crop such as oats, barley, wheat, or rye after harvesting has removed the seed heads. Hay refers to grass that has been cut while green, dried, and then made into square or round bales, and is used to feed animals when no fresh grass is available.

So now that you know the difference between straw and hay, which is better for mulching your garden?

Pros and Cons of Straw Mulch

Straw is a terrific insulator. The hollow stems retain air and their chopped light fluffy texture allows for easy spreading. When used in a garden, it also tends to keep a beautiful golden appearance for quite a long time. The surface remains dry even as the lowest layers touching the soil begin to decompose.

However, straw can act as a home to rodents, because of its fluffy texture. It also has a higher tendency to blow away in strong winds. Straw adds bulk to your soil but it adds fewer nutrients back into the soil when it decomposes, and soil borne bacteria tie up the available nitrogen for a longer time. Because straw is fluffier and makes less direct contact with the soil, it takes longer to decompose, which is both a plus and a minus. If you want to add nutrients this is a minus, but it’s a plus if you’re maintaining a walkway. Weeds are more easily able to push through a straw mulch from the bottom due to its fluffy nature, but blown in weeds won’t land in a moist environment so they do not sprout.

Pros and Cons of Hay Mulch

Hay is readily available and it’s possible to cut your own if you have a grassy area on your property. Just cut it, let it dry, and then fork it over to where it’s needed. Even long grass clippings can function the same way as hay because they’re essentially the same thing. Hay left over from a previous year is often considered trash by farmers; consequently, hay is sometimes available for free during hay season in the summer. It contains a variety of grasses, including both the leaf and stalk, so plant nutrients are all there. When hay decomposes, it adds significant nutrients to the soil to increase its fertility. Hay generally doesn’t harbor mice because it’s too dense. Hay decomposes fairly quickly and has more of a sponge effect than straw does, which helps prevent erosion and leeching of nutrients. Because hay packs down densely, weeds from underneath get smothered and die very quickly.

But in moist soil, hay has a tendency to harbor slugs and snails. Hay holds moisture, allowing seeds on top to sprout, which is why hay bale gardening is popular. But if you’re trying to suppress weeds do you really want this? And often the hay itself contains seeds that will sprout once they get wet, so you could end up having to do more weeding. As hay decomposes, it is broken down by various bacteria and other organisms that all use nitrogen, the same as straw. So what happens is that these organisms get the hay as a new food source and multiply rapidly, depleting the soil of nitrogen. As they run out of food, the organisms die and the nitrogen is once again available for the plants to use. So planting directly into hay mulch without any supplemental nitrogen source available probably isn’t the best idea.

So now that you know more about hay and straw as mulches, which one is best? In a perfect world, the solution is to use both. A thick layer of hay mulch on the bottom, topped off with a few inches of straw. But we don’t all live in a perfect world, do we? So, I’d suggest that if you have to choose, use hay simply for the fertility it will add to your soil. But as all practical gardeners know, you use what you have or can easily get.

Planning the best method of mulching your garden is important for fertility and moisture retention, which will in turn increase your enjoyment of your garden. A well mulched garden also makes better use of the precious water resources that are becoming scarce in so many places. Try new things and experiment with mulches to see what works best for you. Give thanks for the bounty that our soil can provide. Happy Thanksgiving!