The turning of the seasons brings new garden chores, and right now, mulch is at the forefront of many a gardener’s mind.
For those in the US and Europe, it’s time to lay fresh spring mulch as the growing season begins, and here Down Under in Australia, we’re preparing for autumn and winter’s slumber.
No matter where you are, using straw as mulch great option, perfect for flower beds and veggie gardens alike.
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What is Straw Mulch?
If you hear ‘straw mulch’ and immediately imagine a bale of hay, you’re not far off the mark. Straw is the stalk of any grass, dried and compressed.
Hay might be grown as bedding or animal feed, but the long golden stalks also make excellent mulch. Other forms of straw mulch include rice straw, oat or barley stalks, or even processed sugar cane pressed free of its sweet nectar and dried.
It’s all essentially the same stuff. There are subtle variations in the texture, smell, and overall appearance, but it all brings the same benefits to the garden.
If you’re in an agricultural area, straw bales are sold for fodder and animal bedding at local farms or feed stores. For us city folk, small bales of straw are often sold at garden supply stores alongside other mulches too.
What Are the Benefits of Using Straw as Mulch?
It’s Easy to Apply
Straw mulch is light and easy to spread around your garden. While the bales of hay themselves can be pretty heavy, straw mulches are very easy to handle once opened.
Commercially packaged straw is often compressed for shipping and will almost explode from its wrapper once opened. From there, it’s just a matter of spreading it out. Each bale will cover many square feet depending on how thickly you layer the mulch.
Obviously, a lightly layered garden won’t need as much straw as a vast community garden preparing for winter chills, and a small garden may only need a single bale.
All you really need is a rake to drag it into place on the soil surface, leaving the base of the plant clear. It doesn’t take a long time to spread it around, making it a good option for folks who have a large garden area to cover and not a lot of spare time.
Anyone trying to keep new lawns in check can attest to how fast grass grows. Hay is the same fast-growing type of plant, so there’s no fear we’ll run out. It’ll pop back up again in no time, ready for a fresh harvest.
It’ll grow just about anywhere, so there’s no need to waste fuel transporting the best straw from remote artisan farms. It’s common and replaceable.
It’s also commonly made from agricultural byproducts. Once the valuable part of the harvest is taken, the straw would otherwise need disposal. Using it as mulch puts it to far better use than sending it to a landfill.
If you’re in a rural area, local farmers may be delighted to get rid of oat or barley straw for next to nothing after the harvest.
Potted Exotics Pro Tip: I get the most from my straw mulch by layering it with other sustainably sourced materials. An old packing box laid over exposed areas of a garden bed provides a great foundation for straw mulch. The cardboard will break down over time, enriching the soil, and the straw mulch will help keep it and the soil below nice and moist.
It Helps Control Weeds
My number one use for straw mulch is weed suppression. A layer of weed-free straw a few inches thick prevents weed seeds from germinating and starves the ones that do of light.
It’s an easy way to suppress weed growth without chemicals or the hard work of actually pulling them out, especially for invasive plants that shrug off commercial herbicides.
It Keeps the Soil Moist
Straw mulch itself is excellent at absorbing and holding water. Those hollow stalks suck up moisture, whether it comes from rainfall, dew, or the garden hose. Even spoiled hay that’s broken down almost completely within the soil helps with water retention.
It also prevents the evaporation of soil moisture once it’s in the ground. Any extra moisture added stays under the mulch layer and benefits the plants that need consistently moist soil e.g. eggplants. If you’re in an area of the country prone to seasonal rainfall shortage, repeated layers of mulch materials will keep your soil well hydrated.
It Insulates and Protects Roots
Like a fluffy blanket or the walls of an insulated cooler, thick layers of straw insulate your garden beds and keep them at an even temperature.
A dense cover of hay is a good idea on flower beds as the mercury starts to drop. It’ll protect plant roots from sudden chills and frost. Dormant annuals will stay safe and warm under half a foot or so of straw, no matter how windy and wild it becomes above.
In warmer areas, a good deep layer of straw prevents soil temperature from spiking during early to late summer and prevents heat stress. Since straw is generally paler in color, it reflects a lot of light and stops sunlight from heating up dark garden soil.
The insulation it provides makes that all the more effective, too.
It Builds Soil Mass
All soil is a mixture of sand, clay, stones, and decayed organic material. To improve the quality and volume of soil, you need to add more of any one of them – and organic mulch like straw is the best option for the job.
The straw breaks down over time and works into the ground, building healthy soil. It’s one of the most significant benefits of mulch, and straw is one of the fastest and most effective options.
Mulching also prevents erosion and runoff. Some of this is because soil becomes more stable when it’s chock full of good organic matter. The layer of physical protection provides substantial protection too. You might lose the mulch if conditions get rough, but the soil will stay safe.
It Protects Against Disease and Pests
Many common fungal diseases found on plant leaves start their lives in the soil. The pathogens that cause Pythium, Rhizoctonia, and Fusarium occur naturally in the dirt.
They reach the leaves when muddy water splashes from the ground into foliage, typically during irrigation but often during rainfall.
Even a thin layer of mulch serves as an effective barrier between these soil-borne pathogens and vulnerable leaves. Low-growing food crops like lettuce and cabbage are especially vulnerable, so it pays to put a few inches of mulch close to the base of the plant.
Many insect pests also spend their winter in the soil, ready to come up and eat their way through your tender spring growth.
While a lot of people prefer to let their winter protective layer rot down as spring compost, you can remove the mulch in early spring, and it’ll take hibernating pests with it, too.
Where to Lay Straw Mulch
In Vegetable Gardens
Even strawberries will thrive when using straw as mulch. It’s a highly-versatile cover that you can use in a thousand different ways – which is exactly why I love it so much!
Adding straw will keep the soil nice and moist, protect against disease and pests, and eventually decompose to add more soil mass and nutrients to the bed.
When added to worm castings or new compost, straw also extends the application’s volume and prevents nitrogen burn.
As each crop comes out, you can just turn the lot, ready for the next season’s planting. It has the added benefit of being comfortable to sit or kneel on, too – good news for hands and knees!
Potted Exotics Pro Tip: Using straw mulch in your Rosemary garden can provide the soil with added nutrients and heat to keep Rosemary growing strong.
Straw makes a great material to line pathways through your garden.
It doesn’t have the same cache as gravel, but it’s far more comfortable to walk on, less noisy, and easier to deal with if you want to relocate garden features over time.
You don’t have to rake it all up, but you can just put beds or new lawns right over the top. It’ll also work into the soil as people walk over it, adding structure rather than causing soil compaction.
It also serves well as a temporary pathway material and can make the garden safer in wet weather.
I love putting it between my raised veggie beds during the rainier parts of the year. It reduces slip hazards and stops the whole thing from becoming a muddy nightmare.
Across Ornamental Beds
Adding straw to ornamental beds has all the same benefits as adding it to vegetable gardens. It retains moisture, protects roots, and provides nutrition and structure.
For ornamental beds, it can help stabilize the soil over time and provide enduring, reliable cover crops for much-loved perennials. If you’re in a cold climate, a good thick layer of straw in the fall will keep slumbering roots nice and safe until the following spring.
Challenges of Using Straw as Mulch
It Decomposes Rapidly
Straw breaks down quickly. It needs to be replaced regularly if you want to keep its benefits. Depending on the aspect of the bed and what rainfall is like in your region, you may need to replace it as often as once every three months.
It Can Promote Mildew and Mold
While the more hazardous plant diseases have a hard time dealing with straw mulch, for smaller nuisances, it’s an ample buffet. Particularly cool, damp beds can develop powdery mildew if the upper layers of straw become waterlogged.
This isn’t much of a major issue for large stands of trees or shrubs, but for food crops like cucurbits that are particularly susceptible to mildew, you’ll need to keep an eye peeled for fuzzy leaves.
It’s Extremely Lightweight
While overly wet straw can become moldy in a too-wet environment, the loose, light straw tends to blow around in a too-dry environment. It can collect around and over plants, trapping moisture where you don’t want it, or drift off out of the bed entirely.
You can prevent this by dampening it down regularly and being mindful of your local conditions. If brisk winds are common in your area, you may need a heavier type of mulch, like bark or wood chips.
It Has a Poor Nutrient Profile
Hay mulch is just not that great in terms of fertility. Even when broken down, straw is mostly carbon. It’s one of the reasons it works so well for weed control – seeds that land on top have nothing to nourish their growth.
You can counter this by using water-soluble nitrogen fertilizer when watering, mixing slow-release options through the soil before planting, or layer compost or well-rotted manure under the straw.
The latter choice will do a great job preventing pets or children from having way too much fun with stinky garden beds!
Other Gardening Uses for Straw Mulch
Straw is pretty versatile stuff. I’m always finding all kinds of different ways to use it around the garden.
Hay is an excellent ingredient for producing my own compost. I pop a small bale of mulch by my compost pile and toss in handfuls every now and then. It regulates the carbon levels and prevents the compost from becoming boggy or aerobic. It also helps manage any leaching too. This has always helped me successfully with planting, especially when growing peppers.
Hay Bale Veggie Garden
You need to water and fertilize well, but potato plants, pumpkin vines, and even fussier crops will grow quite happily as the straw decomposes.
No-Till Soil Support
No-till garden beds rely heavily on straw. Sometimes called lasagna beds, this technique involves layering cardboard, straw, compost, and other sundry materials until a fertile raised bed develops.
Break Up Heavy Soil
Hay is also great to add to heavy clay soil to break it up. Sandy soil also benefits from the long-term use of hay to improve structure.
Hay Bale Cold Frame
Cold frames are basically just protective structures that people use to keep their plants and vegetables from freezing when during the shoulder months of fall and spring.
One great idea is to use hay bales to create a low-cost cold frame – which pretty much acts as a mini greenhouse for your vegetation!
To create a hay bale cold frame, simply box in an area around your garden by stacking hay bales in a square or rectangular shape. Once you have the area surrounded, cover the top of the rectangular bales with one of the following:
- An Old Window
- A Polyethylene Sheet
- Bubble Wrap
6 All-Organic Straw Mulch Alternatives
Lawns are some of the most over-fertilized, coddled parts of the modern garden. All that nutrition has to go somewhere, and once you mow, you take it all out again as clippings.
Grass clippings make for a fantastic cheap, and readily available mulch. Pile yours in the corner of the garden to dry out, and in a few weeks, you’ll have your own mulch indistinguishable from commercial ones you’d get from garden centers.
It’s nitrogen-rich, rots well, and, best of all, is free!
The only drawback is you need to mow before the grass develops seed heads. Those seeds wind up in the mulch, drastically reducing its usefulness for weed suppression.
Much like lawn clippings, leaf mold is something you can make at home with almost no work whatsoever. Falling autumn leaves piled into a heap will break down in time into a rich, moist material that makes a stunning mulch.
While leaf mold is not particularly rich in nutrients, it contains a host of naturally occurring chemicals called humic acids. These form a vital role in maintaining soil health in complex ways that science is only just discovering.
If you’re in timber country, wood chips make for a pretty good choice. Close to lumber mills, it’s cheap to the point of being free, and it’s far more long-lasting than other mulches.
Each chunky wood chip is heavier than a piece of straw, making it one of the best for weed suppression. It won’t blow away, and it keeps its color for longer.
Pine straw mulch is made of pine needles, bark, and other offcuts of pine trees. It’s fragrant, with a gorgeous pine forest aroma as it decays. I personally love it for ornamental beds close to windows for that very reason.
It breaks down at around the same rate as straw, so it’s good to turn through the soil once it’s gone. You can also remove it to control pests in the same way. It’s an excellent soil amendment all around.
Chipped bark is another by-product of timber milling and is very cost-effective. It’s chunky and great for weed suppression.
It’s not a great choice for vegetable gardens, as it’s uncomfortable to kneel or sit on when working, but it’s a great call for ornamental beds and pathways. It’s as pretty as gravel without the drawbacks.
Paper and Cardboard
Surprisingly, shredded paper or packing boxes are another great way to turn waste into mulch. After all, it’s natural plant material no different than straw.
It’ll hold water, reduce erosion and keep weeds at bay. Cardboard packing boxes work well as weed matting under more conventional mulches, and both paper and card can be added to your compost heap.
It’s not as pretty as a pale swathe of straw shining between the garden plants, but it’s much cheaper.
You’ll need to stick to non-glossy paper, as the shiny stuff is often coated in a thin layer of plastic. It’s also good to pull out staples, peel tape and otherwise check for non-biodegradable elements.
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