Organic Mulch and Living Mulch

Posted by on Aug 13, 2015 in Grow Better Greens Podcast | Comments Off on Organic Mulch and Living Mulch

We’re talking all about mulch in Episode 11. We discuss the benefits of mulching, the correct way to apply mulch, as well as the most popular options available to the home gardener. We’ll introduce you to the major upside to using organic mulch as opposed to synthetic mulch, and, because this is the Grow Better Greens Show, we also tell you about our favorite technique for mulching – planting greens to use as a Living Mulch!

You can listen in here, or download for later:




Organic Mulch and Living Mulch

What is Mulch and Why do you Need it?
Mulch Lays on Top. Period.
Mulch: What are Your Options?
Living Mulch for Edible Harvests
Cover Crops as Living Mulch
Why Do You Grow Food?



What is Mulch and Why do You Need it?

While mulch may mean different things to different gardeners (and landscapers), in my mind, mulch is four things:

  1. Erosion Prevention – mulch protects the soil and its nutrients from damaging wind and water, so that it doesn’t evaporate into the air or wash away. Think about driving rains and dust storms – mulch helps soil to stay put!
  2. An Opportunity to Build Soil – when you choose natural mulches, such as wood chips, bark, shredded leaves, grass clippings, straw, hay and other decomposing plants (all sources of carbon!), they will eventually break down and become mineral-rich soil someday, adding to your garden’s overall value. This is important work!
  3. Weed Control – for many gardeners, the whole reason that they opt to cover their soil in the first place is in an effort to suppress weeds. In my experience, many weeds are so tenacious that they’ll still make their way through whatever material you lay down, BUT they’ll also be so easy to pull that you’ll still be glad you used mulch!
  4. For some, Mulch is Purely Decorative. From colorful mulches to beautiful pebbles, plenty of gardeners are simply after aesthetics when they put down mulch.


Mulch Always Lays on Top. Period.

Mulch, unlike compost, fertilizer, and other soil amendments does not get turned into your soil, but rather just sits right on top.

After all, we’re simply mimicking nature at work!

Some of the best soil that’s been identified on Earth, known as Top Soil, is created in the woods as it lies beneath all of the fallen parts and pieces of the surrounding ecosystem – decaying wood, green leaves, brown leaf litter, berries, twigs, bark – you get the idea.

This thick carpet of natural materials is the ultimate, undisturbed compost pile. A perfect blend of carbon (woody materials) and nitrogen (green, leafy materials), the ‘carpet’ breaks down into Top Soil over the course of hundreds of years, speeding up and slowing down based upon the internal temperature of the pile – just like it happens in our own backyards.

As rain water trickles through the pile, nutrients are released into the soil below, in the form of compost tea. This is an excellent side-benefit for the deeper layers of soil that lie beneath ‘the top’.

But what would happen if the ‘carpet’ (pile) were turned into the soil instead of just landing on top? Three things:

  • It would break down much more rapidly
  • It would rob nutrients from the soil to help speed up the process – at the expense of all of the neighboring trees and plants!
  • No compost tea would be delivered to deeper layers of soil or plant roots below, leaving the subsoil unfed

Remember, the belly of a compost pile is a decomposing beast! All kinds of miniature life forms are busily digesting the pile, and plowing through any available nutrients and energy to do their work.

If we give them an all access pass to the nutrients in our soil – the ones that are earmarked for our plants – they’ll think nothing of using them all up without a second thought for our poor veggies!

As good plant parents – we just can’t let this happen…


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What are your Mulching Options?

Let’s get down to it.

To start, let’s quickly cover some synthetic possibilities: plastic sheeting and ‘landscape fabric’, aka ‘weed barrier’, ‘weed cloth’ or ‘weed mat’. Basically, what you’ve got here are impenetrable materials that can be laid down over the soil to prevent erosion and suppress weed growth.

While that’s a huge plus in most gardening books, if you choose a synthetic material as mulch, you’ll lose out on any opportunity to build soil. Rather, you may be building soil directly on top of the plastic or fabric (like I did for years on top of weed cloth in my own garden paths!) but that soil won’t be improving what lies beneath – your ‘sub soil’.

Many gardeners will lay down plastic and then place a natural mulch on top, simply because it looks better than staring at black plastic. If you allow that natural mulch to break down over time, especially if you add to it by throwing weeds and other plant waste into the mix, you can then remove the resulting soil that you’ve built (usually ready by the next season) into your garden beds – not a bad system!

However, if you choose to lay your natural material directly on top of the soil with no synthetic barrier, you’ll not only be building soil on top, but you’ll also be transforming the existing sub soil beneath.

When gardeners wonder “How can I loosen and improve my tight clay soil?” or “How can I add bulk and nutrients to my light, sandy soil?” mulching without a barrier IS always a great suggestion. Any natural material will work:

Leaves, grass clippings, straw, hay, cedar or pine needles, wood chips, bark mulch, unfinished compost, spent bird seed, super-teeny pebbles, shells, cocoa shells, mushroom compost (spent soil that was used to grow mushrooms), sea weed, etc…

Newspaper, by the way, is a long-time favorite mulch and one that I’ve used with great success. In fact, using a thick layer of wet newspaper underneath wood chips and/or straw is a great way to build a new garden site. I should point out that newspaper with black and white ink is preferable to newspaper with colored ink or magazines; colored ink is not considered an organic mulch by organizations enforcing the organic certification process on farms, likely because some are still generated with heavy metal-based inks.


Living Mulch for Edible Harvests

Maybe you’ve heard the term living mulch before? This is a method of using plants themselves to provide the benefits of mulch. Low growing, spreading plants that are thick with vegetation can help to prevent erosion and keep moisture in place by shading out sunlight and stabilizing soil with their roots.

One of the best examples of a living mulch is a vining squash plant, which will send low-to-the-ground, wide-leaved runners in every direction, if left to its own devices. With a little timing, you can use this behavior to your advantage.

Winter squashes, planted well after you’re other garden plants have a head start, are a perfect choice, as they prefer to be harvested at the end of the growing season. As they grow, spread and reach, they can offer loads of protection to your taller, more upright plants, such as bush beans, peppers, eggplants, corn and tomatoes. Leaving the dead vines in place to overwinter (providing that they were healthy specimens with no evidence of disease) means that they will begin to breakdown and become part of your carbon-based mulch layer.

Other options for living mulches include herbs, which are usually harvested a bit at a time, instead of all at once. Likewise, you can cycle your short-lived greens through a spot that needs to be mulched, by planting, harvesting, and re-planting. This works well when you’ve started your greens in cell trays or soil blocks and can just stick them into place as you’re ready.

Though they won’t get a chance to fill out as nicely as a long-season plant, they can still be of service. You can see below how the shallow-rooted lettuces are holding on to the soil all around the deep-rooted tomato plant. As their heads fill out, they’ll offer even more protection. Just a little gardening double-duty in action!



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Cover Crops as Living Mulch

Cover cropping, a technique used most often by farmers has been gaining a lot of attention in the gardening community. The idea is that when you’re not growing a food-crop in your beds, you can easily sprinkle a bit of seed to grow a plant that can help to improve your soil.

Most often, the cover crop you choose will be doing some much-needed work, such as:

  • adding a particular nutrient
  • driving away an unwanted pest
  • loosening the soil below with it’s notoriously strong roots
  • dying-off at a specific temperature, to add carbon and value upon its decay

As a home gardener, you don’t necessarily need to give up any gardening space to use a cover crop. You can still get their benefits by planting them close to your plants, around the edges of your beds, or in pathways. Some to try include clover (seen below at this rooftop farm in Brooklyn, where they’ve strategically planted it in paths), buckwheat and rye.

Always make note of how cold it needs to be to kill off any given cover crop – you don’t want to plant one that won’t ever go away without having a plan in place!

Why Do You Grow Food?

In this section we ask our listeners to share why they are growing food. This week urban gardener Sam shares why she loves growing food!

Sam won a collection of Liz’s heirloom leafy green seeds, available on Amazon.

Thanks for reading my blog : ) I appreciate your time and wish you much success in growing healthy food!

Jenny