Mulching the Vegetable Garden: Why it’s essential and how to do it

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When we think of the early spring in our gardens, most of us think of PLANTING! Yes, while this is the number one task most of us are doing right now, not far behind it is a process we cannot skip — mulching the vegetable garden.

Most of us who mulch, and even those who don’t, know that one of the main reasons for doing so is to help prevent weeds. However, weed control is only the beginning. Mulching with organic mulch carries with it a whole host of benefits that we all need in our gardens.

You can listen to our latest podcast where we go into these benefits in detail, or continue reading the article below.

What is Mulch?

Before we understand the why let’s talk about the what. Mulch is any kind of material that you put on top of the soil. It’s like a blanket for your soil, meant to cover it. Because I’m an organic gardener, I only work with mulch made with organically derived materials that will nourish the garden as it breaks down.

Weed Control

Most of us who start mulching do it initially for the purpose of weed control. I can tell you from personal experience that every year I mulch my garden (without tilling at all, which brings up more weed seeds), I have fewer and fewer weeds that I have to manually pull up.

kids applying mulch to garden
My kids are adding wood chip mulch between these rows of peas in the early spring.

Does mulching get rid of weeds completely? No, but as we add mulch on top of the soil (and the prior year’s mulch) each year, we’re smothering those weeds. As the years have passed, the weeding time gets less and less. According to this article, three inches of mulching can reduce your weeding time by about two-thirds. In my anecdotal experience, I would concur.

But the prevention of weeds is only the beginning of why mulching is critical for the health of your vegetable garden. Let’s look at the other benefits below.

Moisture Regulation

We gardeners can deal with two extremes when it comes to rainfall and the garden. One is when the rain just doesn’t stop and your garden looks like it could drown (that’s the early spring for my garden). The other is when you’re in the middle of the hot summer with no rain in sight.

For both of these extremes, mulch is going to help regulate the soil moisture considerably. Mulch helps absorb the excess water during those hard rains, but it also keeps the soil moisture locked into the soil as much as possible, buffering evaporation when the weather turns hot and dry.

The same article that I read about reducing weed control by two-thirds also referenced a study that showed that soil moisture was twice as high in gardens that were mulched compared to those that weren’t.

Let me give you a real-life example. I recently planted a new garden plot of strawberries in an area that I knew to be a little bit saturated. I mulched around those berries with straw and a little bit later, we had 2 inches of rainfall in a matter of two days. I went out and checked on my berries and they were thriving, due to the fact that the straw had helped absorb that moisture.

boy applying straw mulch to garden

Temperature Regulation

Just like the mulch helps with the moisture regulation for both extremely dry and wet periods, it does the same with the soil temperature. When you are in that extreme summer heat, when your cool-weather plants want to bolt, adding a layer of mulch to the garden keeps a more moderate soil temperature, prolonging your growing season and keeping your plants from bolting as quickly as they would in an uncovered environment.

A study referenced in this article again showed that gardens that were mulched had a soil temperature of 8 to 13 degrees lower than those that weren’t. That is significant when it comes to the garden!

Adding a thicker layer of mulch can also work in the winter by protecting your winter crops from extreme cold, especially if you’re overwintering some crops.

Reduces Erosion and Crusting

Too much erosion in the garden leads to topsoil washing away. As most of us know, topsoil is full of the nutrients, vitamins, and benefits that plants need. Mulching helps keep that topsoil in place.

Crusting is another issue and one I definitely have to deal with in my clay-heavy soil. When it rains, the soil is damp and muddy, and then when it dries out, it turns into a hard, cracked crust. If you have a lot of clay in your zone, more than likely you are dealing with crusting, too. Mulch, however, prevents this crusting over in the short term while adding organic matter to help with soil tilth for the long term.

Moderates Soil Structure

Speaking of ideal soil tilth, mulching year after year helps change that soil structure over time. A more healthy soil structure leads to more healthy plants that can access nutrients and water more easily. While the desired results can take several years to begin seeing, mulching is a great way to start rehabilitating poor soil in the garden. I’ve seen it first-hand over my 8+ years. Areas of my garden that barely produced a harvest at first are now full of life and production.

Prevents Diseases

A lot of the time the fungal spores that go on to cause diseases like early blight and powdery mildew persist in the soil. Especially in the case of early blight, those spores splash onto the plant with rainfall. However, a thick layer of mulch can create a barrier, helping to prevent those spores from splashing up onto the plants.

tomato plant with early blight
Early blight on tomato plants.

Feeds Soil

Eventually, when mulch breaks down, it is feeding the soil. So, by adding mulch, you are investing in your garden soil in the short and long term. According to this article from the Texas A&M Extension Service, gardens that are mulched provide 50% more production than an unmulched garden. I believe it!

How to Apply Mulch

Have I convinced you to make mulching a regular part of your vegetable gardening? If so, how do you make it work best for you?

Depth Matters

The first thing to consider when it comes to mulching is the depth. For most organic mulches, I recommend three to four inches, though that may vary depending on the kind of mulch you use. For example, if you’re using untreated grass clippings, you can get away with less and if you’re using straw, you’ll want to add more.

The important thing to remember here is that when it comes to weed prevention, too little mulch is worse than none at all. If the light is allowed in, the weeds will grow towards it, and then you’ll be weeding around and through the mulch. Weeding a mulched garden is more labor-intensive because using a hoe to weed through mulch continues to bring up more weed seeds, exacerbating the problem.

weed coming up through thin mulch

That’s why it’s imperative to ensure your mulch layer is deep enough to block the light from getting to the ground as much as possible. Sure, you’ll still deal with some pervasive weeds, but they will be fewer and further between — and more manageable.

Wait until the soil is warm

If this is your very first time mulching your garden, wait until the soil has warmed up in the spring before adding a layer of mulch. Because the mulch helps regulate soil temperature, it can work against you if you mulch too early because the soil will take longer to warm up in the spring. Plants and seeds need that warm soil in order to germinate and grow.

thermometer testing soil temperature
59F is too cool for seeds for most summer crops, like beans and cucumbers, to germinate.

If you’re planting seeds, ensure that the soil temperature is warm enough for the seed you’re planting to germinate. In general, cool-season crops will germinate in cooler soil (50F-60F), while warm-season crops need above 65F to germinate. You can get this information on the seed packet, a simple Internet search, or in the charts in my book, Vegetable Gardening for Beginners.

(If you already have mulch in your garden, keep reading for what to do in the early spring.)

Don’t apply mulch on top of weeds

If your weeds have already sprouted, adding even four inches of mulch is very unlikely to kill them. Make sure you remove weeds first and add your mulch after. (The only exception here is if you lay a barrier like newspaper down and mulch on top of it. More than likely this will kill your established weeds.)

Leave breathable space around transplants

If you’re adding mulch to a garden where you’ve already planted transplants, then make sure and keep a few inches of space around the plant.

wire caged tomatoes with mulch around the plant

What if I Already have Mulch in My Garden?

How you deal with mulch really depends on what type of mulch you use. I use high carbon mulch and you never want to work those into your garden soil or til them in as it can rob your soil of nutrients.

I tend to rake my mulch back and allow the soil to warm up ahead of my plantings. After I’ve planted and my plants are well established (six inches or taller) I will move my mulch back. However, I never have enough mulch and always have to mulch each season. So, plan on mulching each year.

I also do this when planting a fall crop, as I show in the video below:

What if I have Raised Beds?

A lot of people who garden with raised beds ask the same question: do the mulching benefits still apply? Absolutely! There are benefits to having a raised bed, though. For instance, you don’t need near as much because you’re not having to mulch the pathways.

Now that you know why to use mulch and how to apply, which mulch should you choose? Here are some organic mulch options to consider.

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