Why You Use Organic Mulch For Gardens

I mulch my gardens for several reasons:

Lazy Gardener Alert

The first is that I’m a lazy gardener and mulches cut down on weeds. I mulch the plants with a 4-inch layer of straw or leaves but I leave an 8-12 inch circle around the base of the plants that is not mulched.

The reason I leave this space is for slug control. Slugs will eat your young plants to the ground if you mulch right up to the transplant. And later in the season, slugs will climb up your staked plants to reach the fruit. This circle of bare ground allows me to lay a protective barrier of diatomaceous earth around the base of the plant so the slugs can’t cross over.

Note:

IMHO, there are a great many different mulches at your favorite garden shop but the reason I use straw or hay is because it breaks down quickly. I want a quick breakdown in the vegetable garden because I want those microorganisms happy, well-fed and fat. They’re taking care of my tomatoes, so I want to take care of them.
Bark and Pine needles etc are wonderful for ornamentals such as annuals or perennials  but not the vegetable garden.

Straw Versus Hay

Just in case you don’t know –

  • Straw contains the stems/leaves (mostly stems) of grain bearing plants such as wheat and oats. The grain is removed by a combine-harvester and what’s left is “straw”
  • Hay is  a grass-type plant such as alfalfa, timothy or clover. The entire plantis cut and baled – leaves and stems to make “hay”

And yes, there is a difference in garden performance in my opinion as I indicate in the video below

Ideal Root Growing Conditions

The second reason I mulch is to provide an ideal growing environment for the roots. I like to pull the mulch back from the growing area in the early spring – leaving bare ground – so the soil will warm up naturally. Once the plants are in the ground, then I re-mulch to preserve an even soil temperature and an even soil moisture. I want those roots to think they’re in heaven.
If you do not stake your tomatoes, then you’re going to have to accept some slug damage in exchange for higher yields and less weeding work. Or you can use the super-easy ladder system of growing tomatoes that I use for my canning tomato crop. (see the section on staking for details)

Do Not Disturb The Roots

The third reason is that I don’t want anybody hoeing or disturbing plant roots. For example, In a good soil, tomato roots are going to grow three to five feet in circumference around the tomato plant. I don’t want anybody hacking at those roots with a hoe – this will reduce the yields.

The role of organic mulches:

  • Organic mulches work well for main season growing.
  • They do reduce water evaporation from the soil and conserve moisture – giving the plant roots first crack at the available water.
  • They rot down and add organic matter to the soil – and organic matter is the lifeblood for great tomato gardening.
  • What material to use? University research did not find an appreciable difference (other than with sawdust) between different organic mulch materials.
  • However, understand that a soil mulched with a ongoing deep layer of organic mulch will be slow to warm up in the spring. If you’re looking for an early crop of tomatoes or other crop, then it starts with getting that soil warmed up fast in the spring. The solution is to remove the organic mulch in the area you need for growing tomatoes and then replace it once the plants start growing and the heat of the summer appears.

Sawdust

  • Is fine as a mulch.  It works well as a simple mulch.
  • The problem is that if you dig it into the soil, then it will take extra nitrogen from the soil to decompose.  This means there won’t be enough for your garden plants. If you don’t dig it in – it doesn’t rob your garden of nitrogen contrary to the advice on the Net.
  • If in doubt, don’t use it.   Or spread it very thinly on top of your existing mulch.

The Role of Plastic Mulches:

Warming soils in the spring is the role of plastic mulches. In the home garden, use a clear layer of plastic over the area you want to warm up for early crops. Lay down the poly and then cover the edges so air can’t get underneath.
You’re making a mini-greenhouse and the heat has only one place to go during the day – straight into the soil. Use this system for two weeks before you want to plant and your soil temperature will increase by several very important degrees. Remove the clear plastic just before you plant.
Remove all clear plastic once the plants are in the ground. Clear plastic will heat up the soil too high during the growing season and either kill the plants outright or stunt them terribly.

Commercial growers have traditionally used black plastic mulch for the growing season but even this mulch can increase soil temperatures too high in some years.

A garbage bag with its sides slit makes cheap and easily recycled mulch for home gardeners. And it can be easily removed.

There is some research showing that plants mulched with black plastic are less susceptible to tomato blight – largely because of the reduced amount of soils splashed back up onto the leaves during rain storms. I suspect that any mulch, organic or plastic will have the same effect.
If you want to experiment with commercially available plastic-film mulches at the garden center, buy the red ones. Red plastic mulch has been shown to decrease the effect of root knot nematodes and increase the top growth of tomato plants. Scientists are not sure why this happens but the results are very clear and sometimes quite dramatic (dramatic on soils heavily infested with nematodes). The research team from South Carolina speculate the growth has to do with the mulch reflecting the red spectrum of light back up to the plants.

Organic Growing Mulch System for Vegetables

Organic gardeners in USDA zones six or warmer might find that planting Hairy Vetch (Vicia villosa) in the garden in the late summer where you want your tomatoes to be the following spring. A late summer planting will produce a short vine by late fall but the root systems develop before the top growth and there will be an extensive root system producing nitrogen in place.
The vetch gets a quick start on the season – well before the time you want to plant tomatoes so let it grow and by the time you want to plant, it should be several feet long. The day before you want to plant your tomatoes, simply cut it to the ground to kill it.
Plant tomato transplants without digging. Then mulch with organic matter as normal using the vetch debris and other organic matter. The vetch produces nitrogen that is now available to the tomatoes and this will increase your yields.
Hairy vetch requires a long growing season to produce the nitrogen and top growth and northerly gardeners don’t have a long enough season to use it in this way. Northern gardeners can use peas or other legume to replace the Hairy Vetch. Either that or use a crop rotation system that puts the tomatoes in the garden spot formerly occupied by the peas.
Hairy vetch has also been shown to attract potato beetles so that damage to tomatoes is reduced.  You can read other vegetable gardening tips here.

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