Mulch: when and how to use it on our plants and soils

You may have noticed that some front gardens incorporate a technique to protect and maximize soil resources. At first glance, it looks like decorative bark, which gives a minimalist and rustic touch to exteriors. However, these bits of plant matter aren’t just there for aesthetics: they have a number of benefits that can work well for your plants.

“Mulch is any type of layer, organic or inorganic, that we use to cover the soil in our garden or in our pots,” explains Wilma Borchers, environmental and natural resources engineer. “It simulates the mulch present in nature, this layer of leaves that protects the soil and its small inhabitants from changes in temperature or humidity”, adds Verónica Blackburn, agronomist gardener.

“We’re not used to seeing it around town, because people are obsessed with sweeping up every leaf that falls on the ground,” says Blackburn, who creates and distributes botanical content at @plantivista .

Borchers, which also offers gardening tips and advice on @eljardindeirenee summarizes that the mulching It has the following benefits for soil and plants:

If the soil is bare, that is to say without mulch, the evaporation of the water retained in the substrate is facilitated, which would require more frequent watering. But if we have padding, it acts like a kind of sponge, improving the absorption of irrigation or rain water and keeping the soil moist for longer. Likewise, it becomes a great ally in summer, as it dampens solar radiation and prevents the ground from overheating.

Clay soils tend to compact quickly, so water – both from irrigation and rain – tends to pool on the surface and does not flow to deeper layers. This is how a garden that looks well watered is actually dry underneath, which also means a waste of water resources. The miraculous mulch also has something to say here: when applied, it helps to improve the structure of the soil, and if it is also organic, it will provide nutrients as it breaks down.

By filtering the amount of solar radiation that reaches the soil, the mulch also prevents – or at least delays – the appearance of weeds or unwanted vegetation, which tend to proliferate in dry and very sunny substrates.

As we said, mulch works as a filter against solar radiation and also as a moisture retention agent. For this reason, its services also include offering a protective layer that reduces thermal gaps. Roots need a range of temperatures to develop properly, and mulch helps to both keep the soil warmer in the winter – as it slows the progression of surface freezing – and cooler in the summer – as it retains moisture and protects against the sun.

As if all this were not enough, the mulch also makes an aesthetic contribution. It helps contain environmental dust and makes even the most arid areas look neat, healthy and well maintained. It can be used in tree and shrub rates to add color to the garden.

“Bare soil is the worst,” says Blackburn, so mulch can be used over any type of substrate. However, keep in mind that “plants in arid climates prefer gravel or stones, as the excess moisture provided by organic mulch does them no good.”

Borchers is convinced that “mulch can be a great ally in new gardens, where the plants are small and not yet sufficiently rooted. This will help them stay hydrated and fresh longer.

Due to the benefits mentioned above, mulch is able to make our patios or gardens even more sustainable. “Areas that have residual grass can be replaced with mulch; thus, irrigation will be reduced without leaving ‘arid’ areas exposed,” he adds.

There are two main types of mulch: organic and inorganic. “These two include different varieties. Everyone must find the one that best suits their soil, climate or the type of plant they want to grow,” explains the creator of Irene’s Garden.

“Beyond protecting the soil, which is the most important thing, when this type of mulch decomposes, it also has fertilizing properties,” he explains. This means that when it breaks down, it enriches the substrate and makes it more nutritious for the plants that inhabit it. The classic organic mulches are:

• Tree bark—usually pine (those The latter are highly recommended in soils with acidophilic plants (such as camellias or rhododendrons, which need a more acidic substrate).
• wood chips or straw

• Mowed lawn. You can turn grass clippings into mulch so you don’t waste it. Of course, it is necessary to use a very thin layer, because in excess it can generate putrefaction. The detail is to wait for it to dry before applying it.
• Dry leaves. Its excellent carbon/nitrogen ratio allows it to compost naturally, bringing many nutrients to the soil.
• Walnut shells. They are rich in phosphorus, potassium, sodium, iron and zinc. Whole or chopped shells release these nutrients as they break down.

“They are a great option on sloping terrain, around downspouts,” says Borchers. “They can make a place like a flower bed cleaner and more attractive.” The best known alternatives are pebbles and rocks, as well as different types of gravel, gravel or crushed brick, among others.

“Because they don’t break down, they perform their coverage function longer than organics because they won’t need to be reapplied or recharged as often as a mulching pine, for example. This makes it a cost-effective alternative, although its initial cost may be higher than its organic counterparts.

It is also advisable to use it for plants with low mineral needs — such as cacti or succulents — because inorganic mulch does not add nutrients to the soil. This point is important “to respect the corresponding fertilization in the most demanding plants”.

Before getting to work, Borchers recommends following the following checklist for home gardeners.

• Do not mulch on frozen or frosted ground, as this will delay warming. Always—always—it must be applied before the frost.
• Be sure to remove weeds, aerate the soil and add compost before applying mulch.
• Water thoroughly before and after performing the mulching.
• If you opt for the organic option, add 2 to 3 cm of mulch each year to compensate for losses.
• Play with textures and colors in your garden. It must be considered that if a colored mulch is used, the dye is lost with irrigation, rain, sun and the passage of time. This is normal and needs to be reset.

It will always be good “to use dead leaves – high in carbon – and grass clippings – high in nitrogen – in flowerbeds,” adds Blackburn. “By the end of the season, they will be completely gone, as they are immensely biodegradable and many beneficial insects hibernate there.”

“The most important thing in a garden is its maintenance,” concludes Borchers. “Whatever the intervention carried out, the mulch must be maintained to achieve the desired end result.”

*Prices for products in this item are current as of April 28, 2022. Values ​​and availability may change.