Indoor horticulturists constantly strive to find techniques and products that will help increase their garden’s yields. Common sense will tell you that a plant with a strong and healthy root structure is more likely to have strong and healthy stems, leaves, and flowers. Simply put, healthy roots will equate to more bountiful harvests.

Unfortunately, indoor growers do not always give a plant’s root system the attention it deserves. It is like the old saying, “out of sight, out of mind”. Because the roots are generally hidden from a horticulturist’s view, they can often be forgotten. Horticulturists who focus some of their energy on making the plant’s root system thrive will usually have better yields and less problems overall. There are a few different ways for an indoor grower to help stimulate root growth and maintain a healthy root mass.

Oxygen and Plant Roots

Many horticulturists don’t think about the important fact that plants need oxygen to thrive and survive. Most of us think of plants as living organisms that produce oxygen during photosynthesis (a process which requires CO2) and not as organisms that also need oxygen to grow.

Like other organisms, plants need oxygen to perform cellular respiration. Roots grow like other parts of the plant, but since they are under soil or contained in a hydroponic system, they are not exposed to light and cannot photosynthesize.

Instead, they gain energy for growth by cellular respiration that requires oxygen and releases CO2. This is why a plant’s root mass must be exposed to some form of oxygen. For soil growers, the soil’s texture will determine the amount of open spaces for air (oxygen).

In hydroponic systems, such as deep water culture where the plant’s roots are submersed in water, the roots will rely on dissolved oxygen found in the nutrient solution. This dissolved oxygen will need to be replenished as the plant uses it. In both soil and hydroponic systems, if there is not a sufficient supply of oxygen, the roots will not be able to survive and will die off, eventually killing the entire plant.

How to Increase Oxygen for the Root System in Soil

To increase a soil’s oxygen capacity, a grower can add a variety of soil amendments. Perlite, pumice, hydroton, or any other porous substance can significantly increase a soil’s ability to harbor oxygen. Coco coir is another soil amendment praised for its ability to not only hold oxygen, but also have good water retention.

Most prepackaged soil mixes will contain at least one amendment aimed at increasing aeration. However, it is not a bad idea for indoor growers to add more aeration amendments to a soil mix. In fact, well-aerated soil can provide two advantages.

First, well-aerated soil increases the soil’s ability to hold oxygen, thus providing the plant’s root system with all the oxygen it needs to grow and flourish. Second, well-aerated soil will need to be watered more frequently, which gives the indoor horticulturist the opportunity to implement a more aggressive feeding regiment.

A good rule of thumb is to mix three to four parts prepackaged soil to one part perlite or other aerating amendment. This ratio will create a fast-draining soil that can hold a high amount of oxygen.

How to Increase Oxygen for the Root System in a Hydroponic System

It is crucial in hydroponic systems to focus on the temperature of the nutrient solution and mechanical aeration. The nutrient solution is usually contained in a reservoir, which needs to be mechanically aerated. Submersible pumps or air pumps that inject air into the reservoir are the best ways to replenish dissolved oxygen.

Temperature is another crucial factor affecting the dissolved oxygen content of the nutrient solution. The ideal temperature for most hydroponic systems falls in the 65-70°F range. As the water temperature creeps above 75°F, its ability to hold oxygen diminishes.

This is why water chillers are an essential piece of hardware for any hydroponic system where the roots are fully submersed. In other hydroponic systems, the plant’s root system will be contained within some sort of inert medium. There are many different hydroponic specific media available and they all have one thing in common: the ability to hold a good amount of oxygen.

Nutrients and Plant Roots

Aside from increasing the amount of oxygen provided to a plant’s root system, a grower can pay attention to the nutrients that will play a role in root health. A good blooming fertilizer will usually contain the nutrients needed for healthy root growth. Phosphorus and potassium are the two main nutrients associated with root growth.

Many horticulturists like to use a blooming base fertilizer in the clone and early growth stages. A blooming base fertilizer is likely to contain a higher ratio of phosphorus and potassium to nitrogen than a vegetative base fertilizer. Phosphorus and potassium encourage plants to put out new root shoots and help to strengthen existing roots as they continue to develop. A diluted bloom fertilizer (one-quarter normal strength) makes a great nutrient solution for aerobic clone machines or for conditioning stone wool or other clone media.

Root Stimulators (Hormones)

Plant hormones, known as auxins, can also be used to stimulate root growth. A couple of hormones commonly found in rooting gels are indole butyric acid and naphthylacetic acid. These two hormones are considered root stimulators. Although some growers will use these hormones to stimulate root growth in early vegetative stages, I have only used them to stimulate new roots on cuttings. Auxins are known to promote lateral root development so they are more suitable for cuttings versus seeds.

Beneficial Microorganisms

There is a vast invisible world living in and around the root system of virtually every plant on the planet. This microscopic world is made up of millions of bacteria and fungi that have evolved to have synergistic relationships with plants. Beneficial microorganisms are associated with root enhancement and overall plant growth enhancement. The most commonly used beneficial microorganisms supplemented by indoor horticulturists are types of beneficial fungi and beneficial bacteria.

Mycorrhizae (Fungi)

Mycorrhizae are naturally occurring fungi that form symbiotic relationships with more than 90 per cent of the world’s plant species. Mycorrhizae have even become a common additive in gardening products like prepackaged potting soils. Mycorrhizae fungi become an extension of the root system that can stretch far into the depths of the soil.

This immediately broadens the plant’s access to vital nutrients and, therefore, increases growth. Mycorrhizae have synergistic relationships with the plant’s roots. The extending web of mycorrhizal fungi assimilates nutrients for the plant and, in return, the plant’s roots secrete sugars or carbon on which the fungi feed.

Since the relationship between mycorrhizae and the plant’s roots is synergistic, it is safe to say that if a gardener has a healthy population of mycorrhizae in the soil or medium, he or she will usually have a healthy root system as well.

Trichoderma (Fungi)

Trichoderma are a group of fungi that are usually used by horticulturists as a natural defense against root damaging pathogenic fungi. Trichoderma can work wonders against pathogenic fungi that could otherwise destroy a healthy root system. In fact, some of the most powerful root rot treatments available are formulas rich in trichoderma.

Trichoderma can help maintain a healthy, vibrant root system by fending off potential threats. In most cases, trichoderma can be added to a feeding regiment to maintain a healthy trichoderma population.

After all, if there aren’t enough pathogens for the trichoderma to feed on, their population will diminish (not a bad thing). However, by maintaining a healthy population of trichoderma, a horticulturist can nip pathogenic fungi in the bud before they can negatively affect a plant’s root system.

Beneficial Bacteria

As with beneficial fungi, bacteria can be added to the soil or medium to break down organic matter, facilitate nutrient uptake, and add protection against pathogens. One huge advantage of using beneficial bacteria in indoor horticulture is that bacteria can quickly colonize and explode in population.

The larger the population of beneficial bacteria, the quicker they can destroy pathogenic microorganisms and/or break down organic matter. As with mycorrhizae, it is safe to say that if the soil has a bountiful population of beneficial bacteria, it is more likely to have a healthy root system.

Providing plants with the right nutrients, hormones, and beneficial microorganisms are ways an indoor gardener can maximize the strength of a plant’s roots. Although mostly unseen, the root system of a plant is a huge factor in determining the overall success or failure of an indoor garden.

At the end of the day, growers who spend the extra time on developing a strong, healthy root structure are more likely to achieve prolific yields and are less likely to encounter potentially devastating problems.