A robust root system is vital for a plant’s ability to absorb nutrients and water from the soil. The root system is a plant’s main point of contact with the soil and is the method by which it absorbs what it needs to grow and thrive.
The roots also serve as the plant’s anchor during its life and during inclement weather. For example, this past winter, when we had record rainfall and strong winds, the established plants in my garden were able to weather the storms (pun intended), while the newer plants and flowers sadly didn’t fare as well.
Investing in a high-quality fertilizer will speed up growth and root production, as well as offer some protection against diseases and pests. It will also keep your plants strong and healthy.
Fertilizing your plant’s roots may be something you haven’t thought about before, but it can make a world of difference, especially for young plants and seedlings.
Keep reading to learn more about the best fertilizers for root growth and why fertilizing your roots is a good idea!
In this guide, you’ll learn:
- Why you should fertilize your plant roots
- How to choose the right fertilizer for root growth
- How fertilizer will promote healthy root growth and keep your garden strong
- And much more!
Since almost all plants have roots (except maybe air plants), all types of plants could benefit from a high-quality root fertilizer. This is true whether we’re talking about your front lawn, indoor houseplants, or backyard garden.
Below is a quick list of my favorite fertilizers for root growth. Many different types are available, including organic, inorganic, granular, liquid, or powder (such as in #5 below). Keep scrolling to learn my top tips for choosing the best fertilizers for root growth.
Organic Root Stimulant, Salmon and Kelp Formula
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Fertilome 10645 Root Stimulator and Plant Starter
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Bonide Garden Rich Root & Grow Root Stimulator & Plant Starter
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Miracle-Gro Quick Start Planting & Transplant Starting Solution
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Mycorrhizal Fungi Root Enhancer for Plants
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My Overall Top #1 Pick: Organic Root Stimulant, Salmon & Kelp Formula by Bloom City
Although you will surely get stellar results with any of these products, my favorite is the Organic Root Stimulant by Bloom City.
This product is an excellent all-in-one, in my opinion. It contains nutrients from fish and kelp and has humic and fulvic acids to stimulate growth and improve nutrient absorption.
This nifty product also has beneficial bacteria and mycorrhizal fungi. For those who don’t know, mycorrhizal fungi bond to your plant’s roots and grow with the plant to improve the reach and surface area of the roots, thus improving its water and nutrient absorption.
I don’t know about you, but with fertilizer and soil prices rising, I love anything that will help my plant be more efficient and give me more bang for my buck!
Some other awesome features: It is organic, sustainable, and safe for all types of plants (including fruits and vegetables). It’s proudly made by a small business in Seattle, and who doesn’t love supporting small businesses?
Another great thing about this is it can be used in any growing medium, whether it’s coir, regular soil, peat, or even hydro! This formula is gentle enough for seedlings and propagation and is effective at all stages of plant life.
Their proprietary “Super Microbe” mix can give your compost a boost, too, making your homegrown compost even more powerful.
Top 5 Best Fertilizers For Root Growth
In a hurry? Check out our top 5 fertilizers for Root Growth:
- Organic Root Stimulant, Salmon and Kelp Formula (Best Overall Pick)
- Fertilome 10645 Root Stimulator and Plant Starter (Best Pick for New Seedlings or Transplants)
- Bonide Garden Rich Root & Grow Root Stimulator & Plant Starter (Best Budget Pick)
- Miracle-Gro Quick Start Planting & Transplant Starting Solution (Most Versatile Pick)
- Mycorrhizal Fungi Root Enhancer for Plants (Best Organic Pick)
Why Should You Invest in a High-Quality Fertilizer for Root Growth?
When I first started gardening (a hobby that grew out of the early pandemic lockdowns), I never gave much thought to the necessity of a good root fertilizer. I figured (and maybe you have, too), “Doesn’t the plant just get what it needs from the soil?” So I quickly built some raised garden beds, threw in a couple of bags of the cheapest “potting soil” I could find, and set off to make my dream garden.
The hard lesson came last year when I was trying to grow ornamental pumpkins. Everything that I had read about growing pumpkins said that they grew huge, beautiful vines and that they grew QUICK. They also reportedly love abundant sunshine and warm temps; here in Southern California, there is no shortage of either!
After about six weeks, though, my plants were still stunted, small, and spindly. So, I dug up one of them to see what was going on, only to find small, mushy brown roots ravaged by gnats and root rot. And since pumpkin roots notoriously hate being disturbed, it was already too late, and the weak little seedlings quickly died.
At that moment, I realized that bagged soil isn’t all it’s cracked up to be. Investing in a high-quality fertilizer for root growth is essential to give plants the nutrients and minerals they need to thrive while promoting strong and healthy root systems. But unfortunately, as I witnessed firsthand, on their own, plants will be more susceptible to disease, pests, and weak growth.
A high-quality root fertilizer will ensure that our plants can absorb water and nutrients effectively, leading to better overall growth and higher flower, fruit, or vegetable yields.
What Should You Consider When Choosing the Right Fertilizer for Root Growth?
Knowledge of fertilizer composition is vital for a healthy garden. As mentioned in our Top 5 Fertilizers for Oak Trees article, fertilizer comprises three main ingredients: nitrogen,
phosphorus, and potassium (N, P, K). Any fertilizer you buy will have three numbers labeling these three key ingredients (they look like this: 4-12-6). These numbers represent percentages.
- Nitrogen (symbol N) is used for leaf development and vivid green color
- Phosphorous (symbol P) is used to encourage root growth
- Potassium (symbol K, sometimes called potash) is used for root development and disease resistance
A good root fertilizer will have higher phosphorus (P) and potassium (K) to promote root growth. In contrast, other fertilizers, such as those for houseplants, will have a higher nitrogen content (N) to encourage more green, leafy growth.
Organic Versus Inorganic
Organic fertilizers, derived from natural materials like compost, bone meal, burnt hardwood ashes, or chicken manure, release nutrients slowly over time and can improve soil health. In addition, they don’t disrupt the ecosystem in the soil and don’t tend to leave a residue behind.
Organic fertilizers usually contain low concentrations of plant nutrients, which are then converted into inorganic forms by soil bacteria and fungi before plants can use them. Organics also improve water movement, add soil structure, and feed beneficial microbes. You’ll probably want to choose organic fertilizers when growing fruits and vegetables or other plants that will eventually be consumed.
In contrast, inorganic fertilizers are usually made from synthetic materials (such as ammonium sulfate or phosphate) and are designed to release nutrients rapidly. However, they are quickly lost from the soil, so you may have to fertilize several times during the growing season unless you use a specially formulated, slow-release product.
Many inorganic fertilizers are super-concentrated, however, so it is easier to use too much and damage your burgeoning root system. But on the plus side, this type of fertilizer is usually easier to find and will be a bit cheaper than its organic counterpart.
Ultimately, the selection between organic and inorganic fertilizers comes down to your specific needs and the soil’s overall health.
My Reviews of the Best Fertilizers for Root Growth
1. Bloom City’s Organic Root Stimulant, Salmon and Kelp Formula (My Top Pick)
0-1-1 Root fertilizer/all-in-one. 100% organic plant rooting supplement that boosts soil quality and gives roots what they need to grow.
Contains various nutrients from fish and kelp (super foods for plants), as well as humic and fulvic acids to stimulate root growth.
Top off this super-powered formula with beneficial bacteria to enrich the soil and you have a winning combination that makes your daily watering super beneficial for your plants’ health and nutrient absorption.
|PROS (+)||CONS (-)|
|+ Promotes vigorous root growth through a mix of vitamins, minerals, microbes, and plant hormones|
+ Is formulated with fish and kelp nutrients that plants love
+ Suitable for both mature plants and seedlings
+ Can be added to compost or compost tea for creating healthy, living soil.
|– Needs to be diluted before use|
2. Fertilome 10645 Root Stimulator and Plant Starter (Best Pick for New Seedlings or Transplants)
This plant starter formula contains Indole Butyric Acid (a plant hormone that stimulates root growth), and has a nutrient ratio of 4% nitrogen, 10% phosphate, and 3% soluble potash.
This product is unique because it also contains a wetting agent, to help combat the soil dehydration that sometimes happens during shipping (for new plants) or soil depletion (for older plants). The wetting agent will help the soil absorb more moisture and nutrients.
It also reduces transplant shock and promotes greener, more vigorous plants.
|PROS (+)||CONS (-)|
|+ Stimulates early root formation and stronger root development|
+ Reduces transplant shock
+ Suitable for trees, shrubs, roses, annuals, and perennials
+ Contains a wetting agent and IBA root stimulator
|– Slight chemical smell upon first application, but it dissipates quickly.|
3. Bonide Garden Rich Root & Grow Root Stimulator & Plant Starter (Best Budget Pick)
This budget-friendly root stimulator and plant starter is an excellent option if you’re looking to boost your plant’s health without breaking the bank.
The 4-10-3 NPK ratio has higher phosphorus to stimulate root growth, as well as an IBA root stimulator (which is a plant hormone used to initiate root formation).
It can be used for transplants, houseplants, vegetables, fruit trees, berries, flowers, shrubs, and ornamentals.
|PROS (+)||CONS (-)|
|+ Contains IBA root stimulator – a plant hormone used to initiate root formation|
+ Mix with water and apply by pouring directly onto the soil and roots
+ Suitable for most every type of plant
|– Needs to be diluted with water before use – but that means it takes up less storage space!|
4. Miracle-Gro Quick Start Planting & Transplant Starting Solution (Most Versatile Pick)
This versatile 4-12-4 concentrated solution can feed all flowers, vegetables, trees, shrubs, transplants, and seedlings.
The higher phosphorus content stimulates root growth, yet it is gentle enough for seedlings.
It’s made by Miracle-Gro, which has been a trusted name in gardening since my mom’s gardening days!
Plus, it’s easy to measure with the pre-measured cap. Mix one capful into a standard 2-gallon watering can.
|PROS (+)||CONS (-)|
|+ 4-12-4 NPK ratio boosts seedling growth quickly|
+ Easy to mix and apply
+ Trusted name of Miracle-Gro
|– Needs to be used frequently (every 7-14 days)|
5. Mycorrhizal Fungi Root Enhancer for Plants (Best Organic Pick)
This product is a bit different than the others. It contains a natural and organic species of beneficial soil fungi that attaches to and grows with the roots, increasing the surface area.
This creates a sponge-like mass that collects and stores nutrients and water, which increases availability and absorption..
Simply sprinkle the granules on the roots at planting time to stimulate new root growth.
|PROS (+)||CONS (-)|
|+ Organic formula is gentle enough for seedlings and hydroponics|
+ Works fast and creates strong roots in 95% of common plants
+ Improves the efficiency of the roots and soil, reducing the need for fertilizer
|– Pricier than other options, but you only need to apply it once!|
In my opinion, you can’t do better than Bloom City’s Organic Root Stimulator Supplement. It contains everything your plants need to grow vigorous roots.
- Nutrients from fish AND kelp – both are potent sources of micronutrients for all plants
- Humic acid – helps transport nutrients to the roots and plants
- Fulvic acid- stimulates root growth and nutrient absorption
- Beneficial bacteria – enriches the soil and helps break down nutrients
- Mycorrhizal Fungi – bonds to and grows with the roots – increasing their surface area and hardiness while improving water and nutrient absorption
This product can be used on lawns, indoor plants, and garden beds. It is suitable for any growing medium, such as coir, soil, peat, or hydro, and is safe to use with other fertilizers.
How to Fertilize to Promote Root Growth
When selecting and applying root fertilizer, there are a few things to keep in mind.
- Start by selecting the right fertilizer for your specific plants. As you can see in my table above, you will get a different mix of nutrients and additives depending on which root fertilizer you buy.
- Whether you’re going with liquid or powder, organic or inorganic, it’s best to start in early spring before the growing season is in full swing. When adding root fertilizer to the soil, knead it into the soil by several inches, where the roots can reach it (be sure to wear gloves!). Do this before adding your plants to give them the nutrients to start strong.
- Fertilizers come in all different strengths and application methods (see table above), depending on your intended purpose. Too much fertilizer can harm plants, so follow the instructions on the fertilizer package carefully and use caution when diluting the product to the proper strength.
- Unless we’re talking about root vegetables (I’m looking at you, carrot), a plant’s roots typically extend several inches out in all directions from the center stem. In the case of trees, the root system can extend out several feet!
That’s why evenly applying the fertilizer around the entire root zone is vital.
For young seedlings or transplants, you can sprinkle the root fertilizer directly on the root ball and put a bit into the bottom of the pot for extra nutritional support. This will ensure that the roots receive the nutrients they need.
A Word About Soil pH
Soil pH can significantly impact the uptake of nutrients in plants. The level of acidity or alkalinity in the soil directly affects the availability of nutrients.
Personally, my biggest gardening challenge has been in trying to amend and perk up the highly alkaline, clay soil here in the high desert. Almost nothing will grow in it except for chaparral and cactus, and our pH typically runs between 8.0-8.4. My solution to this has been to use raised garden beds with store-bought soil and amendments.
For most plants, the ideal range falls between 5.0 and 6.5, as explained in this excellent article from Clemson University. This is because certain nutrients may not be readily available if the soil pH is too high or low. Soil pH test kits are readily available at local garden centers or online and may even offer suggestions to fix any deficiencies.
As we touched on above, nitrogen, phosphorus, and potassium are primary nutrients that are required in larger quantities compared to other plant nutrients. At pH levels above 6.5, phosphorus and most micronutrients are less available. A balanced soil pH will ensure healthy plant growth and optimal nutrient uptake.
Final Thoughts on Best Fertilizer for Root Growth
Whether you choose granular, liquid concentrate, or beneficial fungi and microbes, your plant’s roots will benefit from the added nutrients and support, especially during the fragile early stages when root development is just starting.
The proper root fertilizer can give your plant a vigorous, healthy root structure and the building blocks needed to ensure healthy foliage and abundant flowering and fruiting.