How To Promote Root Growth In Plants (6 Ways To Speed It Up)

A strong root system is key for a healthy plant. However, it does not happen by accident!

So, how do you promote root growth in plants? To promote strong, healthy root growth in plants, try these 6 tips:

  • Use a root trainer (at the germination and seedling stage)
  • Repot as Needed (if the plant outgrows its container and becomes root bound)
  • Loosen and Aerate Soil (compacted or waterlogged soil slows down root growth)
  • Practice Deep, Less Frequent Watering (this promotes a more extensive root system)
  • Provide Proper Nutrition (get the pH and nutrient levels right)
  • Add Rooting Hormone (usually for cuttings when propagating plants)

In this article, we’ll get into more detail about each of these methods. Then you’ll know exactly how to promote a stronger root system in your plants.

Let’s get started.

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How To Promote Root Growth In Plants

If you want to promote root growth in your plants, there are 6 key ways to do it:

You can read about these tips in more detail below (or click on the links above to skip to the relevant section).

plant roots bottom of plug plant
Take the right steps to promote root growth in plants and help them get a good start.

Use A Root Trainer

A root trainer is a container that encourages a plant’s roots to grow downward, instead of sideways. This results in a deeper root system, which can then branch out sideways after the plant is moved into the garden.

A root trainer has grooves on the inside that prevent a plant’s roots from circling around the container (avoiding “root bound” or “pot bound” plants). Instead, the roots are “funneled” down towards a hole at the bottom of the root trainer.

root bound
A plant will get root bound if it outgrows its pot.

Once the roots reach the hole at the bottom of the container, they are exposed to the air. At this point, air pruning occurs – that is, the roots stop growing once they touch air.

Air pruning encourages the plant to grow more roots in other locations. This results in a stronger and more extensive root system that will grow deep into the soil after transplant.

According to the University of Washington, air pruning encourages the plant to continuously produce new roots. These new roots replace the old ones that stop growing after they make contact with the air.

Plant Roots
Plant roots stop growing when they touch air, called air pruning. A root trainer encourages air pruning and a more extensive root system.

Air pruning can also be used to propagate larger plants (such as trees). Air pruning means that a tree will have a dense root ball with lots of small roots, rather than a few large roots.

A root trainer also lets you to grow seedlings in separate cells. This prevents roots from getting tangled together.

Later on, it will be easier to transplant seedlings. It also reduces the risk of damage when plants go into the garden.

transplanted lettuce
Using root trainers keeps seedling roots separate, making transplant easy.

Root trainers are often used at the seedling stage to help plants grow a stronger root system. However, you can also use larger root trainers for young trees.

(You can learn more about root trainers in my article here).

Repot As Needed

If your plants get large enough, you may need to repot them at least once before transplant. The reason is that plants will eventually become root bound in a pot that is too small.

A root bound plant has roots that start to circle around the inside of the container. This happens when they have nowhere else to go.

As the roots continue to circle around in search of nutrients, they make their way around the whole pot.

root bound
This plant is root bound – the roots have nowhere else to go in a small container!

At that point, there is no new soil left for the roots to grow into. Eventually, the plant stops growing – although it can maintain its size with enough water, light, and fertilizer.

According to the Penn State University Extension, a root-bound tree in a pot will face trouble at some point. Eventually, the roots will wrap around the stem and trunk of the tree – in effect the tree strangles itself.

After transplanting into a larger pot, the plant’s roots will have more room to grow. You can sometimes tell that a plant needs repotting if you see roots in the drainage holes at the bottom of the pot.

clay pots
When repotting a plant, choose a container that is slightly larger than the old one.

To repot, first find a container that is slightly larger than the current one. Next, add some soil to the bottom of the new container.

Then, gently take the plant out of its old container to avoid damaging the roots. Put the plant, roots, and soil in the new container, on top of the layer of soil you put down earlier.

Finally, add more soil until the new container is filled to where you want it (just don’t cover up too much of the plant’s stem!)

pottings soil mix plant in container
Add enough soil to the new pot after repotting – but not so much that it is overflowing.

You can learn more about repotting plants (including what type of container and growing medium to use) in this article from the University of Maryland Extension.

Loosen & Aerate Soil

If you loosen up the soil for your plants, it will help to keep the roots healthy and allow more oxygen into the soil. Loose, aerated soil will make for a stronger, more vigorous plant.

According to the Colorado State University Extension, compacted soil restricts root growth. This makes sense – it is easier for roots to grow into a softer medium rather than a hard one.

Use a shovel to loosen and aerate the soil before transplanting into the garden. This will allow the roots to grow more freely.

So, before you transplant seedlings into the garden, it is a good idea to loosen the soil a bit. You don’t have to rototill (unless it’s a new garden) – a shovel will probably suffice to break up any clumps or compacted soil.

In addition to providing looser soil, digging will aerate the soil. This is a good thing, since plant roots need oxygen for respiration (in a sense, they need to breathe like we do).

If your soil is compacted or too wet, there will be less room for oxygen. This will decrease the health of the plant, possibly even causing root rot.

Heavy clay soil is more likely to become compacted. To counter this, add some compost to provide organic material and make the soil a little looser.

compost bin
Add compost to help loosen up clay soil a bit.

(You can learn how to make compost here).

Finally, avoid walking on your soil to prevent compaction.

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Practice Deep, Less Frequent Watering

After a plant is established in its new location in the garden, proper watering is important. Soil that is too wet has no space for oxygen, and this causes root rot.

root rot
Root rot causes roots to turn brown and mushy.

(You can learn more about the signs of over watering in my article here).

Watering too often leads to a shallow, weak root system in your plants (since they won’t need to work hard to get water). Instead, provide deep watering less often – this leads to a larger, stronger root system.

Provide lots of water less frequently so a plant’s root system spreads out in search of water.

When plant roots cannot easily find water, they branch out sideways or grow deeper to find more water. Allowing the soil to dry out a little bit between waterings encourages this type of root growth.

Provide Proper Nutrition

In addition to water and air, plant roots will need nutrients in order to grow and to support the plant.

A good first step is to do a soil test to find out the pH and nutrient levels in your soil. You can learn more about how to do a soil test in my article here.

soil test kit
A soil test tells you if your soil needs a pH or nutrient adjustment.

The ideal pH will vary by plant, but most plants are fine in soil with a pH between 6.0 and 7.0 (slightly acidic to neutral). Some plants (such as blueberries and azaleas) prefer soil that is a bit more acidic (4.5 to 5.5).

If your soil is too acidic (low pH), you can add lime (calcium carbonate) to raise the pH. If your soil is too basic (high pH), you can add elemental sulfur to lower the pH.

If your soil test shows a deficiency of any nutrients, you can add some fertilizer to provide NPK (nitrogen, phosphorus, and potassium).

Remember that it is possible to over fertilize, so follow the instructions on the package, and remember that not all fertilizers have the same strength!

fertilizer burn on leaf
Over fertilized plants show signs of burn on the leaves.

Also, remember that the strength of the fertilizer is not the only important factor.  You also need to consider how fast the fertilizer releases its nutrients.

For example, according to the University of New Hampshire Extension, fast release fertilizers may inhibit root growth in plants.

(You can also learn about the best fertilizers for root growth in this article.)

Be sure to fertilize the entire root zone. According to the University of Missouri Extension, the root zone of a tree can extend out twice as far as the branches.

For example, let’s say the branches of a tree spread out 15 inches from the trunk of the tree. Then its root zone may extend up to 30 inches (2×15 = 30) away from the trunk of the tree. So, fertilize this entire area (a circle of radius 30 inches around the tree trunk).

To avoid heavy use of artificial fertilizers, your best bet is to replace nutrients in the soil by adding compost or aged manure. Both of these contain organic material and release nutrients slowly.

Compost or aged manure are good ways to add nutrients and organic material to soil.

This organic material attracts organisms that help the soil (such as earthworms and beneficial bacteria).

What Fertilizer Helps Root Growth?

When choosing a fertilizer to help root growth, pay attention to the NPK ratio on the label.

For example, 10-10-10 means that the fertilizer is 10% nitrogen, 10% phosphorus, and 10% potassium by weight.

On the other hand, 10-20-10 is 10% nitrogen, 20% phosphorus, and 10% potassium by weight.

Phosphorus is a necessary nutrient for proper root growth. Phosphorus helps plants to move energy (carbohydrates) from leaves to fruit or roots.

plant roots bamboo
Phosphorus and potassium both promote healthy roots and plant growth.

Even more relevant here: according to the North Carolina State University Extension, a phosphorus deficiency will limit root growth.

Phosphorus deficiency is common in commercial farmland and more likely in cold soil. Still, it is somewhat rare in home gardens.

Phosphorus deficiency is also more likely where plants have been grown for a long time with no replacement of nutrients (no addition of fertilizer, compost, or manure.)

Without manure, compost, or fertilizer to replace nutrients, a deficiency may occur.

Remember that too much phosphorus interferes with a plant’s ability to absorb nitrogen and micronutrients. (New roots and root hairs are essential for absorbing water and nutrients!)

Potassium is also important for a plant to develop properly. A lack of potassium causes poor root development – but too much potassium causes nitrogen deficiency.

Calcium is necessary for the growth of root tips. A lack of calcium can cause black, rotten roots.

A lack of calcium can cause black, rotten roots in plants.

Does Nitrogen Promote Root Growth?

Nitrogen is a necessary nutrient for plant growth, but it is possible to have too much of a good thing. Too much nitrogen in “hot” (fresh) manure or in strong fertilizer can burn plant roots.

Also, according to the University of Missouri Extension, fertilizing newly planted trees with lots of nitrogen can cause lots of green growth (leaves) at the expense of roots.

Fresh manure may be too “hot” (nitrogen-rich) and can burn plants if applied directly.

When choosing a fertilizer, use a balanced fertilizer that is not too heavy on nitrogen. You can learn about low-nitrogen fertilizers in this article.

When requesting a soil test from your local agricultural extension, let them know what you are growing. That way, they can give you recommendations for the type and amount of fertilizer to use.

Add Rooting Hormone

Rooting hormone is often used when propagating plants by cuttings. Rooting hormone can come as a powder, gel, or liquid.

According to the Michigan State University Extension, rooting hormone increases the chances that a plant cutting will take root. Rooting hormone also causes faster rooting, and it increases the number of roots that appear.

ginger root
Rooting hormone causes faster rooting and makes more roots appear.

There are many different types of rooting hormone available, including this one from Home Depot that contains Indole-3-butyric acid. Remember that liquid formulas are usually more effective than powder formulas.

To use rooting hormone, all you need to do is dip the base end of the cutting into the mixture. Then, plant the cutting normally in a container with the growing medium you want to use.

Be sure to use gloves to protect your hands when using rooting hormone. Follow the instructions on the package label as well.


Now you know how to promote root growth in your plants, and when to use each method. You also know what to avoid (for example, over watering and over fertilizing) to keep plant roots healthy and growing.

Thank you for reading – I hope you found this article helpful. If so, please share it with someone who can use the information.

To find books, courses, seeds, gardening supplies, and more, check out The Shop at Greenupside!

Join 1000+ gardeners to get access to news, tips, and information.

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If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!


To find books, courses, seeds, gardening supplies, and more, check out The Shop at Greenupside!

Join 1000+ gardeners to get access to news, tips, and information.

Delivered right to your inbox – once per week.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!


Jon M

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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