What’s up With My Tomato’s Roots?
Tomato roots growing vertical towards water
Why Are My Tomato’s Roots So Shallow?
"I planted my tomatoes about a month ago in a 30-inch container with old Miracle Grow moisture control soil (the dirt has been in the pot since 2023, so I added some fertilizer).
While scratching the fertilizer in, I found a lot of roots on the surface (barely under the soil). Is it normal for roots to be so close to the surface? The tomatoes are indeterminate, not even five feet tall, but they do have tomatoes. The plant looks scraggly, with light green and tiny leaves and few limbs."—Melissa
Understanding Adventitious Roots and Your Tomato
A tomato plant has an exceptionally large and dense root system. You are probably seeing a combination of dense fibrous roots and adventitious roots.
Since your tomato is in a container, the growth of the central taproot is probably hindered which results in a denser growth of hair-like fibrous roots. Not only that, tomatoes can grow roots from buried portions of the stem, which is why you see so many roots directly below the surface.
In truth, the whole area underneath your tomato is full of roots. Let’s look at how a tomato’s roots grow throughout its life:
TIP: The scraggly growth is most likely from nutrient deficiency (hopefully you have fixed that with fertilizer), excessive heat, over- or under-watering.
Adventitious roots from a tomato stem
Tomato Root Development
When grown from seed, tomato plants have very large roots that can penetrate quite deep into the soil. A tomato’s root system consists of a central taproot with many lateral roots developing off it, and this central core is surrounded by a dense fibrous root system of hair-like roots.
As a general guideline, most sources say a tomato’s roots are about 60cm (2ft) wide and just as deep. In fact, the root system of a tomato plant can be much larger, with the taproot penetrating at least 1.2m (4ft deep) and equally as wide.
Here is a look at how a tomato’s roots grow throughout the growing season:
1. Roots on Young Tomatoes (3-Week-Old)
When a tomato plant is three weeks old, it will be about 10cm (4 inches) tall with approximately four sets of true leaves. Underground, it already has a deep taproot and puts out a tremendous amount of lateral and fibrous roots:
- Taproot: The taproot grows at approximately 2cm to 3cm (1 inch) per day, reaching a depth of around 55cm (22 inches).
- Laterals: There will often be around 60 to 70 laterals in the first 15cm (6 inches) of soil, and around 6-8 laterals per inch below that.
- Fibrous Roots: These will be very dense in the top 25cm (10 inches) of soil, with rather thin threadlike roots below that.
2. Roots on Mid-Season Tomatoes
In the middle of the growing season, an average tomato plant will be around 50cm (20 inches) tall with a spread of around 60cm (2ft) and around 10 branches. At this point, the plants are well-established with an extensive root system:
- Taproot: The main taproot will continue to grow or, if it was damaged, the strongest lateral will take over and grow straight down.
- Laterals: The top 25cm (10 inches) of soil will be full of strong laterals. These will easily spread out 60cm (2ft) from the stem and can penetrate 1m (3ft) deep or more.
- Fibrous: Fibrous and adventitious roots (see below) will have taken over the entire soil surface surrounding the plant.
On average, the entire 1 cubic meter (35 cu ft) of soil beneath the plant will be filled with roots.
3. Roots on Mature Tomato Plants
Once your tomato plant is mature, it will have a massive root structure. In many cases, there will be 15 to 20 major roots, often covering an area 1.5m (5ft) wide and deep beneath the plant (equal to 3.5 cubic meters or 125 cubic feet).
This area will also be filled with dense hair-like fibrous roots.
Adventitious roots
Adventitious Roots
Tomatoes (like many other plants) have the ability to grow roots from non-root material when in contact with soil or in overly humid conditions. In normal terms, this means a tomato can grow roots from any point along the stem.
- When these roots grow from the stem below the soil, they are called adventitious roots.
- When the roots grow above ground, they are called aerial roots.
If part of the stem is buried when transplanting (as is common), roots will grow from the stem. This creates a very dense mass of roots right below the surface of the soil.
Those little hairs on a tomato plant are NOT adventitious roots; the hairs are trichomes.
Effects of Transplanting on Tomato Roots
Above, we have discussed the development of a tomato’s roots when they are grown from seed in the soil. However, most of us start our seeds indoors (or buy seedlings from a nursery) and then transplant them into the garden. The process of potting and transplanting tomatoes affects the overall development of the root structure.
Transplanting tomatoes typically damages the growth of the taproot. In most cases, the taproot curves sideways (or even grows slightly upwards) at around 15cm (6 inches) deep. At this point, it forks into several larger laterals, which often take over the vertical growth.
To compensate for the damaged taproot, most transplanted tomatoes develop a denser growth of fibrous roots below the surface of the soil.
Effects of Containers on Tomato Roots
Growing tomatoes in containers further damages the growth of the taproot and laterals. As these larger roots reach the edge of the container, they are forced downwards or begin circling the pot (and the plant can become rootbound in severe cases).
In most cases, container-grown tomatoes form dense fibrous roots near the soil surface.
When growing tomatoes in a container, it is important to choose a pot that is both deep and wide.
References and Further Reading
- Root Development of Vegetable Crops: Chapter XXVI
A very detailed study on the development of a tomato plant's roots.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
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