What’s the Difference Between Roots and Rhizomes?
Have you ever noticed the words root and rhizome used interchangeably and wondered if there is a difference? I’m here to tell you there is! Join small-scale farming expert Jenna Rich as she discovers the true meaning of root and rhizome and provides insight that should make you feel confident about the meaning of both terms and how they affect plant growth.
Is it a root, or is it a rhizome? Although these terms are sometimes used interchangeably, they have different functions in the botanical world.
Interestingly, the short answer is that a rhizome is a group of roots, sort of. While on the surface, these ‘Rs’ seem to have similarities, they are quite different when it comes to plant functionality. Let’s explore each of them further.
What Is A Root?
A root is the underground system of fibrous, thread-like membranes or thick main roots that help hold a plant in place, reach down into the soil in search of moisture and nutrients, and send it back up through the stem to nourish the plant.
What Is A Rhizome?
The word rhizome is derived from the word rhizoma, which means “a bunch of roots” in Greek. Rhizomes, in short, are a storage area for starches and proteins. They grow horizontally in the soil and have the ability to grow a new plant by setting roots and growing shoots upwards. They are sometimes called creeping rootstalk due to their horizontal growth pattern. A rhizome is essentially an underground, horizontally growing stem.
The answer to this question is complicated. People often call popular crops like ginger and turmeric roots when they are actually rhizomes.
Let’s try to clear up the differences.
|Main role||Absorbs water and nutrients||Stores nutrients and spreads to self-propagate|
|Growing pattern||Grows below the ground and comes from the plant’s base; may also form at the bottom of a rhizome. If a plant is started from seed, roots form at the bottom and grow down into the soil. Roots do not have growth nodes as rhizomes do.||Develops in a sideways spreading fashion rather than developing taproots that go down deep below. May create roots and shoots from their growth nodes.|
|Existence||When starting from seed, roots do not exist until the seed has germinated and a plant has begun growing. If dormant in winter, roots can begin to sprout new growth as the weather warms, signaling your plants to start growing.||Rhizomes are harvested at the end of the season, and their nodes may act as the “seed” for the next generation. A rhizome stays dormant until ideal conditions are presented.|
|Reproduction||Roots develop at the base of a newly germinated seed or off the bottom of a rhizome or tuber when conditions are right. Some roots can be divided, but most plants with a central taproot cannot be divided for propagation.||A brand new, identical plant can be asexually reproduced by a chunk off the parent plant.|
|Types||Taproots, fibrous roots, adventitious, and tuberous||Above-ground, below-ground|
Types Of Roots
There are four main root types, each serving a different purpose.
- Taproots are one main root formed off a plant that dives downward into the earth for water and nutrients. Some smaller roots may shoot off the main taproot to help with security and continuing life. Many gardeners consider dandelions a nuisance weed. It breaks off from the main taproot when pulling it out. This allows the plant to sprout new life from any remaining pieces of the taproot. Plants with large taproots are common worldwide, and these roots that reach deep into the soil profile can assist the plant in surviving periods of drought.
- Fibrous roots, unlike taproots, form a crazy network of small roots that stay closer to the soil surface rather than going deep. These are more common in areas where water is abundant. Most grasses and some common weeds like crabgrass and chicory have fibrous roots and assist in keeping soil in place. An excellent way to envision a fibrous root system is to imagine the canopy of a tree with branches going in multiple directions; fibrous roots form similarly just below ground.
- Adventitious roots stem off the main growing stem above ground. Epiphytic plants often use adventitious roots to anchor themselves to vertical surfaces, such as the sides of trees or rocks. Non-epiphytes use adventitious roots to take advantage of extra moisture in the air; a good example is tomato plants forming white, nubby root stubs off of lower stems.
- Like rhizomes, tuberous roots serve as a location for food storage. However, don’t confuse them with tubers. Tuberous roots are modified roots, not shoots. Sweet potatoes and dahlias are common examples. These tubers attach to the main root system so the plant can use the energy they store, but they are not limited to a sideways spread as rhizomes are and may be in any orientation underground.
The Lowdown On Rhizomes
In annual plants, rhizomes store starch, fats, and carbohydrates and serve as a food source. This food storage helps protect perennial plants throughout the winter, especially during harsh conditions. This helps us understand why perennial plants can be the first to appear in the spring, even after a long and cold winter.
Think of rhizomes as giving plants a head start to other plants started from seed and transplanted when the conditions seem ideal. Rhizomes surviving underground is nature’s way of carrying on native plant life without human interaction! The plant has snacks for the winter, and growth is happening on that underground stem, even when snow’s still on the ground. Nature gives the rhizome a signal that tells it the time is right, and just like that, new vegetative growth appears above the surface.
The main difference between a rhizome and a tuberous root is that rhizomes grow horizontally just below the surface. Tuberous roots, or underground stems, can and will grow in any direction, whereas rhizomes only form roots alongside the bottom as the stem grows horizontally.
Irises and ferns are examples of this simple system. Simply put, you plant these rhizomes at the soil surface, and the roots start to form, going to work underground. New stems begin to sprout above ground, and a new generation of life begins.
Raspberries have below-ground rhizomatous systems growing horizontally just below the surface, and lots of roots shoot off the bottom of the rhizome. Raspberries can easily become invasive due to their intricate root system. Try growing them in raised beds or containers to reduce their spread.
Crops such as ginger reproduce asexually by putting a ginger rhizome into the soil. They don’t need spores or seeds! They spread via vegetative reproduction, meaning the variety created from the rhizome is an exact replica of its parent. This fairly simple reproduction process explains why there is very little genetic diversity.
Ginger plants grow to around three to four feet above ground, and when it’s time to harvest, you dig beneath the surface to harvest the rhizome, or what we know as ginger root. You can eat the rhizome or store it until the next season when it’s time to plant the next generation of ginger.
So Ginger Is a Rhizome, Not A Root?
Some rhizomes are edible, and I bet you already eat some without even realizing it. Ginger and turmeric are two very popular culinary rhizomes that you have probably eaten. The ginger you see at a farmers’ market is often called a root. However, it’s actually a rhizome. True roots have the ability to absorb and transport nutrients and water. While ginger has a fine network of true roots, the portion we eat is the juicy storage receptacle.
The ginger rhizome stores nutrients for next season’s crop. When planted and provided with proper conditions, the rhizome will begin to set roots from the bottom that will grow below the soil surface, and shoots will begin to sprout from the top of the nodes. The above-ground shoots will become the stem. The new roots will anchor the plant, locate nutrients in the soil, and send them back up.
The plant world can often seem overwhelming, but we’re here for you! Now that you understand their key differences, I hope you feel more confident when planting, caring for, and eating plants that develop roots and rhizomes.