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Chapter 9: Stems With Superpowers: Crawling, Climbing, Storing, and Defending

Not all stems grow straight up toward the sky. Some stems have gotten creative with their job descriptions! These stems do special tasks that help plants survive, spread, and thrive in ways that would make a regular upright stem jealous. Let’s explore some of the weirdest and most wonderful stem modifications in the plant world!

Rhizomes: Underground Stems on the Move

What’s a Rhizome? A rhizome (RYE-zome) is a stem that grows horizontally underground instead of reaching for the sky.

How can you tell a rhizome is a stem and not a root? Look for the telltale stem features: nodes, internodes, and buds. Rhizomes have all of these! At each node, you’ll find scale-like leaves, buds that can sprout into new shoots, and roots growing downward into the soil. It’s like a regular stem lying on its side underground, sending up new plants wherever it goes.

Walk into any grocery store and head to the produce section. See that knobby, tan-colored chunk labeled “ginger”? That’s a rhizome! Those bumpy sections are nodes, and if you look closely, you might even see tiny buds ready to sprout. When you plant a piece of ginger in soil, those buds wake up and send green shoots upward while roots grow downward. The rhizome itself stays underground, getting thicker and producing more nodes as it grows.

Iris plants are rhizome champions too. If you’ve ever seen an iris garden, you might have noticed thick, fleshy stems lying partially exposed on the soil surface. Those are iris rhizomes, and they’re doing something clever: they’re creeping horizontally across the ground, sending up beautiful flowers at intervals. Each spring, new shoots emerge from buds along the rhizome, creating clusters of iris blooms. Gardeners often have to divide iris rhizomes every few years because they spread so enthusiastically!

Many ferns also use rhizomes to spread. Boston ferns, sword ferns, and bracken ferns all have underground rhizomes that creep through the soil, sending up new fronds (fern leaves) as they go. This is why ferns can form such dense colonies in forests. One fern plant can become dozens through rhizome growth, all connected underground like a secret network.

How Rhizomes Spread: The Underground Highway

Rhizomes grow horizontally through the soil using the same apical meristem system that regular stems use, just pointed sideways instead of up! The growing tip of the rhizome pushes through the soil, adding new nodes and internodes as it goes. At each node, the rhizome can:

• Send roots downward to absorb water and nutrients
• Send shoots upward that break through the soil surface and grow into new plants
• Branch off and create more rhizomes spreading in different directions

This horizontal growth strategy is incredibly effective for spreading. A single ginger plant can produce a rhizome network that fills an entire pot in one growing season. Bamboo rhizomes (yes, bamboo uses rhizomes too!) can spread several feet per year, which is why bamboo can take over a yard if you’re not careful. Some gardeners install underground barriers to keep bamboo rhizomes contained!

The rhizome acts like an underground highway system, transporting water, nutrients, and sugars between all the connected plants. This means that even if one shoot gets damaged or eaten by an animal, the rhizome can support it with resources from other shoots. It’s like having a backup power supply!

Winter Survival: The Rhizome’s Secret Weapon

Here’s where rhizomes really shine: they’re survival experts!

When winter arrives and temperatures drop, the aboveground parts of many rhizome plants die back completely. The leaves turn brown, the stems wither, and it looks like the plant is gone. But underground, the rhizome is alive and well, safely insulated by the soil.

Soil temperature stays much more stable than air temperature. Even when the air is freezing, the soil a few inches down might be 40-50°F. The rhizome sits in this relatively warm, protected environment, storing food (starches and sugars) that it made during the growing season. It’s like the plant packed a lunch and found a cozy underground bunker to wait out the winter!

When spring arrives and soil temperatures warm up, the rhizome’s buds sense the change and spring into action. New shoots emerge from the soil, using the stored food in the rhizome to fuel their initial growth. Within weeks, the plant looks like it was never gone. This is why iris, ginger, and many ferns can survive harsh winters even though their leaves can’t tolerate frost! The rhizome keeps the plant alive underground.

Rhizome-atic Success!

By growing horizontally underground instead of vertically aboveground, rhizomes help plants:

• Spread efficiently across large areas
• Survive winter cold and summer drought
• Store food for tough times
• Create new plants without needing seeds
• Share resources between connected shoots

Millions of rhizomes around the world are creeping through the soil, sending up new shoots, storing food, and preparing for the next growing season. That ginger in your kitchen? It’s a rhizome waiting to grow. Those iris in the garden? Connected by rhizomes underground. The ferns in the forest? They are all part of a vast underground rhizome network. Stems don’t always reach for the sky; sometimes they’re perfectly happy spreading sideways in the dark!

Stolons: The Plant’s Cloning Machine

A stolon (STOW-lon) is a stem that grows horizontally along the ground surface instead of underground like a rhizome.

Stolons are sometimes called “runners” because they literally run across the ground, and that’s exactly what they look like: stems making a break for it!

Like rhizomes, stolons have nodes and internodes, but instead of tunneling through soil, they creep along the top of it. At each node, a stolon can produce roots that dig into the soil and shoots that grow upward into new plants. It’s like the plant is playing hopscotch across your yard!

Stolon Superstars: Strawberries, Spider Plants, and Bermuda Grass

If you’ve ever grown strawberries, you’ve witnessed stolons in action! Strawberry plants are stolon-producing champions. After a strawberry plant flowers and produces fruit, it starts sending out long, thin stems that arch through the air and touch down several inches away from the parent plant. Where the stolon touches the soil, it grows roots and a cluster of leaves, and eventually a brand-new strawberry plant!

Here at Guest Hollow, we planted some strawberry plants one spring. By the end of the next year, we had TONS of baby strawberry plants, all connected by stolons! It was like the original plants were building their own strawberry empire!

One strawberry plant can produce dozens of stolons in a single growing season, and each stolon can produce multiple new plants. This is why strawberry patches spread so quickly. Gardeners often have to trim stolons to keep strawberry plants from taking over the entire garden!

You may have watched this video in the previous chapter. If so, feel free to skip it. 😉

How Stolons Work: The Cloning Process

Strawberry plants are secretly running a cloning factory, and they’re not even subtle about it.

Watch a strawberry plant through a single growing season and you’ll see it send out long, thin horizontal stems that creep along the ground like searching fingers. These are stolons (also called runners), and they have one mission: find new territory and build a copy of the parent plant there.

Here’s how the operation works. The parent plant sends a stolon out from a bud near its base. The stolon grows horizontally along the ground, adding nodes and internodes as it extends further and further from the parent. It’s not growing leaves or flowers. It’s not trying to photosynthesize. It’s just reaching, looking for a good spot to set up a new plant.

When the stolon hits a promising location, something remarkable happens at one of its nodes. Roots suddenly shoot downward into the soil. Leaves push upward toward the light. A brand new plant starts taking shape, connected to the parent by the stolon like a biological umbilical cord. The parent plant pumps water, nutrients, and sugars through that connection, supporting the baby plant while it gets established and learns to feed itself.

Once the new plant has a strong enough root system to survive independently, the stolon that connected them shrivels up and decomposes. The connection disappears. The new plant is on its own.

But here’s the truly wild part: that new plant is genetically identical to the parent. Not similar. Not related. Identical. It’s a perfect clone, produced without flowers, without pollination, without seeds, and without any outside help whatsoever. The plant just photocopied itself using a stem.

This is called vegetative reproduction, and stolons are one of the most efficient ways plants do it. One strawberry plant sends out multiple runners simultaneously, each one potentially establishing a new clone in a different location. Those clones send out their own runners. Those runners establish more clones. A single strawberry plant can colonize an entire garden bed in one growing season if you let it, building an expanding network of genetically identical plants all descended from the original.

Spider plants are another stolon superstar, and you’ve probably seen them in hanging baskets. Those long, arching stems with baby plants dangling from them? Those are stolons! Each baby plant (called a “plantlet” or “spiderette”) is a complete miniature spider plant with its own leaves and roots. When the stolon gets long enough, the baby plant touches soil and roots itself, becoming independent. You can also snip off the plantlets and pot them yourself—instant new plants!

Bermuda grass uses stolons to spread across lawns with impressive speed. Those thin stems creeping across your sidewalk or driveway? Stolons! Each node can root down and send up new grass blades, which is why Bermuda grass can fill in bare spots so quickly. It’s also why it’s nearly impossible to get rid of once it’s established. Every little piece of stolon left in the soil can regenerate into a new plant!

Why Stolons Are Brilliant

Stolons give plants some serious advantages:

• Speed: Stolon reproduction is much faster than growing from seeds. A strawberry seed might take weeks to germinate and months to produce fruit. A stolon can create a fruit-producing plant in just a few weeks!
• Reliability: Seeds need the right conditions to germinate: proper temperature, moisture, and light. Stolons work almost anywhere the parent plant can survive because the new plant stays connected to the parent until it’s established. It’s like having training wheels!
• Resource sharing: While the stolon is still connected, the parent plant can send water, nutrients, and sugars to the baby plant, helping it get established. Once the baby plant has good roots and leaves, it can support itself.
• Space conquest: Stolons help plants spread across open ground quickly, claiming territory before competitors can move in. This is especially useful in disturbed areas like gardens, lawns, or forest clearings.

Right now, in gardens and lawns around the world, stolons are creeping across the ground, touching down, rooting, and creating new plants. That strawberry patch is expanding. That spider plant is dangling babies. That Bermuda grass is marching across the sidewalk. Stolons prove that stems don’t need to grow up—sometimes growing sideways is the smartest strategy!

Tubers: The Underground Food Vault

A tuber (TOO-ber) is a swollen, underground stem that stores massive amounts of food, usually starch.

Tubers are basically the plant’s emergency food supply, packed with energy and ready to fuel new growth when conditions are right.

The Most Famous Tuber: The Potato

Let’s settle this once and for all. A potato grows underground, stores food, and looks like it should be a root. But it’s not.

Here’s how you know a potato is a stem and not a root: Look at those little dimples all over the potato’s surface. Those are called “eyes,” and they’re actually nodes! Each eye contains buds that can sprout into new potato plants. If you’ve ever left potatoes in your pantry too long and found them sprouting weird white shoots, you’ve witnessed potato eyes activating their buds.

The potato plant grows underground stems called stolons (hey, we just learned about those!) that swell up at their tips, forming tubers. The plant pumps these tubers full of starch throughout the growing season, creating dense storage organs. When the aboveground part of the plant dies back, the tubers remain underground, waiting.

Carrots, on the other hand, are genuine roots. They don’t have eyes or nodes. They grow straight down following gravity. And if you try to regrow a carrot from a scrap, new shoots emerge only from the crown at the very top (the transition zone between root and stem), not from buds along the root’s length.

Same job (food storage), totally different plant parts.

Here at Guest Hollow, we grow our own potatoes. We plant seed potatoes in the spring, little cut pieces that each have one eye, and in the early fall we dig them up. Each planted “eye” turns into a plant and eventually grows multiple tubers underground, all connected by stolons. Digging them up is like a treasure hunt!

Other Tuber Champions

Potatoes aren’t the only tuber in town! Jerusalem artichokes (also called sunchokes) produce knobby tubers that taste nutty and sweet.

Yams are tubers (though sweet potatoes are actually roots, not tubers—confusing, right?). Caladiums, those colorful ornamental plants with heart-shaped leaves, grow from tubers too.

Why Tubers Are Survival Experts

A potato sitting underground in winter looks like it’s doing nothing. It’s not. It’s waiting, and it’s very good at doing so.

Surviving Winter

When temperatures drop and the above-ground plant dies back, the tuber just sits there underground completely unbothered. The soil acts like natural insulation, keeping temperatures stable enough that the tuber doesn’t freeze solid even when the air above is brutal. Every eye on that potato is a dormant bud, locked and loaded, waiting for spring soil temperatures to rise. When they do, those buds fire up, tap into the stored starch, and push new shoots upward through the soil before the plant has access to a single ray of sunlight. The starch is the fuel that makes this possible. Without it, the shoots would have nothing to run on.

Surviving Drought

In regions with dry seasons, tubers pull off the same trick horizontally in time. When the soil dries out and conditions turn harsh, the above-ground plant dies back and the tuber goes dormant underground, where soil retains moisture far better than the open air. The tuber’s thick skin prevents water loss. It just sits there, waiting. When rain finally returns and conditions improve, the buds activate and the whole plant rebuilds itself from scratch using stored energy.

It’s the botanical equivalent of hitting pause on the entire plant and resuming later like nothing happened.

Storing Ridiculous Amounts of Energy

A single potato contains enough stored starch to fuel the growth of an entirely new plant: multiple stems, multiple leaves, flowers, and eventually more tubers. All from one lump of underground stem tissue. The energy density is remarkable. It’s why humans figured out thousands of years ago that potatoes are one of the most efficient food crops on Earth. We’re not just growing potatoes. We’re raiding a plant’s emergency energy reserves. 😉

The Built-In Cloning System

Like stolons, tubers can reproduce the plant without seeds, flowers, or pollination. Every eye on a potato is a bud, and every bud can potentially grow into a completely new plant. This means you can take one potato, cut it into chunks (making sure each chunk has at least one eye), plant them separately, and grow multiple new potato plants from a single tuber.

Gardeners call these chunks “seed potatoes,” which is genuinely confusing because they’re not seeds at all. They’re stem pieces. But the name stuck, probably because it’s easier to say “seed potatoes” than “carefully cut chunks of underground stem tuber with dormant buds that will sprout into genetically identical clones of the parent plant.”

Take a look at this short video that shows how to prepare seed potatoes for planting:

One tuber becomes many plants. Those plants make more tubers. Those tubers make more plants. It’s a self-perpetuating underground multiplication system that keeps running season after season, completely independent of seeds, pollinators, or anything else. Just stem tissue, stored starch, and a lot of patience.

Bulbs: The Layered Stem Surprise

Bulbs: The Ultimate Underground Survival Pod

Bulbs are the plant world’s greatest imposters. They live underground like roots, get dug up like roots, and look suspiciously like roots, but they’re not roots at all. A bulb is actually a short underground stem wrapped in thick, fleshy leaves stuffed with stored food, like a survival pod the plant builds for itself before winter hits.

The word “bulb” comes from the Greek word “bolbós” meaning onion or rounded swelling. If you’ve ever held a bulb in your hand, you’ll agree that’s a perfect description.

Slice One Open and See For Yourself

Here’s a botany experiment you can do in your kitchen right now: grab an onion and slice it in half from top to bottom. Congratulations, you just performed a bulb dissection. Don’t have one, here’s a video of an amaryllis bulb being cut open that you can watch instead.

Masters of Patience (And Speed)

Bulbs are the ultimate wait-and-explode survival strategy. When winter arrives or conditions turn brutal, the above-ground parts of the plant die back completely. The bulb stays underground, fully alive, fully stocked, and completely unbothered by the cold. It’s not dead. It’s just waiting.

Then spring arrives. Soil temperatures start to rise. And the bulb absolutely launches.

Using all that stored food energy, bulbs rocket up leaves and flowers at astonishing speed, often before most other plants have even started thinking about growing. This is why tulips and daffodils are some of the first flowers to appear in spring. They’re not particularly tough or cold-resistant above ground. They’re just cheating by using pre-stored energy instead of starting from scratch like everyone else. They came to the race already fueled up while other plants were still warming up.

The Multiplication Machine

Why Bulbs Are Brilliant

Bulbs offer plants some serious advantages:

• Rapid spring growth: Because bulbs have pre-made food stored in their leaves, they can send up shoots incredibly fast in spring. Tulips and daffodils can go from underground bulb to blooming flower in just a few weeks, beating most other plants to the spring sunshine.
• Winter survival: Bulbs are protected underground during winter. The soil insulates them from freezing, and the stored food means they don’t need to photosynthesize during the cold months.
• Perennial power: Bulbs allow plants to be perennial (coming back year after year) without maintaining aboveground structures through winter. The plant can die back completely and still return next year.
• Reproduction: Many bulbs produce offset bulbs (called bulblets) that grow attached to the main bulb. Over time, one bulb becomes a cluster of bulbs, creating more plants. This is why daffodil patches get bigger and denser over the years!

Corms: The Solid Stem Storage Units

What’s a Corm? A corm looks a lot like a bulb from the outside, but slice it open and you’ll see the difference immediately. While a bulb is mostly thick leaves wrapped around a tiny stem, a corm is mostly stem—solid stem tissue packed with stored food. The word “corm” comes from the Greek “kormos,” meaning “tree trunk,” which makes sense because corms are basically chunky little stem trunks!

Corm Champions

	Gladiolus produces spectacular flower spikes from corms that look like small, flattened onions. But cut one open and instead of layers, you’ll see solid tissue with a few thin, papery leaf scales on the outside. The entire inside is stem tissue loaded with starch.
	Crocuses are those cheerful purple, yellow, and white flowers that pop up in early spring, sometimes pushing right through snow! They grow from small corms about the size of a large marble. Each fall, gardeners plant crocus corms, and each spring, those corms send up flowers and leaves, using their stored food to bloom before most other plants have even woken up.
	Taro (also called dasheen) produces large corms that are a staple food in many tropical regions. When cooked, taro corms become soft and slightly sweet. In Hawaii, taro corms are pounded into poi, a traditional food. One taro corm can weigh several pounds. That’s a lot of stored stem!

The Corm’s Wild Survival Strategy: Death and Replacement

Here’s where corms get genuinely weird. Unlike a battery that recharges itself, a corm doesn’t refill when it runs out of energy. Instead, it does something much more dramatic.

Every spring, the corm burns through its stored food to push up leaves and flowers. It spends everything it has, holding nothing back. By the time it’s done flowering, the original corm is basically exhausted and shriveling up like a deflated balloon. A normal storage organ would just refuel and reset. Not a corm.

Instead, as the plant photosynthesizes through the growing season, it takes all that new energy and builds a completely brand new corm right on top of the old one. Not beside it. Not inside it. On top of it. By fall, the original corm is a shriveled husk sitting at the bottom, and a fresh fully loaded replacement corm is sitting right above it, fat and ready for next year.

The old corm essentially sacrificed itself to build its replacement. It’s less like recharging a battery and more like the plant just builds a brand new battery every single year and throws the old one away.

But wait, it gets weirder. Many corms also produce tiny baby corms called cormels that cluster around the base of the main corm like small satellites. These cormels are miniature clones of the parent, and they can be separated and planted to grow entirely new plants. This is how gladiolus growers multiply their stock. You plant one corm in spring, dig it up in fall, and find a new replacement corm sitting on top of the shriveled original, surrounded by a handful of baby cormels. One corm becomes many. Those become many more. It’s an underground multiplication operation that runs automatically every single year.

Corms vs. Bulbs: Spot the Difference

Here’s a quick way to tell them apart:

• Bulb: Cut it open and you see layers (like an onion)
• Corm: Cut it open and you see solid tissue (like a potato)
• Bulb: Mostly modified leaves with a tiny stem
• Corm: Mostly modified stem with thin leaf scales

Both store food underground and help plants survive tough conditions, but they do it with different structures!

Thorns: Stems Turned Bodyguards

Some plants take defense very seriously. Instead of hiring security, they turn parts of their own bodies into weapons.

Thorns are modified stems. That means they grow from the same places stems normally grow, such as buds or branch tips, but instead of turning into leafy branches, they harden into sharp, pointed structures. Their job is simple: make the plant unpleasant, painful, or downright dangerous to eat. Thorns are a defense against hungry animals. A mouthful of leaves is much less appealing when it comes with a jab to the nose or tongue. Thorns also help protect young buds and tender growing tips, which are often the most valuable parts of the plant.

You can find true thorns on plants like hawthorn and many citrus trees. If you look closely, thorns are not just stuck onto the surface. They are deeply connected to the plant’s internal tissues, including vascular tissue. That makes them strong, woody, and very hard to break off.

Thorns, Spines, and Prickles: Nature’s Weaponry (And Why You’re Probably Using the Wrong Word)

Most people call any sharp pointy thing on a plant a “thorn.” Most people are wrong. There are actually three completely different structures that plants use for defense, and they’re built differently, attached differently, and come from completely different plant tissues. Getting them mixed up is like calling every insect a “bug.” Technically incorrect, and any botanist within earshot will wince.

Here’s how to tell them apart:

Thorns are modified stems. Real thorns have nodes, internodes, and sometimes even tiny leaves or buds growing right from them, because they’re genuine stems that hardened into weapons. Because they’re deeply embedded in the plant’s vascular system, true thorns are extremely difficult to snap off. Try to break one and you’ll likely damage the branch instead. Hawthorn trees, honey locust trees, and citrus trees have true thorns. If it laughs at your attempts to remove it, it’s probably a thorn.

Here’s a picture of thorns on a honey locust tree. How’d you like to climb that? 😂 They also have thorns on their branches.

Spines are modified leaves. Cacti don’t actually have regular leaves at all. Those sharp points covering a cactus are leaves that transformed into spines over time instead of becoming flat photosynthetic surfaces. They grow from nodes (exactly where leaves would grow) and connect to the plant’s vascular tissue. Barberry shrubs also have spines. Spines are tough and firmly attached, but they’re modified leaves doing a completely different job than the one leaves usually do.

Prickles are neither stems nor leaves. They’re outgrowths of the epidermis (the plant’s outer skin) and cortex (the outer tissue layer), with no connection to the vascular system whatsoever. Because they’re not attached to anything critical, they snap off relatively easily with sideways pressure. Roses have prickles. Blackberries have prickles. Raspberries have prickles.

Those “thorns” on your rose bush? Prickles. Technically.

Those terrifying spikes on a cactus? Spines. Modified leaves.

The brutal weapons on a hawthorn tree that will absolutely destroy you if you walk into one? True thorns. And they deserve their name.

Does this distinction matter in everyday life? Not really. Nobody at the garden center is going to correct you for saying “thorn.” But now you know the difference, and knowing the difference tells you something genuinely interesting about plant anatomy: plants know how to turn stems, leaves, AND skin tissue into weapons. They’re defending themselves with whatever materials they have available, and they’re surprisingly creative about it.

Why Thorns Work: The Defense Strategy

Thorns serve one main purpose: keep herbivores away! A deer might nibble on a thornless shrub, but it’ll think twice before munching on a hawthorn. Thorns make the plant painful or dangerous to eat, which protects the leaves, flowers, and fruits.

Some plants take thorns to the extreme. The honey locust tree, which we showcased above can have thorns up to 8 inches long that branch into multiple points, creating a seriously intimidating defense system. These thorns are so strong that they were used as nails by early American settlers!

Thorns also provide unexpected benefits: they create safe nesting spots for birds! Small birds like to nest in thorny shrubs because predators (like cats and snakes) can’t easily reach the nests. The plant gets protection from herbivores, and the birds get protection from predators. It’s a win-win!

Climbing Stems: Plants That Refuse to Do the Hard Work

Climbing plants are the freeloaders of the plant world, and they’re brilliant at it. Instead of investing resources in wood and thick stem tissue, they stay lightweight and flexible, redirecting all that saved energy into growing fast and reaching sunlight. They just need something nearby to grab onto.

Tendrils: Nature’s Grappling Hooks

Some climbing plants use tendrils, which are thin, wiry, touch-sensitive structures that reach out into the air like searching fingers. The moment a tendril brushes against something solid (a fence wire, a branch, another plant’s stem), it starts coiling around it like a tiny spring, tightening its grip and pulling the plant upward.

Grape vines do this. So do peas, cucumbers, and passion flowers. Watch a tendril under time-lapse video and it looks almost alive and deliberate, slowly rotating through the air until it finds something to grab, then rapidly spiraling tight.

Take a look at these pea plants and see how their tendrils help them climb:

Here you can see a cucumber tendril reaching and coiling:

It’s genuinely one of the coolest things plants do, and it happens too slowly for us to notice in real time.

Twining Stems: The Full-Body Wrap

Other climbing plants skip the tendrils entirely and just wrap their entire stem around a support. Morning glories, pole beans, and wisteria all do this, spiraling upward around whatever’s available like a living corkscrew.

The video quality of this video isn’t great, but it does a good job at showing the twining motion of this vine:

Here’s where it gets interesting: twining stems don’t all twist the same direction. Some always spiral clockwise. Others always spiral counterclockwise. This isn’t random and it’s not caused by sunlight or wind. It’s genetically programmed into the plant. Cells on one side of the stem grow slightly faster than cells on the other side, which forces the stem to curve and twist consistently in the same direction every single time, no matter what. Most varieties of honeysuckle twine clockwise. Bindweed always twines counterclockwise. It’s baked into their DNA and never changes.

Which means if you tried to train a counterclockwise twiner to spiral the other direction, it would fight you the entire way. The plant’s growth pattern is completely non-negotiable.

The Climbing Payoff

By outsourcing their structural support to fences, trees, walls, and trellises, climbing plants get access to full sunlight without spending a single resource on building a trunk. A morning glory can climb ten feet in a single summer on a stem barely thicker than a pencil. A wisteria vine can eventually get so heavy it collapses the structure it’s climbing on, which seems like a design flaw until you realize the wisteria doesn’t care at all. It just keeps climbing whatever is left.

Water-Storing Stems: The Desert’s Living Water Tanks

In a desert, leaves are basically a death wish. They lose water constantly through transpiration, which is the process of water evaporating from leaf surfaces (something we’ll talk about more in the chapter about leaves). In an environment where it might not rain for months, that kind of water loss is a serious problem for plants. Some plants handle this challenge in a remarkable way. Their leaves are greatly reduced, sometimes to spines, and the stem takes over the entire job of photosynthesis.

Cacti are the most famous example. A cactus stem is essentially a living water tank wrapped in green photosynthetic tissue and armored with spines. During a rainstorm (which might happen only a few times a year), the stem absorbs and stores as much water as possible. A large saguaro cactus can soak up and store hundreds of gallons of water in a single rainstorm. Then it slowly rations that water out over the following weeks or months until the next rain arrives.

Ribbed Stems: The Expandable Water Tanks

Look closely at a cactus stem and you’ll notice it has vertical ribs and grooves running up and down. These aren’t just decorative—they’re functional!

When it rains, the cactus absorbs water rapidly through its roots. The stem tissue swells with stored water, and the ribs expand outward like an accordion or a pleated skirt opening up. The grooves between the ribs flatten out as the stem gets fatter.

During drought, the cactus slowly uses its stored water. As water is consumed, the stem shrinks, and the ribs become more pronounced again. The grooves deepen as the stem contracts.

This accordion-like structure allows the stem to expand and contract dramatically without splitting or damaging the tissue. It’s like the cactus is wearing stretchy pants that can accommodate a big meal (water) and then shrink back down when the meal is digested!

Fun Fact: Some barrel cacti can expand their diameter by 20-30% after a heavy rain! If you could watch a time-lapse of a cactus during and after a rainstorm, you’d see it visibly plumping up as it drinks! Oh, hey, look, I found a video that shows that (plus some other interesting facts)! 😉

Is it true that you can cut open a cactus for water if you are stranded in the desert, though? Let’s find out:

Make sure to check out the video in our Botany Curriculum schedule about how cacti can possibly help in a desert survival situation!

Chlorophyll in Stems: Green Stems at Work

Most plants do photosynthesis in their leaves, but cacti and many other succulents do it in their stems. If you look at a cactus, you’ll see it’s green. That’s chlorophyll in the stem tissue!

The stem has a thick, waxy coating (called a cuticle) that prevents water loss, but underneath that coating are layers of cells packed with chloroplasts. These cells capture sunlight and convert it to energy, just like leaf cells do.

The Night Shift Strategy

Some cacti have a really clever trick! Most plants open their tiny breathing pores (called stomata) during the day to collect carbon dioxide from the air. Carbon dioxide is a gas that plants need to make food through photosynthesis. It’s one of their essential ingredients, like flour for baking bread. But there’s a problem with opening your pores during the scorching daytime heat in the desert—when you open them, precious water escapes!

So desert cacti work the night shift instead! They open their stomata at night when the air is cool and damp, collect all the carbon dioxide they need, and then slam those pores shut before the sun comes up. They store the carbon dioxide inside their tissues overnight (kind of like packing a lunch), and then use it for photosynthesis during the day when the sun is shining.

It’s brilliant! The cactus gets its photosynthesis done without losing water to the hot, dry daytime air. Scientists call this CAM photosynthesis (which stands for Crassulacean Acid Metabolism—try saying that five times fast!), but you can just think of it as the “night shift” strategy.

It’s like the cactus is saying, “Why work in the blazing heat when I can do my shopping at night when it’s cool and comfortable?” That’s a great design!

Let’s Eat Some Stems!

Humans have been eating plant stems for thousands of years. Before moving on to the next chapter, let’s take a look at some of the most common, surprising, and useful stems that show up on our plates!

Asparagus is one of the most obvious edible stems. Those green (or purple or white) spears you see in the grocery store? Those are young stem shoots! If you let asparagus keep growing instead of harvesting it, those stems would grow tall and produce feathery leaves and eventually flowers. But we harvest them young when they’re tender and delicious.

	Celery is another obvious stem vegetable. Those crunchy stalks are actually the leaf stalks (petioles) and stems of the celery plant.
	Rhubarb has thick, tart stems (technically leaf stalks) that are used in pies and jams. The leaves are toxic, but the stems are edible when cooked. Rhubarb is one of the first plants to emerge in spring, and those red or green stems are a welcome sight after winter!
	Kohlrabi is a weird-looking vegetable that looks like an alien spaceship! It’s a swollen stem that grows above ground, with leaves sprouting from it at odd angles. The name comes from German words meaning “cabbage turnip,” and it tastes like a mild, sweet cabbage. You can eat it raw or cooked.
	Broccoli and cauliflower are actually clusters of flower buds on thick stems. When you eat broccoli, you’re eating the stem and the unopened flowers!
	Sugar cane is a grass whose stems are packed with sweet, sugar-rich juice The stems are crushed to extract the sweet juice, which is then processed into sugar. Most of the sugar in your kitchen probably came from sugar cane stems, but it’s also possible that it comes from sugar beets!

By now, stems should never look ordinary again. They are not just green sticks holding leaves in the air. They crawl underground as rhizomes, sprint across the soil as stolons, swell into food vaults as tubers, layer themselves into survival pods as bulbs, and even sharpen into thorns for defense. Some grow into towering trunks that record centuries of history in wood. Others quietly clone themselves and take over entire gardens.

Stems support, transport, store, defend, and sometimes completely reinvent themselves to survive. But even with all these superpowers, stems still rely on one critical partner. They lift leaves into the light. And in the next chapter, we’ll discover why those leaves are the real energy factories that keep the entire plant world alive.