Large Garlic Bulbs and Phosphorus
- Jere Folgert
- Mar 22, 2023
- 11 min read
Updated: Nov 27, 2025
The Hidden World Beneath Your Feet: Unlocking the Power of Soil Nutrients
Our kids are crazy about LEGOs. We’re always building awesome stuff together with them. We were thinking about our garlic garden - like a busy little city. The plants are the people who live there, and way down in the soil they’re all connected by a secret underground system that brings them food (nutrients) so they can grow strong. The most important “food” in that system is something called phosphorus. It’s like the basic LEGO bricks you need for any big, cool build. Phosphorus is the key piece that helps plants grow big and healthy. If your plants don’t get enough phosphorus, things go wrong. For example, your garlic bulbs will stay tiny and weak—like trying to build a giant LEGO skyscraper when someone took away half the bricks. Scientists already know a lot about dirt (like the tiny germs in it, how acidic it is, and how nutrients move around), but there’s still a ton of mysterious stuff we haven’t figured out yet!
A soil test, which you absolutely should get, might miss critical nuances. So, before you toss another handful of NPK fertilizer into your garden, pause. Too much phosphorus can harm your plants and the environment, like overloading a LEGO tower with mismatched pieces.
Phosphorus is a superstar, fueling everything from robust roots to vibrant garlic bulbs. It’s woven into plant DNA, the blueprint for growth, and powers ATP, the energy packets driving photosynthesis and respiration. Without enough phosphorus, your garlic is like a chef without ingredients—struggling to produce plump, flavorful bulbs. Yet, not all soils lack this vital nutrient; some are brimming with it, while others hold phosphorus in forms plants can’t use.
A soil test is your map to this hidden world, revealing whether your garden craves a phosphorus boost or already has plenty. In this article, we’ll unearth the science and secrets of soil nutrients, empowering you to nourish your garlic wisely. Don’t just follow old habits—test, experiment, and discover what makes your soil sing.
What is Phosphorus?
Phosphorus is a nutrient that is essential for the growth of garlic bulbs. It is a component of the cell walls and helps to store energy in the bulbs. Phosphorus is also involved in the production of Adenosine triphosphate (ATP) which is the source of energy for use and storage at the cellular level. The structure of ATP is a nucleoside triphosphate, consisting of a nitrogenous base (adenine), a ribose sugar, and three serially bonded phosphate groups.
Phosphorus is important for growing big garlic bulbs. Phosphorus is a macronutrient that is essential for plant growth. It is involved in a number of important processes, including cell division, energy production, and root development. Garlic plants need phosphorus in order to form large bulbs. If the soil is low in phosphorus, the garlic plants will not be able to grow large bulbs. Here are some tips for ensuring that your garlic plants have enough phosphorus:
Have your soil tested to determine the phosphorus levels.
Add phosphorus-rich fertilizer to the soil before planting.
Water the plants regularly to help the phosphorus move through the soil.
Mulch around the plants to help retain moisture and keep the soil cool.
Phosphorus is found in soil, but it is not always available to plants. Some soils have more than enough phosphorus, some do not. The phosphorus in soil needs to be in a form that plants can absorb. This form is called soluble phosphorus. Soluble phosphorus is found in the soil water.
A generalized map of the United States showing the distribution of phosphorus in the soil C horizon, conterminous U.S. can be viewed from this link:
When garlic plants are growing, they need phosphorus. This is because phosphorus is involved in many important processes in the plant. Without phosphorus, the garlic plant would not be able to grow properly. Phosphorus can be found in a variety of sources, including bone meal, manure, and phosphate rock. It can also be found in some fertilizers. There are a few things that you can do to make sure that your garlic plants have enough phosphorus: First, you can avoid over-fertilizing the garlic by performing a soil test first, to determine if you need to add this element. Second, you can add phosphorus to the soil when you plant the garlic. You can use a fertilizer that contains phosphorus, or you can add phosphorus-rich compost to the soil. Third, you can keep the soil moist. Phosphorus is more available to plants when the soil is moist.
Large bulb development requires a variety of other nutrients too, in addition to Phosphorus, including:
Potassium: Potassium helps to regulate water balance and nutrient uptake.
Nitrogen: Nitrogen is essential for the production of proteins and nucleic acids.
Calcium: Calcium helps to strengthen the cell walls and support the bulbs.
Magnesium: Magnesium helps to convert food into energy and regulate water balance.
Sulfur: Sulfur helps to produce proteins and amino acids.
Zinc: Zinc helps to regulate the immune system and promote growth.
Iron: Iron helps to transport oxygen throughout the plant.
Manganese: Manganese helps to regulate photosynthesis and promote growth.
Copper: Copper helps to produce enzymes and protect the plant from damage.
Boron: Borom helps to transport sugars and regulate growth.
Molybdenum: Molybdenum helps to convert nitrogen into a form that plants can use.
In addition to these essential nutrients, garlic bulbs also require a number of trace nutrients, including chromium, cobalt, iodine, selenium, and vanadium. These trace nutrients are involved in a variety of important processes in the plant, and their deficiency can lead to a number of problems, including stunted growth, yellowing leaves, and decreased bulb size.
To ensure that your garlic bulbs have the nutrients they need, you can provide them with a balanced fertilizer. You can also add compost to the soil, as compost is a good source of nutrients.
What Causes Small Garlic Bulbs?
There are a few common causes of small garlic bulbs at harvest:
Not enough water. Garlic needs plenty of water to grow large bulbs. If the soil is too dry, the garlic will not be able to get the water it needs and will produce small bulbs.
Not enough nutrients. Garlic also needs plenty of nutrients, especially nitrogen, phosphorus, and potassium, to grow large bulbs. If the soil is not fertile, the garlic will not be able to get the nutrients it needs and will produce small bulbs.
Too much shade. Garlic needs full sun to grow large bulbs. If the garlic is planted in too much shade, it will not get the sunlight it needs and will produce small bulbs.
Harvesting too early. Garlic bulbs need time to mature before they are harvested. If the garlic is harvested too early, it will not have had time to develop large bulbs.
If you are experiencing small garlic bulbs at harvest, you can try the following to improve your results:
Water the garlic more often. Make sure the soil is moist but not soggy.
Apply a balanced fertilizer. Apply a balanced fertilizer to the garlic in the spring.
Plant the garlic in full sun. Plant the garlic in a sunny spot in the garden.
Harvest the garlic at the right time. Harvest the garlic when the leaves start to turn yellow and die back.
Here are some tips on how to grow large garlic bulbs:
Choose the right variety. Some varieties of garlic are better suited for growing large bulbs than others. Choose a variety that is known for its large bulbs.
Plant in the fall. Garlic bulbs should be planted in the fall, about 6 weeks before the first frost.
Plant in well-drained soil. Garlic bulbs need well-drained soil to grow properly. If the soil is too wet, the bulbs will rot.
Water regularly. Garlic bulbs need to be watered regularly, especially during the first few weeks after planting.
Fertilize regularly. Garlic bulbs need to be fertilized regularly, especially during the first few months of growth. Use a balanced fertilizer that is high in nitrogen.
Thin the plants or plant 6" apart in the fall. Garlic plants should be thinned to about 6 inches apart. This will give the bulbs more space to grow and develop. Ideally, plant garlic cloves 6" apart in the fall.
Harvest when the bulbs are mature. Garlic bulbs are ready to harvest when the lower three leaves the plants start to yellow and fall over. Carefully dig the bulbs out of the ground (use a garden fork) and cure them in a cool, dry place for a few weeks before storing them.
Don’t Be a Soil Fool: Test Before You Mess with Phosphorus!
Imagine your garden as a finicky chef, demanding just the right ingredients to whip up a gourmet salad. Dump in too much phosphorus without checking, and you’ve got a toxic soup that’ll make your plants gag! Soil tests are your kitchen scale, measuring exactly what’s in your soil so you don’t poison your green babies. They reveal the dirt on nutrient levels, pH, and sneaky problems like acidity or compaction, helping you keep your garden thriving like a five-star restaurant.
Why Soil Tests Are Your Garden’s BFF
Soil tests are like a health checkup for your dirt. They spill the tea on:
pH Level: Is your soil a grumpy acidic lemon (below 7) or a chill alkaline smoothie (above 7)? A neutral pH (around 7) is the sweet spot for plants to slurp up nutrients. Get it wrong, and your plants are basically on a hunger strike.
Organic Matter: This is the decomposed plant and animal goo that makes soil fertile and drains like a dream. Too little, and your soil’s as lifeless as a bad comedy club.
Nutrient Levels: Nitrogen, phosphorus, potassium, calcium, and magnesium are the VIPs of plant growth. Too little, and your plants are scrawny; too much, and you’re in toxic territory.
Contaminants: Heavy metals, pesticides, or herbicides can lurk like uninvited guests, harming plants and maybe even you. Yikes!
Hold Up—Don’t Touch That Phosphorus Yet!
Before you go rogue and dump fertilizer like a kid with a glitter obsession, STOP. Adding phosphorus without a soil test is like playing Russian roulette with your garden. Too much can turn your soil into a toxic wasteland, harming plants and polluting nearby water. Get a soil test first, and don’t even think about fertilizing until you’ve got those results in hand. A test will tell you if your soil’s starving for phosphorus or already overdosed.
What to Do with the Results
Once you’ve got your soil test results (cue dramatic music), a qualified pro—like someone from your local cooperative extension or a soil lab—can decode them. If your pH is too low, toss in some lime to perk it up. Low organic matter? Add compost for a nutrient boost. Nutrient levels looking sad? Only then should you consider fertilizer, and even then, follow the pro’s advice like it’s a treasure map.
Where to Get a Soil Test
You can snag a soil test from:
Your local cooperative extension office (they’re like the wise gardeners of your county).
Your state’s department of agriculture.
A commercial soil testing lab (fancy, but effective).
Tests usually cost $10–$100, depending on how deep you want to dig into your soil’s secrets. Results roll in within a few weeks, giving you the lowdown to make your garden the envy of the neighborhood.
The Bottom Line
Don’t be the gardener who yeets phosphorus into the soil and hopes for the best. That’s a recipe for disaster! Always test your soil first, wait for the results, and consult a pro to keep your garden healthy and your soil non-toxic. Your plants will thank you with vibrant blooms and veggies so good, they’ll practically sing.
A Heartbreaking (and Hilarious) True-ish Tale of Loss, Love, and Phosphorus
Joe the grizzly never planned on becoming a farmer. He was just a bear.
Three years ago, he still had Bertha — his mate of twelve seasons. They ruled the Yellowstone backcountry together: two tons of muscle, mischief, and pure love. Bertha had the softest ears in the Rockies and a laugh that sounded like a rumbling avalanche of joy.
Then one October morning, a speeding tourist truck took her from him in an instant.
Joe stopped eating. Stopped fishing. Stopped being Joe.
He wandered for months, hollow-eyed, until he found an abandoned homestead on the edge of the park, near bozeman, Montana. Something about the overgrown garden spoke to him. Bertha had always teased him for nibbling wild chives. “You and your stinky breath,” she’d growl, nuzzling him anyway.
So Joe stayed. He planted hardneck garlic the only way a grieving 900-pound bear knows how — with clumsy paws, endless tears soaking the soil, and a broken heart that needed something to grow.
His first crop was a disaster. The bulbs came up the size of marbles. Joe sat in the dirt and cried harder than the day he buried Bertha. “Even the garlic left me,” he sobbed to the empty field.
That’s when John showed up.
John was a human farmer — weathered ball cap, kind eyes, and a limp from an old rodeo injury. He’d heard rumors about “the crying bear with the sad little garden” and came to check.
He found Joe curled around a handful of pathetic garlic cloves, whimpering.
“Hey, big guy,” John said softly. “Mind if I sit?”
Joe growled at first — a reflex — but John didn’t flinch. He just sat in the dirt and waited. After an hour of silence, Joe finally spoke, voice cracking like thunder with tears in it.
“I just wanted something to take care of… something that would stay.”
John nodded. He knew loss too — lost his wife to cancer five years back. Two widows in the dirt, different species, same ache.
“Your soil’s starving, Joe,” John said gently. “Plants need food just like bears do. Let’s feed it together.”
They sent a soil test to the lab. The results came back brutal: almost zero phosphorus.
“Phosphorus deficiency,” John explained. “It’s like trying to build a life with no bones. No strength. No future.”
Joe stared at the report, then at the tiny graves he’d made for his failed garlic. Something clicked.
“I’m not letting anything else die because I didn’t know how to help it.”
They bought rock phosphate — real stuff, slow-release, made from ancient seas. Joe carried 50-pound bags like they were pillows. John showed him how to work it into the soil without crushing everything.
Every evening, Joe talked to his rows the way he used to talk to Bertha.
“Grow for me, babies. Please grow.”
And reader… they grew.
By June, the garlic scapes stood taller than John. The bulbs swelled so huge Joe had to dig them with a shovel instead of his claws. Harvest day, he pulled up a bulb the size of a cantaloupe and laughed — actually laughed — until he cried again.
He named the biggest one Bertha.
Tourists started coming. Kids hugged Joe’s legs (carefully). Someone took a photo of the massive bear gently placing a giant garlic plant around John’s neck like a victory lei. The picture went viral: “When kindness crosses species.”
John still visits every week. They sit on the porch Joe built (badly) out of logs, sharing roasted Bertha-brand garlic and silence that doesn’t hurt anymore. And how about that garlic bread. Homemade. Yum.
Joe learned something the soil already knew:
Love isn’t just what you lose. Sometimes it’s what grows afterward — slow, stubborn, and stronger than before — when someone teaches you the missing piece you never knew you needed.
And that missing piece? Nine times out of ten, it’s phosphorus.
(And one time out of ten, it’s a friend who refuses to let you grieve alone.)
Ready for your own giant garlic miracle? Start with a simple soil test and real rock phosphate. Your plants — and maybe your heart — will thank you.
Mr. Jere Folgert is the owner of GroEat Garlic Farm in Bozeman, Montana. GroEat Farm is a small, sustainable family farm located in the beautiful Hyalite Foothills, in the shadows of the Gallatin Mountain Range. The hardneck varieties that they grow on their farm flourish, due to the combination of the very cold winters, heavy snowpack, moist spring, temperate summers, and the nutrient-rich and dynamic alluvial soils, washed down from the Gallatin Mountain Range.
