If you’re dedicating effort and garden space to growing pumpkins, you want the maximum harvest your plants can produce. To develop the biggest, healthiest fruits, pumpkins need lots of nutrients at their disposal.
Pumpkin fertilizer enriches soil with essential macro and micronutrients that plants need to produce a healthy root system, foliage and fruits. The primary nutrients that pumpkins need are nitrogen (N), phosphorous (P) and potassium (K), and fertilizers are available in granular, liquid and slow-release spike form. You can fertilize with a balanced formula for moderate growth all season, or use targeted formulas at different growth stages to significantly boost production.
In this article, you’ll learn about the key nutrients in pumpkin fertilizer and how to understand the numbers on the package. You’ll also find out why soil testing is a good idea before adding fertilizer along with how and when to apply the various formula types. Finally, we’ll finish up with a few of our favorite fertilizers for pumpkins.
Let’s dive in!
Do Pumpkin Plants Need Fertilizer?
Yes, they do. It takes a lot of energy to produce those broad leaves, long, trailing vines and of course, large, fleshy pumpkins. Just like people, plants need enough vitamins and nutrients to grow to their projected size and to produce their fruits. People eat food, and plants process fertilizer.
Even if you have a garden with soil that you’ve been building for years, it’s still worth it to add at least some fertilizer each season. This is because the plants you grow in your garden actually extract a certain amount of fertility each year, especially sprawling plants with large fruits like pumpkins.
A good rule of thumb is to apply fertilizer every year to replace nutrients that were lost in last season’s growth.
What Nutrients Do Pumpkins Need?
Pumpkins need fertilizer that contains both macronutrients and micronutrients.
Macronutrients are nitrogen, phosphorus and potassium– also known as NPK.
- Nitrogen (N) powers the growth of green tissues and aids in photosynthesis.
- Phosphorus (P) helps the plant set blossoms and transform them into buds and then into pumpkins.
- Potassium (K) supports the transport of water and other nutrients through the plant’s cells.
Additional nutrients that are also sometimes classified as macronutrients are calcium, magnesium and sulfur. Many commercial fertilizers also supply these nutrients.
Gabriel J. Croteau, Certified Master Gardener and consultant for Juliei Salone says, “Calcium is necessary for root development and proper cell division in fruits. Magnesium is important for enzyme activation that catalyzes many reactions within cells and is vital to photosynthesis. Sulfur helps plants convert carbon dioxide into sugars during photosynthesis.”
Micronutrients are also known as trace minerals or trace elements. Ohio State University lists these as the eight essential micronutrients:
Pumpkins need less of these nutrients than they do NPK, but that doesn’t mean they’re less important. Micronutrients are essential to plant functions, including:
- Disease resistance
- Sugar transport
- Cell wall strength
- Cell division
- Pollen formation
Not all fertilizers have both macro and micronutrients, so make sure you know what you’re looking for! You may need to buy an NPK fertilizer and supplement with a micronutrient fertilizer.
What to Fertilize Pumpkins With
Compost is always a welcome addition to the pumpkin patch. Since it’s made from a variety of organic materials, well-prepared compost is rich in a wide array of nutrients. And compost is considered to be organic matter in itself, so it also helps improve the soil’s overall structure and drainage for long-term benefits.
RELATED: Making compost at home is a great way to boost the nutrition in your garden and recycle food scraps/yard waste at the same time. Read about how a compost tumbler works in my small yard to get some ideas!
However, you may be hard-pressed to produce/find enough compost to nourish your pumpkin plants, or you may prefer to purchase a product that has a guaranteed nutrient profile. And that’s where commercial fertilizers come into the picture.
For the remainder of this article, we’ll be looking at commercial fertilizers.
Before Fertilizing Pumpkins: Get a Soil Test
If you’re just starting a garden or you’ve had disappointing results from your pumpkins in the past, we recommend soil testing.
Soil tests are kind of like blood tests for your soil. They measure the amount of:
- Organic matter in your soil
Soil tests will tell you if your soil is low in a particular element or if you have enough (or too much!) of another. Use this information to fertilize appropriately, so that you give your soil exactly what it needs and nothing it doesn’t.
You can find simple do-it-yourself soil tests on Amazon, but lab testing often offers greater insight into your soil profile. We’re big fans of SoilKit, a mail-in comprehensive laboratory test that gives readings on 14 nutrient levels with easy-to-read results. They even offer suggestions for the best fertilizer for your soil!
Reading a Pumpkin Fertilizer Package
Remember that you read about macronutrients just moments ago– nitrogen, phosphorus and potassium (a.k.a. NPK, after their designation on the periodic table). These three nutrients are generally indicated with a three-number label on the front of a fertilizer bag, such as 10-20-20.
These numbers indicate the percentage of each element contained in that bag of fertilizer. With our example number of 10-20-20 fertilizer for pumpkins, that equals 10% nitrogen, 20% phosphorus, and 20% potassium, for a total of 50% active nutrients. The rest of the volume of fertilizer is often inert transport medium and additional micronutrients.
When it comes to fertilizers, there can be too much of a good thing. Too much nitrogen will generate leaf burn, while boron or iron surplus will result in discolored yellow leaves. A plant that is overloaded with fertilizer is also more susceptible to disease and insect infestations.
Always fertilize according to the directions on the bag or box, and never exceed the recommended fertilizer dosage.
Plus, there are other far-reaching impacts of being over-zealous in your fertilizing, as this video from Joe Gardener points out:
When to Apply Pumpkin Fertilizer
Plan to fertilize your pumpkins a bare minimum of twice during the growing season: Once when flowers begin to appear, and again when fruit starts to form.
Some growers prefer to use a balanced fertilizer that supplies all three primary macronutrients at once, while others take a more tailored approach.
Pumpkins go through eight distinct growth stages on their journey from seed to harvest, and the plant’s nutritional needs change throughout that time.
Use a nitrogen-rich fertilizer when planting your seeds/seedlings or for fertilizing early in the season. A nitrogen boost helps your brand-new pumpkin plant develop healthy, vibrant green leaves that photosynthesize the sugars that feed the plant.
Once you spot pumpkin blossoms starting to form, apply a fertilizer that’s high in phosphorous. This helps your plant produce lots of healthy blooms, and the more flowers, the more chances for pumpkins to grow. Some nitrogen is still ok now, but you don’t want to encourage your plant to produce too many leaves rather than flowers/fruit.
After the flowers die away and the fruits begin to grow, add a potassium-heavy fertilizer to your phosphorus formula. Potassium is a key nutrient that helps optimize your plant’s energy regulation. And it definitely takes a lot of energy to produce large, robust pumpkin fruits.
Remember the 10-20-20 fertilizer for pumpkins example we mentioned earlier? That would be a great NPK number for fertilizing pumpkins in mid-to-late summer because it has a higher percentage of phosphorus and potassium than nitrogen.
This means that it feeds the plant what it needs to set blossoms and create healthy buds that grow into pumpkins instead of high nitrogen which produces lots of leafy green growth but fragile blooms and stunted pumpkins.
How to Use Pumpkin Fertilizer
How do you apply a fertilizer for the best results? That depends on whether the fertilizer is granular, liquid or a spike.
Granular fertilizers are, as the name implies, small granules that dissolve over time as they contact water. This is what I tend to use most often on my pumpkin plants. Here’s how to apply it:
Consult the package directions and measure out the amount you need for your plants. Scatter the granules around your plant:
Use your hand or a trowel to scratch the granules lightly into the soil:
Here’s what it looks like when you’re done:
And don’t forget to gives lots of water whenever you fertilize. This helps the granules break down and disperse throughout the soil:
Powdered fertilizers primarily fall under the granular category. Most powder formulas are designed to be applied dry into the soil, like granular fertilizers, although some types need to be mixed into water and watered in.
Liquid fertilizers usually come in concentrated formulas that need to be diluted in water. Once you’ve prepared the fertilizer, use it to water the roots of the pumpkin plant.
Some liquid fertilizers are also useful as foliar sprays, which means that you apply the diluted fertilizer directly to the plant’s leaves. This is especially helpful when fruit is forming.
You can usually apply liquid fertilizers more frequently than solid formulas since they tend to be a little weaker. But always follow the schedule on the product!
Spike fertilizers are the easiest of all- just insert them into the soil near your pumpkin plant’s base and care for your plant as usual. The formula has a very slow-release design, and one spike may last for the entire season.
6 Top Picks for the Best Fertilizer for Pumpkins
1. Dr. Earth Home Grown Tomato, Vegetable and Herb Fertilizer
This is my personal favorite fertilizer for anything in the garden, including pumpkins. With an NPK value of 4-6-3, you can apply this formula throughout the season for comprehensive, balanced nutrition. Plus, it’s made from organic ingredients.
As a granular formula, apply the fertilizer around the base of each pumpkin plant, gently scratch it into the top 1-2 inches of soil and water it in well. Since it’s a lower concentration of active ingredients, you can safely feed your pumpkins several times throughout the growing season.
2. Pumpkin Juice Foliar Liquid Fertilizer
This liquid fertilizer is specifically formulated for foliar application. That means that you dilute the fertilizer in water and spray it directly on the leaves. The plant then absorbs the nutrients through each leaf’s surface cells.
The Pumpkin Juice bottle has an easy measure-and-pour design and an NPK 11-8-5. This formula also contains several key trace minerals for healthy pumpkin growth:
It’s also highly concentrated– one container of this makes 32 gallons of fertilizer! Unless you’re creating a massive pumpkin patch, that’s more fertilizer than you’re likely to need in one growing season.
3. Wallace Organic Wonder Super Starter Packs
This is a great start-of-season fertilizer with enough NPK to give the entire plant a boost. Healthy plants at the beginning of the season will resist diseases and pests and have a greater ability to take up nutrients and water, leading to more pumpkins!
This fertilizer is ideal for new pumpkins transplants just going into the garden as opposed to seeds sown directly into the soil.
4. Burpee Organic Blood Meal Fertilizer
Blood meal is one of the best organic pumpkin fertilizers out there for early-season use. It’s rich in nitrogen, which is just what your baby pumpkins need when starting out.
We recommend adding a few tablespoons to a bag of potting soil, amending your entire garden bed, or dropping a scoop of blood meal into the bottom of the hole when transplanting.
5. Jobe’s Organics Bone Meal
Another great organic option, Jobe’s Bone Meal is especially high in phosphorus, which supports bloom and pumpkin fruit growth. It’s also organic and easy to apply. This is a good mid-season pumpkin fertilizer.
Jobe’s also offers the same bone meal fertilizer in a convenient spike form. All you need to do is push the spike into the soil where it gets watered, and it will slowly release fertilizer all season long.
6. Down to Earth Organic Langbeinite Fertilizer Mix
Langbeinite is a natural crystalline mineral that supplies all the trace elements that pumpkins need, plus a hefty dose of potassium for strong plant cells and pumpkin fruit production. This fertilizer is an ideal addition to your phosphorous fertilizer once you see the pumpkin fruits start to grow.
Single-ingredient fertilizers like these are also known as “simples.” You can use them to amend a garden bed, side-dress an individual plant and add nutrition at transplanting.
Frequently Asked Questions about Pumpkin Fertilizer
Fertilizing pumpkins isn’t too complicated once you understand the basics:
We hope this article helps you feel more confident about the best fertilizer for big, beautiful pumpkins!
We’d love to hear from you! Do you have any other questions about fertilizing pumpkins? Or maybe you have some giant-pumpkin-growing tips you’ve picked up along the way. We learn best from one another, so let us know your thoughts in the comments below!