Pumpkin Fertilizer Requirements: Guide To Feeding Pumpkin Plants
By: Liz Baessler
Whether you’re after the great pumpkin that will win first prize at the fair, or lots of smaller ones for pies and decorations, growing the perfect pumpkin is an art form. You spend all summer tending your vine, and you want to get the most out of it that you can. Keep reading to learn more about pumpkin fertilizer requirements.
Fertilizer for Pumpkins
Pumpkins are heavy feeders and will eat up whatever you give them. Different nutrients promote different kinds of growth, however, so when fertilizing pumpkins, it’s important to pay attention to what stage of growth your pumpkin is in and feed it accordingly.
Commercial fertilizers come with three numbers on their packaging. These numbers represent nitrogen, phosphorus, and potassium, always in that order. When feeding pumpkin plants, apply three successive fertilizers, each heavy in one of those numbers, in that same order.
Nitrogen promotes green growth, making for plenty of vines and leaves. Apply a weekly nitrogen-heavy fertilizer early in the growing season to produce a healthy plant. Once the flowers start to form, switch to a phosphorus-heavy fertilizer for plentiful blossoms. When the actual pumpkins appear, use a potassium-rich fertilizer for healthy fruit.
Feeding Pumpkin Plants
Fertilizer is important, but sometimes a little can go a long way. Nitrogen promotes growth, but if you add too much, you risk burning your leaves or reducing flower growth. Similarly, too much potassium can sometimes encourage pumpkins to grow faster than they’re meant to and cause them to explode right out of their skins!
Apply your fertilizer in moderation and wait to see what results a little gets you before adding a lot. If you’re new to growing pumpkins, a very basic and balanced 5-10-5 fertilizer applied moderately all through the growing season is much less intensive and should still yield good results.
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How to Fertilize Pumpkins for Maximum Success
Pumpkins are heavy feeders. GardenZeus recommends testing your soil to determine nutrient levels prior to applying fertilizer.
Work compost, composted manures, or well-rotted organic matter into soils before planting, and maintain nutrient-rich surface dressings under mulch. Bury plugs of finished compost or worm compost a few inches outside of the driplines of established pumpkin plants 2 or 3 times per growing season and water thoroughly. For soils low in calcium, crush or grind up eggshells and add to the soil surface under mulch at the base of each plant. Grow pumpkins or other cucurbits only once every 2 to 4 years in a given bed or garden area to allow the soil to recover between plantings.
This photo shows crushed eggshells, ready to be applied to the soil.
GardenZeus recommends adding nitrogen in the form of diluted urea or a cup of chicken manure diluted in 4 gallons of water (half cup if fresh manure) and mixed thoroughly, after seedlings are a few to several inches tall and about once or twice per month thereafter. Adding too much nitrogen may result in rapid growth and lush, high-carbohydrate leaves that attract insect infestation and slowed or reduced yields.
In hot-summer areas, reduce or discontinue fertilizing with nitrogen by late spring or early summer to avoid producing large, lush leaves that will tend to wilt and cause stress to squash plants during summer heat.
Fish emulsion or seaweed extracts applied as drenches or foliar spray may be beneficial in soils that are infertile, alkaline, or lacking micronutrients.
To view customized information for growing pumpkin in your area, go to GardenZeus and enter your zip code, then go to pumpkin.
Best Fertilizer For Pumpkins - How And When To Fertilize Pumpkins - garden
Which fertilizer is best to grow a giant pumpkin? I hear that question a lot. The answer that any good grower will tell you is that it is the one that the plant needs. You'll only know that through a soil test, tissue test or an experienced eye.
About every four days or so lately I've been giving the plants a little RAW Grow 7-4-5 fertilizer. That isn't as aggressive as I know some growers will do, but I think it is sufficient at this stage. The Grow fertilizers I like because they are water soluble and have a little more than just NPK in them. The main nitrogen source in it is plant protein hydrolysate, which I've read good things about. It also has humic acid, cane molasses, boron, copper, seaweed, iron DTPA, magnesium, manganese, silica, zinc and azomite. And the qualities of each are sufficient to see results from them.
The little extra nitrogen will help support the rapid growth of the plants at this stage. Ideally I would like something like a 7-2-5 at this stage, but a 7-4-5 is close enough.
Soon, I'll be adding a little blood meal to that fertilizer mix to add more nitrate nitrogen. The studies I've read suggest that during rapid growth nitrate demands of the plant go up, so this will help support that. I've also read that too much nitrate nitrogen can help vine growth, but diminish root growth, so to me, it makes sense that June is the time of the season for nitrate nitrogen (like blood meal and calcium nitrate) and then stop that once you start getting into the fruit growing stage.
So, which fertilizer is best to grow a giant pumpkin? It is a balance of what your soil has and what the plant is asking for at that time of the season. But at this time of the year, something with some nitrogen should be given regularly in spoon feeding quantities.
Top 10 Tips to Growing Giant Pumpkin
Top 10 Tips to Growing a Giant Pumpkin
The average homegrown pumpkin weighs nine to 12 pounds, but with the right seeds, a little soil preparation, and a lot of tender loving care, you can grow a pumpkin to enormous proportions. Professional pumpkin growers are gardening enthusiasts who share a passion for growing potential contenders to compete for the title of largest pumpkin. Although this hobby is time-consuming, the rewards are enormous. Kirk Chenier, president of the Giant Vegetable Growers of Ontario (GVGO), shares his passion and advice on how you can grow your own 300- to the 500-pound orange monster. Even if you don’t plan to enter your gourd in a contest, you can grow the biggest jack-o’-lantern on the block.
So there are many tips and steps on how to grow pumpkins in your home garden:
1. Prepare the pumpkin patch
It’s best to start preparing the pumpkin patch in the fall. Designate a spot that is six feet by six feet, level and in full sun. Chenier suggests amending the soil with compost, manure, shredded leaves, dried grass clippings and natural additives like granular humic acid fertilizer, kelp meal, cornmeal, and even molasses. The soil and additives should then be mixed together and allowed to sit over the winter. Giant pumpkin growers have their soil tested in the spring to see if anything needs to be tweaked before the final tilling of the pumpkin patch.
2. Sowing the Seeds
To get a head start on Mother Nature, start your pumpkin seeds indoors in mid-April. Chenier recommends Dills Atlantic Giant variety as the best seeds to use when growing giant pumpkin. Plant individual seeds in four-inch peat pots filled with lightly moistened soil. Place the pots in a warm, sunny location and keep them moist. The seeds will sprout within three to five days.
3. Transplant the Seedlings
Once the seeds have sprouted and the first true leaves appear, it’s time to transplant the seedlings outside. The pumpkin plants are extremely delicate, and care must be taken when transitioning them outdoors. Don’t remove the plant from the pot you risk damaging the roots. Dig a hole and place the peat pot directly into the soil the pot will eventually break down.
4. Shelter your Plants
To keep your plant sheltered, a mini-greenhouse can be used to keep the plants warm. Pumpkin professionals use ground-heating cables to keep the soil warm and toasty in early spring. Once the cool spring mornings have passed, the greenhouse or cables can be removed. Chenier explains that wind barriers erected around the plants help keep the young plants sheltered, especially since the seedlings have shallow roots that prevent them from anchoring into the soil. Once the plants have had enough time to establish themselves in their new home, the barriers can be removed.
5. Keep your Pumpkin Patch Weed-Free
Until your seedlings are established, it’s best to weed your pumpkin patch regularly, but don’t stop there: By eliminating weeds throughout the growing season, you’ll also help prevent insects and other diseases from potentially spreading to your vines.
6. Pollinate the flowers
In late June or early July, flowers needs to be pollinated in order for pumpkins to develop. Pollination may occur naturally through bees and other insects in the garden, but Chenier and his fellow giant pumpkin growers hand-pollinate the female flowers with male flowers from other plants.
You can tell the difference between a male and a female flower by looking at the base of each bloom. If there is a small bulb resembling a tiny pumpkin, then you know the flower is female. If the bulb is missing, then the flower is male.
Once a chosen female flower develops into a pumpkin, the growth is tracked to see if it will reach certain benchmark levels that usually indicate a giant pumpkin in the making. Professional growers estimate the final size of their pumpkins by comparing measurements with a growth chart filled with data collected by GVGO members. The chart allows growers to compare the growth rate of their current crop to giant pumpkins from previous seasons that became record holders.
7. Choose your Champion Pumpkin
Check your vines every few days to see when new pumpkins are developing. In the beginning of July, choose one or two of the fastest-growing pumpkins and remove all of the others from the vine. By thinning out the crop, you’ll be directing all the energy and nutrients from the plant to your potential champion.
8. Caring for your vines
Many things can go wrong in the pumpkin patch during the growing season. Home gardeners need to be wary of several pests and diseases. Animals like raccoons, chipmunks, and moles may eat or mark the pumpkins. Insect pests like cucumber beetles, aphids, squash vine borers among other insects can also wreak havoc on the plants. By being vigilant, you’ll be able to deal with any pests and diseases before an invasion occurs.
9. Feed and Fertilize to Growing Pumpkin
Since pumpkins have shallow roots, the plants need a generous amount of water, especially during the hot summer months. It’s best to water them in the early evening, but allow the plants to dry out before nightfall. If the moisture is not kept even, the pumpkin might split after a heavy rainfall, which can cause a growth spurt. Giant pumpkins have an unquenchable thirst, and some of these monsters can use as much as 100 gallons of water a day during peak growing season. On average, giant pumpkins grow about 30 pounds a day, but some giants can gain as much as 60 pounds in twenty-four hours.
Pumpkin growers fertilize their plants with liquid kelp and fish, molasses, humic and fulvic acid, and calcium, as well as homemade compost teas, which are very easy to brew.
3. Getting the Soil Ready For Your Pumpkins
Once you have selected a growing area, the next step in how to grow pumpkins revolves around assessing the soil quality and fixing anything that might be wrong with it. Pumpkins are surprisingly aggressive plants, but good growing soil is more or less the only consideration needed for how to grow pumpkins that are health and flourishing. Large, healthy pumpkins can be grown on marginally rich soil and with only little attention, but this is the exception to the rule and more luck than anything. Still, keep in mind that the more knowledge you gather and apply when learning how to grow a pumpkin, the luckier you may get.
3a. pH Testing
The first step to how to grow pumpkins in rich soil is to have your garden soil tested. The very minimum test you perform or have performed should be for the pH of the soil. This test can be performed by the home gardener with a high degree of accuracy, while other tests should be sent to labs or agencies trained in their application.
A pH test can be done in only fifteen or twenty minutes depending on the texture of the soil and the number of random tests you want to make. pH of soil is an important measurement to understand because it bears heavily on the availability of other major plant nutrients. pH measures the amount of hydrogen present in the soil and as such determines whether soil is acidic or basic. pH is measured on a scale of 1 – 14. Soil is considered neutral when its pH is 7, acidic when it is lower than 7 and basic when it is higher. People sometimes refer to acid soil as “sour” and basic soil as “sweet.”
The pH of most soils will fall into a broad range around neutral (7) with some measurements going as low as 4 and others, as high as 9. The majority of soils in the US will have pH test results in the 4 – 9 range depending on the region where you live. Generally speaking, most gardeners will have pH regions below 7, but some regions of the US never experience acidic soils and can even be plagued with high amounts of calcium and basic soils with pH measurements well above 7.
When you are making a test of soil, especially for how to grow pumpkins, which will range all over their garden plot, you should begin by gathering a random sample of the soil in your garden. It is very unlikely that the soil pH will vary too much from one section of your yard to another, unless you have carried out soil improvements for many years in only one section. Within your garden area, this fact is even truer. It is not likely that pH will vary much within a garden area, but a random sample is made to ensure you have accurate results.
Pumpkins grow best in soil that has a pH range between 6.5 – 6.8, or that is slightly acidic. This is a range which also suits most summertime vegetable crops, so it is not surprising that pumpkins do well in the same soils as tomatoes, squash, corn, or grass have done well. Following good cultural methods for your region of the country as it relates to growing tomatoes will also guarantee success in pumpkins.
The reason pH levels are so important is because all plants have some preference as to what range of pH they prefer. The pH preference range is determined by what elements are most necessary to that plant. Acid loving plants require more of elements like iron, sulfur, and aluminum, while most vegetable crops need more calcium and magnesium.
The procedures for adjusting soil pH are easily carried out with common soil additives. If your soil is too acidic for how to grow pumpkins (pH below 6) add limestone at a rate of fifty pounds per 1000 square feet. If the soil is too basic (pH above 7) add sulfur, aluminum sulfate, or a healthy dose of organic matter. The process of correcting soil pH may take a full growing season because changing the chemical properties of the soil is a slow process. In most cases, correcting pH will be rewarded in the next growing season. Test for pH four to six weeks after the addition of lime or sulfur to see if the pH has changed. You should see some movement towards the target range of 6.5 – 6.8.
The next test you should make when getting the garden ready for how to grow pumpkins is for the major plant nutrients. These are Nitrogen, Phosphorous, and Potassium. Their symbols of N, P, and K should be recognizable to most gardeners because every package of fertilizer on the market has the symbols of these nutrients in the order N-P-K. When we talk about a fertilizer with an analysis of 15-8-12 that means it contains fifteen percent nitrogen, eight percent phosphorous and 12 percent potassium by weight. Each of these major nutrients plays a different role in plant growth and metabolism, and all are important.
Nitrogen is responsible for the development of vines and leaves, as well as the overall green growth of the plant. Nitrogen deficiencies can be detected if there are yellowing leaves, or slow or retarded growth. Nitrogen is very water soluble and so it can leach from sand very quickly. Therefore, nitrogen should be added to soil periodically throughout the growing season.
Phosphorus is responsible for the flower and rood development, and is also important for helping the plant fight off diseases. Phosphorus has a tendency to remain in the soil, and will not leach as quickly as nitrogen does. Because of this, phosphorus should be mixed into the soil, rather than simply spreading it on top. Bone meal and rock phosphate are both good sources of organic phosphorus.
Potassium is responsible for many of the metabolic functions of the pumpkin plant, including the development of carbohydrates into fruit. Therefore healthy amounts of potassium are required to produce large, healthy pumpkins. Much like phosphorus, potassium tends to stay in the soil, and not leach through it like nitrogen it should therefore be worked into the soil.
Test kits for nutrients are available online and at garden centers, but laboratories will also do comprehensive soil tests for affordable prices. These labs will not only provide a full listing of the pH and nutrient amounts in your soil, but will also often provide recommendations for how to amend the soil to make it suitable for vegetable gardening.
3c. Building the Soil into Hills
In addition to preparing the overall soil of your garden to make it ready for the growing season, a special consideration in how to grow pumpkins is in the preparation of the immediate area of the seedlings once they are planted. Pumpkins are typically planted in small hills. This affords the benefit of growing in raised beds, and also describes the practice of planting more than one seedling in the same area.
The most obvious benefit to raising the soil bed into a small hill is that mounded soil will heat up faster than compacted belowground soil. This aids in seed germination and also in overall pumpkin growth. Hills also create better air circulation and water drainage in the soil. The act of preparing the hill will loosen the soil and allow for more air to enter, and raising beds aids in draining excess moisture away from the planting area.
All in all, building the soil into hills can benefit pumpkin growers because it is one of the few soil preparations that can accomplish increased soil temperature and better drainage at the same time. Obviously, the addition of mulch and row covers can greatly enhance the benefits that planting in hills affords.
Pumpkin hills should be constructed so that soil is elevated by 12-18 inches and gradually slopes downward in an area about eight to ten feet in diameter. This area will be the nursery for your young pumpkin plants at that start of the season.
How to Water Pumpkins
Pumpkins are hungry and thirsty plants and they need to be watered regularly. Aim for at least 1 inch of water per week, and if it is an especially hot summer, don’t be afraid to double this amount.
While it can be tempting to water the entire plant, only the roots of the pumpkins need to be watered, so just aim for this area. Too much dampness on the plants means that rot can set in.
Micronutrients, also known as trace minerals, are not present in the soil at rates as high as nitrogen, potassium or phosphorus. Yet these micronutrients are beneficial to the overall health of your pumpkin vines, helping them ward off diseases and pests. If your soil has a serious depletion in some or all of these micronutrients, using a fertilizer that offers more than N, P or K may be helpful. Some artificial N-P-K fertilizers additionally provide trace minerals. The organic sources of potassium granite meal and kelp meal also contribute several other nutrients. Liquid kelp, as well as other seaweed and fish liquid fertilizers, are high in micronutrients and offer the advantage of giving wilting vines a quick pick-me-up when sprayed on foliage, or a slower, longer-lasting application when watered into the soil near the roots.
If you prefer to use premixed N-P-K fertilizers, apply one higher in nitrogen just before planting, such as 10-5-5. As pumpkins begin to form, switch to one higher in phosphorus and potassium, such as 5-10-10. Both organic and chemical fertilizers are available in N-P-K formulations.
- University of California Agriculture and Natural Resources: Nutrient Management for Cucurbits
- Virginia Cooperative Extension: Specialty Crop Profile: Pumpkins
- Rodale's Ultimate Encyclopedia of Organic Gardening: Fern Marshall Bradley, et al
- Pumpkin Nook: Fertilizers and Nutrients for Pumpkins
Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.