How and When to Fertilize Your Pumpkin Plants

For those first two summers, they bloomed and produced fruit – even after heavy pruning following a moose attack. The excess nitrogen from the lawn fertilizer has caused the trees to produce a lot of leafy growth, but no flowers – or fruit. While there are many nutrients that plants need in various quantities in order to thrive, nitrogen, phosphorus, and potassium are the three most important macronutrients.

First, know that the three numbers each have an invisible tether connecting them to one of the letters, in the order of nitrogen (N), phosphorous (P), and potassium (K).

If you have a chance before sowing seeds or transplanting seedlings to your garden, it’s smart to conduct a soil test. My raised beds are new, and they are filled with a garden mix of topsoil, peat moss, and compost.

The test results will give you a basic understanding of your soil before you add any nutrients or amendments to it. Make sure you amend your soil with compost, well-rotted manure, or a general-purpose balanced fertilizer before you plant.

Now it’s time to break down pumpkin fertilization during the different phases of plant growth, which is a little more involved than just adding a general-purpose product whenever inspiration strikes. The first thing you should know about feeding a pumpkin is that the plant requires different nutrients for each of its three main growing phases.

It’s a heavy feeder, and while applying a general, balanced NPK fertilizer throughout the growing period is better than nothing, it’s less than ideal. In the 55 or so days before your vine begins to flower, you need to make sure the plant has sufficient nitrogen.

Nitrogen is crucial to any plant’s early growth because it’s an important component of chlorophyll, the compound responsible for the green color of stems, vines, and leaves. Chlorophyll absorbs energy from the sun and uses it to create sugars to feed the plant, via a process called photosynthesis.

Nitrogen promotes leafy green growth, which helps your young plant produce healthy vines and foliage while it becomes established. If you test your soil and discover that it’s nitrogen deficient, you can add blood meal (12-0-0), according to package instructions.

This will satisfy your plant’s nitrogen needs and also provide a head start on the pumpkin’s heavy phosphorus and potassium requirements in the second and third growing stages. If you notice a lot of leafy green growth but few (or no) buds starting to develop – especially as you approach day 55 after germination – stop applying nitrogen.

This element is an essential component of adenosine triphosphate, or ATP, which provides the energy needed to form buds and fruit. With a hand cultivator, I gently worked the bone meal into the top two inches of soil, so as not to disturb the roots.

Plus, I looked carefully at the plants and found a couple of tiny male flowers beginning to develop, too.

Now I’ll be watching the buds closely to make sure I can catch them both in bloom at the same time so I can hand-pollinate them.

Once you’ve got several small fruits developing on your vine, it’s time to channel some of your fertilizer focus to potassium. Don’t ease up on the phosphorus too much once the pumpkin starts growing, but do make sure you also give your developing gourds potassium.

Potassium is also a critical part of energy-producing ATP, and helps regulate the amount of water and carbohydrates stored in the plant tissues.