If asked to sum up zucchini in one word, I would say “prolific.” It seems as though once it takes off, it doesn’t stop until that first frost at the end of the season.
And no matter how much you love zucchini, there comes a point where you’re sick of it, at which point it’s time to start passing it off. Anyone is fair game – friends, neighbors, random strangers on the street, anyone who leaves their car unlocked during Sunday service. They all become nervous when they see you approaching with a lumpy paper bag.
Unless, of course, you struggle to get your zucchini going, and a lot of that comes down to fertilizing correctly.
I can say with some authority that, as a gardener, it’s kind of embarrassing to be hoping you’ll be gifted a lumpy bag of zucchini because your own plant isn’t pumping out green Louisville Sluggers every other day.
So, if you want to make sure everyone at church locks their cars when they see you roll up in August, you need to know how to take care of this notoriously heavy feeder. Zucchini requires the right nutrients at the right time.
Let’s start with the right nutrients.
What’s the Best NPK Ratio for Zucchini?
Like most of your heavy feeders, zucchini does best with a balanced fertilizer. Look for something in the 10-10-10 range or similar. You can even go a bit lighter on nitrogen (the first number). Each nutrient plays a role in your zucchini’s overall health:
- Nitrogen (N): Promotes leafy growth.
- Phosphorus (P): Supports root development and flowering.
- Potassium (K): Enhances overall plant health and fruit quality.
What you don’t want is a fertilizer that’s heavy in nitrogen.
Too much nitrogen will lead to lots of foliage but fewer zucchini. (Okay, maybe your neighbors want you to use a high-nitrogen fertilizer to save them from inheriting your excess, but we aren’t taking their considerations into account here.)
Likewise, a high-nitrogen fertilizer can lead to increased pest and disease issues.
The leaves can grow so quickly under their nitrogen-fueled haze that they come in much more tender, making them the perfect snack for squash bugs, aphids and other pests. Also, when you have lots of leaves, your plant is more susceptible to powdery mildew. And then you’ll need Fawn’s perfect powdery mildew control. (It clears up within two weeks.)
When it comes to fruiting plants in the garden, balance is key.
You want all the nutrients that the plant needs to be readily available in the soil as it needs them. The best way to do that is with a balanced fertilizer.
I like Espoma’s organic Garden-Tone. It comes in with an NPK of 3-4-4, and it’s pretty easy to use and I can find it near me. However, if you want to go the organic route, it will require a little mixing to ensure you get that balance you’re after.
Fish emulsion (I have feelings about this stuff.) is a good organic option, but it’s high in nitrogen, so you’ll also want to add bone meal for phosphorous and kelp meal for potassium.
Now that we know what we’re feeding our zucchini let’s go over when to feed them.
When to Fertilize Your Zucchini
As we’ve already covered, zucchini are hungry green beasties who require consistent fertilizing throughout the season to ensure your pantry shelves are lined with jars of Cheryl’s delicious zucchini relish. (If you get it right, your neighbors can make some, too.)
The Beginning of the Season
Your zucchini grows a lot right from the start of the season, so you’ll want to be sure it has plenty of food to support that growth. But how you fertilize, all comes down to what you plant – seedlings or direct-sown seeds.
Regardless of which you choose, start with compost, worm castings or both. These improve drainage, add slow-release trace minerals and nutrients over time, and inoculate the soil with healthy microbes. Mix a few trowels of each into the top 6-8 inches of soil a few days before you plant your seedlings or seeds.
Seedlings
If you’ve got zucchini seedlings that are ready to go in the ground, work a balanced fertilizer into the ground where you’ll be planting. You want to mix it in well to ensure it’s not touching any delicate roots. If you really want to do the thing right, mix your fertilizer into the soil first, then plant your seedlings a few days later. (But who has time for that?)
Seeds
When direct-sowing zucchini seeds, don’t add fertilizer; it’s already included in the seed. Each seed contains all the nutrients needed to get that future zucchini growing. Plus, depending on what you use, fertilizer in the soil can burn brand-new roots as they emerge, killing the plant.
However, once the seed successfully germinates and produces its first true leaves (not the cotyledons), it will need to be fertilized.
You’ll want to fertilize every couple of weeks at half-strength at the beginning of the season until your zucchini plant starts producing flowers. (If you’re lucky, this will be pretty quick.)
Flowering & Fruit Production
Now comes the real work – this is where zucchini earns its reputation for being a heavy feeder. It takes a steady flow of nutrients to keep cranking out zucchini all summer long.
Once your plant begins producing flowers, you’ll want to continue to feed at half-strength every two to three weeks.
Pro-tip: You’ll likely notice that most of the first flowers are male. Don’t worry; within a week or so, your plant will catch up and start producing female flowers, too.
Continue to fertilize every couple of weeks throughout the growing season, and you’ll have tons of zucchini to eat. (Or pass it to everyone else; let’s be honest here.) It’s also important to pick new fruit frequently, as this will encourage new flower production.
Along with the what and when of zucchini fertilizing, sometimes it helps to know what not to do. With that in mind, here are a few mistakes to avoid.
Never Fertilize Dry Soil
Adding fertilizer to dry soil is a recipe for an unhappy zucchini plant. Dry fertilizer can burn tender roots. If you’re organized and good at planning (not me), water your zucchini thoroughly the day before you fertilize. For the rest of us (hi, friends), water the soil well around your zucchini and then let the water soak into the soil for about fifteen to twenty minutes before adding fertilizer. Then water it again.
Don’t Forget the Micronutrients!
We usually focus on the big three: nitrogen, phosphorus and potassium. But plants also need micronutrients such as calcium, magnesium, zinc and a plethora of others.
While nearly all seaweed “fertilizers” on the market have little to no NPK value, they are a great resource for micronutrients. So don’t be fooled by the word fertilizer in their descriptors; seaweed supplements for plants are meant to be used in addition to a balanced fertilizer, not to replace it.
(You can read more about this sly little marketing trick here.)
This one is a great option for ensuring your zucchini gets the micronutrients it needs.
Be Careful Where You Put Your Fertilizer
Something we rarely give much thought to could be causing your plant undo stress. And let’s face it, in this day and age, even your zucchini plants are having a hard time managing all the stress. They’re out in the garden like, “This housing market. Am I right?”
If you’re using a granular fertilizer, don’t put it right up close to the stem of the plant.
You can burn the stem. Instead, add your granulated (or other dry fertilizer) about 2-3 inches away from the stem around the plant. Scratch it into the dirt well (about 2-3 inches deep) and then water it in.
While zucchini is one of the easier crops to grow in our gardens, getting them on the right feeding schedule is key if you want to be the local green caveman club menace. Get it right, and you’ll be up to your eyeballs in everyone’s favorite summer squash.
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