How to Grow Hydroponic Summer Squash

By: Chris | Last Updated: October 9, 2021

Summer squash is one of my favorite summer-time vegetables. I love it fried, sauteed, grilled, stewed, casseroled, and made into delectable squash tots. They go great with just about any summer meal. If that line about squash tots got your attention, stick around to the end for a link to the recipe!

I was a little sad this year when heavy summer rains made life hard on my container garden squash. The plants got off to a great start, but the rain didn’t let up for several weeks. That was more than my poor plants could handle. Instead of accepting defeat, I threw a few seeds into starter plugs and starting growing hydroponic summer squash indoors. Take that mother nature!

What did I learn? It’s pretty easy to grow squash indoors! I’m rating the growing difficulty at medium, only because more work is involved when compared to growing hydroponic spinach or a similar leafy green. What kind of work? Keep reading!

In this article, you’ll see the exact steps needed to successfully grow hydroponic squash indoors. These steps also work for zucchini!

The Best Way to Grow Summer Squash

Dutch buckets are my favorite hydroponic system for growing squash, but you can use any system that supports larger plants. I like Dutch buckets (or bato buckets) for large plants because of the support the system offers to the root structure.

Squash in dutch bucket hydroponic system

In my systems, I use a large expanded clay pebble base that’s covered with perlite. The expanded clay acts as a filter and keeps the perlite from draining out of the bucket. A lot of people use paint strainers to keep their perlite contained. I have a ton of expanded clay, so that’s what I use and it works great.

Quick Tips to Grow Summer Squash

If you’re a seasoned grower and just need the highlights, these quick tips will get you started.

Need more detailed information? Keep reading!

How to Grow Summer Squash from Seed

Time to Germinate: 3 to 15 days | Germination EC: 0.9 to 1.2 mS

One of my favorite things about squash and zucchini is how easy they are to grow from seed. They don’t need any special treatment. Start them in your substrate of choice, cover them with a humidity dome, and keep them under a grow light.

Temperatures ranging from 70° to 75°F work great for germinating squash seeds. I normally keep the thermostat in the grow room set to 72°F. Keep in mind that the grow light will also provide heat to seeds. Don’t worry too much about keeping an exact temperature, just keep the seeds somewhat warm.

I normally use Rapid Rooter starter plugs when starting new seeds, but that choice is up to you. As long as the seeds germinate your method is great!

Use a diluted nutrient solution for germination. I normally start with an EC of 1.0 mS and a 6.0 pH. It’s important to use distilled or reverse osmosis water for seedlings since the EC is low. If your tap water contains a lot of minerals, the water alone could have an EC as high as 0.5mS. That doesn’t leave much room for hydroponic nutrients.

Distilled water is pretty inexpensive, and you won’t need much to get seeds started. Two gallons is enough to carry a 1020 flat of seedlings from seed to transplant-ready.

You should start seeing new seedlings emerge in 3 to 5 days, but some may take up to 15 days.

Growing Hydroponic Summer Squash

This method works for growing all summer squash varieties, so feel free to plant your favorite and get ready to help it grow! It’s amazing how fun it is to grow these big plants when you don’t have to worry about pests like squash beetles.

The following sections include important tidbits from my own experience and research. I hope they help you produce a successful harvest!

Summer Squash Spacing & Transplanting

Transplanting Size: | Plant Spacing: 24 to 36 inches

Squash plants grow huge root masses, so it’s important to transplant them before they get too big. If you follow my Instagram, then you know I waited a little (actually a lot) too long to remove my squash plant from the germination tray. I ended up having to carefully cut the tray away from the plant. It was a pain in the butt. Lessons were learned.

Check out this YouTube Short I made showing this poor plant.

I waited too long to transplant this hydroponic squash

Transplant squash as soon as roots begin to emerge from the bottom of the starter plug. The plant itself will be around two to three inches tall.

If you’re planting in perlite, simply dig a hole large enough for the starter plug. Once the plant is in place, cover the plug with perlite. As the perlite gets wet it will firm up and provide great support for the plant and root system.

Space plants 24 to 36 inches apart. Even when pruned, the large leaves of squash plants need some room to spread out.

Hydroponic Summer Squash Nutrients

Nutrient Strength: EC 1.8 to 2.4 mS (1,800 to 2,400 μS) | pH: 6.0

Since summer squash is a fruit-bearing plant, you’ll need to adjust the nutrient profile as the plant matures. In the early stages, focus on providing nutrients that develop strong root systems and lush vegetative growth. This initial stage will be high in nitrogen.

For this grow, I used Flora Series nutrients from General Hydroponics. This is a 3 part system that’s easy to use, and the bottle has dosing instructions on the back. These instructions include recommended doses for vegetative, flowering, and fruiting phases.

General Hydroponics FloraNova Combo Kit: Grow and Bloom (1 Quart)
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The only supplement I add to the nutrient solution is CaliMagic, also from General Hydroponics. This supplement adds a little boost of calcium and magnesium. In my experience, it produces noticeable gains in plant health and production.

Throughout all stages (except germination) I mix nutrients to a strength of 2.0 with a pH of 6.0. A solution with an EC ranging from 1.8 to 2.4 mS will work great, so don’t worry about being spot on. If the solution is too weak, add nutrients. If the solution is too strong, add water.

If you want an even easier way to mix nutrients, check out the Flora Nova series from General Hydroponics. The series consists of two products: Flora Nova Grow and Flora Nova Bloom. Use Flora Nova Grow during vegetative growth, use both products when transitioning to flower, and then use Flora Nova Bloom once your plants enter the fruiting stage.

Light Settings for Summer Squash Production

DLI Range: 25 to 30 | Duration: 14 to 18 hrs ON / 6 to 10 hrs OFF

Squash grows fast and produces a lot of fruit. It’s going to need a lot of light to help fuel that production. A daily light integral (DLI) of 25 will keep the plant producing well, as long as you provide it with plenty of nutrient solution. You’re gonna need a grow light that can really crank out the intensity. Lately, I’ve been really happy with the performance of ViparSpectra grow lights. They’re affordable, evaluated by a third party, and the output is great.

VIPARSPECTRA XS2000 LED Grow Light, 4x2 ft Coverage
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The higher the DLI goes, the more nutrients the plant will consume. Keep that in mind so you don’t end up with an empty reservoir.

I typically light starter plants 16 hours on and 8 hours off. Once the plant starts flowering, I’ll dial that back to 14 hours on and 10 hours off. When you reduce the lighting duration, make sure to adjust your lights to maintain that DLI of 25-30.

Confused about what DLI is? This article will help you understand daily light integral and get perfect plant lighting.

Airflow & Temperature

Temperature: 60° to 85°F (70° to 75°F Germination)

Summer squash like yellow squash and zucchini are adapted to growing in warmer climates. After all, they did originate in Mexico and Central America. With that in mind, most indoor climates will be a great growing environment.

I normally keep the grow room thermostat set at 72°F, but any temperature within 60° to 85°F will allow the plants to produce at optimal levels. Colder and hotter temperatures will reduce production.

Use small fans to create airflow through the plant leaves. This helps prevent disease and fungal growth, and also helps the plant use nutrients more efficiently.

How to Prune & Hand Pollinate Summer Squash

The main reasons to prune squash are to control the overall size of the plant and to improve airflow around all the leaves. Plus, we eat the fruit. Fewer leaves equal more nutrients and energy going to fruit production.

Pruning hydroponic squash is really simple. Once the first fruit has been harvested, you can remove the lower leaves on the stalk. As the plant continues to grow, prune off lower leaves. If leaf stems break (some probably will) go ahead and prune them.

To prune the leaves, use a sharp clean pair of shears and cut the leaf off about half an inch away from the main stalk. Be careful not to cut into the main stalk.

Unless you keep bees indoors, you’re gonna be responsible for the “brown chicken, brown cow”. That’s right, you’re gonna need to pollinate those female flowers. It’s easy to tell the difference between male and female flowers. Male flowers will have long skinny stalks, and look like a flower. Female flowers grow on the end of the emerging fruits, so they’ll look like miniature squash with a flower sticking out the end.

Check your plants every morning for newly opened female flowers. These flowers will only stay open for a few hours, and you need to pollinate them. If a female flower closes before you can pollinate it, open the flower up and pollinate it anyway. I’ve had pretty good success doing this, but it’s not optimal.

There are several ways to hand pollinate. The easiest is to take a q-tip and load it up with pollen from inside the male flower and then rub the q-tip against the inside of the female flower to pollinate the pistil.

Female and male summer squash flowers

Confused? Look inside each flower, the males have a conical center (stamen) that’s loaded with pollen. The center of a female flower will look like a used hollow point bullet (pistil). Rub the pollen on that hollow point to make a little squash baby.

It’s really simple. As long as you can see pollen on the pistil, you’ve done your job. Each fruit only needs to be pollinated once.

How to Train Hydroponic Squash

You can grow hydroponic squash in a relatively small footprint if you train it. Training simply means managing the direction the plant grows in.

In nature, squash plants sprawl out along the ground and take up a significant amount of space. In a controlled environment, space is a luxury we don’t always have. By training the plant to grow vertically, you’ll save a lot of floor space that can be used to grow other plants!

How to train hydroponic summer squash

Squash can easily be trained to grow up a stake or twine. As the main stalk grows, loosely tie the stalk to the stake or clip it to the vertical twine. Stretchy nylon is normally recommended for tying plants to stakes, but I’ve used twine with squash plants and it worked just fine. Use what you have available. Old pantyhose works great!

As the plant grows, tie or clip it every 6 to 8 inches. The leaves will rotate toward the light on their own, so don’t worry about their orientation when you first stake the plant.

Harvesting Summer Squash

How to harvest hydroponic summer squash

You can start harvesting individual squash once they reach 6 to 8 inches in length. For most varieties, it’s best to harvest before the fruit gets longer than 10 inches. Beyond that point, squash will start to lose flavor and become starchy.

Squash plants thrive when harvested frequently, and will be more productive than a plant that’s not harvested regularly. I normally harvest fruits at around 8 inches, or at least what my eyeball tells me is close to that length.

It’s a good idea to use clean shears or a knife to carefully harvest squash fruits. Twisting or pulling hydroponic squash can easily damage the plant stem and/or the root system. The plant quickly heals over clean cuts, reducing the chances of disease or pest infestation.

My Favorite Hydroponic Summer Squash Varieties

It’s boring to grow a single type of plant. I want variety. Different colors, textures, and tastes are what make this whole gardening journey interesting. Don’t settle for a boring monocolor squash garden.

These recommended summer squash varieties will bring a diverse splash of color to your hydroponic garden.

True Leaf Market: My Go-To Seed Source

True Leaf Market has a great selection of high-quality seeds. Below are some of my favorite squash varieties they offer. When you purchase seeds through the links below, I earn a commission at no extra cost to you. Your support allows me to keep producing useful content!

Yellow Squash Tots Recipe

Credit: Yellow Squash Tots Recipe from Kate at Babaganosh

So the thought of squash tots hooked you to the very end? I totally get it, and they’re worth the wait!

Kate over at Babaganosh has developed this delectable treat and I think you’re going to love it! It’s the perfect mashup of squash, zucchini, cheese, onion, and garlic. It might become your new favorite summer-time snack!

Check out Kate’s Yellow Squash Tots recipe!

Chris Cook started Happy Hydro Farm to share his passion for hydroponic gardening! Growing your own food is incredibly rewarding both physically and mentally. His mantra - "Take excellent care of your plants, and your plants will take excellent care of you."