How to Grow Zucchini - Zucchini Growing Guide

Zucchini bread, spiralled pastas, dipping into Hummus, or simply charred on the grill. 

If you're looking for an easier to grow, high-yielding vegetable to grow that is incredibly versatile in dishes, look no further.

Zucchinis are for you.

Zucchinis are one of those vegetables that as you practice Mindful Gardening, can quite literally observe its growth over the course of a week in the peak of summer. From its sprawling foliage to fast maturing fruit, when properly fed with worm castings and organic fertilizer it puts on quite the show.

Let's Grow!

How to Grow Zucchini from Seed 

Zucchini seeds are one of the largest individual seeds that you'll come across and there won't be any mixing them up for something else. As you'll see over the course of this guide, Zucchinis love to be well-fed, well-watered and in a warm environment - and that starts from Day 0. To get your Zucchini seeds started:

  1. Fill a 3" seed cell to approximately 1cm from the surface.
  2. Drip 1x Turkey Baste of Water onto the worm casting seedling mix
  3. Place 5 Zucchini seeds evenly spaced throughout the seed cell
  4. Drip 1x Turkey Baste of Water onto the seeds and worm casting seedling mix
  5. Cover the seeds with approximately 1cm of worm casting seedling mix
  6. Drip 1x Turkey Baste of water onto the top of the worm casting seedling mix

For the Zucchini seeds to germinate they need to be both moist and in a warm environment:

  • Temperature: Make sure where they are placed in an environment that is at least 70F/21C. 
  • Moisture: Water with 1x Turkey Baste of water every 2-3 days to ensure the worm casting seedling mix remains moist.

Use Worm Castings to Start Zucchini Seeds? 

To give your Zucchini seeds the highest likelihood of germinating, you want to make sure that they have that moist and warm environment. One of the best parts of utilizing Worm Castings is that they retain significantly more moisture than traditional seed starting mixes that are heavy in peat moss.

Worm castings themselves hold up to three times their own weight in water. - Epic Gardening

What you'll notice is that very quickly the traditional peat moss will dry up and appear light brown while your Worm Casting Seedling Mix will remain a darker colour due to the water it has retained and level of moisture.

 Image of Worm Casting Seedling Mix compared to store bought peat moss

After 3 days since watering you can see that the Worm Casting Seedling Mix on the left is still dark and moist while the traditional peat moss mix on the right has fully dried. 

You can purchase your Worm Casting Seedling Mix right here

Zucchini Days to Germination 

Once you have sown the Zucchini seeds and placed them into a warm environment, they generally take 7-14 days to germinate. Of the 5 seeds you put into the seed cell, it is possible that 1 or 2 will germinate before that but Zucchinis are notorious for taking a little longer to germinate and push through the surface.

Additionally, once they do push through the surface they will grow very quickly. As such, my rule of thumb with Zucchinis is to start them about 4 weeks before your desired transplant date. 

Given that Zucchinis need a warm environment to thrive in, they're one of the last plants that I transplant and given how quickly they grow, they're one of the last seeds that I start. 

Zucchini plant on Day 21 thriving in worm casting seedling mix

After only 21 Days in its Worm Casting Seedling Mix, this Zucchini plant is green, lush, thriving, and growing at a tremendous pace. 

Transplanting Zucchinis with Worm Castings

Once the average nighttime low temperature has hit 10-12C and your Zucchini plant has 6 leaves, you can begin the process of hardening it off and transplanting it into the outdoor garden. To ensure it is setup to thrive: 

  • Temperature: Ensure the average night-time low is at least 10-12C before transplanting.
  • Soil: Plant into a well-draining rich soil. +50% Compost is a great growing environment for Zucchinis (the remaining 50% being either more compost or a combination of peat moss and perlite/vermiculite)
  • Fertilizing: Zucchinis are heavy feeders so make sure to transplant the Zucchini with Pure Worm Castings and an Organic Fertilizer
  • Sun: Zucchini love the sun and will thank you by growing massive foliage as well as large fruit. Reserve one of your sunniest spots in your bed for your Zucchini. 
  • Spacing: As they mature, you'll quickly see just how much space they take. Utilize our Space Planner for fitting them in alongside the rest of your veggies, and give up to 4 square feet for them to have sufficient space to thrive. 

Once you are all set to transplant your Zucchini (whether it is into a raised bed, container, or grow bag), simply:

  1. Dig: Dig a hole about 5" deep that you can use to transplant the Zucchini into.
  2. Feed: Place 1 handful of worm castings and 1tbsp of 4-4-4 Superfood (or another organic fertilizer) into the base of the hole.
  3. Place: Remove the Zucchini from its seed cell and place it into the hole. Backfill with the surrounding soil until it is secure in the garden bed or container.
  4. Feed: Sprinkle 1 handful of worm castings and 1tbsp of 4-4-4 Superfood around the stem where it enters the soil. Gently massage this into the top 1" of soil.
  5. Water: Generously water. Do multiple rounds of watering it for 10 seconds of watering directly around the main stem and then watering a few other plants before another round of watering the Zucchini plant.

Keep a close eye on your Zucchini plant as it settles into its forever home. It will likely go through a little bit of transplant shock and not put on too much new growth. However, as you approach 7 days after transplanting you will begin to notice new growth going onto the plant. 

How do Zucchini Flowers get Pollinated? 

Once your Zucchini plant has established in the garden, it will put on both new foliage growth as well as its first flowers.

What you will notice is that there are two distinct flowers for Zucchinis: Male flowers and Female flowers. When it comes to flowers, plants fall into two categories - either Complete flowers or Incomplete flowers.

Zucchinis are Incomplete because each flower contains either the male or the female reproductive elements opposed to both within the one flower. 

Picture comparing male and female flowers on a zucchini plant

The Female Zucchini flower on the right is followed by the fruit that will develop into our Zucchini, while the Male flower on the left is followed by no fruit - a clear distinction between the two types of Zucchini flowers. 

In order for the fruit to begin growing, pollen from the male flower must make its way to the female flower at which point pollination has occurred and the fruit begins to grow into a Zucchini. This is generally accomplished by bees, insects and other pollinators - one of which could be you!

To hand pollinate your Zucchini:

  1. Grab a QTip or small paint/make-up brush
  2. Find a male flower and rub the brush on the inside of the flower (specifically, the stamen where the pollen resides)
  3. Take the brush with the pollen on it over to the female flower and rub the pollen on the inside of the female flower (specifically, the pistil). 

This simulates the action of a pollinator and shortly thereafter you will see the Zucchinis beginning to grow!

Image of multiple zucchinis growing on a zucchini plant

Multiple Zucchinis pollinated and growing on this Zucchini planting in a grow bag container. 

How much do I need to water my Zucchini?

As your Zucchini plant passes Day60 and is fully mature and producing Zucchinis, it is going to require a significant amount of water. It is absorbing a ton of sunlight but in order for it to grow those large leaves and fruits, it also requires a significant amount of water (as they both primarily consist of water). 

However, each of our regions, weather patterns, and watering systems will differ. As such, dig about 2" into the soil a few inches off of the main stem to see if the soil is moist. If it is still moist and your plant is showing no signs of wilting or yellowing, then you don't need to water just yet.

If the soil is dry then it is time to give a thorough watering. Do this in multiple rounds to ensure that the water is absorbed into the soil. I like to give each plant 10-15 seconds before moving to the next plant and then doing a few rounds of this each time I water.

    Do I prune my Zucchini plant?

    With its feeding of worm castings and organic fertilizer, being well watered and in a full-sun location, your Zucchini plant has likely put on a lot of growth - and as a result is taking up a significant amount of space.

    Not only that, but all the foliage growth is decreasing airflow and increasing humidity - prime conditions for one of the most common Zucchini diseases, powdery mildew, to establish.

    To help combat this, prune about 25% of the leaves on your plant every month. I start with the oldest leaves that are beginning to yellow and die off as they have served their purpose. And if there ever are any early signs of Powdery Mildew, I prioritize pruning those even above the older growth.

    Common Zucchini Diseases 

    It is nearly inevitable that in the back-half of summer during the hottest and most humid days that your Zucchini plant will get powdery mildew. This very common white fungus will appear in white and blue patches on the top and bottom of your Zucchini leaves.

    Don't worry as this is entirely common. To combat it, you want to practice watering the soil, spacing correctly, and pruning.

    Additionally you can use a spray of 1litre water, 1tsp Neem oil, and 2-3 drops of Dr. Bronner's soap. Spray this fully coating the top and bottom of the leaves that display any signs of powdery mildew. Repeat every 2-3 days as you see new signs of it emerging and after a few weeks the plant will have built u some resilience to it.

    The other most common disease that you'll come across on your Zucchini plant is Blossom End Rot. This is when the fruits are successfully pollinated, but then slowly rot and die off due to a lack of calcium in the soil. If you notice this happening on any of your fruits, you will want to get your soil tested to confirm the calcium deficiency and then find a calcium amendment to cover the deficiency. 

    How to Harvest & Preserve Zucchinis

    Once the Zucchini is successfully pollinated, you'll notice that the fruit grows incredibly quickly. Most often you will be harvesting a large Zucchini within 5-7 days of it being pollinated - it truly is remarkable how quickly they grow. 

    While there is no right or wrong, my preference is to harvest my Zucchinis on the earlier side opposed to letting them stay on the plant for +7 days. I take this approach for two reasons.First, I find that the taste of the younger fruit is better than an over-developed Zucchini. Second, the plant only has so much energy and by removing the fruit at an earlier stage it frees up the plant to redirect that energy to new and more fruit and plant development - in turn yielding more Zucchinis over time.

    What you'll likely notice is that as a Zucchini gets to a significant size on the plant, simultaneously the number of new female flowers and fruit growing decreases. But as soon as you harvest that Zucchini, new female flowers and fruits begin to emerge shortly thereafter!

    Zucchini FAQs 

    Q: Can you grow Zucchini in a raised bed?

    Yes - Zucchinis will love all the soil and nutrients that are made available to them in a raised bed. If you do end up planting Zucchinis in a raised bed just make sure to follow our space planner to ensure that they have been given sufficient space. As they reach maturity they will really begin putting on a lot of foliage and sprawl across multiple square feet. 

    A personal preference of mine is to plant them towards the edge of a raised bed as this allows the foliage and stem growth to start in the raised bed but then spill over the edge into the path or onto the grass - which was space that previously wasn't producing or dedicated to a separate vegetable.

    Q: Can you grow Zucchini in a pot?

    Yes - as illustrated in the images above all of those Zucchinis are grown in 5 Gallon Grow Bags. Additionally, given how large Zucchinis grow having them in containers or pots or grow bags that you can easily move is very beneficial. They can start closer together but as the growth takes off you'll likely find yourself moving them to free up more space for one another. That flexibility is really nice to have as it's hard to picture just how much they'll grow when transplanting them!

    Q: What size of container to grow Zucchini in?

    The Zucchinis in the images above were grown in 5 Gallon Grow Bags. I really like this size of grow bag because it matches up perfectly well with 1 square foot. However, the more soil the better so if you have the ability to get your Zucchinis into grow bags anywhere from 10 Gallon to 30 Gallon in size they will be very happy!

    Q: How do I grow bigger zucchini?

    To grow bigger Zucchinis make sure that your plant is in full-sun (+8hrs direct sun per day), has a consistent and steady watering, and is well-fed with Worm Castings and an Organic Fertilizer. You can re-apply both the worm castings and organic fertilizer on a monthly basis by sprinkling it around the base of the plant to top it up with nutrients. 

    Additionally, you can start your seeds indoors in worm casting seedling mix to ensure that they are well developed seedlings by the time that they make it into the garden - this will simultaneously help you maximize the hottest days of summer. 

    Q: What to grow near Zucchini?

    Zucchini companion plants well with Corn, Lettuce, Melon, Peas, Radishes, and Strawberry plants. They will rival with brassicas (i.e. Broccoli, Cabbage, Brussel Sprouts) so avoid planting them near these plants if possible.  

    Q: Can you grow Zucchini on a trellis? 

    Some choose to trellis Zucchinis for more vertical growth. My personal experience has been that they don't need to be trellised because the main stem does not grow that far in length. As such, I allow mine to crawl and then prune the oldest leaves.