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Growing Zucchini Containers & Controlling Blossom End Rot and Powdery Mildew

By on Jun 16, 2017 in Blog, Container Gardening, Summer Garden | 15 comments

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Zucchini is a real power producer!

Growing a large veggie like a zucchini in a small growing space CAN be done when you follow a few simple tips!  It’s very important to choose a container that is large enough to accommodate the plant’s extensive root system so that you get the abundant harvest that zucchini is famous for.


20 gallon Smart Pots are a perfect container to grow a large veggie like zucchini in.

My favorite container for growing a large veggie like zucchini is a 20 gallon fabric Smart Pots container.  Smart Pots containers work beautifully for a large plant like zucchini because the containers are made from durable, aerated fabric.  When the roots hit the sides of the pot, they “air prune”.  Instead of encircling the bottom of the pot, and becoming root bound, they prune themselves and form a fibrous root ball that is able to effectively take up water and nutrients, feeding the plant and helping it grow large and be productive, even in a container.

The aerated fabric also provides the zucchini plant plenty of airflow, keeping it cooler on a hot summer day.  It also drains water effectively so the plant doesn’t become waterlogged and the roots don’t rot.  See my previous blog post, Growing Large Veggies in Containers for more info on growing in containers.

Once you have your zucchini planted and established in the container, follow these tips to help it thrive.

Tip #1: Support your plant

Support your container zucchini with a large store-bought tomato cage.

A zucchini grows like a bush, but does tend to have some trailing vines as it grows.  Provide it with support, such as a sturdy store bought tomato cage. Place your cage deep in the container at the time of planting and feed the large leaves up through the tomato cage as they grow.  This will give your plant stability and help save space.  Make sure to check your plant every few days when it is getting established, as it is a fast grower!



Tip #2 – Hand pollinate if necessary

Hand pollinate to help the bees along!

As your zucchini plant grows, you should see flowers bloom.  First, the male flowers will bloom, sometimes they will fall off, or shrivel up.  Don’t be alarmed, this is normal!  Soon you will see the female flowers bloom – they are attached to tiny immature zucchini. If the fruit does not continue to grow, this is a clue that you do not have enough pollinators around your garden and need to hand pollinate the flowers.  Don’t let hand pollinating scare you – it’s so easy!  See my previous blog post on “Growing Watermelon in a Container” so you know exactly what to do!  The hand pollinating process is the same for zucchini and watermelon.


Tip #3 – Water and Fertilizer

Fertilize once a week with a liquid fertilizer.

Container plants dry out quicker than in-ground plants.  Check your container zucchini daily to see if they need water.  I have my container plants on a separate drip irrigation system from the rest of my garden, due to the different watering needs they have.  If you do not have a drip irrigation system, check your containers daily by sticking your finger into the soil.  If the soil feels dry, you need to water.  In high temperatures (over 90 degrees) you may need to water your plants twice a day.  Water with your hose or watering can at the base of your plant (avoid getting the leaves wet) until water runs out the bottom of your container.

Zucchini is a heavy feeder and a power producer.  It needs a lot of nutrients produce over a long growing season.  Fertilize your container zucchini once  a week with a liquid water soluble fertilizer.  A water soluble fertilizer will provide nutrients that will be immediately available to the plant.  My go to liquid fertilizer is Verimisterra worm tea, made from worm castings. Worm tea contains beneficial bacteria and microbes and feeds your plants just what they need to grow healthy and strong in a container.  (Available at the above link for a 10% discount with the promo code “calikim”.)


Common Zucchini Problems

Blossom End Rot (BER)

Water regularly and add calcium to control blossom end rot.

Blossom end rot or BER, is a condition that often affects zucchini plants.  A zucchini has BER when the end of the veggie is soft and looks like it is rotting.  Remove any zucchini affected by BER from the plant.  Affected fruit are edible as long as you cut off the soft portion.  BER is caused by a lack of calcium in the soil, or by the inability of the plant to take up calcium from the soil due to irregular watering.

Controlling BER

Help prevent BER on future zucchini by sticking to a regular watering schedule, or by adding calcium to the soil.  Add calcium to your soil one of 3 ways:


Powdery Mildew (PM)

Powdery mildew on zucchini leaves.

Powdery mildew (PM) is a fungal infection that is common to zucchini plants.  It looks like baby powder coating the tops and undersides of leaves.  PM thrives in humid, rainy weather when the leaves don’t have a chance to dry.  It can also occur in dry conditions, as I usually get it toward the end of every growing season, in spite of our warm California summers.



Controlling PM

Avoid overhead watering

Watering at the base of your plants is healthier for your plants and helps avoid diseases like PM  Use a drip irrigation system, or water with your hose at the base of the plants.

Prune affected leaves

Pruning leaves affected by disease not only keeps PM  from spreading but also keeps your zucchini plant under control in a small space.  This prevents the plant from shading itself, or smaller plants and re-directs the energy into growing lots of squash!


Foliar spray

Control powdery mildew with a foliar spray.

Spraying the leaves (foliar spray) with an organic fungicide is helpful to prevent PM.  Spray the tops and undersides of leaves before you see PM, as a preventative measure.  Spray early in the morning so the leaves can dry before evening.

My favorite foliar spray is Vermisterra Worm Tea.  It coats the leaves of your plants with beneficial microbes and bacteria that will multiply and crowd out diseases and protect it from pests.  (Available at the above link for a 10% discount with the promo code “calikim”.)

Watch the video from my YouTube channel, “Growing Zucchini in Containers & Controlling Blossom End Rot and Powdery Mildew”  so you can see exactly what to do to be successful at growing zucchini in your container garden and keep blossom end rot and powdery mildew under control!



Comment below – let me know if you are growing zucchini in containers in your garden!

Zucchini is delicious grilled, roasted or stuffed!

Harvest your zucchini while they are young for nice tender veggies.  I love zucchini grilled, stuffed or oven roasted.

Harvest zucchini while they are young, otherwise you may end up with baseball bats!

If you wait to long to harvest, beware, you might end up with a baseball bat, which are delicious shredded up for zucchini muffins, bread or cakes.  Any way you slice it, garden fresh zucchini is bound to be delicious and will be a family and neighborhood favorite – you’ll have plenty of it to share with anyone who stops by!



Some of the links in this post are affiliate links –  I make a small commission when you order through these links and its helps me keep the garden content coming!


My eBook * My Partners Store * My Amazon Store


You can follow me, view how-to videos, photos of my garden, and lots of growing tips and tricks, on YouTube, Instagram, Facebook, and Pinterest



  1. Yolanda

    June 17, 2017

    Post a Reply

    Thank you for this, I always have PM on my zucchini and cucumber plants, this helps a lot

    • Robyn

      June 18, 2017

      Post a Reply

      Thank you, I am going to try the worm tea and hand pollinating. I get flowers and small fruit but after a few days when I go to check on the fruit I find they have completely disappeared It’s strange, maybe rats eat them. ?

      • CaliKim

        June 19, 2017

        Post a Reply

        Hello Robyn – often if the fruit doesn’t get pollinated, it shrivels up. Hand pollination is so easy, and they worm tea really gives the plants a boost – let me know how it goes for you! Thanks for stopping by!

    • Elizabeth

      June 19, 2017

      Post a Reply

      Do you find that certain types of zucchini plants are heavier producers then others?

      • CaliKim

        June 19, 2017

        Post a Reply

        Hello Elizabeth – I’ve had the best luck with Black Beauty and Golden Zucchini. I’m growing a striped zucchini this year, will let you know how it does! Thanks for stopping by!

    • CaliKim

      June 19, 2017

      Post a Reply

      PM can be hard to get rid of once it starts. Give the worm tea a try and let me know how it goes! Thanks for visiting my website!

  2. Marc

    July 11, 2017

    Post a Reply

    Thanks for a great article, Kim. Also love your Videos – still working through them! Envious of your warm climate – we have mild winters here (west coast of British Columbia) but short daylight in winter.

    I have BER as well on my zucchini. I will have to try some eggshells. Also had one zucchini that was hollow, wonder if that was from inconsistent watering?

    Happy gardening!

    • CaliKim

      July 11, 2017

      Post a Reply

      Hi, Marc! So glad you are enjoying the videos- I bet it’s just beautiful where you live! Calcium deficiency can definitely be a contributing factor to blossom end rot- keep me updated on how your eggshell treatment works. You can also try dissolving a few Tums in water and applying once or twice a week. In my experience, hollowed zucchini are often just overripe. I have found when I pick my zucchini consistently, they are nice and full! =) Keep me updated and thanks for stopping by!

      • Marc

        July 11, 2017

        Post a Reply

        Yes, we have lots of rainforest here. Beautiful places to go hiking and camping. 🙂

        I tried putting some calcium-magnesium tablets that I had leftover in the soil so I’ll see what happens. Good point about picking them early enough – I’m always waiting, hoping for bigger ones. Same with kohlrabi – they need to be picked when they are medium size otherwise they end up being woody.

        I’m getting excited though about my watermelon – watched your (very timely) video at lunchtime with the slings for the watermelon. I will have to find some old t-shirts for when the melons get bigger – right now they are still marble size.

  3. Before my husband and I were married, he made this for me. OMG, any man who can cook this good needs to be my husband!! LOL! During both my pregnancies I craved Moussaka! SOOOO yummy! He also bakes his eggplant instead frying, which makes for a healthier Moussaka. Happy Birthday Suzy. ?
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  4. Cherie

    July 26, 2018

    Post a Reply

    Hi Kim, I love your YouTube videos and blog and am grateful for all the advice you provide. So thank you!!

    I currently have a zucchini in a large container. My first question is how often should you provide zucchini with calcium? I used the crushed up tums method about 3 weeks ago and have had 2 really beautiful zucchini. Unfortunatley my pollinators aren’t abundant and I’ve lost 4 baby zucchini girls. I’ve considered hand pollinating but the stems are so tight in the tomato cage that it’s hard to get to anything without breaking a stem. As it is, the weight of the plant above is squashing the stems below on the lowest rung of the tomato cage. Which brings me to my 2nd question. This zucchini is a big, happy girl (unfortunatley with PM). Do you think I should try cut out the bottom rung of the tomato cage? We will probably damage the plant but it seems to be strangling it. 🙁

    Thanks again,

  5. Shonda T Stansbury-Beck

    August 23, 2018

    Post a Reply

    Hi Kim,

    What size pot did you have that zucchini plant in? Also, if I have a 20 gallon smart pot, how many zucchini plants can I grow in it? I was a little over zealous and planted too many seeds indoors and have 20 transplants ??‍♀️

    • CaliKim

      August 27, 2018

      Post a Reply

      Hello Shonda!!
      Congratulations on planting zucchini’s!! A good rule of thumb is one plant per 5 gallon container. Over-zealousness is a gardeners best trait- I always plant extras as back-up??Thanks for stopping by!!

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