Rustic Zucchini Sourdough Bread Recipe with Walnuts

Need more veggies in your life? Try our rustic sourdough zucchini bread! This recipe will show you how to incorporate fresh zucchini into a classic, savory sourdough bread loaf (like a boule or batard) – including optional walnuts for extra protein and crunch. This is one of my go-to ways to use extra zucchini from my summer garden. The result is chewy, nutritious and delicious bread!

If you’re looking for a more traditional sweet bread (you know, the kind that’s baked in a loaf pan), don’t miss our other sourdough zucchini bread recipe!

RELATED: If you’re new to baking sourdough, come learn the basics with our easy no-knead sourdough bread recipe here.

Ingredients

I personally like to use a mix of white, whole wheat, and rye flour to make my sourdough zucchini bread extra nutritious. However, you can easily make this recipe using 100% white flour – simply use 460 grams total.

• 300 grams of white bread flour or all-purpose flour
• 140 grams of whole wheat flour
• 20 grams of rye flour
• 110 grams of active sourdough starter. If you need a starter, you can buy one here or learn how make a starter from scratch.
• 1 ¼ cup of warm filtered water
• 1 to 1 ½ cups grated zucchini* (see sliding scale notes below)
• 9 grams of salt
• ½ cup of walnuts. I like to use raw, unsalted halves and pieces. Unsalted sunflower seeds or pumpkin seeds are a great substitute for those with nut allergies!
• Optional but delicious: 1/2 tsp of garlic powder and/or 2 tsp onion of powder

*If you desire a more tall, open-crumb sourdough loaf, use closer to 1 cup of grated zucchini. I usually use around 1.5 cups (it’s zucchini bread after all) but the additional moisture and weight from the zucchini can make the loaf slightly more flattened than our average loaves. I don’t mind!

RELATED: Looking for more zucchini recipes? Try our sweet and tangy zucchini relish recipe, parmesan zucchini fritters, easy zucchini noodles (zoodles) with pesto, or tips on how to freeze zucchini too.

Baking Schedule/Timing

I generally make sourdough over the course of two days: I feed my sourdough starter in the morning, mix the dough once the starter reaches peak activity in the afternoon, allow it to rest for several hours (and do stretch and folds during that time), and form the loaf in the evening. Then I let the dough cold proof in the fridge overnight, and finally bake it the following morning. 

Instructions

1) Feed Sourdough Starter 

Wake up your sourdough starter and get it ready for baking! Feed your starter as you typically would, at least several hours before you plan to make dough. Allow it to reach peak activity before using it in the recipe. If you starter has been stored in the refrigerator, I recommend taking it out the night before to warm up, and feeding it at least twice to fully perk it up. 

Learn more about feeding sourdough starter here.

2) Mix Flour and Water (Autolyse)

About an hour before your sourdough starter will reach peak activity, weigh and combine the called-for flour and water only in a large mixing bowl. Avoid adding cold water to the flour. Mix well – I use my hands!

Let the flour and water mixture sit for 1 hour, covered with plastic wrap or a damp tea towel. If possible, keep it in a location with an ambient temperature between 70-75 degrees Fahrenheit for the best fermentation.

This sourdough zucchini bread recipe uses less water than regular sourdough bread, so it may seem more dry than usual. That’s intentional! We need to reduce the water to compensate for the additional moisture the zucchini will add later. 

PRO TIP: When my house is cold (which is often!) I like to use a handy sourdough warming plate to keep both my sourdough starter AND the bowl of proofing dough at the ideal temperature.

3) Grate and Drain the Zucchini

Once the autolyse has been mixed and resting for about 40 minutes, begin prepping the zucchini. It needs about 15 minutes of its own rest time before you add to the dough.

• Grate the zucchini into medium-fine shreds and add it to a strainer. (I use a basic box cheese grater.)
• Next, add a light sprinkle of salt (no more than 1/2 tsp) over the grated zucchini and toss to mix. Rest the strainer in a very clean sink, or set it over a larger bowl to drain.
• Over the next 15 minutes, the salt is going to help draw excess water out of the zucchini. I recommend tossing, pressing, and lightly wringing out the zucchini a few times to help remove as much moisture as possible.
• Do not add the collected zucchini water to the recipe!

4) Mix Zucchini and Dough

• Now combine the shredded (drained) zucchini with the autolyse (flour and water mixture) along with 120 grams of active sourdough starter and 9 grams of salt. Wait to add the walnuts until the first stretch and fold.
  
  
• Here’s where I also like to add ½ tsp of homegrown garlic powder and 2 tsp of onion powder too. If you’re interested, learn how to make your own homemade garlic powder and onion powder here!
  
  
• Thoroughly mix to combine all of the ingredients. I usually use clean hands to pinch, mix, and knead everything together. I also like to use the “slap and fold” method to help further combine and tighten the dough.
  
  
• Once mixed, cover the dough and bowl and let it rest for 30 minutes. 

5) Stretch and Fold, Bulk Ferment

• Now allow the dough to bulk ferment at room temperature in a covered bowl for about 4 hours.
  
  
• During the first 2 hours, repeat at least 3 more sets of stretch and fold, about 30 minutes apart. Then let the dough rest and rise undisturbed for the remainder of bulk ferment.
  
  
• I like to fold in the walnuts during the first set of stretch and fold, which gives them plenty of time to get evenly distributed throughout the zucchini sourdough during the following sets.
  
  

6) Form Loaf and Proof

Now that your sourdough has finished fermenting at room temperature, it is time to get the loaf formed, tucked into its banneton (proofing basket), and put away to sleep in the fridge.

On a lightly floured surface, form your loaf into the desired shape with a few folds and tucks. Afterward, we generally let it sit to bench rest for about ten minutes, give it one final fold and form, and then slip it into a floured banneton.

Cover the banneton with a tea towel once again, and allow the dough to cold proof overnight in the refrigerator. 

7) Bake 

Before baking, I recommend preheating your oven to 475°F for one hour with your empty cast iron combo cooker or dutch oven inside.

Then, carefully slip the cold dough straight from the fridge into the piping hot dutch oven or cast iron. For a smooth transition, we place a piece of parchment paper on top of the banneton, a cutting board on top of that, then flip the whole thing upside down.

Before easing the dough into the hot pan, you can give it a very light dusting of flour and score with a bread lame across the top if you wish.

Bake covered for 40 minutes, then remove the lid and bake for an additional 5 minutes. 

PRO TIP: If you struggle with the bottom of your sourdough bread burning or browning too much, try putting an empty baking sheet on the empty oven rack below the Dutch oven. It helps absorb and deflect some of the heat while it bakes. No more burnt bottoms!

8) Cool and Enjoy

Once the loaf is finished baking, immediately (and carefully!) transfer your finished zucchini sourdough bread from the hot pan to a cooling rack. As difficult as it is to resist, allow the bread to cool for several hours before slicing into it. Otherwise, valuable steam will escape and the bread will become stale much faster.

I love to enjoy our zucchini sourdough bread on its own, with veggie sandwiches or avocado toast, or served alongside soup, vegetarian chili, scrambled eggs and more.

Fresh sourdough bread is always best enjoyed within a few days of baking, though it can stay good for up to 5 days or more. For storage, I suggest wrapping the bread in a lint-free tea towel and then storing it inside a paper bag at room temperature. (Storing it in the fridge will make it dry out faster.) Pop it in the toaster if it gets a little stale!

I really hope you enjoy this sourdough zucchini bread as much as we do! Please come back by to leave a review once you give it a try.

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• Easy Sourdough Discard Crackers Recipe (Optional Cheese or Herbs)
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• Simple Sourdough Focaccia Bread Recipe
• Easy Sourdough Pancakes Recipe (Discard or Active Starter) + Topping Ideas
• Sourdough Corn Bread Recipe (with Vegan Options)