Rhubarb Leaves: Don’t Let Them Go to Waste

rhubarb leaves in compost
Photo: CC0 Public Domain / Pixabay - Ulleo

While you shouldn’t eat rhubarb leaves (they are somewhat poisonous), you also shouldn’t just throw them away. We’ll show you how to put rhubarb leaves to good use – as a brew for your plants or in the compost.

Rhubarb is a tart and versatile spring vegetable…not fruit! You can use it to make things like jams, sauces, and pies. However, you should remove the leaves before using the stalks, because rhubarb leaves are poisonous to humans. The reason for this is the high amount of oxalic acid contained in these parts of the plant, which can be harmful to the kidneys in high concentrations. 

But don’t throw them away! Instead, use the leaves in your compost, or use them to make a brew for your garden.

Uses for Rhubarb Leaves

are rhubarb leaves poisonous
Although the leaves are poisonous, they aren’t a threat to the compost pile. (Photo: CC0 Public Domain / Pexels - Eva Elijas)

Rhubarb leaves are poisonous to humans, but a strong rhubarb leaf brew is great for your plants. Perfectly suitable for an organic garden, a concentrated rhubarb liquid can be used as a natural fertilizer or a safe pesticide spray. 

  • Strengthen your plants: Use the brew to help your plants grow and make them more resilient. Your plants will enjoy a growth aid in the spring, and a strength booster again before winter.
  • Prevent potassium deficiency: Leaves of the rhubarb plant contain a lot of potassium, which plants need. Potassium deficiencies make plants more susceptible to diseases.
  • Use as a remedy in case of diseases: Rhubarb leaves can help if your plants are already sick. In case of blight, remove the affected parts of the plant and spray the unaffected parts with a high-concentrate brew. This remedy may also help to get rid of aphids.

Another useful remedy: Homemade Weed Killer from Organic Ingredients

Making a Concentrated Brew 

rhubarb brew
Making a rhubarb leaf brew is very similar to making very strong tea. Simply add the leaves to hot water and let them steep for half an hour — just don’t drink it! (Photo: CC0 Public Domain / Pexels - Lucas George Wendt )

To make a brew out of rhubarb leaves, you’ll need a pot, a strainer, and a tea towel. A watering can or a spray bottle will come in handy when it’s time for application. 

For use against disease infestation: use 1 part water to 1 part leaves. 
To use as a fertilizer: use 5 parts water to 1 part leaves.

  1. Use a sharp knife to chop the leaves into small pieces.
  2. Add the chopped rhubarb leaves and water to the pot and bring to a boil.
  3. After about one minute, turn off the heat and let the rhubarb leaves steep for 30 minutes.
  4. Filter the liquid through a sieve. Squeeze the leaves with your hands or with the help of a tea towel.
  5. Toss the rhubarb leaves in the compost pile. 

Another method is to put the leaves in a sealable container with warm or hot water. Place the lid on and let the brew infuse for 24 hours.

Note: This brew will keep in the refrigerator for a few days. It is best to use it up quickly to avoid fermentation. You can also freeze it, but be sure to label it as poisonous before putting it in your freezer.

Also read: How and When to Harvest Rhubarb


  • As a fertilizer or disease prevention: Water your plants with your rhubarb leaf brew during their growing season. Keep in mind that harvest time for rhubarb is spring/early summer.
  • To fight plant diseases: Spray the affected plant with the rhubarb leaf brew once a day for about three days in a row.

Tip: Don’t use the brew on any plants that are food bearing.

Do Rhubarb Leaves Belong in the Compost Pile?

While rhubarb leaves aren’t safe for human consumption, there’s no reason not to add them to your compost pile! The oxalic acid has seemingly no effect on soil microorganisms and is not absorbed by plant roots. This means that plants grown in rhubarb-leaf compost are also safe to eat.

This article has been translated from German to English by Karen Stankiewicz. You can find the original here: Nicht wegwerfen! So kannst du Rhabarberblätter verwenden

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