Is Wood Ash Good for Tomatoes? A Surprising Fertilizer You Never Knew You Needed

Tomato season is upon us, and as gardeners, we’re constantly on the lookout for ways to give our precious plants a boost. Fertilizers are an essential part of any gardener’s toolkit, but sometimes it’s nice to find an organic alternative that won’t break the bank. Enter wood ash: a surprising and eco-friendly amendment that you might already have in your backyard! But is wood ash really good for tomatoes? In this blog post, we will discuss the benefits of using wood ash in your tomato garden, how to apply it correctly, and some precautions you need to take when using this natural fertilizer. So, let’s get started!

What is Wood Ash?

Wood ash is the fine powdery residue left behind after burning wood in a fireplace or stove. It consists mainly of calcium carbonate (lime), along with other trace minerals such as potassium, phosphorus, magnesium, and sodium. These nutrients can be beneficial for plants when applied appropriately.

Benefits of Using Wood Ash on Tomato Plants

There are several reasons why using wood ash on your tomato plants can be beneficial:

1. Raises Soil pH

Tomatoes thrive in slightly acidic soil with a pH between 6.0 and 6.8. However, many garden soils tend to become more acidic over time due to rainfall and organic matter decomposition. Adding wood ash raises the pH level because it contains calcium carbonate – which acts as a liming agent.

By raising the pH level of your soil through the application of wood ash, you can prevent issues like blossom end rot – a common problem caused by calcium deficiency in tomatoes.

2. Supplies Essential Nutrients

In addition to its ability to raise soil pH levels and provide calcium necessary for healthy tomato growth, wood ash also contains vital nutrients like potassium (K), phosphorus (P), and magnesium (Mg).

Potassium is essential for the overall growth and health of your tomato plants. It helps with the development of strong roots, disease resistance, and fruit quality. Phosphorus is vital for healthy root development and better fruit production. Magnesium plays a crucial role in photosynthesis, enabling your tomato plants to generate energy from sunlight.

3. Deters Pests

Wood ash can help deter common garden pests such as slugs, snails, and certain insects that might otherwise harm your tomato plants. The fine ash particles can be abrasive on their soft bodies or create an inhospitable environment when ingested.

How to Apply Wood Ash to Your Tomato Garden

Now that you know about the benefits of using wood ash on your tomatoes let’s talk about how to apply it correctly:

  1. Collect and Store Wood Ash: If you have a fireplace or wood stove, start by collecting the cool ashes in a metal container with a lid. Ensure that the ashes are completely cool before storing them – hot ashes can be a fire hazard! Alternatively, you can source wood ash from friends or family members who burn wood for heat.
  2. Test Soil pH: Before applying any amendments to your soil, it’s essential first to test its pH levels using an at-home soil testing kit or sending samples off to a professional lab for analysis.
  3. Determine Application Rate: If your soil tests show that it has low pH levels (below 6.0) or lacks nutrients like potassium and calcium, you may want to consider adding wood ash as an amendment.

    A general guideline is:

    • For soils with pH below 6.0: Apply 10-20 pounds of wood ash per 1,000 square feet.
    • For soils with pH between 6.0-6.8: Apply 5-10 pounds of wood ash per 1,000 square feet.

    Keep in mind that these are general recommendations and may need to be adjusted based on your specific soil conditions.

  4. Apply Wood Ash: Spread the recommended amount of wood ash evenly across the surface of your tomato garden, working it into the top few inches of soil with a rake or hoe. It’s best to do this before planting your tomatoes, but you can also apply wood ash around established plants as a side dressing – being careful not to get any ash directly on their foliage.
  5. Monitor pH Levels: After applying wood ash, continue monitoring your soil pH levels periodically throughout the growing season to ensure they stay within the optimal range for tomato growth.

Precautions When Using Wood Ash

While using wood ash on your tomatoes can provide several benefits, there are some precautions you should take:

  1. Avoid Over-application: Applying too much wood ash at once can raise soil pH levels too high and lead to nutrient imbalances or toxicities in your tomato plants. Always test your soil before adding amendments and follow recommended application rates closely.
  2. Do Not Use Treated Wood Ash: Wood ashes from treated lumber or painted/stained surfaces should never be used in gardening applications, as they may contain harmful chemicals that could contaminate your soil and harm your plants.
  3. Protect Yourself: When handling wood ash, wear gloves and avoid inhaling any dust particles by wearing a mask if necessary. Additionally, keep children and pets away from areas where you’re applying or storing wood ashes due to potential health risks associated with ingestion or inhalation.


So is wood ash good for tomatoes? Yes! When applied correctly, it can help raise soil pH levels, provide essential nutrients like calcium, potassium, phosphorus and magnesium while deterring pests that might harm your precious tomato plants.

Remember always to test your soil first before adding any amendments and follow recommended application rates to avoid over-application. With proper precautions, wood ash can be an effective, eco-friendly addition to your tomato garden that will help your plants grow stronger and produce more delicious fruits.