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Guide To Using Ash for Your Plants: Benefits & Precautions

Guide To Using Ash for Your Plants: Benefits & Precautions

The gardening community is dedicated to environmental responsibility and making efforts to minimize waste and prevent pollution.

Instead of throwing food scraps and garden debris in the trash bin, they dump them into the compost bin instead, and when they burn leaves and branches, they use the ash as fertilizer.

Is ash good for plants? You can use ash to fertilize plants either raw or composted. Ash is an excellent source of trace nutrients such as calcium and magnesium, and it contains decent concentrations of potassium, which most plants need. Ash also contains lime, which is good for acidic soil. 

Ash can have great benefits to the soil and the plants you grow in your garden. Some plants will thrive when you add ash to the soil while others may not be affected positively.

Read more to find out when and how to use ash for your plants.

Using Ash for Plants – What To Know

The soil in your garden has a delicate balance. Its pH levels fluctuate depending on the fertilizer and mulch you use.

So before you add ash to enrich the soil, you should test the acidity of the soil (either by having a sample analyzed or by using a pH monitor like this one) to determine if you need ash in its raw form or if you should compost it instead.

Benefits of Wood Ash for Plants

The more plants you grow in the garden, the more depleted the soil gets. This is why you use fertilizers regularly to enrich the soil.

Ash is a good fertilizer since it contains trace amounts of valuable nutrients that all plants need to grow and thrive.

The keyword is “trace amounts.” Unlike commercial fertilizers, ash will not burn the roots or stress the plant with sudden growth outbursts.

Ash also contains lime, which amends the soil and reduces its acidity. Most plants thrive in slightly acidic soil.

So if your garden soil has a low pH reading, adding ash can fix the problem and bring the acidity levels to close to neutral. 

Nutrients Found in Wood Ash

Ash is what remains of organic materials that you put in the fire. That means that ash still retains some of these nutrients.

However, the nutrients are only available in small amounts. In wood ash, you’ll often find low concentrations of sodium, calcium, aluminum, magnesium, potassium, sulfur, and phosphorus

Is Wood Ash Acidic or Alkaline?

Wood ash is alkaline. The chemicals in ash score 10.0 to 12.0 on the pH scale. This is why when the soil is acidic, you add wood ash to raise the pH levels and bring it close to neutral.

It’s also the reason that spreading wood ash on the soil in large quantities is discouraged.

If the soil pH is 7.0, which is neutral, you could inadvertently make the soil alkaline, which reduces its ability to release nutrients to plants. 

Which Plants Like Wood Ashes?

While most plants prefer slightly acidic to neutral soil, some plants like slightly higher-pH soil.

These include lavender, chives, garlic, onion, asparagus, lettuce, roses, hydrangeas, citrus plants, and stone fruit trees.

Does the Type of Wood Burned Matter?

The ash you get varies in its content and chemical construction depending on the type of wood you burn. Oak, poplar, walnut, and silver maple produce the best ash for fertilizing or composting.

Trees with plenty of resin content or toxic chemicals are not recommended for using as fertilizer once burned. 

Some ash may even contain heavy metals, such as lead and cadmium, especially if the trees grow near industrial areas or the wood has been treated.

Basic Guidelines For Using Ash in the Garden

Before you start sprinkling ash everywhere, you need to make sure that the soil is a little more than slightly acidic.

The last thing you’d want to do is raise the pH levels of neutral soil making it alkaline. This is why many experts recommend using composted ash since it has neutral pH levels.

How Much Ash To Use

When adding ash to the soil to benefit plants, less is more. The rule of thumb is to apply about 5 gallons (15-20 pounds) for every 1,000 square feet of soil every year.

This trace amount of ash will not impact the soil pH in a way that will harm the plants or change the soil’s chemical structure drastically. 

If you have limited space in the garden, then apply about half an inch of ash to the soil, and mix it in thoroughly.

When To Apply Wood Ash to the Garden

Before you spread the ash on the soil, sift it thoroughly. This will remove any lumps of charcoal or live embers. Test the soil pH beforehand to determine the adequate amount of ash to spread.

The best time to apply wood ash is in the winter. Spread it evenly over the surface of the soil. To prevent the ash from being blown away, apply it to moist soil, and avoid windy days. 

How To Use Wood Ash for Plants

Due to its high alkalinity, don’t use wood ash with just any plant in your garden. Only plants listed above that thrive on wood ash should get the treatment.

Apply between ¼ to ½ inch of ash, and work into the soil with a spade or a rototiller. Always wear protective gear to protect your mouth, nostrils, and eyes from the fine particles in the ash. 

Wood Ash for Pest Control

Many pests will perish if they crawl over wood ash. This is especially true of soft-bodied bugs, such as slugs.

To prevent pests from attacking your plants, sprinkle wood ash around the base of the plant you want to protect. Make sure the soil is dry before applying the ash.

If it rains or the ash gets damp, it will lose its edge, literally speaking. You’ll have to wait for the soil to dry out before applying a fresh layer of ash.

Precautions When Using Wood Ash for Plants

  • Whenever you’re dealing with ash, you should always protect your face from the highly alkaline ash particles. 
  • Don’t spread ash on windy days. 
  • Make sure the soil is moist before application to keep the ash from being blown away.
  • Always test the soil pH before applying wood ash to determine how much ash to apply.
  • Apply ash in the winter once a year.

A gardener using a small shovel to add a white powder to garden soil.

Is Ash a Good Fertilizer?

Ash is not a good substitute for the regular fertilizers and compost you add to the soil. Wood ash has trace amounts of nutrients at best.

It doesn’t have high concentrations of phosphorus or potassium and has zero nitrogen. These are the basic nutrients that most plants need.

You can use ash as a plant food supplement but not as the main fertilizer.

Is Ash Good for Soil?

The impact ash has on the soil varies depending on that soil’s pH levels. If the soil has low pH levels making it acidic or very acidic, then adding ash can increase that pH and make the soil suitable for most plants.

Ash also contains some nutrients that can help the soil when it’s depleted. 

Is Ash Good for Compost?

If you’re into home composting, then you know firsthand that your compost pile tends to get too acidic. Adding ash to the compost bin tends to balance the pile and produce neutral to slightly acidic compost.

Plants, in general, prefer neutral compost. Experts recommend adding ash to compost to neutralize its alkalinity without reducing its nutrients.

Is Ash Good for Grass?

Grass, like most other plants, can benefit from ash and the low nutrient concentrations it has. You can sprinkle ash on the wet grass to use it as a food supplement.

If the soil is already rich or the grass is not a heavy feeder, that could be all the fertilizing you have to do.

Is Wood Ash Good for Clay Soil?

You should use wood ash with clay soil more than sandy soil. Wood ash loosens the texture of the heavy soil and improves aeration.

Make sure to work the ash well into the soil using a rake to prevent clumps of ash from damaging the roots of the plants. 

Is Charcoal Ash Good for Plants?

You can use charcoal ash with the same results as wood ash. Charcoal ash pumps some much-needed nutrients into the soil, increases its pH levels, and amends the texture of the soil.

That said, the same precautions I mentioned with applying wood ash to the soil and plants apply to charcoal ash.

Always wear protective gear, sift the ash for debris, and apply it on wet soil. Mix the ash well into the soil to neutralize its alkaline impact on the roots of the plants.

That’s a Wrap!

You can use ash to fertilize plants, but you should do so in moderation. Only use between 15 to 20 pounds of wood ash once a year for every 1,000 square feet of soil.

For potted plants, spread a quarter-inch of ash evenly to the top of the soil, and water immediately.