Adding wood ashes to your garden can be a great way to amend your soil. Knowing which plants like wood ashes is the key to using this resource effectively and avoiding harm.
Wood ash is the powdery residue left after burning clean wood. It’s not a complete fertilizer, but it’s a valuable source of certain minerals. It can raise soil pH, add potassium, and provide trace elements. Used wrong, however, it can damage your garden. This guide will help you use wood ash safely and successfully.
Which Plants Like Wood Ashes
Wood ash is alkaline, meaning it raises the pH of your soil. Therefore, plants that thrive in wood ash are those that prefer sweet, or non-acidic, soil conditions. It’s a fantastic amendment for these specific plants, providing potash and calcium they love.
Vegetables That Benefit from Wood Ash
Many common garden vegetables will perform better with a light application of wood ash. Focus on these heavy feeders.
- Tomatoes: Ash helps prevent blossom end rot by supplying calcium. The potassium boosts fruit quality.
- Asparagus: This perennial loves alkaline soil and the potassium in ash promotes strong spear growth.
- Garlic & Onions: They benefit from the added potassium for good bulb development.
- Spinach & Swiss Chard: Leafy greens often appreciate the nutrient boost and sweeter soil.
- Broccoli, Cabbage, & Brussels Sprouts: These brassicas generally prefer a higher pH soil.
- Leeks: Similar to onions, they use the potassium for healthy stems.
Fruiting Plants and Trees
Fruit producers need potassium for flower and fruit development. Wood ash can be a good supplement.
- Apple & Pear Trees: Apply moderately around the drip line to support fruiting.
- Grape Vines: Potassium is crucial for grape sweetness and vine hardiness.
- Strawberries: A light dusting after harvest can help next year’s crop.
- Raspberries & Blackberries: Use very sparingly, as they tolerate only slightly alkaline soil.
Ornamental Plants and Lawn
Don’t forget your flowers and lawn. Many classic ornamentals prefer neutral to alkaline conditions.
- Lilacs: They flower best in sweeter soil. Ash can help achieve that.
- Clematis: Many varieties appreciate the conditions ash helps create.
- Lavender: Thrives in alkaline, well-drained soil. Ash is a perfect match.
- Hydrangeas (for pink blooms): To get pink hydrangea flowers, you need to lower soil acidity. Wood ash can help shift the color from blue to pink.
- Lawn Grass: A very light dusting can help neutralize acidic soil and provide potassium for root growth.
Plants to AVOID with Wood Ash
This list is just as important. Never put wood ash near acid-loving plants, as it can harm or even kill them.
- Blueberries
- Rhododendrons & Azaleas
- Camellias
- Potatoes (can promote scab fungus in alkaline soil)
- Sweet Potatoes
- Strawberries (if your soil is already neutral or alkaline)
- Most evergreen trees and shrubs
How to Test Your Soil pH First
Never guess your soil’s pH. Always test it before applying wood ash. You can buy an inexpensive test kit from any garden center. Here’s how to do it.
- Collect soil samples from a few spots in your garden bed, about 6 inches deep.
- Mix the samples together in a clean container.
- Follow the instructions on your test kit precisely.
- If your soil pH is below 6.5 and you’re growing ash-loving plants, an application may be beneficial. If it’s 7.0 or above, do not add wood ash.
The Right Way to Apply Wood Ash to Your Garden
More is not better. Wood ash is potent and should be used with caution. Follow these steps for safe application.
1. Use Only Clean Wood Ash
Only use ash from untreated, unpainted, natural wood. Never use ash from coal, charcoal briquettes, trash, or colored paper. These can contain harmful chemicals that will pollute your soil.
2. Timing is Important
The best time to apply wood ash is in late winter or early spring. This gives it time to integrate into the soil before the main growing season. You can also apply it in the fall after harvest. Avoid applying it during windy days or when foliage is wet.
3. Apply Lightly and Evenly
Never dump piles of ash. A general rule is to use no more than 10-15 pounds (about a 5-gallon bucket) per 1,000 square feet per year. For a small garden, a handful per square yard is often plenty. Always wear gloves and a dust mask to protect yourself.
4. Work it Into the Soil
Lightly sprinkle the ash over the soil surface. Then, use a rake or hoe to gently work it into the top few inches of soil. This prevents it from forming a crust and helps it start neutralizing soil acidity. Watering it in after application is also a good idea to stop the ash from blowing away.
5. Composting with Wood Ash
You can add modest amounts of wood ash to your compost pile. It helps maintain a neutral pH and adds minerals. Sprinkle thin layers between your green and brown materials. Too much ash, however, can slow down the composting process by making the pile to alkaline.
Understanding the Nutrients in Wood Ash
Wood ash is primarily a source of calcium carbonate (lime), potassium, and trace elements. Here’s what it offers.
- Potash (Potassium): This is the main nutrient, vital for flower/fruit formation, disease resistance, and overall plant health.
- Calcium: Essential for cell wall structure and preventing disorders like blossom end rot.
- Trace Elements: Contains small amounts of magnesium, phosphorus, and micronutrients like zinc and copper.
It’s important to note that wood ash contains almost no nitrogen. You will still need to use other fertilizers or compost to supply nitrogen for leafy green growth.
Common Mistakes to Avoid
Even with good intentions, it’s easy to misuse wood ash. Steer clear of these errors.
- Over-application: This is the biggest mistake. It can raise pH too high, locking up vital nutrients so plants can’t absorb them.
- Using on Acid-Loving Plants: Always double-check your plant’s preferences.
- Applying to Dry, Foliage, or Seeds: Ash can burn plants if applied directly. Keep it on the soil.
- Mixing with Nitrogen Fertilizers: Don’t mix ash with ammonium-based fertilizers. It can cause nitrogen to be lost as gas. Apply them at different times.
- Storing Ash Improperly: Store wood ash in a completely dry, metal container with a tight lid. This prevents it from leaching nutrients and becoming a messy, corrosive paste.
Frequently Asked Questions (FAQ)
Can I use fireplace ashes in the garden?
Yes, but only if you burn only natural, untreated wood. Ashes from paper, cardboard, or manufactured logs often contain chemicals you don’t want in your soil.
How much wood ash should I add to my soil?
A light dusting is sufficient. Never exceed 15 pounds per 1,000 square feet annually. Always test your soil pH first to see if you even need it.
Is wood ash good for all plants?
No, it is not. It is harmful to acid-loving plants like blueberries, azaleas, and rhododendrons. Always know your plant’s pH preference.
Can wood ash kill plants?
Yes, if used incorrectly. Applying to much can create overly alkaline soil that locks up nutrients, leading to poor growth or death. It can also burn plant roots and foliage if applied directly.
What is the difference between wood ash and lime?
Both raise soil pH, but wood ash acts faster because its particles are finer. Wood ash also provides potassium, while most garden lime does not. Lime is often a more consistent product for solely adjusting pH.
Can I put wood ash on my lawn?
Yes, in very small amounts. A light dusting in early spring can help sweeten acidic lawn soil and provide potassium. Avoid clumps, as they can burn the grass.
Final Tips for Success
Wood ash is a wonderful garden amendment when used thoughtfully. Start with less than you think you need—you can always add more later. Keep a garden journal to note where you applied ash and how your plants responded the following season. This hands-on experience is invaluable.
Remember, soil health is about balance. Wood ash is one tool in your toolbox. Combine it with plenty of organic matter like compost, which helps buffer pH and improve soil structure. By understanding which plants like wood ashes and following these simple guidelines, you can turn your winter fires into a bountiful summer harvest and a more beautiful garden.