4 Natural Ways to Raise Soil pH for Plants That Need Less Acidity

Most plants thrive in soils with a slightly acidic to neutral pH of around 6.0 to 7.0. If you’re struggling with overly acidic soil, knowing how to raise pH in soil closer to that neutral range will help you create better growing conditions for many types of herbs, flowers, and veggies that won’t grow well with too much acidity. Find out the best natural soil amendments to use to raise soil pH, plus get simple tips to keep your soil from becoming too acidic again.

Understanding Soil pH

Soil pH affects how well plants take up nutrients. Garden soils that are either too acidic or alkaline make it hard for plants to absorb the nutrients they need. In acidic gardens, this leads to magnesium, potassium, calcium, and other nutrient deficiencies, but it can also reduce the population of beneficial microbes and make soils less healthy and robust. On top of that, overly acidic gardens cause the build-up of soil nutrients like manganese and aluminum in excessive amounts, creating toxic conditions for plants.

When to Raise pH in Soil

Sandy gardens and areas with lots of granite are more likely to have acidic soil than clay-heavy gardens with an abundance of shale or limestone. But even alkaline garden soil may become acidic over time as a result of environmental factors, such as acid rain, or the overuse of synthetic fertilizers and other soil amendments. The best way to determine if you need to adjust soil pH or not is to research the pH needs of the plants you’d like to grow and test your soil at least once every three years.

If you’re growing acid-loving plants such as blueberries, you may not need to adjust your soil pH at all. However, if you want to grow plants that prefer more alkaline conditions, including lilac, arborvitae, hellebores, lavender, and asparagus, you may need to raise or “sweeten” your soil pH. Any of these signs of stress in plants may indicate that your soil pH is too low and it’s time to take action:

• Stunted growth
• Poor crop yields
• Yellow, brown, dried, or deformed leaves
• Blossom end rot in tomatoes and other fruiting plants
• Scorched-looking leaves with purple or red edges

Ways to Make Soil Less Acidic

Before applying any type of soil amendment, always test your soil. This will help you determine how much product to use and which of the following products is right for your garden.

Lime

Adding lime is the most popular way to reduce soil acidity and make gardens more alkaline; however, it’s important to use the right type of lime. Calcitic lime, also known as garden lime, agricultural lime, or aglime, consists of ground limestone or chalk; it is the most common lime used in gardens. Dolomitic lime is also approved for organic gardens, but it contains higher levels of magnesium and should only be used if you know your soil is magnesium deficient. Quicklime, on the other hand, is not suitable for use in garden soils due to safety issues.

Wood Ash

Using the ashes from your fireplace or firepit is a no-cost, DIY approach to raising soil pH and adding calcium, potassium, and other nutrients to your soil. For safety, only use wood ashes from
untreated wood, and don’t use ash from pellet stoves or from any materials that contain chemicals you wouldn’t want in your garden. Wood ash generally works quicker than lime, but it doesn’t last as long in the soil and needs to be reapplied more regularly.

Compost

While lime and wood ash significantly raise soil pH, compost and leaf litter are less potent ways to bring your soil pH closer to 7.0. Most compost has a relatively neutral pH and working a 2- to 3-inch layer of compost into the top 6 inches of your soil reduces acid levels, and improves your soil structure and nutrient content at the same time.

Other Methods

Products like crushed oyster shells, clamshells, and eggshells contain calcium carbonate that can make soils more alkaline and add calcium too. However, these products take a while to work and they need to be crushed very finely to be effective. They also leach out of soils faster than lime or compost, which means they need to be reapplied more regularly.

Tips for Applying Soil Alkalizers

When working with soil alkalizers such as lime, be sure to read the instructions on the product packaging and wear appropriate safety gear, including gloves, goggles, and a dust mask. Application instructions vary depending on the product you’re using, but these basic guidelines apply to most natural soil alkalizers.

• The amount of product you’ll need to use depends on your existing soil pH, the plants you’d like to grow, your soil structure, and the size of your garden. A soil test is necessary to determine how much product you need.
• To apply soil alkalizers, spread your product of choice over your soil by hand or with a broadcast spreader. Soil alkalizers usually come in powdered, granular, or pelleted forms, but some are sold as liquids and are applied with a garden sprayer.
• After applying, work the alkalizing product into the top 6 inches of soil with a rake, shovel, or tiller, and then deeply water the area to activate the product.
• Test your soil pH after a few months and apply more product if the pH values are still too low.
• Adding soil alkalizers little by little will allow you to slowly raise soil pH over time and avoid damaging your plants with too much product.
• Soil alkalizers are easier to apply in empty gardens, but they can also be worked into the soil around existing plants in spring or fall.
• Lime products take a while to work. They are generally applied in fall or winter if you want to plant in spring.
• Maintaining soil pH levels is an ongoing process and testing your soil regularly will help you determine when you need to reapply products.
• Switching to organic fertilizers and other soil amendments may help you avoid soil acidity issues in the future.