How Can I Manage A Garden With Alkaline Soil?

Do you have acid-loving plants mixed with non-acid plants?

Do you have a plant that is suffering from alkaline conditions in the mid- to late season?

Can you apply flowers of sulfur in your garden?

Do you use acidifying mulches?

If your acid-loving plants are mixed among other non-acid plants, it may not be practical to amend the soil, since the increased acidity might then affect other plants. Here, the best option is to fertilize with one of the many water-soluble products available, such as Miracid. Begin with mild solutions until you understand the impact on your plants.

If you have a plant that is suffering from alkaline conditions in mid- to late season, you can give it a quick fix when you water. Simply replace one watering a week with common white vinegar, which contains 5 percent acetic acid. Remember to apply enough to penetrate the soil, down to the area where the roots are actively growing and taking in moisture and nutrients. Monitor the soil with a home test to be sure you aren’t making it too acid, and stop when the pH reaches a level between 6.8 and 6.5.

Sulfur helps to lower the pH of alkaline soils, but it must be applied correctly. For every 100 square feet, apply no more than one pound of flowers of sulfur. Don’t be tempted to add more than this, even if your soil needs to be lowered to more than one unit. Adding more will disrupt microorganisms and soil animals, harming your soil more than it helps. Instead, apply additional sulfur the following year. It’s important to water immediately after applying the sulfur. Because it will work better if the soil contains high levels of organic matter, it’s wise to apply a layer of compost, about half an inch deep, at the same time as you apply the sulfur.

Even with yearly applications of sulfur, some soils will drift back to an alkaline state by the end of the season. You can continue to fight them by applying treatments twice a year, watering with vinegar, and using acidifying mulches, but it's much easier to plant alkaline-tolerant plants in as many areas of the yard as possible. Some annuals and perennials that thrive in alkaline soils are hollyhocks, lady's mantle, columbine, elephant's ear, cosmos, baby's breath, iris, sweet pea, ornamental sage, nasturtium, lobelia, phlox, etc.

If your soil is excessively alkaline, you can change it slightly through your choice of organic mulches. Don't expect to change the pH in any significant way with a mulch, but if you have added flowers of sulfur to a garden bed and want to slow down its movement back to an alkaline state, a mulch can help. Materials that are good for winter cover as well as for annual and perennial beds during the growing season are evergreen boughs, pine needles, shredded bark, sawdust, sugarcane, etc.