10 Plants That Can Thrive in and Even Improve Compacted Soil
Many aspects of gardening are easy to control—like how much water your plants get and how often you fertilize—while other factors are harder to maintain. Unless you're using raised beds and filling them with commercial potting mix, soil quality is one element of gardening that is difficult to change.
Most plants need soil with pockets of air, which allows water to easily drain and prevents root rot. But if your yard has hard or compacted soil, you may find it challenging to successfully grow greenery on your property. Luckily, it's not impossible. Certain plants were built to withstand less than ideal growing conditions, like compacted soil.
What Is Compacted Soil?
The best soil for plants should be 45 percent mineral matter, five percent organic matter, and 50 percent pores—with half containing air and half containing water. "When mineral particles are pressed together, reducing the spaces between the particles, soils become compacted," says Melinda Myers, gardening expert and host of the Great Courses How to Grow Anything DVD series. "Compacted soils have few large pores for exchanging gases including oxygen needed by roots and for providing drainage." While these soils are dense and strong, they're hard for plant roots to penetrate.
How to Know If You Have Compacted Soil
You may have hard or compacted soil in some areas of your yard and not others. "This most commonly happens in high-traffic areas of the landscape, whether from walking or playing," says Kristen Smith, rose evaluation manager of Star Roses and Plants. "You may have compacted soils if water pools on top of the surface and does not percolate into the ground." Another tell-tale sign of hard soil is having difficulty penetrating it with hand tools and small equipment.
Why Soil Becomes Compacted
Soil can become compacted for a handful of reasons. "Compaction occurs when heavy equipment is used on soils, when working soils get wet, and when rain falls on bare soil," says Myers. Tilling soil at the same depth every year can cause the soil beneath to become compacted.
Side Effects of Compacted Soil
If you try to grow non-hardy plants in compacted soil, they will likely have a difficult time thriving. "Without water sifting through the soil, plants are at risk for suffocation and will not receive the nutrients that they need to thrive," says Smith. Because hard soil is tough to penetrate, it restricts deep rooting systems and can cause shallow plant roots. "Seeds are slower to germinate and planting is more sparse and irregular than non-compacted soils," says Myers.
Plants That Grow in Compacted Soil
Despite having adverse effects on plants, some—primarily native—species can grow in compacted soil. Many plants tolerant of these conditions are not only able to survive the poor drainage and low air levels of compacted soil, but can also improve the soil's quality. "These plants push through compacted soil and air spaces form near roots due to the disruption of the compaction," says Myers. "As their old roots die and decompose, they add organic matter deep in the soil and also create pathways for water and air to infiltrate the soil."