No matter how green your thumb is, you're likely to have trouble growing plants if you don't have the right conditions. One of the biggest culprits behind plants that fail to grow is the type of soil being used. The wrong soil can wreak havoc on plants and may prevent them from getting the moisture, nutrients and sunlight they need to thrive. What makes gardening difficult is that there are so many different types of soil to choose from, and it can be hard to know which will work best with certain plants.
Before you choose soil for your garden, it can help to understand how different types are identified. Classification is often based on the texture and size of the particles that make up the soil, as well as on the mineral and nutrient content of each type. While the majority of soils are made up of clay, silt and sand, the ratio of these materials can greatly impact the properties of the soil, as well as its ability to support plant life. Soils can also be identified based on their level of acidity, which is measured on a scale from 1 to 14, known as the pH scale. Lower numbers on this scale are linked to higher levels of acidity, while higher numbers mean the soil is more alkaline. Though most plants thrive when acidity measures between 6.2 and 7.2, most types of soil have an average pH of 5 [source: Lowe's Home Improvement].
Of course, the type of soil in your yard is also determined by factors such as rainfall and organic material content. By adjusting things like moisture retention, pH and mineral distribution, you can transform your existing soil to create a more hospitable environment for the type of plants you want to grow.
Chalk, or calcareous soil, is found over limestone beds and chalk deposits that are located deep underground. This type of soil is sticky and hard to work with when wet, and it can dry out very quickly in the summer. Chalk is also very alkaline, with a pH of 7.5 or more on average [source: BBC]. This high pH is caused by lack of moisture and high lime content, which can cause stunted growth in plants. Excess lime can also turn these plants yellow [source: Gardening Data].
To make chalk more plant-friendly, try adding acid-rich materials like peat, compost or manure. These materials will help to neutralize the soil and can eventually reduce lime content by improving water absorption. If you'd prefer to keep things simple, focus on plants that thrive in alkaline-based soils, including lilacs, lilies and many types of flowering shrubs. Avoid richly colored flowers like rhododendrons that need a more acidic environment [source: BBC].
Sandy soil is made up of large particles of silica, quartz and other rocks. It has a very rough texture that allows many air pockets to form within the soil. This loose soil base tends to allow moisture to drain quickly and also leads to increased evaporation rates. Because sand doesn't hold moisture well, it can also be difficult for plants to access nutrients before they're washed away due to drainage [source: City of Bremerton].
Any plant that can survive in drought-like conditions can be grown successfully in sandy soil. Consider desert plants like shrubs and cacti, as well as flowering plants such as tulips and hibiscus. To improve the quality of sandy soil and expand the type of plants that can be grown in it, take steps to slow drainage and limit evaporation. Organic materials like mulch or compost can be added in with the sand to keep moisture and nutrients in place. Instead of adding large quantities of these products once a season, try adding smaller amounts more frequently to combat the quick-draining properties of the sand.
While mulch isn't a type of soil in itself, it's often added to the top layer of soil to help improve growing conditions. It's made from wood chips, tree bark, leaves, yard waste and many other types of organic materials. Mulch helps keep the surface of the soil porous, allowing water and air to reach the roots of the plants. It also helps to keep sunlight and rain from reaching the soil directly, which can keep heat levels in check and minimize erosion and evaporation [source: Better Homes and Gardens].
One of the most beneficial properties of mulch is that it tends to decompose over time, adding even more organic nutrients to the soil. Mulch can be spread over planting beds and gardens, or can be used around individual plants and bushes. To discourage bugs and other pests from taking up home in your mulch beds, keep layers thin and leave a gap in the mulch bed around the base of each plant [source: Chesman and Lloyd].
Silt is similar in texture to chalk but is much more versatile and easy to use. It's made up of very fine particles that give the soil a smooth, slippery texture. Because they're so fine, the particles in silt can be compacted very easily, which helps hold moisture and nutrients in place for long periods. Silt is often a good compromise between sand and clay soils, as it offers a density and weight that falls between these two materials [source: Gardening Data].
While silt is often chosen for its ability to be easily compacted, this tight compaction can also lead to problems with drainage. The tightly packed particles keep water from exiting the soil, which can be problematic for some types of plants. While silt holds water well for long periods, it can sometimes be difficult for air and water to enter the soil to access the roots. To remedy this problem, gardeners can take steps to break up compacted soil deposits periodically. Try adding compost to the top layer of the silt, or simply turn the top few inches of soil when it seems to be packed too tightly. Most moisture-loving plants will thrive in silty soil, including richly colored flowers and lush grasses or vines [source: BBC].
Topsoil is a commercially produced material that can be used to supplement or replace difficult soil in gardens. Most topsoil blends contain between 2 and 10 percent organic materials, making them very nutrient-dense. If you find that your existing soil is making it difficult for plants to grow, try mixing topsoil in with the top 2 to 5 inches (5.1 to 12.7 centimeters) of earth. The topsoil can provide vital nutrients, balance pH levels and help control moisture and evaporation rates. Even experienced gardeners can turn to topsoil when the existing earth has been depleted by frequent planting [source: Whitcher].
One common problem with topsoil occurs when it's poured on top of existing soil without blending or mixing. This creates a water absorption barrier where the two soil types meet, which can lead to issues with drainage and over-watering. To remedy this, always mix in your topsoil with the existing dirt so that water can flow freely between the two.
Sometimes the best soil for the job is none at all. Hydroponics, or soil-less gardening, is the process of growing plants in water rather than soil. By eliminating the soil, you deliver nutrients and moisture straight to the roots of the plant. In most cases, hydroponics also reduces or eliminates problems with bugs and other garden pests, resulting in healthier plants that are often easier to grow [source: Maccini].
Many hydroponics systems require some type of medium to stabilize the roots of the plant as it grows. This medium may include sand, gravel or even rigid foam, depending on the application and the type of plant being grown. Hydroponics use can range from small homemade setups to large industrial systems used to grow food for the commercial market. These systems can be used indoors or out and are a perfect option for those who don't have the space for a traditional soil-based garden. Virtually any type of plant, fruit or vegetable can be grown hydroponically by using the right medium and appropriate blend of nutrients.
Gravel consists of pea-sized stones that are laid across the top of a planting bed to help improve growing conditions. While gravel doesn't add nutrients to the soil, it does help to control moisture levels and impede evaporation. Thicker layers of gravel will reduce the amount of water that reaches plants, while even thin layers of gravel can reduce soil erosion and slow evaporation.
One of the most beneficial properties of gravel is its ability to expand the heat zone of a garden. Because these rocks collect sunlight during the day and release it at night, they can allow gardeners to start planting earlier in the season without worrying about low temperatures and frost. Using gravel may even allow for a wider range of plants to be grown, including those that would normally not survive in a given climate. Gravel also serves a decorative function in the garden; it's available in many different shades and textures to complement the visual appeal of each plant.
Compost is a nutrient-rich material that can be used to improve any type of soil. It can be made from a variety of organic waste products, including kitchen scraps, manure and yard waste. Compost is generally kept in outdoor bins, where it's given time to decompose before being applied to the garden. As it decomposes, the levels of plant-friendly nutrients in the compost are increased even further. Even after it's applied to the garden, the compost continues to break down, giving it a much longer-lasting impact than fast-acting chemicals and fertilizers [source: Stell].
Compost will improve plant growth in nearly any type of garden. In loose, sandy soils, compost helps to bind the soil together to retain moisture and nutrient levels. In denser soils like clay or silt, the compost reduces compaction to increase air and moisture flow to the roots. To provide maximum benefit, the compost must be mixed in with the existing topsoil layers. Plan to use about 4 to 6 inches (10.2 to 15.2 centimeters) of compost per 6 to 12 inches (15.2 to 30.5 centimeters) of soil [source: City of Bremerton].
In areas with poor drainage, consider using equal amounts of commercial topsoil and compost to create raised planting beds above the existing soil. This will allow excess moisture to flow down below the root levels, which can keep plants growing successfully.
Clay is one of the smallest of all natural soil particles, and it tends to pack tightly together with little air space. This lack of air space and high level of compaction make clay the heaviest and densest type of soil. Its density allows it to retain large amounts of water and nutrients, but this makes it difficult for air and moisture to penetrate the soil [source: City of Bremerton].
One of the keys to successfully gardening in clay soil is to work only under certain states and conditions. Dry clay is fairly smooth and soft, while wet clay is heavy and hard to work with. Try planting in autumn or spring when using clay, and avoid working on days when the soil is overly wet. To resist winter freezing, add compost or mulch to the top layer of clay each autumn, then leave the soil undisturbed until spring. The added organic material should make planting easier, and will also help to improve drainage and air flow.
The best plants for clay include richly colored flowers that require high levels of moisture. Try wisteria, rhododendrons and most flowering perennials [source: BBC].
Loam is hands-down the best all-around soil for gardening. Any type of plant can be grown in loam without making major modifications or additions to the soil. It holds its shape when squeezed or compressed and crumbles slightly under pressure, which means that loam isn't overly dense or loose. Most loam is made from fairly equal parts of silt, sand and clay, giving it all the best qualities of each of these materials with few of the drawbacks. The sand content keeps the loam open so air, moisture and sunlight can reach the plants, while the clay and silt content slows down drainage and evaporation, keeping water and nutrients in place. Loam warms up early in the spring, won't dry out in the summer and still drains well in heavy rain, making it the perfect soil for year-round planting [source: BBC].
While loamy soils can vary in their specific makeup, they're usually easy to bring into balance by using simple additives. Compost or mulch can make up for minor imperfections in the soil content, creating a versatile planting base for virtually any type of plant [source: Gardening Data].
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- BBC. "How to be a Gardener: The Complete Online Guide." BBC Gardening. (Nov. 7, 2009). http://www.bbc.co.uk/gardening/htbg/module1/soil_types3.shtml
- Better Homes and Gardens. "All About Garden Mulches." (Nov. 7, 2009). http://www.bhg.com/gardening/yard/mulch/all-about-garden-mulches/
- Chesman, Andrea and Louise Lloyd. "The Big Book of Gardening Skills." Garden Way Publishing. Chicago. 1993.
- City of Bremerton. "Soil Types." Bremerton Washington Department of Conservation. (Nov. 6, 2009). http://www.cityofbremerton.com/content/wc_soiltypes.html
- Gardening Data.com. "Different Types of Soil." 2009. (Nov. 6, 2009). http://www.gardeningdata.co.uk/soil/soil_types/soil_types.pHp#chalk
- Lowes Home Improvement. "The Scoop on Soil." (Nov. 7, 2009). http://www.lowes.com/lowes/lkn?action=howTo&p=LawnGarden/soilScoop.html
- Maccini, Rachel. "Gardening Without Soil." University of New Hampshire Extension. (Nov. 7, 2009). http://extension.unh.edu/Counties/Hillsboro/Hydropon.htm
- Moor, Fred. "Golden Rules for Difficult Soils." The World of Soil. 1993. (Nov. 7, 2009). http://soil.hostweb.org.uk/
- Stell, Elizabeth P. "Secrets to Great Soil." Storey Communications. Vermont. 1998.
- Whitcher, Steve. "3-Way and 5-Way Soil Mixes." Washington State University Extension. 1996. (Nov. 7, 2009). http://gardening.wsu.edu/library/lanb004/lanb004.htm