What to Consider When Choosing the Best Soil for Herbs
Growing herbs, either in a garden patch or on a sunny windowsill, is a rewarding experience that’s even more gratifying when the fresh, tasty results jazz up a dinner recipe. Before planting and choosing the best soil for plants, consider where the garden will be located and the fertilizer, pH level, nutrients, and water needs of the desired herbs.
Location
Herbs that grow in an outdoor garden have different requirements than indoor or container plants. For outdoor success, opt for garden soil, which is formulated for in-ground plants. Garden soil, which is heavy and dense, can become too compacted in a container, reducing its ability to drain and negatively impacting roots.
For indoor and container gardens, potting soil or potting mix is preferable. Though these terms are often used interchangeably, they are technically different products. Potting soil, as the name implies, contains soil (either partially or completely). Potting mix, however, does not contain any actual soil and instead consists of a range of natural ingredients to create a light and well-draining texture. Potting mix tends to be the best choice for container herb gardening because, in addition to draining well, it is sterile and often includes added nutrients.
Fertilizer and Other Ingredients
Soils and potting mixes are scientifically formulated to include ingredients that can help plants thrive. Fertilizer can be chemical or organic material that adds nutrients, and while exact fertilizing needs depend on the particular plant and growing conditions, most herbs can benefit from a blend of nitrogen, phosphorus, and potassium. The rule of thumb is to only fertilize as much as needed; overdoing it can cause some herbs to grow too fast, which risks losing flavor.
For outdoor herbs, a soil test can determine what nutrients may be lacking so the gardener can fertilize accordingly. Container herbs may require more frequent fertilizing because pots hold small amounts of growing medium, and plants can use up nutrients as water leaches them away. Using a potting mix with fertilizing ingredients, then adding a fertilizer later (as needed), can help optimize plant health.
Potting mixes, which are soilless, contain various ingredients—such as coconut coir, peat moss, and perlite—to create and maintain their fluffy, well-draining texture. Garden soil and some potting soils often contain organic ingredients like compost and manure to boost soil health.
Herbs like mint and oregano are voracious growers and get down right aggressive (even invasion) in a garden. To keep the rest of your garden plot safe, consider growing these herbs in pots and burying them in the ground. The added measure of control a pot puts on the roots of these herbs can keep them from moving in to the rest of your garden and prompting taking over. Of course the surest way to protect your garden from this threat is to grow them in pots grown above ground.
Potting soil or topsoil, compost, and sand
A sandy-loam is the best soil for growing the largest range of herbs as it is rarely waterlogged in winter, is dry in summer and it is naturally high in nutrients. Sandy soils are light, dry, warm, low in nutrients and often acidic. This soil feels rough and gritty when handled and are easy to cultivate and work.
pH Level
While most herbs prefer slightly acidic to neutral soil with a pH between 6.0 and 7.0, some common species deviate slightly from this scale. Rosemary, for example, prefers a pH between 5.0 and 6.0. Use a soil pH-testing kit to determine if pH-adjusting amendments, like limestone or sulfur, should be added to the herb garden.
Nutrients
Necessary nutrients may be added to growing mediums to help nourish plants. High-quality potting mixes typically contain important nutrients, which can be organic or nonorganic (chemical) in origin, to help with plant health.
Many companies list nutrients on the product label, displaying the soil’s nitrogen, phosphorus, and potassium content as a ratio of percentages. These nutrients usually release slowly to last for a few weeks to a few months before additional fertilizer is necessary.
Water
While herbs should be watered often enough to keep the soil moist, overwatering will likely result in soggy roots, which can lead to rotting. To prevent overwatering, a well-draining soil is important for herb gardens, especially for container-grown plants.
Different herbs have different water needs. Mint and parsley, for example, do well in fairly moist soil, while rosemary and sage prefer dryer soil. Pro tip: Bunch herbs with similar watering needs close together to help ensure proper watering. Using a moisture meter is a good way to help ensure proper watering. These inexpensive tools are stuck into soil to measure the moisture level at the root level.
Drainage
Precise drainage is important to growing herbs successfully. Too little drainage and the roots can drown, while too much drainage will cause water to flow through too quickly for the roots to absorb. A soil with good drainage allows for adequate water and airflow so both water and oxygen can reach plant roots. Many of the most popular herbs (like basil, bay leaf, cilantro, and lavender) are native to the Mediterranean, so they grow best in soil with good drainage, similar to soils found in that region.