Why You Shouldn’t Use Garden Soil for Plants in Outdoor Containers

Garden soil may seem like the right choice for an outdoor container garden, but as it turns out, there are better options out there. Here’s what you need to know.

Why is garden soil a poor choice for outdoor container plants?

According to the University of New Hampshire’s Extension Division , material labeled “garden soil” at garden centers and hardware stores is generally intended to be used in the ground, not in containers or other pots or planters. In addition to minerals and organic matter, unpasteurized garden soil can also contain weed seeds, insects, and disease.

When this combination is used in containers, the soil can quickly become waterlogged and compacted, leaving limited air space around the roots and potentially resulting in stunted growth or root rot.

What soil to use for outdoor container plants

Instead of garden soil, use outdoor potting mix, according to the UNH Extension Office . Also known as “soilless mixes”, they are lightweight and designed to leave ample air space around the roots.

There are many potting mix combinations, but the UNH Extension Office recommends using one that contains:

• Organic component (e.g. peat moss, compost, bark)
• Vermiculite or perlite (for moisture retention)
• Sand
• Nutrients
• Limestone

You may also encounter potting mixes containing slow release fertilizers or water retaining agents such as “hydrogels” or “water retaining crystals”. This is generally not necessary for your container plant to thrive, but can be beneficial, depending on your plant’s needs.

In addition to a light soil, be sure to choose a loose and dry potting mix. While some compost will do, avoid compost mixes. When in doubt, choose an all-purpose soil mix or make your own.