Navigating container gardening requires selecting the appropriate pot size when repotting a thriving plant. As a plant grows, its roots need more space to absorb water and nutrients efficiently, making the transition to a larger container necessary for continued health. Choosing the correct subsequent pot is important for the plant’s long-term growth and prevents health issues that arise from either cramping the root system or providing too much space.
Defining the 5-Gallon Standard
The designation “5-gallon pot” in horticulture is often misunderstood by home gardeners. This labeled size is typically not a true measure of five US liquid gallons. Instead, commercial nurseries use the “trade gallon” system to standardize container sizes. A 5-gallon trade pot usually holds an actual capacity closer to 3.5 to 4 US liquid gallons of soil. Physically, a common 5-gallon nursery pot generally measures around 11 to 12 inches in diameter and 10 to 12 inches in height.
The Rule for Upsizing: Choosing the Next Pot
The general recommendation for repotting a container plant is to only increase the pot size incrementally. When moving a plant from a 5-gallon container, the next appropriate step is generally to a 7-gallon or 10-gallon size. This increase should be limited to roughly a 1- to 2-inch increase in the pot’s diameter, translating to a volume increase of about 50% of the current container.
Jumping directly from a 5-gallon container to a much larger size, such as 15 gallons, is ill-advised. A sudden, drastic increase in soil volume can overwhelm the existing roots. The goal is to provide just enough new space to encourage root expansion without creating a significant area of unused, wet soil that could lead to problems. Doubling the size of the container is generally reserved only for very fast-growing plants or those that show extreme root-binding.
The appropriate next size up is the 7- to 10-gallon trade size range. For example, a 7-gallon trade pot typically holds around 5 to 6 actual gallons, while a 10-gallon trade pot holds approximately 7.5 to 8 actual gallons.
Sizing Mistakes and Their Impact
Using a container that is too small negatively affects a plant’s health and growth. When roots become restricted, it leads to root binding, which limits the root system’s ability to efficiently absorb water and nutrients. This results in stunted top growth and nutrient deficiencies because the small volume of soil is rapidly depleted. Furthermore, the limited soil mass dries out quickly, subjecting the plant to frequent water stress.
Conversely, selecting a pot that is significantly too large presents dangers related to moisture management and aeration. When a small root mass is placed into a vast amount of soil, the roots cannot absorb water quickly enough from the perimeter. This excess unused soil retains moisture for an extended period, creating a perpetually soggy environment. This waterlogging displaces oxygen, leading to poor aeration and anaerobic conditions that cause fungal diseases like root rot.