Starting seeds indoors is an exciting way to kick off your gardening season, and the choice of container is crucial for success. A common question among urban gardeners is whether shallow planter boxes are suitable for this purpose. The direct answer is yes, you can use shallow urban planter boxes to start seeds indoors, but with some important considerations and potential limitations.
Shallow planter boxes, often defined as those with a depth of less than 4 inches (10 cm), can be perfectly adequate for many types of seeds. Herbs like basil and cilantro, as well as flowers such as marigolds and alyssum, typically have shallow root systems in their initial growth stages and can thrive in these containers for the first few weeks. The key advantage of using shallow boxes in an urban setting is their space efficiency. They fit perfectly on windowsills, under grow lights, or on small shelves, maximizing your limited indoor area.
However, the primary challenge with shallow containers is root space. Seeds that grow into large plants, like tomatoes, peppers, or zinnias, develop extensive root systems quickly. In a shallow box, these roots can become cramped, leading to a condition called "root-binding," which stunts growth and stresses the plant. For such varieties, shallow boxes should only be considered as a very temporary starting point before the seedlings are transplanted into deeper pots.
To use shallow planter boxes effectively, ensure they have adequate drainage holes to prevent waterlogged soil, a common cause of seedling disease like "damping-off." Use a high-quality, sterile seed-starting mix, not regular garden soil, to provide the right balance of moisture retention and aeration. Since the soil volume is small, it can dry out rapidly. You must be vigilant about watering, likely checking the moisture level daily. Gentle bottom watering is often the best method to avoid disturbing the tiny seeds and delicate seedlings.
In conclusion, shallow urban planter boxes are a viable and space-saving tool for starting many types of seeds indoors, particularly those of herbs, leafy greens, and some flowers. They are an excellent solution for the space-conscious gardener. Just be mindful of their limitations regarding depth and moisture retention. For a wider variety of plants, especially those that will reside in the container for more than 3-4 weeks, planning for a subsequent transplant into a deeper pot is essential for cultivating strong, healthy plants ready for the outdoors.