When it comes to planting in containers, pots can be too big, too small or just right. Plants that are too small for their containers could be over-watered because soil will retain the water and potentially cause root rot. Plants that are too big for their containers may dry out quickly.
No matter what you’re placing in a container, keep in mind that roots grow so they can support the growing plant. When you first plant seeds, you may think that they will have plenty of room, but after a month or so, you may find out that individual plants are cramped, which stunts growth.
You also need to take into consideration the type of plant you’re putting in a container. Plants like succulents need to dry out between waterings, so shallow containers work best. And, regardless of the type of container you choose, make sure it has drainage holes! If it doesn’t, punch several into the bottom.
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If you’re planting seeds or bulbs in containers, or if you’re transplanting seedlings or houseplants into larger containers, here are some tips for choosing the right container sizes.
Seeds/seedlings
Have an idea of how large the seeds or seedlings will become. Pay attention to seed packet directions for seed spacing for an idea of how much surface room you’ll need in a container.
Ideally, you want to have a couple of inches of soil between the bottom of the container and the plants’ roots. You also should have 1-2 inches of soil between the top of the soil and the top of the container, for watering purposes.
Bonnie Plants offers some container sizes and what types and amounts of plants could be grown in them.
Bulbs
Choose a container that’s 1-2 inches wider in diameter than the bulb, according to Gardener’s Supply Company.
You also want to be able to put 1-2 inches of soil in the bottom of the container before placing the bulb in it and another 1-2 inches of soil on top, all while leaving an inch of so of space between the top of the soil and the top of the container.
Repotting houseplants
If you notice that your houseplants have stunted growth, or that their roots are coming out through drainage holes, they need larger containers.
Repot houseplants in the spring when roots are active, making it easier for them to grow into new potting soil. Don’t trim roots to get plants to fit into containers.
Leave an inch or so of space between the top of the soil and the top of the container, so there’s room for water as well as plant growth.
Sources: University of Illinois Extension, Penn State University Extension, Rutgers New Jersey Agricultural Experiment Station, University of Nebraska-Lincoln Extension in Lancaster County, Gardener’s Supply Company
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Thank you for sharing that for every size of the seedling or the plant, there are varying potting sizes that are suitable. My wife was looking at potting machines the other day. I will forward this article to my wife so she can be informed when making decisions.