I was speaking at a garden center this weekend and it was obvious that people are really starting to get anxious for spring. More than our fare share of snow has visited the normally sunny Colorado winter this year. As I watched people shop, it looked like some of them were hoping to hasten spring along by acquiring the paraphernalia of gardening.
So, I gave my talk then opened the floor to questions. I was surprised how many inquiries I got about container gardening. Many wanted to know, among other things, how to pick a container. I did my best to answer them, and then realized there were lots of factors that could inform one’s choice. I had to admit to myself that my answers had been a bit disjointed and I had better organize my thoughts before it came up again with a less forgiving crowd. So, here goes…
SIZE. Simply put, size matters. Bigger containers are often better. They hold more soil, and therefore, potentially more water and nutrients. This gives your plants more resources and room to grow. This also gives you a bigger margin for error…always a good idea when dealing with living things.
What’s the right size? When is it big enough? I like to use some common comparisons to help answer this. Most people are familiar with a ½ wine barrel. This is big enough for 1 large, or 2 small tomato plants, or about 10 bush bean plants, or 6-8 heads of lettuce, or about 3 pepper plants. Flowers are another story. There are so many types of flowers that grow to so many different sizes, that it’s hard to say. Look at the final size of the plants to start. If you want a really full look, plan for them to touch each other when full-grown and choose accordingly. If you want your container more or less overflowing, then give them a little more or less space. I tend to over-ambitiously jam them in, fertilize, and let them fight it out.
Lastly, size has two dimensions, volume and depth. If you are growing long- or deep-rooted things, like carrots or Echinacea, in a container, then your plants will be better served by a deep pot than a wide shallow one.
DRAINAGE. Let me say it again, DRAINAGE. Make sure that your containers have a few holes in the bottom to allow excess water out. Containers that don’t drain lead to soggy soil that suffocates plants’ roots. If your container is watertight (and it’s not a water garden) put some holes in it. If your container sits very close to the ground or some other surface, you may want to raise the container up slightly or add some hole to the side of the container very near the bottom. I drilled some holes in the side of the bottom of a huge pot I had that I couldn’t put on risers and it made a big difference.
MATERIAL. Almost anything can be a container. That being said, you need to consider how what it’s made of will affect its performance. Porous containers, like terra cotta, allow water to escape through the side of the container. This may be good if you live in a wet area or tend to over-water. This may be challenging if your containers are small or you live in a windy or dry area. You can line the inside of porous containers with a layer of plastic and reduce water loss. Just remember to maintain drainage.
Think about whether you plan to move your container in case of frost. If not, make sure it is made of a frost proof material.
If you are choosing wood, remember to use a rot resistant wood like cedar or oak barrels. Just be sure not to use pressure treated wood if you are growing edibles. You don’t want the chemicals to affect the quality of your food.
CLEANLINESS. If you are reusing or repurposing a container, be sure to clean it thoroughly. Scrub away all dirt and debris. Wash it well and if you want to get it really clean, rinse it with hydrogen peroxide or a 1:10 bleach solution. One of the best sanitizing agents is the sun. If you have the time, let your clean containers bake in the sun for a week before filling them with soil.
Almost anything can be a container. Some standards are buckets, watering cans, and wine barrels. But, I’ve seen some great containers made from tree stumps, baking pans, bags, and nylons. Just be sure they’re clean, have drainage, and are the right size and material for your needs. You’ll be a container gardener in no time.