Potted plants aren’t always a snap

I planted several large pots this spring. To save weight I put crushed aluminum cans in the bottom of the containers. Now I’m hearing that’s not a good thing to do. Also, what about the water holding crystals you mix in the soil?

Dorothy MacEachern, Spokane

While your concept was a good one, there are some major drawbacks to replacing part of the soil in a container. First, you are depriving the plants of a few inches of soil to grow in. In small containers, this means there is less food and water storing capacity for the plant. Secondly, when you water a container plant (or a houseplant for that matter), gravity pulls water down into the container, pooling more water at the bottom of a container than in the top. Generally, plant roots need a specific air and water balance in the soil and don’t like to grow in this saturated environment so they stop growing before they reach it. When you put the cans or pine cones or Styrene pellets in the bottom, you raise this saturated zone reducing the depth of the soil the plant has to grow in even more. If you need to lighten a pot, use a lightweight container and a lightweight planting mix instead.

The water holding crystals you are referring to are a good idea if you use only the amount recommended. The “crystals” can either be a silicon-based gel or one made of corn starch. Both absorb many times their weight in water and then slowly release it back to the plant. I have used both over the years in container planting and they have bought me time when I was a little slow in getting things watered. The silicon ones will last several years while the starch based ones need to be renewed every year. Use only the recommended amounts because the granules expand quite a bit and can actually displace too much soil. There are some concerns that over time the silicon-based crystals break down into less than desirable chemical byproducts in the soil.

Hot tomatoes

Help! I planted tomatoes in containers this year and they were nice and bushy with lots of fruit until recently. Now they look terrible.

Ann Pitsnogle, Spokane

Our early heat wave probably warmed up the container and the soil too much causing the plants to shut down and drop any fruit just to survive. This is especially true if you planted them in small containers. Tomatoes like their space. Try carefully transplanting the plants into a larger pot. Try not to disturb the roots too much. Set them in a shady spot for a few days to recover. If you can’t transplant them, shade their containers with a board or put them inside a larger container. Grouping a bunch of containers together also can provide some shade.