Nested pots reduce damage to plant roots


: I purchased some glazed ceramic pots for a few cacti and agaves that will be placed in a patio area that gets about four hours of fairly intense sunlight. I was concerned about the roots getting too hot so I decided to put a second pot inside the ceramic pots. I wanted to use clay pots but they would not fit, so I settled on plastic nursery containers instead. Now, I am concerned that the plastic pots might create drainage problems for the plants and cause root rot.

A: It is a good idea to give plant roots in above-ground pots some added protection from the heat in our climate. Roots are very sensitive to both cold and heat, much more so than the above-ground part of the plant. High air temperatures are not that much of a problem since plant roots are blanketed and protected.

The real culprit is sunlight. When direct sunlight shines on black plastic nursery containers, we can expect the surface temperature of the container to reach about 170 F. We could expect similar temperatures from other containers.

Most plant roots will be damaged at temperatures starting around 120 F. When direct sunlight shines on the surface of containers and generates this kind of heat, it is transferred to the soil mix inside the container. The soil blanket around plant roots begins to heat up to unbearable temperatures and radiates through the pot, with the highest temperatures on the side of the container facing the sun. This kind of heating is enough to kill some or all of the plant's roots.

Heat damage and partial death of the roots may or may not kill the plant. Partial root damage may just cause the plant to have a lack of vigor and not do very well visually. Keeping direct sunlight off of the surface of above-ground containers helps reduce root damage.

Different methods of handling this problem include having extra large pots so that there is a larger volume of soil, watering just before the heat of the day so that roots are better protected by the wet soil, and nesting pots so that less heat is transferred to the inside container.

The inside pot must always have drainage holes in the bottom. The outside pot may or may not have drainage holes. When nested pots are put together, usually something is put in the bottom of the outside pot so that the inside pot does not rest in standing water. This also helps adjust the height of the inside pot.

When both pots have drainage holes, coarse gravel is frequently used in the bottom of the larger container. But if the outside pot does not drain, the standing water will need to be dumped frequently. Placing gravel in the bottom, in this particular case, would be a pain in the neck.

Soil is typically not used between the two pots. The gap between them can simply be air or loose material that can be taken out easily if the outside pot needs to be drained, cleaned or replaced.

Q: At Indian Springs we have been inundated with grasshoppers for the past couple of weeks. My tomato, squash plants and beans grown from seed have disappeared. Do you know how long these hoppers live or have any suggestions how to handle them?

A: Grasshoppers live the entire season; they get larger and the problem gets progressively worse as the season progresses.

Other insects, such as moths and butterflies, go through stages in their life cycles that include a wormlike or larval stage. The larval stage can be the most destructive in an insect's life; at this stage, the insect can be a voracious eater. An adult moth or butterfly eats little to nothing.

In the case of grasshoppers, the insect that hatches from the egg is a tiny replica of what it will be like when it's an adult. Grasshoppers look the same but get larger and larger as they get older, molting or shedding their outer skins. They usually molt about five times before they reach sexual maturity. In its last stage or molt, the grasshopper frequently develops wings so it can fly. This helps the grasshopper find a mate so it can lay eggs for the next cycle.

Some grasshoppers in our area can have two generations or cycles each year. It is very important to try and get some control of grasshoppers very early in the season or your garden can be overwhelmed.

Grasshoppers are difficult to control when there is a large scale infestation and they are coming in from the desert.

Since grasshoppers can move about, a large area needs to be treated. This means applying a pesticide to your area may not be enough. You may have to apply some sort of pest control measure to an area much larger than your own.

There is a pesticide bait that is fairly effective for grasshopper control but it has to be applied pretty early in the growing season when the hoppers are still small. This organic product contains a parasite that kills grasshoppers. The active ingredient, which is the name of the parasite, is called Nosema locustae.

The parasite is impregnated onto bran flakes and grasshoppers eat the flakes taking in the parasite. The parasite colonizes inside the hoppers, which slows them down, reduces their feeding and makes them easy prey for birds. The birds are not affected. You will get some control yet this year if you were to apply it now.

Another method you can use is physically keeping them away from your plants with crop covers and screening. A third method would be chickens, ducks or guinea fowl, but they have to be kept out of the garden areas or they will damage the plants.

Your last resort is the so-called hard pesticides such as malathion and sevin that permit use for controlling grasshoppers on food crops.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at extremehort@aol.com.

 

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