Southern catalpa is quite similar to northern catalpa. Both are native to the south, but northern did occur slightly farther north and inland before we started spreading them around. Southern's flowers are slightly more colorful. The easiest way to spot southern is in early spring as the leaves appear. The previous year's pods will still be on the tree, and will last until the flowers open. This tree has an interesting relationship to insects, beyond its pollination needs. Hawkmoth caterpilars eat the leaves. When they do, the catalpa produces more nectar. This attracts more ants. The ants can help pollinate, but more importantly they protect the tree from predators, ranging from mites to larger bugs. That includes the caterpilars, which could otherwise do more damage.