Question
In the Spring when oxalis wilts, does it come back in summer as a type of grass?

Answer
Bob, forgot to mention:
At temperatures above 75 degrees F several of the oxalis species may experience heat dormancy. E.g. dieback which return only when moderate temperatures return.

Kenneth

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No Oxalis and grass are different plants entirely. What may happen is that the temperatures are not conductive to the growth of oxalis and it dies back to the ground due to the heat. The warm season grass, which grows best when temperatures are very warm, will take over and cover the area. When cooler temperatures return and the warm season grass is dormant, the oxalis may then again resprout from the crown.

The crown is a central area between the roots and the leaves where the carbohydrates (foodstuffs) are storaged and which can be used for example to overwinter, or carry the plant through a period of hot temperatures when the plant will be dormant. From this crown, new shots appear.

Many grasses in warmer areas of USA are so-called C4 grasses, grasses which are genetically capable of photosynthesizing (e.g. produce carbohydrates) during very hot temperatures. Grasses found in the nothern half of USA are typically C3 grasses which means that they are not capable of photosynthesizing in very hot climates. This generally result in dieback in mid summer in regions with very hot temperatures.

This is probably what you are seeing. The warm season (C4) grass is growing while the C3 plant (oxalis) dies back temporarily.

From your question, I guess that you are located in a hot climate (hot summers, wild winters ?)

Kenneth