They sat silent in the coal-black cave of vines. Ma said, “How’m I gonna know ’bout you? They might kill ya’ and I wouldn’ know. They might hurt ya. How’m I gonna know?” Tom laughed uneasily, “Well, maybe like Casy says, a fella ain’t got a soul of his own, but on’y a piece of a big one–an’ then–”
“Then what, Tom?”
“Then it don’t matter. Then I’ll be all aroun’ in the dark. I’ll be ever’where–wherever you look. Wherever they’s a fight so hungry people can eat, I’ll be there. Wherever they’s a cop beatin’ up a guy, I’ll be there. If Casy knowed, why, I’ll be in the way guys yell when they’re mad an’–I’ll be in the way kids laugh when they’re hungry an’ they know supper’s ready. An’ when our folks eat the stuff they raise an’ live in the houses they build–why, I’ll be there. See? God, I’m talkin’ like Casy. Comes of thinkin’ about him so much. Seems like I can see him sometimes.”
“I don’ un’erstan’,” Ma said. “I don’ really know.”
“Me neither,” said Tom. “It’s jus stuff I been thinkin’ about. Get thinkin’ a lot when you ain’t movin’ aroun’. You got to get back, Ma.”
“You take the money then.”
He was silent for a moment. “Awright,” he said.
“An’, Tom, later–when it’s blowed over, you’ll come back. You’ll find us?”
“Sure,” he said. “Now you better go. Here, gimme your han’.” He guided her toward the entrance. Her fingers clutched his wrist. He swept the vines aside and followed her out. “Go up to the field till you come to a sycamore on the edge, an’ then cut acrost the stream. Good-by.”
“Good-by,” she said, and she walked quickly away. Her eyes were wet and burning, but she did not cry.
(John Steinbeck, The Grapes of Wrath, p439)
It seems it refers to cotton picking and blowed takes a role of linking-verb, so the highlighted part means when the picking is over. But Tom has to go out as a fugitive and his family are just itinerant workers. So this seems their last face-to-face talking for Tom’s mother, as is with her other son Noah and her son-in-law. Then what does her saying mean?