How do you repair plants? Also,do you have to keep assigning workers to crop the same produce? I'm puzzle cause the PC keeps saying"I need to assign someone to do this" .Please help!

You can leave them alone and the settlers will eventually replant them, otherwise you use that particular fruit/veg to "repair/replant" it.

ETA: You need to assign a settler to the crop?

Since your first question is answered, the most you can do with your second question about assigning settlers to crops is first make sure the crops are repaired, either by replanting yourself or waiting for the settlers to replant. Then make sure the crops you wanted harvested are closer together because settlers assigned to one crop will automatically also work on (I think) 5 other crops around the crop you assigned them to. The red Vault Boy marker for the crop should turn the color of your HUD (probably green) once the settler reaches the crops you assigned him to and starts working. After this, your PCmight keep saying that it needs to be assigned, but he should stop saying that once the first batch of crops comes out.

Thanks so much guys!!

Note that you may be unable to repair crops in certain locations, Abernathy Farm for instance. Ignore the tato field there, and plant new crops.

Each settler can work 6 food, which means either 6 mutfruit, or 12 of anything else. And, they'll apparently only work within a certain area once assigned to a particular plant, so keep your crops planted in organized rows.

It appears there's no reason to plant anything besides corn, tatos and mutfruit, currently, other than OCD. No other crop has any truly valuable usage. Dirty water is more useful than melons, gourds and carrots.

The plus side to that is that corn, mutfruit and tatos lend themselves to nice, orderly rows, making things much easier to assign.