TextField(

  decoration: InputDecoration(

    border: InputBorder.none,

    hintText: 'Enter a search term'

  ),

);

​

import 'package:flutter/material.dart';

​

class MyTextForm extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(

        title: Text('Text Input Example'),

      ),

      body: Padding(

        padding: EdgeInsets.all(16.0),

        child: TextField(

          decoration: InputDecoration(

            labelText: 'Enter text',

            border: OutlineInputBorder(),

          ),

        ),

      ),

    );

  }

}

​

void main() {

  runApp(MaterialApp(

    home: MyTextForm(),

  ));

}

TextFormField(

   minLines: 6, // any number you need (It works as the rows for the textarea)

   keyboardType: TextInputType.multiline,

   maxLines: null,

)