Ember Form Input Undefined

I'm running into a weird issue with Ember.js.

I built out a basic search form like so, with an Ember input field that submits to a form action 'submitSearch':

import Ember from 'ember';

export default Ember.Route.extend({
        actions: {
          submitSearch: function() {
                  var searchItem = this.get('searchItem');
              this.transitionTo({queryParams: {'q':searchItem}});
          }
  }
});

<div class="search">
                <form {{action "submitSearch" on="submit"}}>
                        <fieldset>
                                {{input type="text" class="form-control" value=searchItem}}
                                <input type="submit" name="submit" id="submit-search" class="btn btn-default" value="Search" />
                        </fieldset>               
                </form>
        </div>

Any reason why I would be getting a value of 'undefined' when logging out searchItem? I've tried just about everything including creating a model, but I can't get the input to save.