Show values from helper method in drop down - Ruby on Rails

I am using a hash constant in my ROR application. I want to show the names from the hash constant to drop down.

helper.rb

PRODUCE_GROWING_METHODS  = [
    {id: 1, name: 'Conventional'},
    {id: 2, name: 'Organic'},
  ]

def produce_growing_methods
    PRODUCE_GROWING_METHODS  
  end

_produce.haml

= f.simple_fields_for :produce_details do |pd|
  = pd.input :produce_growing_method, :collection => produce_growing_methods.collect { |x| [x[0], x[1]] }, :prompt => "Select Growing Method"

I tried as shown above in _produce.haml but i am getting the empty drop down. Names from the constant are not populated in drop down.

Can any one help me how to show the names from the PRODUCE_GROWING_METHODS hash constant to a drop down.

Thanks