weeds only spread to other cropsticks.
Also, beware when you have high growth crops. If one of your recently crossbred crops get a growth of 24, it will weed the crops around it, destroying them.
Also also, go for quality AND quantity. Aurelia and ferru produce much more slower than the other metal crops.
You don't need perfect stats (21/31) just get something around 19-21 and 29-31.