I don't buy from Burpee (I use Geoseed) but saw this on bradsdeals:
"Get 15% off right now with code GARDENS15 at Burpee.com. The, add code AFFSHIPPER for free shipping, which saves you $5-$40 in shipping fees! This makes it one of the best discounts we've seen from them (the last time we saw a sitewide free shipping coupon was back in July). A best bet is the Niko Blue Hydrangea, which drops from $14.95 to $12.71 shipped. Plus, Burpee will send your plants at the optimal growing time for your region. Sales tax is charged in most states."