Experienced gardeners buy plants online or shop for garden gear by mail order for three reasons:
Better selection is the big reason to buy plants online. For example, an online rose specialist will offer scores of varieties and types of roses, while your local garden center can only afford to stock perhaps a dozen or so.
Few garden centers are big enough to stock a fraction of what's available, so web suppliers or mail order catalogues are the best way to find plants and garden products that are difficult to source locally.
Shop Gurney's Sale - Plus Get $20 Off $40: Flower and vegetable seeds, plants (roses, flowerbulbs, berries and small fruit, grasses, ground covers) and growing supplies. Ships to US, but not Alaska, Hawaii.
Breck's Premium Dutch Bulbs and Perennials: Brecks sells bulbs and bare-root perennials, such as oriental lilies, daylilies, dahlias, begonia, and spring bulbs. Lots of interesting new varieties to try. Take advantage of their offer: Save $25 on orders of $50 or more. Shipping to US and Canada.
Roses from Jackson & Perkins: Discover many different new and unusual roses, including award-winning roses for 2009. Also offers perennials, bulbs and an excellent selection of garden gifts. Ships roses and perennials at the best time for planting in your area. US only, including Alaska and Hawaii. Browse the pages of their catalog.
Richters Herbs: Offers an excellent variety of seeds, culinary and medicinal herb plants and ornamental plants. You'll find seeds that are hard to get: for example, they carry the smaller marigolds such as the attractive orange, lemon and tangerine Gem series.
Ritchers prides itself on delivering herb plants in great shape. I've always been impressed with the healthy condition of their plants after shipping. Shipping to Canada and US. Canadian company, ships to US government inspected, with phytosanitary certificate free of charge. (Take advantage of the low Canadian dollar: currently, it's at 80 cents to the US dollar.)
Mantis® - We Make Gardening Easier ® Our best offer ever:
Free shipping and a Free Border Edger Attachment.
Gardens Alive: Offers a variety of environmentally responsible products for your garden and lawn, from sprays and fertilizers to garden gear. Ships to US addresses, including Alaska, but not Hawaii.
Gardener's Supply Company: Offers a wealth of tools and supplies for gardeners, from seed-starting to watering, fertilizing and weeding, even garden furniture and sheds. Good garden tips too. Ships to US only.
Buy plants online - what to look for when ordering
What to do with plants that are shipped bare-root
Tips for buying plants at the garden center