Rhubarb

Rhubarb is a vegetable with a unique taste that makes it a favorite in many pies and desserts. It originated in Asia over 2,000 years ago. It was initially cultivated for its medicinal qualities, it was not until the 18th century that rhubarb was grown for culinary purposes in Britain and America. Rhubarb is often commonly mistaken to be a fruit but rhubarb is actually a close relative of garden sorrel, and is therefore a member of the vegetable family. Rhubarb is rich in vitamin C and dietary fiber.
-Rhubarbinfo.com

Cost: $3.00 per pound.
Availability: Beginning May
Recipies:

Sweet Potatoes

The sweet potato, a tuberous root vegetable belonging to the same family of plants as the morning glory, is a particularly popular food in the southern United States. Sweet potatoes, native to Central America, are considered a staple in many countries and have been cultivated in Southern states since the 16th century. Nutritionally, sweet potatoes are an excellent source of vitamin A and a good source of potassium and vitamin C, B6, riboflavin, copper, pantothetic acid and folic acid. 
-About.com

Asparagus

The fleshy green spears of asparagus are both succulent and tender and have been considered a delicacy since ancient times.
-The World's Healthiest Foods.com

Cost: $3.50 per pound.
Availability: April thru June 7th

Pawpaw trees

[Pawpaw] trees are native to Ohio and bear North America's largest edible native fruit. The flavor is best described as a custard-like overripe banana. The trees are medium sized with soft wood and large leaves. Between the leaves and the fruit, the tree has an almost tropical appearance. It is a sole food source for the Zebra Swallowtail butterfly, and the fruit is eaten by many mammals. Limited availability of 3 - 4' tall trees
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Cost: $45-$55
Sizes:3'-4'
Availability: early spring

Canadian Hemlocks

[Hemlocks] are medium-sized to large evergreen trees, ranging from 20-60(-79) m tall, with a conical to irregular crown, with the latter occurring especially in some of the Asian species. The leading shoots generally droop. The bark is scaly and commonly deeply furrowed, with the colour ranging from grey to brown. The species are all adapted to (and are confined to) relatively moist cool temperate areas with high rainfall, cool summers, and little or no water stress; they are also adapted to cope with heavy to very heavy winter snowfall and tolerate ice storms better than most other trees.
-Wikipedia.org

Cost: $35-$55
Sizes:3'-5'
Availability: early spring

White Pines

Eastern White Pine (Pinus strobus) is a large pine native to eastern North America, occurring from Newfoundland west to Minnesota and southeastern Manitoba, and south along the Appalachian Mountains to the extreme north of Georgia.
-Wikipedia.org

Cost: $80-$120
Sizes:6' and up
Availability: early spring

Blueberry Bushes

Blueberries are flowering plants in the genus Vaccinium, sect. Cyanococcus. The species are native only to North America. They are shrubs varying in size from 10 cm tall to 4 m tall; the smaller species are known as "lowbush blueberries", and the larger species as "highbush blueberries". The fruit is a berry 5-16 mm diameter with a flared "crown" at the end; they are pale greenish at first, then reddish-purple, and finally dark purple on ripening. They have a sweet taste when mature, with variable acidity. Blueberries are one of only a few human foods that are naturally colored blue. Blueberry bushes typically bear fruit from May through October; "blueberry season" peaks in July, which is National Blueberry Month in the United States and Canada
-Wikipedia.org

Cost: $25 for medium (Approx. 3 feet - 4 feet), $30 for large (Approx. 4 feet or larger)
Varieties: (Click each one for details)