Horticultural grafting has been in use for millennia. It involves taking the branches of one tree -- the part of the graft known as the scion -- and inserting it into another -- known as the stock -- so that the two parts grow together and form one single tree. It can be decorative, but it has practical uses, too; grafting a fruit scion to a stock with a hardier root system, for example.
For art professor Sam Van Aken, who grew up on a farm in Pennsylvania, it's a little bit of both: his art project, Trees of 40 Fruit, started in 2008, is a thing of beauty with a more practical purpose: reviving heirloom fruit varieties.
"As a symbolic number found throughout western religion, culture, and even within government, the number 40 symbolises the infinite, a bounty that is beyond calculation. Like the Tree of Life in the Garden of Eden, these trees are a potential; they are the beginning of a narrative that transforms the site they are located in," Van Aken's website reads.
"The far-reaching implications of these sculptures include issues of genetic engineering, biodiversity versus food monoculture, and, ultimately, the symbiosis of humankind's relation to nature. As an allegorical sculpture Van Aken's Trees of 40 Fruit begins a dialogue."
So far, Van Aken has grown 16 of his trees, installed in museums, community centres and private art collections around the US. Each tree consists of three distinct parts: the rootstock, the interstock -- the central part of the tree, chosen for its strength, either a European or Asian plum variety -- and the scions, which form the tree's branches.
For the fruit, Van Aken tries to select heirloom and locally grown stone fruits, which may not be deemed commercially viable (see the popularity of orange carrots compared to yellow, white and purple for an example of how perceived commercial viability can lead to a lack of variety). He then chip grafts these onto the interstock.
"In trying to find different varieties of stone fruit to create the Tree of 40 Fruit, I realized that for various reasons, including industrialization and the creation of enormous monocultures, we are losing diversity in food production and that heirloom, antique, and native varieties that were less commercially viable were disappearing," Van Aken explained to Epicurious.
"I saw this as an opportunity to, in some way, preserve these varieties. In addition to maintaining these varieties in my nursery, I graft them to the Tree of 40 Fruit. Additionally, when I place a Tree of 40 Fruit, I go to local farmers and growers to collect stone fruit varieties and graft them to the trees. In this way they become an archive of the agricultural history of where they are located as well as a means to preserve antique and native varieties."
Each tree takes around five years to develop and has a selection of apricots, plums, peaches, nectarines and cherries. In the spring, its branches are festooned with a riot of pink, purple and white blossoms; in the summer, a rainbow of fruit.
Eventually, Van Aken would like to plant his trees all across America.