[GLBS] Botanical Perspectives - Provenance and Bonsai

Bonsai News

by Ross Clark


As we know, many of the plants we grow as bonsai are not native in our neighborhood.* They are native to other regions, and even to different continents.* Many are special asexually propagated horticultural selections (cultivars) or artificially produced hybrids.* Others have escaped from cultivation in our region, and now grow wild.

"Provenance" is a term used most often by horticulturists and landscape designers.* It refers to the geographic and genetic origin of a plant.* The central idea behind the concept of provenance is that plants still carry within them the genes and ecological tolerances that their wild ancestors had.* Good landscapers try to consider provenance when planning which plants to use in landscapes, because provenance helps predict whether landscape plants will succeed where you plant them.

For example, the ancestors of all 200+ named Acer palmatum (we call it Japanese maple; the Japanese call it mountain maple) cultivars were wild.* The cultivar ancestors’ tolerances to drought, frost, light and other climate factors were shaped by nature, and those genes are still within the cultivars.* However, in nature Acer palmatum is a rather wide-ranging species, so different cultivars of this species have been selected from plants native in widely separated places with different climates.* That is why some Acer palmatum cultivars are tender and need winter protection, and others may be wintered outdoors without anxiety.

Let's bring the idea of provenance closer to home with a few concrete examples.* The eastern edge of the geographic range of ponderosa pine (Pinus ponderosa) includes the Front Range of the Rocky Mountains, with an outlier population in the Black Hills.* In those areas on the extreme edge of its range, highly variable temperature extremes and drought over many generations of trees have selected especially hardy and drought-tolerant plants.* As a result, ponderosa pines from those areas now are noted for their bonsai potential.* Here is another example:* Silver maple (Acer saccharinum) has coarse twigs and leaves that do not reduce much, so it is not a good bonsai subject.* Over much of its range, our common red maple (Acer rubrum) shows the effects of some hybridization with silver maple, which diminishes its potential for good bonsai.* However, on the eastern edge of the southern Appalachians there are more drought tolerant red maples with finer twigs and leaves that reduce more when the plant is in a pot.* We have an unrealized opportunity to select red maples for bonsai from that region.* A third native example of how provenance relates to bonsai is pitch pine (Pinus rigida), an eastern U.S. species that is being used more often for bonsai.* Unlike many pines, pitch pine readily buds back on old wood (the technical term is epicormic branching), because it is adapted to sending out new growth after frequent forest fires in its native habitats.* The ease of budding back is a characteristic valued in pine bonsai material, which is one reason pitch pine is catching on as a bonsai subject.

You cannot treat all species alike and succeed, because their ecological tolerances are different.* To maximize your bonsai success, you cannot even treat all individuals of the same species alike, unless they have the same genetic and geographic origin.* That is the significance of provenance.

A deciduous tree's responses to local environment provide a strong clue to whether the tree’s genetics are a close match for our climate.* If under normal care, a tree's buds open and its leaves shed at about the same time as our native trees, then the climate where it originated probably is similar to ours.* However, if a tree "wakes up" in spring weeks earlier than our native woody plants, or holds its leaves significantly longer in the fall, it almost certainly is from a milder climate.* On the other hand, plants that “hold their fire” in spring until late often show us that they came from a harsher or more variable climate.* The Zelkova tree in my front yard completely escaped last spring’s devastating frost, because it was still in tight bud, while many native species (even some oaks!) had completely leafed out and were severely impacted.* Wherever that Zelkova originated, it was not fooled by the amazingly unseasonable weather of last spring—all because of its provenance, the conditions in its place of origin.




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