Hoyt Arboretum’s plant taxonomist and herbarium curator Mandy Tu answers your budding botany questions! Email us at info@hoytarboretum.org for answers.
How old do Magnolia trees get?
This depends on the species, and there is very little information available on most species. It is thought that most southern magnolia trees (Magnolia grandiflora) have a life-span of 80-120 years, although the oldest tree on record is 320 years old in Italy. Also, in 2017, an old historic southern magnolia tree was removed from the White House that was about 190 years old. You can read more about that tree here.
And, we also know that some Magnolia trees may take decades to reach maturity and flower (for instance, M. campbellii). At Hoyt Arboretum, our oldest Magnolia accessions according to our database is from when the Arboretum was initially planned and planted in 1928. It is hard to know if they were actually planted then, or if they were just automatically given the 1928 date when records were transferred. However, if our star magnolia trees (Magnolia stellata) were really planted in 1928, they would be about 90 years old!
What is up with Magnolia family taxonomy? For instance, is Michelia closely related to Magnolia?
Umm… yes, Magnolia family taxonomy can be completely confusing!! This is because of updates on the taxonomy and classification of the Magnolia group completed by some scientists, and these updates have either not (yet) been fully accepted by the plant taxonomy community, or there is just delays in getting information accepted.
In the most recent Flora of China (2008), the authors of the family Magnoliaceae have split apart the family into 13 different genera, retaining the genus Magnolia only for the species Magnolia grandiflora. Yes, this also includes the genus Liriodendron (the tulip trees). So in this update, the authors decided based on morphological and genetic data (including character traits such as if the plants are evergreen vs. deciduous, how the flowers are borne on its stems, if the fruits open along the outside vs. inside edge, if the young emerging leaves are folded vs. open in bud, number of ovules per carpel, etc), that the Magnolia genus is to now be divided into several genera, of which the more-commonly known genera may be Oyama, Maglietia, Lirianthe, Yulania and Michelia.
However, this splitting up of the genus is not completely accepted by the plant taxonomic community, and since we at Hoyt Arboretum are using the PlantList (based at Kew Gardens) and the Tropicos database (based at Missouri Botanic Garden) as the primary sources for our name changes and updates, and they are both still retaining the broad-use (sensu lato) name of Magnolia to encompass all of these genera and species, and it is easier for us to just use Magnolia and not have to re-do all of our tree signs, etc., we are keeping the wider Magnolia genus name too. Yes, it can be totally confusing!
About the Author
Dr. Mandy Tu works for Portland Parks & Recreation as the Plant Taxonomist and Herbarium Curator at Hoyt Arboretum. In this position, she is responsible for collecting voucher specimens and verifying the identity of the trees within the Arboretum and is often asked to identify plants by natural area managers in the Portland region. She has a B.S. in Botany from the University of Washington and a Ph.D. in Plant Biology from the University of California at Davis. Mandy has taught many plant identification courses and workshops for botanical professionals and plant enthusiasts.