Plants of the Week: July 27

Vitex agnus-castus ‘Shoal Creek’ (Chastetree)

Lamiaceae

As you approach the corner of Mertz Residence Hall, it will be hard to miss the mass of blue-grey foliage and massive blue flower spikes of Vitex agnus-castus ‘Shoal Creek’. I really enjoy this tree because of its multi-season interest and its ability to tolerate hot and dry conditions. Although winter die-back is common in Zone 5 and 6, the specimen on campus seems extremely vigorous. This plant can be limbed up as a multi-leader small tree or left alone as mounding shrub. Vitex is a wonderful option for full sun and lean soils. Photo credit: A. Thomas

Cornus controversa (Giant Dogwood)

Cornaceae

Located adjacent to the Swarthmore Train Station on Mertz Lawn, this sprawling specimen attracted my attention because of its beautiful dark-blue to deep-red fruit. Set amongst a stand of birch trees this Cornus really pops. Native to Asia this is a relatively low maintenance tree and really benefits from cooler summer weather. Fall color seems to be dependent on sunlight and can also vary from plant to plant. I can imagine this tree making an interesting addition to any shade garden.  Photo credit: A. Thomas

Franklinia alatamaha (Franklin Tree)

Theaceae

There is a small grove of Franklin Trees located just behind the Sproul Observatory and they are putting on a big show. Being in the same family as Stewartia, you can expect striking bark, heavy bud set, and wonderful white flowers with a large cluster of yellow anthers. I find the spindling caramel-striped bark to be the most appealing aesthetic of the Franklin tree. This tree needs full sun to part shade and must have well-drained soil. This is a truly special plant that should not be missed. Once native to southern Georgia it has been extinct in the wild since 1803. You can purchase your own Franklinia alatamaha at the 2015 Scott Arboretum Plant Sale. Photo credit: A. Thomas