Some Invasive Viburnums

Hello Invader Detectives!
The best season of the year is just around the corner, which also means a bunch of viburnums will be fruiting (checks watch)... now.

There are a plenty of invasive viburnums to lookout for on the Invader Detectives project page, but
I’ll be going over 5 of them:
Viburnum dilatatum (linden arrowwood),
Viburnum plicatum (doublefile and snowball viburnum),
Viburnum sieboldii (Seibold viburnum)
Viburnum setigerum (tea viburnum), and
Virburnum x rhytidophylloides (lantanaphyllum viburnum).

These viburnums are all native to East Asia, primarily China and Japan, brought in for ornamental use and are still sold commercially. They outcompete native flora, including our own native viburnums, due to dense growth and vigorous growth.

You can also check out Cornell’s Guide to Identifying Viburnums and their express key but note that there will be some variation when keying.

What do these species have in common?
Viburnums are a deciduous, woody shrub to small trees. The leaves for all the species listed are in opposite arrangement (i.e, mirroring each other). Flowering occurs April through August and fruits will start to appear between late August through September. Their flowerheads are flat-topped with clusters of creamy, white, star-shaped florets that boast 5 long stamens and later form clusters of droopy fruits. Of course, there will be some exceptions to these characteristics.

Viburnum dilatatum

Photo credits (Left to Right): msperr , esummerbell , henryfrye , garysmith4 , emilio_c , masebrock

Linden arrowwood (Viburnum dilatatum) can get up to 8-13 ft tall. They have a habit of forming dense thickets and suckers that take extra nutrients from the parent tree. Of all the viburnums, the leaves on V. dilatatum are most egg-shaped and soft to touch as it has hairs on both sides of the leaf with a silverish underside, though this can give the leaves a dirty look since they trap dust. It is worth mentioning that V. dilatatum has the most variation in leaf shapes, even along the same stem. When confirming if it is V. dilatatum, you can check the back of the leaf and see if there are two to four little indentations or glands at the base of the leaf. Young stems are fuzzy with small orange lenticels that will mature to gray-brown color and smooth texture with prominent orange lenticels.
The flowerheads on V. dilatatum are flat topped and may have an unpleasant smell. When looking at the tubular, star-shaped flowers, the petals are rounded. In autumn, the leaves will turn dull red before falling and yellow 5-8mm fruits start to appear. Soon, they will mature to a red color and persist through winter. The fruits of this species are often oblong and may be shaped like the flame of a candle. Most other viburnum species have round fruit.

Viburnum plicatum f. plicatum (Japanese Snowball) and Viburnum plicatum f. tomentosum (Doublefile viburnum)

Photo Credit: reuvenm , shuufly , cuihenggang

Japanese snowball (Viburnum plicatum f. plicatum) is a cultivar of the naturally occurring doublefile viburnum (Viburnum plicatum f. tomentosa). The two are often grouped together when talking about Viburnum plicatum, so I decided to separate them since they have some different characteristics.
Japanese snowball can be considered a small tree as it can group up to 15ft tall. As the common name suggests, the flowers are bright white and round. You’ll see these snowball flowers in opposite arrangement growing from the nodes. Japanese snowball is sterile and cannot cross-pollinate or produce fruit; they don’t have any fragrance to them as well.
Leaves are a dark green with pleated surface, a hairy underside, ovate, and can turn burgundy to purple in autumn. The bark of the trunk is dark gray-brown, hairless, and can have a smooth or ridged texture.

Photo Credit: phaynes

Doublefile viburnum (Viburnum plicatum f. tomentosum) is the fertile version of Japanese snowball. Like many older-younger sibling dynamic, this older sibling can reach only up to 10ft. As far as I could find, they share the same leaf characteristics, with the ovate, dark green, pleated surface, hairy underside, and autumn foliage. In both of these varieties the leaves will have many pairs of veins, typically no less than 11 pairs and often up to 16 on each leaf.

Photo Credits: conuropsis (left and middle), lynnharper

The bark for doublefile is also gray-brown with orange spots throughout the trunk. While the trunk is smooth and hairless, the younger stems are densely hairy. The flowers are not as showy as the other form but have a sweet fragrance. These flowers are a creamy yellow compared to the typically creamy white color of the rest of the viburnums listed here, and are surrounded by showy, bright white bracts (sterile flowers) that each have 4 to 5 petals. The fruits on both forms of this species first occur red and mature to black.

Viburnum sieboldii
Siebold’s viburnum (Viburnum sieboldii) is the tallest amongst its brethren, a 15-20ft tall giant. The leaves on Siebold’s are lanceolate to oblong shape, are dark green with a pale underside, and have no hairs on either side; when crushed, they smell like burnt rubber.
Siebold’s flowers are similar to Viburnum dilatatum but less rounded at the tip of the petal. In August to September, red fruits occur on red stems; when ripe, the fruit will turn black.

Photo Credits: cgrove79, kemper, kitmonster, tkr421, matthewhalley, tkr421

Viburnum setigerum

Photo Credits: josh_rudder, wefwef, spmarkle, jim_keesling(last two)

Tea viburnum (Viburnum setigerum) grows between 8-12ft tall and forms a vase shape. The leaves are lanceolate to oblong, green-blue-silver to dark green in color, have hairs along the back side of the veins, and slight teeth along the margins. During mid-summer, the foliage becomes a unique muted red in between the veins. The flower is most similar to Viburnum dilatatum with similarly shaped petals though with a pleasant smell instead. The flower head appears in much smaller clusters: 1 to 2 inches in diameter compared to the other viburnum inflorescences here being 2 to 6 inches in diameter. In September, the fruit will emerge as yellow-orange and mature to red.

Viburnum x rhytidophylloides
Viburnum x rhytidophylloides is probably the most unique of the viburnums on this post; this is a hybrid between V. lantana and V. rhytidophyllum, both of which are non-native to the US.
Viburnum x rhytidphylloides is a semi-evergreen shrub, meaning that some leaves can be entirely evergreen or just partially fallen if the winter is mild enough. As the plant matures, it begins to mound and grow suckers at the base of the trunk. The foliage is dark green on the front and pale on the underside with entire or sparsely toothed margins. The leaves can be lanceolate to oblong with a crinkled appearance and become wind-burned, especially in the winter. They also have hairy stems that emerge as a fuzzy green-white and become brown-orange as they mature. The inflorescence is more rounded at the top and is clustered tightly together with an unpleasant smell.
This hybrid is able to clone and produce red to black fruit, but best fruit production takes place when one or both parents are present. While V. x rhytidophylloides is not common in the wild within the region , iNaturalist observations of one of the parents, V. rhytidophyllum, have increased over the past 3 years. This could present an issue in the future.

Photo Credits: derwinmcg, jdr2
For more photos and ID, you can check out North Carolina University's Extension Plant Toolbox.

Tips for making a good observation record of species
Take photographs that show:
the landscape around the plant – this shows the context and offers a clue to the scale of the
infestation
if they are flowering, get a close-up photo of the flowers
if they aren’t flowering yet, photograph a whole plant since some of these have different growing habits, and the leaves and stems

Make comments that:
are explicit about the issue of intentional plant vs weed vs escaped
give a rough estimate of the number of patches and the area covered
any other comments you think might be helpful

References
Brand, Mark and University of Connecticut, Department of Plant Science and Landscape Architecture. “Viburnum Setigerum: Tea Viburnum.” University of Connecticut Plant Database, plantdatabase.uconn.edu/detail.php?pid=537. Accessed 27 Sept. 2023.
Missouri Botanical Garden. “Viburnum x Rhytophylloides ‘Alleghany.’ Plant Finder, https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=g260#:~:text=Viburnum%20%C3%97%20rhytidophylloides%20is%20a%20hybrid%20viburnum%20(a,to%208-10%E2%80%99%20tall%20(sometimes%20more)%20and%20as%20wide, Accessed 20 Oct. 2023
North Carolina State University. “Viburnum Plicatum.” North Carollina Extension Plant Toolbox, plants.ces.ncsu.edu/plants/viburnum-plicatum. Accessed 27 Sept. 2023.
---. “Viburnum Plicatum F. Tomentosum (Doublefile Viburnum).” North Carolina Extension Gardener Plant Toolbox, plants.ces.ncsu.edu/plants/viburnum-plicatum-f-tomentosum. Accessed 27 Sept. 2023.
---. “Viburnum Setigerum (Tea Viburnum).” North Carolina Extension Gardener Plant Toolbox, plants.ces.ncsu.edu/plants/viburnum-setigerum. Accessed 27 Sept. 2023.
---. “Viburnum Sieboldii (Siebold Viburnum).” North Carolina Extension Gardener Plant Toolbox, plants.ces.ncsu.edu/plants/viburnum-sieboldii. Accessed 27 Sept. 2023.
---. “Viburnum X Rhytidophylloides (Lantanphyllum Viburnum).” North Carolina Extension Gardener Plant Toolbox, plants.ces.ncsu.edu/plants/viburnum-x-rhytidophylloides. Accessed 27 Sept. 2023.
Rawlins, Karan. “Viburnum Sieboldii/NJ - Bugwoodwiki.” Bugwood Wiki, edited by Susan Brookman, 22 Aug. 2014, wiki.bugwood.org/Viburnum_sieboldii/NJ. Accessed 27 Sept. 2023.
“Sibold Viburnum : Viburnum Sieboldii.” Pennsylvania Department of Conservation and Natural Resources, elibrary.dcnr.pa.gov/PDFProvider.ashx?action=PDFStream&docID=1738687&chksum=&revision=0&docName=Siebold+viburnum&nativeExt=pdf&PromptToSave=False&Size=268822&ViewerMode=2&overlay=0. Accessed 27 Sept. 2023.
US National Arboretum. “Viburnum ×Rhytidophylloides ‘Alleghany.’” US National Arboretum, www.usna.usda.gov/assets/images/as_pdf_image/Viburnum_x_rhytidophylloides_Alleghany.pdf. Accessed 27 Sept. 2023.
Virginia Tech College of Natural Resources. “Range Map Information.” Virginia Tech Dendrology, dendro.cnre.vt.edu/dendrology/maps2.htm. Accessed 27 Sept. 2023.

Publicado el octubre 23, 2023 07:17 TARDE por y-aving