Groundsel Shrub (Baccharis halimifolia)

Work is officially underway to reduce the wildness of the arboretum's volunteer recruitment zone. You can read about this special area on a previous blog post, found here. It can be difficult deciding which plants get to stay and which plants must go. However, given the specific site attributes, some species won't do well here in the long term. This is a shady, uphill area; not a good place to showcase wetland species. As horticulturists and gardeners eventually learn, allowing plants to grow up in a bad location may create unnecessary work down the line, as they still grow large enough to create a big mess when they eventually succumb. Therefore, it was an easy decision to begin the removal of groundsel (Baccharis halimifolia), a shrub that grows profusely along waterways.

The volunteer recruitment zone is home to groundsel, which is no surprise given its regional status as a highly successful colonizer.

Many different unrelated species of plants are called "groundsel," but that name most commonly indicates Baccharis halimifolia.  The groundsel bush is a dioecious, decidious shrub native to the Southeast, from the gulf coast to the mid-atlantic states. Tolerant of both drought & wet locations, rarely browsed by animals, groundsel can form monotonous stands that prohibit the development of other worthwhile species. It is however a major food source for bees and other flying insects during its flowering season.

Groundsel leaves alternate along the stem.

Alternating leaves

This fresh green leaf is noticeably slender and toothed.

Upper leaves are strongly oval-shaped.

Here we can see leaf shape variation.

Lower leaves are rounder, but still show the same "coarse teeth" and smooth texture of the upper leaves.

The bark is striated, with vertical bands of green, grey, and brown. This is young bark; at most, this shrub is four years old.

 

We removed all the tall groundsel shrubs from the volunteer recruitment area. The tallest shrub measured nearly 9 feet. Some of the small to medium size clumps were cut as well, simply because they were visible. This is a hefty amount of green material.

 

 

This photo was taken before the groundsel was removed.

Our mini-wilderness area is still thick with plant life; this is a photo after the groundsel was removed. Not much changed. It's difficult to tell that anything is missing.

 

 

Groundsel is notoriously resilient, so don't worry; even with this culling it'll be back soon. However, this particular location in the arboretum isn't ideal for groundsel: we want to see it in wetter locations. We might try relocating small plants to sunny areas near the drainage channels.

See our previous posts which contain photos (credit to Bonnie Bernard) of groundsel, from January 2012 and March 2012. That's a long time ago! You can also see one of our groundsels covered in this sweetgum post from 2021.

Links:

USGS Plant ID

LSU AG Center

USDA NCRS 

Tree of the Week: Sweetgum (Liquidambar styraciflua) and a special guest

Our tree of the week, a young sweetgum (Liquidambar styraciflua), grows on the grassy slope near Cline Hall Dormitory. It is pictured center (leaning to our left) alongside a groundsel bush (Baccharis halimifolia).

 

For the past few years we have recorded the development of this sweetgum on the blog. You can read about it here and here. Last year, this individual was tagged for removal, but for one reason or another, it thankfully remains standing.

Severe damage to its trunk was the reason it was tagged for removal. In 2020, the arboretum's squirrels made deep cuts into the bark. Why were they peeling bark from the tree? We're not entirely sure, but trees are probably very fond of owls, hawks, and snakes. Those wounds have healed, but the damage is permanent, making the tree susceptible to enemy invaders, particularly fungi and insects. An intact layer of bark is essential protection for a tree to last into maturity.  Consequently, we will be keeping an eye on this sweetgum; it is still a candidate for removal.

 

Looking at the bright green leaves, you wouldn't think that this tree was handicapped, especially if you look a little closer to notice the inconspicuous fruits, the infamous gum balls.

Allowing this young tree to stand another year or two ought to insure a replacement for the arboretum catalogue.

 

This sweetgum is also of interest this week because of its guests. Caterpillars have taken up residence in a few localized areas of the canopy. The caterpillars have built white, gauze tents among the leaves, which they are eating. According to our research, they appear to be fall webworms (Hyphantria cunea). Given the season and their activity, that common name makes a great deal of sense.

 

Although they produce a web-tent that some people might find "yucky," this silk might be worth its weight in gold. Unfortunately, it doesn't weigh much. The LSUAg Center informs us that while unsightly, fall webworms are not harmful to healthy trees.

These little fellows will eat the leaves of nearly a hunded of our native trees, so it's not surprising that they're chowing down on sweetgum, which is a choice of other caterpillars as well.

 

These are harmless insects. When they grow up, they will become beautiful white moths. Did you know that "White Moth" was Vladimir Putin's nickname when he was an intelligence agent? Secretive web-weavers.

 

 

 

 

 

Tree of the Week: Sweetgum (Liquidambar styraciflua)

Fall begins today with the autumnal equinox. As the photos below illustrate, the arboretum remains green―seasonal fall color and cool temperatures arrive late to northwest Louisiana. A close inspection of our tree of the week hints at seasonal change. This week we are examining the green leaves of a young, volunteer sweetgum (Liquidambar styraciflua).

The volunteer sweetgum germinated in the middle of a groundsel bush (Baccharis halimifolia), on a grassy, gradual slope near Cline Hall. In this photo, the groundsel conceals the sweetgum. Note the groundsel bush's gnarly, sprawling branches.

Another view reveals the slender, white trunk of the sweetgum, but its green leaves blend in with the surrounding vegetation.

Our volunteer was added to the catalogue in summer 2017. At that time, the tree was at minimum three years old. An exact age is unavailable.

Standing in its shade, we can appreciate the characteristic 'winged', or 'corky', bark of the young sweetgum.

Can you see the ridge along the branch?

The 'wings' can be flat, straight, wavy, and non-contiguous.

You might simply find bumps or notches along a branch rather than a ridge.

Although our young sweetgum is still green, on the first day of fall, the star-shaped leaves show signs of color change. But what is causing the yellow splotches? Is it simply seasonal color change, or could it possibly be a sign of deficient growing conditions resulting in chlorosis? We shall keep an eye on this individual and hope for dazzling autumnal colors.

Leaf blade and leafstalk each measure approximately 3¼ inches in length.

Leaf size varies. Here we have a bigger leaf with the same yellowish-green splotches.

Underneath, sweetgum leaves are pale green.

Sweetgum leaves have palmate venation.

Zooming in on the base of the leaf blade, we see brown fuzzy patches in between the veins.

Leaf margins are serrate.

Baccharis halimifolia

 

 

Baccharis halimifolia

 

Bark detail.