Tuesday, August 1, 2023

Starry rosinweed is a star in Florida yards

Starry rosinweed is a star in your garden not only
for its beauty and long blooming cycle, but also because
of the wide variety of pollinators that it attracts.

Starry Rosinweed (Silphium asteriscus) is a member of the aster or daisy family, Asteraceae and is a wonderful choice for Florida's wildflower meadows and for pollinator gardens. It's a beautiful, tall, long-lived, drought tolerant, easy-to-care-for wildflower. (See below for more information on how it behaves in gardens and meadows.)

Botanically, the starry rosinweed is an outlier in the aster family. Yes, its flower head has the typical arrangement of disk florets in the center surrounded by showy ray florets that each have one outsized petal. 

In most aster family plants with this typical flower head arrangement such as sunflowers, only the tiny, cylindrical disk florets in the center produce fruits or seeds, while the petal-like ray florets around the outside of the center are sterile and produce no fruits. The starry rosinweed is exactly the opposite with its ray florets producing fruits and the disk florets being sterile.

The arrow points to a forked style of a fertile ray floret. The tubular
disk florets in the center of the flower head are sterile and produce no fruit.

This split spent flower head reveals that there are no seeds or
fruits under or associated with the central disk florets.
Instead, the fruits, or cypselas, are thin and flat and are lined
up around the outside of the flower head. Two fruits
separated out here have greenish "wings" and deep notches
where the ray floret petals were attached.

The fruit, or cypsela, is thin and flat with thin, greenish "wings" on both sides of the dark center, which holds the actual seed. The notch at one end is where the base of the ray floret's corolla was attached before it fell off after the flower was pollinated. The fruits are only at the flower heads' margins beneath corollas of ray flowers. At the bottom of the cluster of disc flowers in the center, you can see that there are no fruits.

Starry rosinweed's range, via The Florida Plant 
Atlas, shows that it's native to western Florida.

Starry rosinweed is a Florida native wildflower

The native range includes most of eastern North America from Texas to Pennsylvania and most of the western counties of Florida. In northeast Florida, where we are located, it does well even several counties east of its native range. The Florida Wildflower Foundation and others recommend this plant for all but southernmost Florida.

There are five varieties for this plant, but most of the Florida rosinweeds and those in the native plant trade are the standard, Silphium asteriscus var. asteriscus. In other regions of its native range, the other four varieties are:  S. asteriscus var. dentatum; S. asteriscus var. latifolium; S. asteriscus var. simpsonii; and  S. asteriscus var. trifoliatum.

There is also another native rosinweed, kidneyleaf rosinweed (S. compositum), which has lobed leaves. Its range includes North Florida and up into Alabama and the Carolinas. 

Starry rosinweed in the landscape

I bought one plant more than ten years ago and it's still growing strong. It's grown larger and has more five-foot-tall shoots. While it didn't reseed much for the first few years, now there are many seedlings, which transplant easily to other places, but they do need several days of irrigation to become established. I've found that it does best in full sun and only slight shade. I have some growing near a western-facing porch at the back of the house and these tend to lean away from the house even though they receive full sun in the afternoons. I think they are anxious to be in the sun as it comes over the house. The leaning detracts from their beauty in the landscape. Those that are growing near the front corner of the house and others that have better morning light are mostly vertical. 

They look best when grown in groups of three or more and with tall bunching grasses, goldenrods, and other tall herbaceous plants. As I have been transplanting seedlings, I've located them to our mailbox garden, a meadow out back, and a few other places. It takes a couple of years for those young plants to establish themselves to these new locations and to begin flowering, but I'm happy to have these beautiful, drought-tolerant wildflowers with a long blooming cycle in several different areas. I think this works to attract more pollinators as well.

Some sources say that deer eat the rosinweeds, but so far that hasn't happened in our yard and we do have deer here. 

Starry rosinweed self seeds. These young plants
have their basal leaves by the end of their first year.
The leaves on the stems are clasping.
The flower heads are subtended by three or four layers of involucral bracts (phyllaries). The disk florets of the starry rosinweed are
more tubular than most other Asteraceae flowers.

A young starry rosinweed has only a few flower heads on its stem. Here you can see its basal leaves and its stem leaves, which are smaller near the top. Even the spent flower heads are attractive as
the starry rosinweed goes through its cycles.

Pollinators of all sizes, even hummingbirds,
come to our starry rosinweed flowers. The caption for this one should be, "She loves me..."
Normally there are five or more flowers on a
stalk and they tend to bloom two or three at a time.

Here is the link to the FNPS plant profile, which includes a link to native nurseries that have this plant in stock and here is the link to the Florida Wildflower Growers Cooperative where you can buy Florida-based seeds.

So, I hope you plant some these beautiful wildflowers, because they will become stars in your yard, too.

Green Gardening Matters,
Ginny Stibolt


  1. Just had one of those beauties show up in my Alachua county yard. Thanks for the informative article.

  2. Thank you for the seed picture! I was looking at some on my plants this morning and was not sure those were the seeds. I agree the spent flower heads are pretty, too.

  3. I saw several plants coming directly from a nursery and it looked like the stems had been nipped perhaps to develop a stronger stalk? Is this a technique to use in my garden to keep them a little shorter so they don’t fall over?