Late-Summer Bloomers Provide Color and Are Important Resources for Pollinators

It’s hard not to notice that the nights are getting cooler and we’re getting less and less daylight as the calendar ticks forward. As our gardens begin to calm down a bit you can’t help but notice that Mother Nature is slowly easing us out of summer and into the fall.

No, the leaves aren’t falling, and for the most part they’re not turning color. Nonetheless MoNa’s clues are there as are her suggestions for gardeners, their gardens and landscapes. The clues are mostly yellow but there’s also a smattering of blues to purples. And while she gives us the clues she also reminds us of some of the dangers of the right plant in the wrong place. Horticulture has learned from this, and you can take advantage of what I call the “fall fade to yellow” without ending up with out-of-control weeds instead of usable plants that are also feeding wildlife, including pollinators.

First, the purples. It wasn’t long ago that you could drive down any country road or highway and, on the sides, or center median where it would remain moist from August into September there was the sight of purple loosestrife, or Lythrum salicaria. Unfortunately, this was not a native and it became a species that endangered wetland, bogs and meadows as it filled in and essentially drained these spots. To counter the use of this invasive (now classified as a noxious weed) breeders introduced hybrids that were “thought” to be noninvasive. In fact, most were, but one tiny thing was overlooked that made things much, much worse.

It was found that these hybrids, while not being invasive, were capable of crossbreeding with the L. salicaria and creating even more havoc. As a result, most states have banned the growing and sale of all types of Lythrum, and that certainly helped. There were however, other reasons why we see less and less of this invasive every year. It’s also one of our greatest success stories when it comes to biocontrol.

In the 1990s two beetles were introduced that adored feeding on the foliage of L. salicaria, and through mass releases these beetles along with a root weevil that dines on the Lythrum roots we saw the spread of this plant stop and we’re now at the point where the Lythrum is manageable with little human input necessary. However, if you do have Lythrum on your property you can learn how to collect these beetles and bring them home to work for you. You can get more information on how to do this by contacting the Long Island Invasive Species Management folks at liisma.org/about-liisma/contact-us.

Another plant, this one a native, that you see blooming in late summer and into the early fall is Joe Pye weed, or Eutrochium purpureum. This perennial can grow from 4 to 7 feet tall, and its late-summer blooms are magnets for a variety of butterflies and other pollinators. The problem, though, is that this plant does get large, and while it looks great at a pond’s edge, in wetlands or in a boggy area, it can overwhelm a formal garden. Ah, but there is a solution.

“Little Joe” is a dwarf version of the taller Joe Pye that rarely gets taller than 5 feet and is more likely to get only to 4 feet tall and as wide. This means that Little Joe might fit well into a more formal garden or into a wet spot where you want the greenery, purple flowers but not the height and width of the species. It will still attract a nice variety of pollinators and seed eaters.

Lastly, before we get into the yellows, there is our native seaside hibiscus, which for complicated reasons, is Kosteletzkya virginica, or the seashore mallow. It takes well to sandy soils, tolerates saltwater flooding and has hibiscus-like pink flowers from August into October. You can see it flowering now along the barrier beaches or were homeowners have allowed it to naturalize in places along roads like Dune Road and Meadow Lane. It’s a pollinator as well as a source of seed for birds in the fall. You may find a white variety called “Immaculata” as well.

It’s the yellows, however, that are the standouts. Rudbeckias, Helianthus and Heliopsis are among those we see flowering now, but we are usually struck by the patches, swaths and meadows covered with the goldenrods. There are about a half dozen species of goldenrods that grow on Long Island, and one, the seaside goldenrod that grows along the barrier beaches, dunes, salt marshes and pinelands, is Solidago sempervirens. It tends to flower in early September and is an important feeding spot for many butterflies and other pollinators. Usually found growing between 2 and 4 feet tall you should never dig the plants from the wild but from seed or a reputable native plant nursery.

The seaside goldenrod is not invasive, but its relatives that grow in meadows, roadsides and possibly in your backyard can be very invasive — and yet they are critical as a source of nectar and pollen for pollinators and attract a wide range of butterflies, moths, bees, wasps and flies that rely on this as a late-summer into fall food source.

The danger for us, though, is that when not properly managed all but two goldenrods can take over a garden or landscape in just a few years with their spreading seeds and adventurous roots. The solution for this is to keep the plants in areas on the periphery of your property, in meadows or wildflower areas and to know what the emerging plants look like so volunteers that pop up in other places can be rogued out in the spring. Take the time to stand a few feet away from these plants when they are in flower and watch the variety of flying insects that visit and feed. It’s pretty amazing.

Also take a moment to look closely at the flower spikes. Each spike contains hundreds to thousands of tiny yellow flowers that look just like asters, which is the family that Solidagos are in. Different species have different habits with most arching but some with upright stems. The colors vary from species to species, and except for the early-flowering Solidago bicolor the rest are various hues of yellow and gold.

Solidago sphacelate “Golden Fleece” is a dwarf variety introduced by Mt. Cuba Center in Delaware. Since it has a compact habit it only needs to be watched and every few years thinned out to keep it neat and local. It’s late flowering for a goldenrod, which adds to its appeal. It may also be a late source of pollen for pollinators, and the deer will ignore it.

One last note on the goldenrods. When I was growing up this was the plant that was thought to be the cause of late-summer and early-fall allergies. Town and village road crews would cut it down with abandon. Well, we made a big collective mistake. It’s actually ragweed, a totally different plant, that gives us the sneezes and sniffles — and not the beautiful Solidagos.

There are still lots more yellows and the vast majority of them are Rudbeckias and Rudbeckia relatives. The ones most familiar are the Rudbeckia hirta varieties and the ubiquitous Rudbeckia fulgida “Goldsturm,” which is reliable, virtually disease and insect free and a great edger. Be careful with the Rudbeckias as some are sold as hardy but aren’t. Others are also sold as pollinators and aren’t. A good clue is that if a Rudbeckia flower has more than one ring of rays — a double flower — it is not a pollinator.

My favorite Rudbeckia is still R. triloba. It has small flowers for this group that don’t emerge until late summer but often persist well into the fall. I’ve seen this plant where it only grows to 3 feet tall but mine are closer to 8 feet tall. Often sold as a perennial, it’s really a self-seeding annual. Wherever you plant it, in the late spring weed out the seedlings so it only grows where you want it or it can become weedy. It’s a hot spot for butterflies and all kinds of pollinators, but the goldfinches love the seeds and add to the riot of color from now into October.

Be careful with the Heliopsis and Helianthus varieties. These plants can be annuals and or perennials, but it’s the Heliopsis helianthoides, or the oxeye sunflower, that’s a true perennial.

If you’ve got the space or are into medicinal plants, try growing Inula helenium, or elecampane. I found this growing in a neighbor’s garden and was taken by the daisy-like flowers with yellow buttons. It was the flower rays that really intrigued me. They reminded me of spider mums with their thin long rays that are fairly unusual. However, this plant is a space hog with the flowers topping out at about 5 to 6 feet but the foliage reaching out 4 to 5 feet. It needs room, is not native but not invasive.

Last on this week’s list is Rudbeckia laciniata “Herbstonne” Autumn Sun. This is another tall Rudbeckia flowering in August and September that grows to 7 feet tall. The flowers have yellow rays that are wide and bright but the center disc that you’d expect to be brown is actually green and striking against the yellow rays. Mine grow up and through the Joe Pye weed where it can be hidden so you have to remember to give it some open space by pruning back Joe a bit.

Again, many, many options here for the meadow, wet meadow, wildflower area and with some skill, even the formal garden. These plants add to the late-summer garden color as well as texture and structure. Keep growing.