Clethra alnifolia

My pick for June's Wildflower Wednesday is one of the most industrious shrubs in our summer garden, Clethra alnifolia, commonly referred to as summersweet. This stunning shrub is thriving in our rain garden as well as a few other garden beds. We grow the straight species, which adorns white blooms and 'Ruby Spice' with pink flowers. Preferring moist soil, this shrub is found naturally along stream banks, marshes and swampy woodland areas.  

Clethra alnifolia 'ruby spice' in rain garden with rudbeckia and Southern Shield fern

Blooming in July, it provides high quality nectar and pollen that brings in the pollinators. This is a great option for smaller gardens because it attracts such a wide variety of bees, wasps, butterflies, flies and hummingbirds. [more bang for your buck]

I enjoy observing all the pollinator activity on the blooms. Large wasps lurch themselves from one flower to the next. Butterflies are more graceful in their approach, gliding gently onto the flowers while bees dance around the spikes in a hurried manner. 

For this post, I am sharing a few of the common wasps we see on the flowers and their contributions to our ecosystem. 

Double banded scolid wasps are solitary and often referred to as scarab hunters because they control the scarab beetle populations. Females dig into the soil to find a beetle grub, sting it and lay their eggs on the grubs. 

Potter wasps make tiny nests out of mud that look like jugs. The adult wasp controls caterpillar populations by paralyzing a caterpillar and inserting it into the pot where it has laid one egg. While developing, the larva feeds on the caterpillar before digging its way out.  

The great black wasp helps pollinate plants and control katydid, cricket and grasshopper populations in the garden. They are in the digger wasp family and lay eggs in underground nests. 

The common thread-waisted wasp is a relative of the mud daubber wasp and feeds on nectar and small insects. These parasitic wasps are beneficial as they feed on caterpillars, spiders and grasshoppers. They ambush their prey and immobilize them with a sting. They then carry their prey back to their underground nest and lay a single egg on the victim. 

Mosts wasps are not aggressive toward humans, however they can sting if threatened. We have learned to live peacefully with wasps and appreciate their contributions as nature's pest control and pollinators.

Clethra alnifolia is unique because it flowers in shade when few other shrubs are blooming. It does, however, grow in sun as well and we selected full and part sun areas for our shrubs. Those in the sunny, rain garden are spreading more productively than other locations. This densly branching deciduous shrub makes an excellent screen and does respond well to pruning (best done in winter). 

The aromatic flowers, once pollinated, will produce dark brown seed capsules in the fall that often persist through the winter.

This shrub can be slow growing, but is easily propagated from stem cuttings in summer or from seed later in the year. This is an low-maintenance plant with a high wildlife value and definitely one to consider for your garden if you live in its natural range. (See USDA Plants Database

Be sure to visit Clay and Limestone for more wildflower contributions.

Comments

  1. I have 'Ruby Spice' but it hasn't flowered that much yet. We have a unique one at work on a standard that I've lusted after. I just don't have room for it.

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    1. If I recall correctly it took a few years before my ruby spice really flowered prolifically. Hope yours comes into its own and is lush with blooms in a few seasons.

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  2. One of my favorites. I wish I had the pink flowered one, but, who can complain about flower color when it blooms in the shade! Happy WW. xogail

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    1. Absolutely! I see more butterflies on the pink blooms but the bees and moths are more attracted to white so its a win win either way.

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  3. Surprisingly my Clethra alnifolia 'Vanilla Spice' had few pollinators on it this year. Most unusual. I do love the fragrance. My 'Ruby Spice' was eaten by the deer, so no blooms.

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    1. Bummer Janet! Your deer must be hungry because typicaly they leave them alone. Hope your ruby spice will be back for you next year with less pruning.

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  4. A beautiful shrub--both the straight species and the cultivar! It's not native here, but many people grow it in the Upper Midwest. The conditions work well for it and the pollinators love it. :)

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    1. So is it an annual for the Upper Midwest or does it survive mild winters?

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  5. This shrub wasn't on my radar but now it is and I want one - such a great post! Does it have to be in a very moist area or will an "average" area do? P.S. Amazing photo of the thread-waisted wasp - you really captured it's barely their waist - it's incredible!

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    1. The shrubs in my rain garden have suckered and filled in whereas in my average soil areas they remain a more clumping shrub.

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  6. Clethra has not worked well for me, but it is a beautiful shrub in the right place. When we were in NY we saw lots of Japanese Clethra on the High Line.

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    1. Interesting. I thought the High Line used mostly native plants. But maybe the non-native works better in the northern climate.

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One of my favorite things about blogging is the conversation with readers. Leave a comment and let's get talking. ~Karin

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