Plants Want to Be Heard

According to a recent study, plants make popping sounds that are undetectable to the human ear. Apart from leaves rustling in the wind, plants have been thought to have been completely noiseless, but now a study has unveiled that the world around us is a cacophony of plant sounds.

Researchers placed tobacco and tomato plants inside soundproofed acoustic boxes rigged with ultrasonic microphones that can record frequencies well beyond those the human ear can detect. They found these plants emitted sounds at a frequency of 40 to 80 kilohertz, which is 2.5 to 5 times beyond the 16 kilohertz maximum frequency an adult human ear can detect. When they condensed these sounds, the noises were similar to bubble wrap bursting or the sounds of the pop of popcorn being made. Take a listen:

Sounds Emitted by a Tomato Plant

These are the sounds made by a dry tomato plant over a one-hour period. The audio has been accelerated and moved to a hearing range audible to humans. An unstressed plant only emitted about one sound per hour, whereas plants that are under stress emitted 30 to 50 of these popping or clicking sounds per hour at seemingly random intervals.

Scientists don’t know exactly how plants make these sounds, but believe the noises come from cavitation—a process in which an air bubble in the plant’s water column collapses under some kind of pressure making a clicking or popping sound.

It doesn't appear that plants are actively communicating with one another, but it’s possible that insects may be able to use these sounds to determine which plants are healthy and which ones are stressed. Perhaps someday we’ll be able to use special equipment to detect plant sounds and use these as indicators of when plants need to be watered or are under stress.

I’ve frequently asked growers, “Plants are talking—are you listening?” referring to how they often give visual cues when they're either healthy or stressed, but now I know they really DO talk.

CAST

I had the opportunity to slip away from the greenhouse for a few days to visit the California Spring Trials, AKA CAST.

Darwin Perennials at Ball Horticultural Company.

If you’ve never been to CAST, you’re not alone. The official number was slightly over 900 attendees. There were 10 trial locations spread out across central and northern California. I logged 555 miles over the three days and saw hundreds of new perennials, annuals, shrubs, herbs and more from over a dozen breeding companies from across the world.

I’ll plan to share several of the perennial standouts in this and in future newsletters.

New from Green Fuse

One of my favorite CAST stops is Green Fuse Botanicals, Inc. in Somis. Green Fuse is known for their cutting-edge breeding efforts in both annuals and perennials. They have two programs they market their perennial genetics under.

First Light Perennials are perennials that do NOT require a cold treatment (vernalization) to flower and are day-neutral plants. These perennials can be programmed to flower as you would annual selections.

Equinox Perennials is the second program and features a collection of perennials that possess extremely unique attributes. These perennials DO require vernalization and/or long days for flowering.

Here are some of the standouts I saw on display at Green Fuse:

Buddleia Leah

Leah Raspberry

Leah Blue

Check out these gorgeous buddleia baskets. I never imagined putting butterfly bushes in baskets, but I can’t deny how awesome these turned out to be. Buddleia Leah isn't just a basket plant, it makes wonderful decorative containers and can be grown in trade containers as you would other buddleia cultivars. Hardy to Zone 5. I almost forgot to mention the series also contains Leah White.

Silene Carol Jean

Carol Jean Pink

Carol Jean White

Carol Jean is a recent, but not brand-spanking-new, introduction from Green Fuse. I haven’t seen much of it in the industry, but I think it has potential. Many are calling it a summer flowering Phlox subulata. Although, it’s not a phlox at all, the flowers and flower power somewhat resemble that of creeping phlox. However, it doesn't require vernalization, is day neutral and flowers all summer long. That’s something a creeping phlox simply cannot do. Hardy to Zone 5.

Leucanthemum Whisker White

Whisker White debuted at last year’s CAST, but I couldn’t help but share it again. It’s a reinvention of the Crazy Daisy type of shasta daisy. It has massive 5- to 6-in. flowers and continues blooming in the garden all growing season. Absolutely no cold treatment required and completely day neutral make this a shasta every perennial grower should offer. Hardy to Zone 4.

Gazania Sterling Silver Yellow

Here’s a plant I never thought I’d feature in a perennial newsletter: Gazania Sterling Silver Yellow is a great groundcover with attractive silvery foliage and large double flowers that won’t close up due to the number of petals in each flower. Burgundy Stripe (not shown) is also in the series. From what I understand, it's hardy to Zone 5.

Darwin Perennials

One must-see destination for perennials is none other than Darwin Perennials displaying with the other Ball companies in Santa Paula. Here are a few of the perennials I saw there:

Echinacea Double Scoop Deluxe

Strawberry

Watermelon

Darwin Perennials is introducing several new Double Scoop Deluxe Echinacea cultivars to their perennial lineup. If you’re familiar with the original Double Scoop Echinacea, I’m sure you’re going to love the improved Double Scoop Deluxe series. They have beautiful double flowers and are more compact like Darwin’s popular Sombrero series. The Double Scoop Deluxe series has four colors: Strawberry, Watermelon, Raspberry and Orangeberry. Hardy to Zone 4.

Caryopteris Emerald Crest

If you’re looking for a great plant for late summer or fall programs, add Emerald Crest to the list. It’s smaller than other caryopteris on the market, reaching around 30 in. at maturity, produces attractive glossy, green leaves and develops clusters of rare blue flowers. Hardy to Zone 6.

Darwin’s Silver Lining

Darwin has three great new silver introductions. These perennials can be used alone or in combination plantings:

Centaurea Silver Swirl

Silver Swirl is my favorite new introduction from Darwin and lots of attendees were also talking about it. The wavy silvery-white leaves provide texture and contrast to wherever it's being used. Zone 6.

Stachys Little Lamb

Little Lamb is a petite small leaved lamb’s ear. It has fine, decorative silver green foliage and a super compact (less than 6 in.) growing habit, making it perfect for the front of borders. The deer and rabbits stay away from its hairy leaves. Hardy to Zone 4.

Salvia Silver Scent

Silver Scent leads a double life—it can be used as both an ornamental sage and as a fragrant herb. It has glaucous, silvery green leaves and produces blue flowers in the spring. Silver Scent is also deer resistant. Hardy to Zone 5.

A New Invasive Thrips Species

There’s a new thrips in town—it’s Thrips parvispinus, AKA pepper thrips or tropical tobacco thrips. Well, I hope that’s not actually true for most growers, but it's a new thrips in Florida that's been wreaking havoc on various tropical crops. With Florida being one of the main hubs for tropicals, it’s only logical that this new pest will easily be distributed across the country. From what I’ve seen, you don’t want these thrips in your production areas. Those in inner circles are referring to it as the “super thrips.”

Here are examples of the severe injury it causes:

Damage on pepper. Photo: L.S. Osborne, UF/IFAS-MREC.

Damage on gardenia. Photo: Lyle Buss, University of Florida.

Not only is this thrips new, but it also causes extensive damage, is difficult to control and has already shown some resistance to pesticides. Not good. Whether you grow tropicals or not, this is a pest you should be aware of before it reaches your neck of the woods.

There's a new website that will be updated regularly and contains lots of information on the biology, identification and managing of this invasive species.

The Horticultural Research Institute will be hosting a FREE webinar, “Thrips parvispinus: Identification, Scouting and Potential Controls” at 1:00 p.m. Eastern on Wednesday, May 10, 2023. Click HERE for webinar registration.

Please stay attuned to the website listed above and attend the webinar on May 10 to stay abreast of any new developments with Thrips parvispinus.

Thanks for reading this edition of Perennial Pulse. My email is paul@opelgrowers.com if you have any comments, article suggestions or if you'd just like to say hello.

Best regards,

Paul Pilon
Editor-at-Large—Perennial Pulse
Director of Growing—Opel Growers

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