I have heard from everyone visiting our gardens this spring that they lost several shrubs this year. So what has happened to our beautiful shrubs? Is that perennial shrub really dead? The shrubs that I am referring to are perennial deciduous shrubs that need a period of dormancy to exist in their lifecycle, such as forsythia, spirea, deutzia, hibiscus, chrysanthemum, Rose of Sharon (althea), and Crepe Myrtles.
There are several factors that tell our plants when it is time to wake up. Not only do they need constant temperatures above freezing, they also need sun, moisture and most importantly time to sleep.
I believe that this year the temperatures played the biggest factor as to why our plants are not behaving normally. Most people do not keep a weather journal but looking back at past data will show us a little about the causes.
Let us start with winter of 2020. Our first freeze according to mesonet.org was October 25th through October 28th (this is only a few days before the first freeze of 2019). The overnight freezes during this period got as low as 24 degrees during the middle 2 days (please note, their temperature readings will be slightly higher than the bottom air that would cause the plants to slip into their dormancy). Temperatures climbed back up into the mid 60’s and 70’s at this point and got as high as 82 on November 14th. I remember telling my husband how odd it was that my shrubs were still green and had not begun their dormancy period. The next freeze we encountered took place the last week of November and into the very beginning of December. It was a 14-day spell with the night low temperatures around 22-31 degrees and the average high day temps of 54 degrees. Let me note that these temperatures during this period were about 8-20 degrees higher than the previous year in 2019.
I believe that at this point is when most our shrubs finally determined enough of the cold, let us rest through the winter. However, some of the shrubs in my gardens, my roses and my honeysuckles were still awake at this point, as were my shoal creek vitex for some reason (they should have gone dormant as well).
At the start of the New Year through February 5th, our winter temperatures were not too bad with daytime highs in the mid 40’s and 50’s and nighttime lows in the mid 20’s to low 30’s. And then we were hit with the Polar Vortex on February 7th, 2021. The Polar Vortex brought our state and most of the United States some of the most crippling weather that I believe I have seen in my lifetime. With 13 days of frigid cold temps, wind chills as cold as -28 degrees and highs only in the low 20’s, our shrubs were put to the test. And just like my roses, honeysuckles, and Shoal creek vitex, all other late dormancy perennials finally were forced to sleep.
Beside the late dormancy for perennial deciduous shrubs, a lot of evergreen bushes also suffered from this frigid cold and experienced some severe die-back which is apparent still to this day, when you see all the dead tops of the evergreens planted around the area.
By March and April, our temperatures rose to the mid 60’s and as high as the low 80’s. Temperatures that tell our dormant plants that spring has arrived. Sadly, but as usual, we had 2 late freezes on March 18th and April 21st. For our perennial shrubs that had begun waking up to these warm temps, these late frosts delayed growth and froze buds, flowers, leaves, and possibly even the stems of some shrubs that were coming out of their dormancy. Thankfully though, the plants will grow on and recover; although we may lack some flowers and fruit that we wait patiently for each year.
Now that the threat of freezing temperatures is finally over and our gardens have turned to green, you cannot help but notice all the dead looking plants that are tucked along the beautiful spring foliage.
As some perennial plants have awakened, others still look dead. So how do we know which ones are dead and which ones are still in dormancy?
The best way to determine is a scratch and bend test. To do a scratch test, scratch into the bark with your fingernail or make a slight scrape with a knife. If you see green or white coloring past the bark, your plant is still alive. To do a bend test, I like to start with the top of a twig that looks lifeless. If it snaps and breaks when I bend it, I will grab a pair of clippers and cut off sections of the stem to determine if there is life anywhere lower on the stem. I am looking for green or white centers just behind the bark. If it is grey, brown, or even black, I will keep trimming the stem towards the bottom of the plant to see if I can find any life in the stem that I am cutting on. If there are multiple stems, I will do this to all the stems until I have cut down the entire shrub. Please bear in mind that there are several shrubs that grow on new wood such as crepe myrtles and hibiscus, so even this test can be deceptive. After I have cut all the stems away and see no life-like signs, I will then dig my plant. I dig them as carefully as I would if I was to transplant them because I am still hopeful there will be signs of life in the roots. If the roots are soggy, frail & thin, or black, I know my plant is in fact dead. However, if the roots have color and are swollen or firm, there is a good chance your shrub is still alive and has not come out of dormancy yet. I will then replant it and give it some more time. Container plantings can actually take 4-6 weeks longer to awaken because the temperature of the soil in the container does not stay as constant as it would in the ground. The scratch and bend test is also a great way to see if you will have to replace the plantings in your container this year.
Our current temperatures are very cool for early May. We have had several cloud covered days and our temps have been averaging around 75. There are several species of shrubs out there that thrive in heat, like Rose of Sharon, Crepe Myrtles, Hibiscus and my Shoal Creek Vitex. These varieties are heat tolerant and are late flowering shrubs. Therefore, they like warmer temps of a consistent 80+ to come out of dormancy so they can complete their growing cycle. So please do not dig them up just yet.
I personally think, from my own experiences, that we just need a little more time and warmer temps- that I am in no hurry to havebefore our wonderful plants fully awaken.
Charla Ingram is a plant, nature, and golfing enthusiast who, along with her husband Chris, owns and operates C&C Gardens in the small town of Bessie, Oklahoma.