- (Focus Area) Yard & Garden
I first heard the term on the local evening news in fall of 2018: Meteorologist Kris Kuyper was talking about hydrophobic soils. This potentially catastrophic natural phenomenon seems counterintuitive: soils which are damaged by the intense heat of fire become water repellent. Their post-fire inability to absorb and filter rainfall can cause problems with erosion and runoff. Adding insult to injury, fire also burns plant roots that can help stabilize the soil, and destroys plant stems and leaves that slow rainfall's contact with the ground surface, allowing more time for percolation into the soil.
According to an article by Douglas Kent (“First Aid for Sonoma County's Fire-Damaged Soil,” Santa Rosa Press Democrat, October 27, 2017), “erosion leaps as high as 200 percent following fires in urbanized areas.” The slopes and vales that comprise the mountain and foothill communities of our region mean that the immediate danger from water repellent soil comes in the form of flash flooding and the flow of debris and mud. Hydrophobia in burn-scarred soils makes them as water repellant as pavement, and the National Weather Service notes that it takes much less rainfall to cause a flash flood in post-fire landscapes. Their rule of thumb is “if you can look uphill from where you are and see a burned area, you are at risk.”
The type of soil and the intensity of the fire determine how deeply hydrophobia penetrates the soil, and how long the condition persists. Paradoxically, the fastest draining soils (light, sandy soils with large pores) are the most prone to post-fire hydrophobicity because they transmit the heat more easily than heavy, dense, clay soils.
The depth of hydrophobic soils can range from one-half inch to three inches, but a depth of about one inch is most common, according to the University of Idaho Cooperative Extension System's Fire No. 5 publication. In some cases, the water repellant soil layer lies a few inches under the soil surface. Although hydrophobic soils can take up to six years to recover their ability to absorb and filtrate rainfall, in most cases this recovery takes about one year. Regardless of the physiology of hydrophobicity, what matters most is how to mitigate its effects.
To hold your ground:
- Clear drainage systems such as culverts, diversion ditches, or narrow swales, of debris. Clogged drains are a primary cause of erosion, even without fire damage.
- Divert water from areas originally designed to sheet runoff to the landscape: instead, redirect the runoff towards your newly cleared drainage systems or, if they exist, towards storm drain systems such as gutters. Use sandbags, diversion ditches, boards stacked on top of one another and staked in place, dry stacked walls, or bales to redirect water flow.
- Minimize foot and equipment traffic on burned landscapes. Such traffic can further compact already damaged soils on flat areas, and can weaken soil bonds and dislodge soil particles on slopes. Develop plans to restore your injured landscape before tramping on it, and keep all traffic to the bare minimum during restoration activities.
- Leave non-toxic debris in place wherever possible. Burnt plant remnants and other garden features can protect the landscape from wind and water erosion, and help protect any seeds and plants that survived the fire.
For more information on dealing with the effects of wildfire on soil, and landscaping with the possibility of fire in mind, see the Fire-Safe Landscape section of the UC Master Gardeners of Butte County website. Among other resources, it contains a link to “The New Normal: Rebuilding Soil After Fire,” a PowerPoint presentation from the UC Master Gardeners of Sonoma County which covers how wildfires affect soil, soil regeneration, and strategies for dealing with toxic soil.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
- Author: Kathy Keatley Garvey
But today we're celebrating International Monarch Caterpillar Day as well, because it's the right thing to do. Now, more than ever, we need ways to help and protect monarchs.
If you have a kitty, every day is International Cat Day. Monarchs? Well, there are:
- National Start-Seeing-Monarchs Day: The first Saturday in May
- Monarch Butterfly Day: May 18
- Monarch Blitz: July 26–Aug. 4, an event to raise awareness and support monarch butterfly conservation
- National Endangered Species Day: Monarch Butterflies: Aug. 3
Our tuxedo cat, Xena the Warrior Princess (2000-2016), sported a butterfly-shaped marking on her leg, and regularly checked out the monarch butterflies that fluttered through out pollinator garden. Once I photographed her looking intently at a monarch butterfly. What are you? What are you doing? Are you okay?
Xena was just curious, just being more princess than warrior.
Felis catus and Danaus plexippus. One purrs. One flutters. One breaks our heart when it crosses the Rainbow Bridge. The other plays a vital role in the ecosystem that we're trying to protect. Monarchs boldly lift our spirits, symbolizing hope, rebirth and transformation.
- Author: Kathy Keatley Garvey
Monarch butterflies seem to be as scarce as hen's teeth around here.
And since hens have no teeth, that's pretty scarce.
And then it happened.
A late in-star monarch caterpillar appeared on our milkweed in our Vacaville pollinator-predator garden on the very last day of July.
We watched it munch the wilting milkweed leaves in the triple-digit temperature.
For one day.
The next day, Aug. 1, it vanished, never to be seen again. Did it pupate? Did the California scrub jays get it?
The scrub jays nesting in our cherry laurel hedges are prime suspects. They devour everything in the garden, from honey bees, longhorned bees and dragonflies to assorted butterflies, lygus bugs and praying mantises. Happy meals. If they eat a monarch caterpillar, that makes for an unhappy meal, the vomiting kind. It's about the naturally occurring toxins (cardiac glycosides) in the milkweed that the 'cats ingest that serve as predatory protection. That's why scientists say "I bet you'll eat only one."
Just one. The one we were watching?
"Known bird predators include brown thrashers, grackles, robins, cardinals, sparrows, scrub jays and pinyon jays," Wikipedia says, but notes that "Several species of birds have acquired methods that allow them to ingest monarchs without experiencing the ill effects associated with the cardiac glycosides (cardenolides). The black-backed oriole is able to eat the monarch through an exaptation of its feeding behavior that gives it the ability to identify cardenolides by taste and reject them. The black-headed grosbeak, though, has developed an insensitivity to secondary plant poisons that allows it to ingest monarchs without vomiting. As a result, these orioles and grosbeaks periodically have high levels of cardenolides in their bodies, and they are forced to go on periods of reduced monarch consumption. This cycle effectively reduces potential predation of monarchs by 50% and indicates that monarch aposematism has a legitimate purpose. The black-headed grosbeak has also evolved resistance mutations in the molecular target of the heart poisons, the sodium pump. The specific mutations that evolved in one of the grosbeak's four copies of the sodium pump gene are the same as those found in some rodents that have also evolved to resist cardiac glycosides."
- Author: Kathy Keatley Garvey
It's nicknamed "the sunflower bee" for good reason.
It forages on sunflowers.
We recently spotted a longhorned bee, Svastra obliqua, also called "the sunflower bee," on Gaillardia, aka blanket flower, a member of the sunflower family, Asteracease.
Asteraceae is comprised of more than 32,000 known species of flowering plants. And Svastra? Fourteen different species occur in North America and seven in California, according to the UC Berkeley Urban Bee Lab, which provides this description:
"Overall they are medium to large, with stout bodies, gray hair on their thorax, and irregular striping on their abdomen. Females can be distinguished by their scopae, which are located on their hind legs. They additionally are larger compared to males and have dark faces. Males have yellow markings on the bottom section of their faces and are typically more elongate in body size. Both male and female bees have long antennae. Svastra sp. look very similar to Melissodes without using a microscope. However, Svastra sp. will have longer antennae than both Anthophora and Diadasia so the difference is more noticeable."
Those long antennae...those eyes...those mesmerizing eyes...
You can read more about California's native bees in California Bees and Blooms: a Guide for Gardeners and Naturalists, a book authored by the University of California team of Gordon Frankie, Robbin Thorp, Rollin Coville and Barbara Ertter. All are affiliated with UC Berkeley. Thorp, who received his doctorate in entomology from UC Berkeley, was a member of the UC Davis entomology faculty for 30 years, from 1964-1994. He achieved emeritus status in 1994 but continued his research, teaching and public service until a few weeks before his death on June 7, 2019.
How is your garden holding up during our all-too-frequent summer heat waves? Chances are you're seeing scorched leaves, deformed flowers, severe die-back, blistered branches, constant wilting, and even plant loss. Plants are unable to tell us immediately that they're suffering heat stress and sunburn until the damage is evident. As their caretakers, we must observe our backyard environment, heed long-term weather forecasts, and plan for future extreme heat conditions, sometimes many months in advance. Let's look at the causes of heat-related problems and consider some emergency strategies to protect our gardens until the cool autumn weather arrives.
When it's hot and windy and the soil is dry, plants can experience wilt and leaf scorch. Wilt is the earliest and most noticeable signal of heat-related problems. Extreme solar radiation quickens it. Wilt is initially observed when leaves or tender new growth droops, curls, or twists unnaturally. Eventually an entire plant can look limp, a sign of extreme plant stress.
Leaf scorch appears as browned leaf margins that eventually become tissue-paper thin. When whole sections of plants display leaf scorch, it's easy to be misled into thinking that the plant is dying.
There are a few things that can be done immediately to address these heat-related issues when you notice them. A close examination of a specific plant's parts and its surrounding environment is essential. A "bottom-to-top-to-outside" strategy is recommended, meaning that you should address stressed root zones first, then the overheated plants, and finally the superheated environment around and above the plants.
Lack of water is the most likely critical factor in extreme heat-related garden problems. The higher the temperature, with increased sunshine intensity or drying winds, the faster water evaporates, leaves transpire, and the soil dries. Watering not only hydrates roots but cools them as well. Remember this point because the initial water in a hose that has been left in the sun might be scalding hot. While we do not advocate wasting water, in this case it is best to run water through the hose until the water is cool. You should have a few buckets near your faucets to collect the hot water to use later on when it has cooled.
Potted plants require even more attention. Watering them two or more times a day might be necessary. When a potted plant is very stressed, try submerging it in a larger tub filled with cool water to re-wet the soil. Leave it in it until all the bubbling stops, then remove it, let the excess water slowly drain out, and place the plant in the shade.
Remove all weeds around your plants because they are competing for water. In addition to sucking up valuable moisture, weeds steal critical nutrients that your plants require. For example, research shows that calcium helps protect plants from heat stress. Be diligent about removing weeds, grasses, and even seedlings if they're suspected of drawing up too much water from their mother plant.
While you're mulching, check for suckers around trunks or from root shoots. While seasonal pruning should be avoided during high heat spells, removing suckers will reserve water for the original plant. Also, refrain from removing unsightly scorched leaves; portions might still be photosynthesizing and shading stems or new growth at the leaf axils. Remember: don't immediately equate burned leaves to a dead or dying plant. Give it time to recover before removing it.
Now that you've addressed the root and plant issues, move on to the environment around and above the plant. One strategy here is to mist the plant, though this is not a replacement for direct watering. Misting helps reduce air temperature and physically cools leaves. When partnered with shading strategies, mist becomes very helpful in locally reducing extreme heat. It is recommended to mist mid-day to early afternoon, allowing moisture to dry before dusk. Excessive moisture on leaves in the evenings can promote unwanted pests and fungus. Many commercial misting systems have timers and attachments to help you create an overhead system that is best for you and your garden. If you don't want to invest in a misting system, periodic mid-day spraying from a cool garden hose can work wonders to perk up limp, stressed plants. One key consideration about misting is to hand water the stressed plant first to revive it before doing any misting. If you hand mist first, the weight and pressure of the water on a heat-weakened plant might snap off new growth.
It is also important to reduce exposure to the light and heat reflected off buildings, concrete hardscaping, and even gravel walkways. Again, applying shade above plants will reduce the problem, but hanging a dark cloth or tarp on a building's walls or temporarily putting mulch onto concrete or other hardscaping can further reduce issues brought on by reflective heat and light conditions.
Lawns can also suffer during extreme heat events. Watering schedules should be set for early morning, with increased frequency (number of days) and extended watering times. Longer watering periods help grass roots grow deeper into cooler soil, creating increased resilience to extreme heat. A good test to see if a lawn is receiving enough water is observing the grass blades after walking across the lawn: if they bounce back, the lawn is well watered. If they remain bent, the lawn is too dry. Let grass grow longer between mowings (set mower up an inch or more), and never fertilize in the summer months.
Finally, observe the changing areas of light and shade in your garden throughout the year. Note areas that are sunny, those that have morning sun and afternoon shade, those with all-day filtered sunlight, and those with deep shade. Take note of places where reflective light and heat might originate. Determine how wind generally moves through your garden. Take pictures every month from the same vantage points at different times of the day. Your mission is to track the movements of sun and shadow on your garden. Make sure to photograph plants damaged by extreme heat. These aren't beauty shots. You can use this information for future long-term extreme heat mitigation strategies.
Extreme heat conditions are tough on the garden. Incorporating these recommendations shouldn't add too much work to your current garden activities. You'll be happy knowing that you helped your plants survive another summer. And remember to use a good sunscreen and wear a hat when out in the garden yourself.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.