- Author: Ben Faber
What Can Happen With Too Much Rain? And Mud?
Rain is wonderful stuff. If it comes and washes the accumulated salts of the last several years out of the root zones of citrus and avocado, that's a good thing. But what happens if there is a little too much of the good stuff? In the winter of 2005, Venture got over 40” of rain, which is 200% of what is normal. The last time big rains occurred prior to that was in the winter of 1997-98. That year the rains were evenly spaced on almost a weekly basis through the winter and into the late spring and over 50" fell. That year we had major problems with both citrus and avocados collapsing from asphyxiation. The same occurred in 2005, but not so pronounced.
This winter we have had a lot more rain than we normally see and in some young trees with poorly developed root systems, we have seen some collapse.from asphyxiation. Avocados tend to be more susceptible than citrus, and some rootstocks more than others. We have also had some trees buried in mud slides, which can also lead to asphyxiation.
Asphyxiation is a physiological problem that may affect certain branches, whole limbs or the entire tree. Leaves wilt and may fall, the fruit withers and drops and the branches die back to a greater or lesser extent. The condition develops so rapidly that it may be regarded as a form of collapse. Usually, the larger stems and branches remain alive, and after a time, vigorous new growth is put out so that the tree tends to recover. Young trees can be harder hit, but sunburn damage from lack of leaves may be more of a problem.
Asphyxiation is related to the air and water conditions of the soil. The trouble appears mainly in fine-textured or shallow soils with impervious sub-soils. In 1997-98, this even occurred on slopes with normally good drainage because the rains were so frequent. When such soils are over-irrigated or wetted by rains, the water displaces the soil oxygen. The smaller roots die when deprived of oxygen. When the stress of water shortage develops, the impaired roots are unable to supply water to the leaves rapidly enough and the tree collapses. The condition is accentuated when rainy weather is followed by winds or warm conditions. These are exactly the conditions we have seen in the last two weeks, hence some of the problems in young orchards on heavier soils.
It doesn't take standing water to have asphyxiation occur.
Canopy treatment in less severe instances of asphyxiation consists of cutting back the dead branches to live wood. If leaf drop has been excessive, the tree should be whitewashed to prevent sunburn. Fruit, if mature should be harvested as soon as possible to prevent loss. In the case of young trees, less than two years of age, recovery sometimes does not occur, and replanting should be considered if vigorous regrowth does not occur by July. As soon as defoliation is evident, whitewashing should be done to protect them to give them a chance for recovery.
Asphyxiation can be reduced by proper planting and grading. If an impervious layer is identified, it should be ripped prior to planting. The field should be graded so that water has somewhere to run off the field during high rainfall years. Heavier soils might require planting on berms or mounds so that the crown roots have a better chance of being aerated.
Hindsight is always great. Post-plant, if an impervious layer can be identified and is shallow enough to break through, ripping alongside the tree or drilling 4-6 inch post holes at the corners of the tree canopy can improve drainage. It is important that the ripper blade or auger gets below the impervious layer for this technique to be effective. If there is a thick layer of mulch reducing soil evaporation, pulling it back to allow the sun to help dry it out faster will help. It's not a lot of work with small trees, but big time work if it's big trees with thick mulch.
Asphyxiated tree that has been whitewashed
In the case of trees being buried, especially covering the bud union, they should be dug out as soon as practical.They need to be dug out down to the original ground level about 3 feet out from trunk. Then over time, excavated out about 6-8 feet from trunk. It doesn't have to be done today, but soon, before the weather heats up and transpiration demand increases. So in the next month at latest. Start slow and gradually the mud can be moved out further from the tree.
Trees buried above bud union that need to have soil removed down to original soil level.
- Author: Melissa G. Womack
- Author: Missy Gable
[From the UC Master Gardener Program Statewide Blog]
Proper irrigation and drainage are critically important for the health of plants and trees. But what happens when Mother Nature throws an atmospheric river curveball, and your yard or garden is now under water from heavy rains or floods?
Good garden soil contains a network of pore spaces filled with water and air. Both are necessary for healthy roots and beneficial soil-dwelling organisms. When the pore spaces fill with water, air is no longer available to the root system, and the roots become susceptible to root-rot organisms. Understanding the effects of flooding on plant health and caring for them after a flood event is important to saving your plants and garden.
Once the floodwaters have receded, assess the damage to your garden and begin the recovery process. There are a few things you can do to minimize the damage to your plants from flooding:
- Remove any debris, such as mud and silt, that may have shifted and accumulated on your plants.
- If the soil is waterlogged, improve drainage by digging ditches or furrows to redirect water away from plants.
- Check the soil for compaction and loosen it up with a garden fork. This will help to improve drainage and make it easier for water and nutrients to reach the roots of your plants.
- Wait until the soil dries out before working with it in order to reduce additional compaction. Avoid walking on waterlogged soil to prevent compaction and further root damage. Stay off a boggy lawn!
- Inspect your plants for damage to the roots, leaves, and stems. Remove any damaged parts, and prune your plants back to healthy growth if necessary.
- Remove contaminated material. Consider that any garden produce touched by floodwater may be contaminated and discard it. While the risk of contamination is low in residential areas, runoff from septic systems, pastures, or industrial areas can carry potentially harmful microbes and chemicals.
- Monitor your plants closely for signs of stress, such as wilting or discoloration, and address any issues that arise as soon as possible.
- Once dry, start to water your plants gently and gradually to help them acclimate to the new soil conditions.
Connect with us!
Recovering from a flood can be a difficult and time-consuming process, but with proper care and attention, your garden can recover and thrive. The UC Master Gardener Program is available to help! For gardening questions and local county resources, click here to Find a Program. You will be redirected to your local county website and contact information.
Source: Flood: Plant Stress in Extreme Wet Conditions, https://marinmg.ucanr.edu/PROBLEMS/EXTREME_CONDITIONS/Flood/
- Author: Melissa G. Womack
- Author: Missy Gable
- Posted by: Lauren Fordyce
[Originally published on the UC Master Gardener Program Statewide Blog on January 10, 2023]
Proper irrigation and drainage are critically important for the health of plants and trees. But what happens when Mother Nature throws an atmospheric river curveball, and your yard or garden is now under water from heavy rains or floods?
Good garden soil contains a network of pore spaces filled with water and air. Both are necessary for healthy roots and beneficial soil-dwelling organisms. When the pore spaces fill with water, air is no longer available to the root system, and the roots become susceptible to root-rot organisms. Understanding the effects of flooding on plant health and caring for them after a flood event is important to saving your plants and garden.
Once the floodwaters have receded, assess the damage to your garden and begin the recovery process. There are a few things you can do to minimize the damage to your plants from flooding:
- Remove any debris, such as mud and silt, that may have shifted and accumulated on your plants.
- If the soil is waterlogged, improve drainage by digging ditches or furrows to redirect water away from plants.
- Check the soil for compaction and loosen it up with a garden fork. This will help to improve drainage and make it easier for water and nutrients to reach the roots of your plants.
- Wait until the soil dries out before working with it in order to reduce additional compaction. Avoid walking on waterlogged soil to prevent compaction and further root damage. Stay off a boggy lawn!
- Inspect your plants for damage to the roots, leaves, and stems. Remove any damaged parts, and prune your plants back to healthy growth if necessary.
- Remove contaminated material. Consider that any garden produce touched by floodwater may be contaminated and discard it. While the risk of contamination is low in residential areas, runoff from septic systems, pastures, or industrial areas can carry potentially harmful microbes and chemicals.
- Monitor your plants closely for signs of stress, such as wilting or discoloration, and address any issues that arise as soon as possible.
- Once dry, start to water your plants gently and gradually to help them acclimate to the new soil conditions.
Connect with your local UC Master Gardeners!
Recovering from a flood can be a difficult and time-consuming process, but with proper care and attention, your garden can recover and thrive. The UC Master Gardener Program is available to help! For gardening questions and local county resources, click here to Find a Program. You will be redirected to your local county website and contact information.
Source: Flood: Plant Stress in Extreme Wet Conditions, https://marinmg.ucanr.edu/PROBLEMS/EXTREME_CONDITIONS/Flood/
- Author: Lauren Fordyce
An immense amount of rain has fallen across California in recent weeks. While rain is incredibly beneficial, in excess it can cause serious problems. The continued wet conditions opens the door for many pests, so see the list of dos and don'ts below for common wet weather pest prevention tips.
DO
- Check for snails and slugs. These critters thrive in moist environments and can often be seen on sidewalks and driveways after rain. Their feeding causes irregular holes on leaves and flowers, and they'll leave behind a slimy trail. Pesticide sprays and dusts will not be effective under such wet conditions and therefore, should not be used. Instead, hand pick them or trap them using a wooden board trap.
- Remove weeds and unwanted plants. When the ground is wet it is much easier to pull weeds and remove unwanted plants from your garden or landscape. Use this time to your advantage by catching up with any winter annual weeds, like oxalis, nutsedge, and groundsel. Be on the lookout for more in the coming weeks.
- Dump standing water. As the weather warms, any areas left with standing water will be a breeding zone for mosquitoes. This wet winter is already favoring a big mosquito season, so do your part to reduce habitat around your home. This can include dumping flowerpots and saucers, wheelbarrows or buckets, and cleaning clogged storm drains or gutters.
- Continue to conserve water. During the fall and winter months, adjust your irrigation schedule to reflect the increase in rainfall. Consider purchasing a rain sensor for your sprinkler system to avoid irrigating while it is raining. Overirrigating your plants during this time can lead to root rots and other water-borne pathogens so do what you can to reduce excess water.
- Be on the lookout for ants, cockroaches, and earwigs. These insect pests may invite themselves into your home when flooding or heavy rains make it unfavorable for them outside. Seal any cracks or openings in your home to prevent them from coming indoors. Use weatherstripping and door sweeps, and place sticky traps near entryways. Keep food sealed tightly and maintain a clutter-free environment to prevent these pests from establishing indoors.
- Remove mushrooms. Wet weather encourages the growth of above ground fruiting bodies of fungi. While not harmful to your garden or lawn, you may want to remove mushrooms to prevent children and pets from consuming them.
DON'T
- Fertilize your garden, lawn, or outdoor potted plants. Any fertilizer applied now will likely be washed off the ground or rapidly leached out of the soil and into our waterways. Wait until the winter storms have passed and there is a stretch to time between days with rain.
- Use pesticides (sprays, dusts, drenches). Similar to fertilizers, these products are more likely to just contaminate waterways than control any pests. Pesticides applied to foliage as sprays will be washed away quickly with daily rainfall and those applied to the soil as a systemic drench will likely not be taken up by the plant in waterlogged soils and instead will become runoff. Pesticide dusts need to remain dry to be effective, so now would not be the time to use those outdoors either.
- Prune plants. Unless necessary to remove damaged limbs or branches from the recent windstorms, avoid pruning plants under wet conditions. Pruning at this time can make plants vulnerable to pathogens and easily spread disease from one plant to another. Apricots, cherries, and olives should never be pruned during cool, wet conditions.
- Worry about tiny piles of soil. Earthworm activity is increased during rainy weather, so if you are seeing piles of soil on top of landscape beds or the lawn, don't worry—it's just the earthworms coming out and getting some air. As they do this, they help aerate the soil. Earthworms deposit castings when they ingest soil and leaf tissue and emerge from the soil surface to remove fecal matter. Castings are rich in nutrients and organic matter and can provide some benefits to turfgrass plants.
- Compact your soil. Avoid driving or excessive walking on soft ground and keep heavy machinery off wet soils. Compacted soils make lawns, trees, and shrubs more susceptible to diseases, drought, and insects as they restrict oxygen and water from plant roots.
For year-round actions to keep landscape plants healthy, reduce pest problems, and prevent future issues, see the Seasonal Landscape IPM Checklist to find monthly activities specific to your county or region.
- Author: Jules Bernstein, UC Riverside
How to help plants in drought-stricken states
A new UC Riverside study shows it's not how much extra water you give your plants, but when you give it that counts.
This is especially true near Palm Springs, where the research team created artificial rainfall to examine the effects on plants over the course of two years. This region has both winter and summer growing seasons, both of which are increasingly impacted by drought and, occasionally, extreme rain events.
Normally, some desert wildflowers and grasses begin growing in December, and are dead by June. A second community of plants sprouts in July and flowers in August. These include the wildflowers that make for an extremely popular tourist attraction in “super bloom” years.
“We wanted to understand whether one season is more sensitive to climate change than another,” said Marko Spasojevic, UCR plant ecologist and lead study author. “If we see an increase or decrease in summer rains, or winter rains, how does that affect the ecosystem?”
The team observed that in summer, plants grow more when given extra water, in addition to any natural rainfall. However, the same was not true in winter.
“Essentially, adding water in summer gets us more bang for our buck,” Spasojevic said.
Their findings are described in a paper published in the University of California journal Elementa.
Over the course of the study, the team observed 24 plots of land at the Boyd Deep Canyon Desert Research Center, in the Palm Desert area. Some of the plots got whatever rain naturally fell. Others were covered and allowed to receive rain only in one season. A third group of plots received additional collected rainwater.
While adding water in summer resulted in higher plant biomass, it generally did not increase the diversity of plants that grew, the researchers noted. Decreasing rainfall, in contrast, had negative effects on plants across both summer and winter, but may lead to some increased growth in the following off-seasons.
Implications of the work extend beyond learning when additional water resources might be applied simply to help plants grow. Whole communities of animals depend on these plants. They are critical for pollinators such as bees and butterflies, and they play a big role in controlling erosion and movement of soils by wind.
“Studies like this one are critical for understanding the complex effects of climate change to dryland ecosystems,” said Darrel Jenerette, UCR landscape ecologist and study co-author.
Desert plants also play an important role in removing carbon dioxide and nitrogen from the atmosphere to use as fuel for growth. Microbes that live in the soil can use the carbon and nitrogen released by plant roots, then send it back into the atmosphere where it can affect the climate.
“Drylands cover roughly a third of the land surface, so even small changes in the way they take in and emit carbon or nitrogen could have a big impact on our atmosphere,” said Peter Homyak, UCR environmental scientist and study co-author.
As the team continues this research over the next few years, they expect to see changes in soil carbon and nitrogen cycling, given that plants are already being affected by changes in seasonal rainfall, as this study shows.
“Can changes in precipitation patterns alter the feedback between plants and microbes, destabilizing the carbon locked in soils and sending more of it into the atmosphere? We are working on figuring that out,” Homyak said.
Editor's note: Jenerette and Homyak are affiliated with University of California Agriculture and Natural Resources through UC Riverside's Agricultural Experiment Station.
