[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:

1. Remove any debris, such as mud and silt, that may have shifted and accumulated on your plants. 
   
   
2. If the soil is waterlogged, improve drainage by digging ditches or furrows to redirect water away from plants. 
   
   
3. 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. 
   
   
4. 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!
   
   
5. 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.
   
   
6. 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.
   
   
7. Monitor your plants closely for signs of stress, such as wilting or discoloration, and address any issues that arise as soon as possible.
   
   
8. Once dry, start to water your plants gently and gradually to help them acclimate to the new soil conditions. 

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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/

This blog article is for readers who may have heard of subsoil, but don't really know what it is, or how it may or may not affect their gardening efforts. 

What is subsoil?

There are several layers (also known as “horizons” to soil scientists) that can be found when we dig deeper and deeper down into the soil. We can imagine all the individual layers of a soil stacked one on top of the other like a layer cake, this is called the soil profile. The surface soil is the uppermost layer of the soil profile, and the one we are most familiar with, because this is where most of the action takes place. Soil mixing with tillage, compost and fertilizer application, irrigation, plant root growth, and animal activity (including microbes) are mainly concentrated within the soil's surface layer. Additionally, decomposition of plant and leaf litter occurs most rapidly in the surface soil, this eventually leads to the formation of new soil organic matter. In comparison, the subsurface soil, or subsoil, is composed of one or more soil layers that lie below the influence of surface soil activities. There is not a consistent depth at which every surface soil layer changes into the subsoil layer(s), rather the subsoil occurs at a different depth from place to place depending on numerous factors, including some of the factors mentioned previously. This is the reason why it is difficult to determine where the subsoil layer begins in the soil profile.  

What does subsoil contain?

Subsoil is found deeper in the soil profile and does not directly experience a lot of the processes that occur in surface soil. As a result, the subsoil has less soil organic matter, less insect and animal activity, slower air and water movement, and a slower rate of decomposition compared to the surface soil layer. However, the subsoil underlies the surface soil and is indirectly influenced by the activities that occur at or near the soil surface. Therefore, the subsoil layer(s) has the excess fertilizer nutrients, herbicides, pesticides, and other dissolved salts that were lost from the surface soil due to heavy rainfall or irrigation. As surface soil begins to erode and age, the water moving into the subsoil can also have a lot of clay that accumulates in distinct regions of the subsoil.

What does subsoil look like? 

It is possible to identify subsoil by recording when and where you notice distinct changes in color, texture, and/or structure of the soil. The surface soil is often enriched in organic matter, giving it a dark appearance, typically dark brown or black. The movement of smaller soil particles from the surface soil into the subsoil increases clay content. The subsoil also lacks many of the rooting channels and biological pores that help build and support soil structure due to the limited presence of plant roots and animal activity. Therefore, as you dig deeper in the soil profile, if you see the soil color begin to fade from a dark brown or black to lighter shades of gray or brown, you notice it becomes harder to dig deeper into the soil, and/or you notice the soil is no longer loose and crumbly but becomes denser and lacks plant roots and worm channels, it is very likely you have reached the subsoil layer.    

What is subsoil used for? 

In general, the subsoil is a less suitable medium for plant growth compared to surface soil because of some of the factors mentioned previously. There are properties of subsoil however that make it suitable for other uses such as a source of “fill soil” for “cut-and-fill” construction operations, as a source of clay for building materials, and as an absorption layer for on-site wastewater disposal.

What can home gardeners do to keep their subsoil in great shape year after year?

Healthy soils are effectively balanced among the chemical, physical, and biological processes that allow soil to function properly and achieve a desired outcome, such as being an optimal medium for plant growth. Therefore, to build or support healthy subsoil, it is important to consider each of these processes, keeping in mind that what occurs in the surface soil layer can, at some point, be reflected by what is observed in the subsoil. With this in mind, to encourage soil health in the subsoil it is important to recognize that certain plant nutrients move with rainfall or irrigation water, such as nitrogen, and may be enriched in the subsoil. Effectively balancing plant nutrient fertilization to avoid excesses can limit the amount of plant nutrients transferred from the surface to the subsoil. The subsoil often has a poorly developed structure due to the lack of plant rooting channels and animal activity (including microbes). Growing a diverse group of plants that have distinctly different rooting depths, ranging from shallow- to deep-rooted, can encourage the formation of rooting channels that extend into the subsoil. The burrowing activity of earthworms also creates channels that deep-rooted plants can easily use and follow into the subsoil. Additionally, the presence of actively growing plant roots acts as a food source in the subsoil that stimulates microbes. The physical structure of subsoil can be improved with deep-rooted annual or perennial plants. As soil structure improves and more of these biological pore spaces are created, the rate of water and air movement into the subsoil layer will increase, helping sustain the balance among chemical, physical, and biological processes.           

What is the substratum layer of soil? Does that layer affect gardening at all, and if so how?

Stratum is a term that is commonly used to identify a distinct layer of rock or soil. Substratum then is a term used to indicate the relative underlying position of a distinct rock layer within stratified rock formations or a distinct layer of soil that lies below the surface soil. The substratum layer of soil has some of the same properties that are common to the subsoil. Although, many of the chemical, physical, and biological processes are further diminished in the substratum layer compared to the subsoil. Specifically, growing roots are not likely to be found in the substratum, so the properties of the substratum layer are unlikely to directly influence plant growth. The limited amount of water and air in the substratum layer will however help breakdown larger solid rock fragments, forming a loose and very coarse structure that closely resembles the mineral composition of the underlying layer(s) of the soil profile.      

What is the bedrock layer? Does that layer affect gardening at all, and if so how?

Bedrock is the bottom layer of the soil profile layer cake. The bedrock layer consists of solid rock that has not yet been exposed to the chemical, physical, and biological processes of the surface soil and subsoil. In some places, bedrock is the foundation from which the overlying soil layers developed, while in other places, the bedrock layer may have become “buried” by windblown sand or sediment. Bedrock does not directly influence plant growth, but it can determine the type of clay minerals found in different layers of the soil profile. 

Dr. Anthony Fulford is the Area Nutrient Management and Soil Quality Advisor for Stanislaus, Merced, and San Joaquin Counties.

If you spend much time outside, chances are you've sought the shade of a nearby tree. Whether walking your dog, visiting a shopping center, or having a picnic, a tree probably made your experience more pleasant. But how much thought have you given to the benefits of trees?

The Benefits of Trees

Trees provide so much more than shade. Here are a few reasons trees are important, courtesy of the International Society of Arboriculture (ISA):

• Air-conditioning costs are lower in tree-shaded homes & businesses; heating costs are reduced.
• In workplaces with trees, people report decreased workplace stress and fatigue.
• Cleaner air: leaves filter the air we breathe by removing dust and other particles.
• Cooler environment: trees reduce heat in and around parking lots and paved areas.

Trees and the Drought

California residents are being asked to lower their water use by 15%. One easy way to do this is to turn off your sprinklers. But wait! What happens to the trees? Although they may look okay for now, the stress of going without water will take a toll. Lawns can be easily replanted and replaced, but trees take many years to become established.

What do Trees Need?

Although sprinklers provide trees with some water, it's not delivered the best way. Trees need deep, slow, infrequent irrigation to stay healthy. As you can see in this photo, tree roots are just below the surface, in the top three feet. Watering underneath the drip line is best, but not too close to the base of the tree.

How Should I Water My Tree?

There is no “silver bullet” on how often or how much to water. This depends on many factors. Instead, after you water, take a shovel (away from tree roots) and check your soil. How deep did the water penetrate? Make sure water penetrates to a depth of 18” by digging with a shovel. Once that area is dry, water again.

Prioritize Watering Trees with the TRIC

One method you can use to ensure your trees receive sufficient water is the TRIC, or “Tree Ring Irrigation Contraption.” The TRIC is designed by researchers at UC Davis using drip irrigation hose placed strategically underneath the dripline of a tree, but not too close to the base. You can visit the California Center for Urban Horticulture for a free supply list and directions on how to create and set up the TRIC. A second method is to purchase a soaker hose and use it in the same way.

For more information about the value of trees, visit the following resources.

Resources

California Center for Urban Horticulture. UC Davis. Tree Ring Irrigation Contraption. https://ccuh.ucdavis.edu/tric

International Society of Arboriculture (ISA). Trees are Good. https://www.treesaregood.org/Portals/0/TreesAreGood_Benefits%20of%20Trees_0321_1.pdf

Water Talk. Janet Hartin. Podcast Episode 21. https://water-talk.squarespace.com/episodes/episode-21

This article was originally published on July 26, 2021.

The month of May is Garden for Wildlife month. Due to factors such as loss of habitat, pesticides exposure, and climate change, much of wildlife is being challenged today. There are many ways home gardeners can directly help birds, bees, butterflies, and other local wildlife. The saying “If you build it, they will come” applies not only to the classic baseball movie “Field of Dreams,” but also to attracting wildlife to your garden.

Plants

If you have the space, plant an oak tree! While it will take several years for the tree to mature, few plants provide more benefits to nature than an oak tree. One Valley oak tree can provide food, water, and shelter to approximately 350 vertebrate species and over 250 species of insects and arachnids.

Plant a variety of native plants which are the foundation of local food webs. Wildlife and plants evolved together in ways that were beneficial to both, plus they are adapted to local soils and weather. Native plants provide food, shelter, and places to care for their young. Native plants also tend to be water-wise, needing little watering once established.

Choose plants that bloom at different times of the year, to ensure something is always blooming during the different seasons thus providing nectar sources year-round.  Include some plants which produce berries to provide food sources attractive to birds and insects.

Create multi-layered planting. Have some canopy trees of different heights, weave in some tall, medium, and small plants, along with some groundcovers. Even a small garden can have plants of different heights to attract and shelter different types of wildlife. Arbors and trellises are also ways to grow vines, providing more variety in your garden.

Lawns lack variety, thus reducing your lawn space and replacing it with native plants will increase the diversity in your garden. Decreasing the frequency of mowing permits grasses to grow taller, allowing flowers to grow and bloom which would attract bees and butterflies. You can also sprinkle some daisy and clover seeds into your lawn to provide forage plants and flowers for many beneficial insects.

Water

Wildlife needs water. The water source(s) can be a small dish, a bird bath, a rain garden, or pond. Water in bird baths needs to be shallow since birds will not use a bath where the water is deeper than their legs. Be sure to clean and change the water frequently to prevent mosquitoes.

Ponds with aquatic-loving plants can encourage amphibians such as salamanders or toads, or wetland insects such as dragonflies, to visit and set up their homes.

Butterflies engage in behavior called “puddling,” where they stop in muddy puddles for water and nutrients. You can recreate this by filling a terra cotta saucer with soil and pebbles, sink it into the ground and keep it moist. Again, change the water regularly.

Plants and rocks around the water source(s) provide shelter, camouflage, and spots for creatures like butterflies, lizards, or turtles who like to sun themselves near water.

Housing for Bees

Most bees are solitary in nature with 70% being ground nesters like mining bees. Cavity-nesters such as mason bees comprise 30% of bees. These live in twigs, abandoned beetle holes, and other tree cavities. The social honeybees and bumble bees who live in hives or colonies make up less than 1% of all bees. Native bees are up to 200 times more efficient pollinators than honeybees. You can attract native bees to your garden by providing bare patches of dirt in out-of-the way sections and/or supply bee housing with hollow reeds or cardboard tubes in a sheltered spot that receives morning sun.

Leave the Leaves

Leaving leaves as they drop from your trees and bushes provides food and shelter for a variety of living creatures including worms, beetles, millipedes, larvae of some butterflies and moths, toads, frogs and more. These in turn attract birds, mammals, and amphibians that rely on the smaller organisms as a food source.

Chemicals

Reduce or eliminate use of pesticides and fertilizers which can be harmful to wildlife (including beneficial insects) and contaminate water resources. Instead use earth-friendly solutions such as garden mulch to discourage weeds and adding nutrients to the soil. UC Integrated Pest Management provides a source of research-based less-toxic solutions for garden pest management.

One Step at a Time

Changing your garden into a wildlife haven will likely be a step-by-step process over a period of time. Building a garden attractive to wildlife will bring you the enjoyment of watching them and the knowledge you are helping wildlife thrive.

Resources listed provide information for ways to you to build a garden attractive to wildlife.

• Butterflies in Your Garden: https://ucanr.edu/sites/CEStanislausCo/files/345791.pdf
• Sustainable Landscaping: https://ucanr.edu/sites/stancountymg/Sustainable_Landscaping/
• Trees in Your Garden:  https://ucanr.edu/sites/CEStanislausCo/files/341553.pdf
• Pollinator-Friendly Native Plants Lists: https://xerces.org/pollinator-conservation/pollinator-friendly-plant-lists
• UC IPM Statewide Integrated Pest Management Program: http://ipm.ucanr.edu/
• The Bee Gardener: The Cavities You Want to Have: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12785
• How to Make and Use Bee Houses for Cavity Nesting Bees: https://beegarden.ucdavis.edu/wp-content/uploads/2018/04/How-to-build-and-use-bee-blocks.pdf

 

Denise Godbout-Avant has been a Stanislaus County Master Gardener since 2020.