Margaret Legg

As we all know rainfall this year has been extremely low.  According to UCCE the rainfall total for this calendar year in the Carneros and Oakville region is recorded as 4.51 inches. If one considers the “rainy” season from October 2021 to the present the total would be 20.86 inches, it's still quite below our average annual rainfall of 26-28 inches as referenced by City of Napa Utilities/Water Division. We all have a responsibility to do what we can to conserve this precious commodity and analyze our usage.  Give cold tap water that would otherwise go down the drain a second chance and water something outside. Every drop counts.

Compost & Mulch…the secret sauce to reducing your water usage in your garden.

The benefits of compost and mulching: 

• Insulates the soil
• Reduces weed seed germination
• Can save 20-30 gallons of water/1000 sq ft each time you water.
• Reduces waste that ends up in landfill
• Amends and improves soil health
• So many more benefits…win-win!

There are multiple options when it comes to compost methods and mulch choices. See references below regarding composting methods including vermicomposting (worm castings). One of the best options for compost to purchase is our own state of the art Napa Recycling Facility.

Watering

Shrink the lawn

• Lawns offer the greatest potential for water conservation.  Consider lawn alternatives; reduce your water schedule; water between 3am-8am; explore water reducing sprinkler heads
• Explore the City of Napa's Cash for Grass program (see reference)
• Control weeds. Weeds complete with desired plants for water and nutrients
• Group plants with similar exposure and water needs. Look for native or drought tolerant plants.
• Water deeply, infrequently, efficiently, and always use a timing device.

Watering systems/application options

• Hose and sprinkler: typical garden hose uses 9-17/gal/min. depending on water pressure.  I filled a 5 gal. bucket in 25 seconds at 80 psi.  A water saving hose nozzle can reduce that usage to 2.5/gal/min.
• Pop-up sprinklers: average use is 4/gal/min/sprinkler.  There are dozens of different types using varying amounts of water, and some frequently have overspray and run-off.
• Soaker hose: uses 1/gal/ft/hr.

 Drip irrigation Tubing:

• Some common size tubing options are:  1/4”, 1/2”, 5/8” plain tubing
• Pressure compensating emitter tubing: 1/2” with emitters every 12” or 18” uses 0.8-1.0 gph/emitter (depends on the brand)
• Pressure compensating emitter tubing: 1/4” with emitters every 6” or 12” uses 0.5 gph/ft

Emitters:

• Applies water directly where it is placed; eliminates overspray and runs off.
• Drip emitters allow water to drip or seep into the root zone; micro sprayers direct water into the air like a miniature sprinkler head.  Both have barbed ends that push into tubing or in the ends of micro tubing. Inline emitters fit between lengths of micro tubing and create custom systems.
• Output rates for emitters range from 1/2-2 gal/hr. and can compensate for plants with diverse watering needs that are run on the same tubing line. 

With this unprecedented time of extreme heat and limited amount of water it seems clear that composting and mulching your garden, along with drip irrigation are clear winners for keeping our gardens alive and the soil healthy.

On a final note, during the rainy season (fingers crossed) there are multiple options to save some of that precious liquid.  Roof runoff offers tremendous amounts of water that can be put to better use than rushing down the street to be deposited in the storm drain, only to end up in our streams and eventually the ocean, carrying with it pollutants from cars, pesticides, garbage, construction refuge, cigarette butts, and the list goes on. 

There are many water saving measures that can be created from simple to complicated:

• Rain barrels/tanks/cisterns
• Graywater catchment
• Underground reservoirs
• Rain Gardens

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Photo credits: Wild Valley Farms with permission

Information Links:

City of Napa-Cash for Grass info https://www.cityofnapa.org/585/Cash-For-Grass

Napa County Rainwater harvesting https://www.napawatersheds.org/managed_files/Document/5748/rain%20harv_updated_2013.pdf

Recycling center https://naparecycling.com/residents/napa-recycling-facility/

Carneros rainwater measurement station https://cenapa.ucanr.edu/about/weather/?weather=station&station=109

UCMG Napa County-Composting information https://napamg.ucanr.edu/Master_Gardener_Programs/Composting/

by Carole Kent

The power of caring and acting, and I emphasize EVERY action to care for the Earth (capital E) and earth (small e) is necessary and important. Greta Thunberg, the young climate activist from Sweden puts it this way, "no one is too small to make a difference".

Climate change is obvious and it affects everything. We can all work to stop and reverse this damage, and it all begins with soil. We can cultivate an attitude of caring and relationship with soils as we understand more about the life of the soil.

Healthy soil is teeming with life: approximately 8 billion microorganisms live in 1 tsp. of soil. Healthy soil has highly complex and organized relationships where everything is connected. Carbon is essential to all life and carbon use and sequestration is out of balance. By improving the health of our soil we help correct the imbalance, at the same time strengthening plant's ability to withstand increasing heat. Plants draw down and sequester carbon, carbon helps feed the microbial life in the soil which helps feed the plant, a true win (slowing climate change), win (feeding the microbes), win (feeding the plant).

There are many ways to increase soil health with innumerable benefits:

1. Increase soil organic matter: All types of soil benefit:sand, clay & silt, because organic matter increases water retention,4" of compost can decrease water use by 40%, and compost attracts and feeds soil microorganisms.
2. Keep soil covered: It can reduce soil temperatures dramatically, reduce evaporation, reduce weeds, reduce compaction and erosion.
3. Practice judicious water use: Water in early morning and use drip irrigation, it reduces evaporation and places water next to roots
4. Avoid chemical fertilizer and herbicides and pesticides: Chemicals kill the life in the soil, birds, bees, beneficial insects, leach into streams and lakes, contaminating water sources
5. Maximize living roots, plant cover crops: Soil organisms need to be fed carbon, carbon comes from plants roots, roots enable carbon sequestration
6. Increase plant diversity: Nature loves diversity, monocrops invite pests and disease. greater diversity above ground increases diversity below ground
7. Minimize soil disturbance-no  till: Disturbing the soil destroys the life in it and breaks up the soil food web, requiring rebuilding of fungal hyphae that link plants sharing water, nutrients and warnings of pest invasions. It breaks up aggregates and releases carbon into the atmosphere, allows water to evaporate and brings up weed seeds and creates hard pan
8. Avoid soil compaction-don't walk on soil: It squeezes air out and soils have less ability to hold water, and thus can cause erosion

Our future depends on us taking action. Taking action depends on knowledge, caring and being aware that everything is connected.  We are part of, not apart from this magnificent web of life. Deborah Koons Garcia, a documentary filmmaker says, "soil is one of the true miracles of the planet and we treat it like dirt."

Our calling is to change that.

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Photo credits: Opensource image

Information links:

UC ANR Healthy Soils for California https://ucanr.edu/sites/soils/

Healthy Soil Basics https://ucanr.edu/sites/soils/Soils_101/

Tips to improve your garden soil https://ucanr.edu/sites/soils/Soils_for_Homes_-_Gardens/

Soils and Nutrients https://ucanr.edu/sites/Soils_and_Nutrients/

Cynthia Kerson

With the weather getting warmer by the year, it's time we recognize the difference between heat and water stresses in our plants. The temperature is averaging 83°, and according to www.GreenCastOnline.com, a service provided by a fertilizer company, soil temperatures have been averaging about 81° in Napa and 85° in Calistoga. Lately, these temperatures have been as high as 84° and 88°, respectively. This company wants to sell you lawn fertilizers, so their warning system is in place to alert when certain weeds or insects might appear because the soil of your lawn reaches the temperature they thrive in.

Most of the plants we grow in our gardens like the soil temperature to be between 65-75°. When the soil gets too hot, they mitigate the effect by wilting, bolting, getting sunburn and dropping leaves. What is the most common, knee-jerk, reaction to this? Water, water, water. However, hot soil and air temperatures don't always correlate with not enough water. In fact, too much water in the soil could contribute to the problem by suffocating the roots, so it's important to recognize the signs of heat stress and manage that. The first line of action is to mulch. I'm sure you've heard a Master Gardener or two assert the importance of mulching. Mulched soil (bark, hay, rocks [sometimes], and leaving leaves), are all forms of mulch. Unmulched soil generally follows the fluctuations of the air temperature and this is especially true in raised beds. Mulched soil tends to stay consistent throughout the daily cycle.

Another way to cool the soil, and hence the plant, is to provide shade cloth, which can cool the air by as much as 10°. In this case, since you are cooling, and not trying to protect from frost, leave the sides open so air can circulate but is cooler due to shade protection of the sun. This will also keep the humidity level constant.

How are heat and water stress different? The most common sign for both too much and not enough water is yellowing of leaves. Mottled leaves can also be a sign of either. The gardener needs to look beyond these symptoms to decide which it is. Overwatering may be expressed by droopy, floppy leaves that will become lighter green than the natural color of the plant's leaves, whereas under-watered plants wilt from the stem and may lose leaves.

When overwatered, the droopy stems occur because the plant loses turgidity. Turgidity is the pressure against the plant's cell walls from the amount of water within them, causing them to be erect, like a water balloon. Without enough water to support the shape of the cell, they'll flatten, or become flaccid, and when enough cells have lost shape, the stems wilt. This is the most obvious sign to determine whether the plant is under- as opposed to over-watered.

An overwatered plant may also shed leaves – but for a different reason: this is because the roots may be experiencing rot due to limited access to oxygen and nutrients in the soil. If you see this, obviously don't water more. Removing the plant and running the roots under water to clean them, removing severely damaged roots, and repotting or replanting is your best, albeit not guaranteed, way to resolve root rot.

A sign of an under-watered plant is leaf drop. Before they drop, though, their tips may brown, and they'll look dull and lack-luster. The plant will put more energy into survival and less into leaf and blossom development. If chronically under-watered, the leaves won't grow back. If intermittent, the leaves will cycle through starting and dying off. Obviously, the resolution is giving the plant water, but in doses. Don't flood the plant out of guilt. Water until you feel wet soil at about 2” depth and remain on whatever schedule works to maintain that level. Removing any blooms or imminent blooms will help the plant put its resources into preparation.

Knowing whether a plant is thirsty, drowning, or experiencing heat stroke is vital to its care. Recognize heat stress and resolve it by maintaining a healthy layer of mulch, covering with shade cloth, or possibly moving the plant to an area where the soil can remain cooler on hot days. If watering is the issue, respond with the appropriate measures discussed above. Hopefully your plant will come back and thrive.

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Diagram: https://qsstudy.com/turgidity-definition-importance/

Reference: OSU extension-heat stress https://extension.oregonstate.edu/gardening/flowers-shrubs-trees/heat-wave-garden-how-identify-prevent-heat-stress-plants

by Maureen Jett

Heat Island Effect is a man-made phenomenon in which air temperatures and surface temperatures are higher in urban areas than in the surrounding rural settings.

A team from the Master Gardener's Climate Change and Soils committee recently recorded temperatures of different surfaces in one neighborhood in Napa (see Surface Temperature Chart). Readings were taken on two different days, March 4th and June 21st. On June 21st, two recordings were done, one at 10:30am and the other at 3:30 pm. The temperature reached 104° that day.

Soil organic matter is what keeps soil alive and healthy, in other words, the living world below. A teaspoon of healthy soil contains millions of living organisms. This graphic from the USDA displays the threshold temperatures that expose your soil to potential “death”, in other words turning your soil into plain dirt.  Read the chart from the bottom up to see what happens to Soil Organic Matter (SOM) at different temperatures.

140° F — Soil bacteria die. (We're talking about good bacteria).

130° F — 100% moisture is lost through evaporation or transpiration. 

113° F — Some bacteria species start dying. 

85% — moisture lost through evaporation. 

90° F — Plant growth slows. 

70° F — 100% moisture is used for plant growth. The ideal range plant growth and planting is (65 to 86 F).  

1. Plant more trees that will protect against high winds, erosion and flooding, as well as keeping carbon in the ground and keeping groundwater clean. The big plus is the shade provided for our homes thereby reducing energy consumption.

2. Cover the ground with living plants to absorb CO2 rather than reflect the sunlight. Given, turf (grass) is green and it is cool, and in many circumstances needed for pets and children, but an expanse of green lawn requires heavy watering for maintenance and it and contributes little to soil health because the roots are shallow. On the other hand, plants and shrubs provide abundant roots, creating healthy soil and sequestering carbon in the earth.

3. Where plants are not growing, try to cover the ground with organic mulch. In the temperature readings, notice that the soil under the mulch is significantly cooler than the mulch itself.  But be aware that all mulch is not created equal. Some dyed mulches may leach toxins into the soil and dark/black mulch heats up and can be detrimental to tender plants. Rock may seem like a good choice and in some cases may be appropriate, perhaps around cactus, but large areas covered with rocks/stones in the sun will absorb and retain heat, later releasing it back into the atmosphere. Keep rocks/stones in shady areas under plants, trees or next to the house.

4. Use permeable hardscapes (including permeable pavers) instead of concrete and other solid surfaces.  Rain is absorbed into the soil rather than running off into the gutters and streets and will not retain the heat like non-porous and darker surfaces.

5. Resist the urge to put down artificial turf. Not only is it hot to the touch, but it kills anything living in the soil underneath of it. There is truly nothing beneficial about it. Notice it is the hottest reading on the Surface Temperature chart.

If you want to learn more about Heat Islands, what can be done, and what's been implemented or being proposed in some cities to mitigate heat island effects, check out these US government's websites: 

Heat.gov (National Integrated Heat Health Information System/ NIHHIS) https://www.heat.gov/pages/urban-heat-islands

EPA  https://www.epa.gov/heatislands 

And for children: NASA has a website, Climate Kids, chockfull of great information and age-related activities: https://climatekids.nasa.gov/heat-islands/

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Photo: Rawpixel