By Susanne von Rosenberg, UC Master Gardener of Napa County
When I first moved to Napa 14 years ago, autumn rains arrived fairly reliably around the middle of October. As we are all painfully aware now, autumn rains have been starting later and later…and sometimes not at all.
There is no rain in the near-term forecast, and the National Oceanographic and Atmospheric Administration (NOAA) Climate Predictions Center foresees a 33 percent chance of below-normal rainfall through November coupled with a 60 percent chance of above-normal temperatures. The longer-term prediction for our area is for slightly below-normal rainfall.
The change in rainfall pattern we've been experiencing, with rains coming later than they used to, is consistent with what climate-change models predict. While we can expect roughly the same amount of rain, we will wait longer for it and it will come in fewer, more intense events.
So we need to get used to longer dry seasons. On the other hand, we need to be prepared for heavy rains. How should we adjust our gardening practices to address this change?
Let's talk about an extended dry season first. It's definitely a good idea to continue all the water- conservation practices that we instituted during the last drought. Choose drought-tolerant plants, including natives that are adapted to summer-dry climates. Install proper irrigation systems, such as drip irrigation, to water only those plants that truly need it and in the amount they truly need.
Adjust your watering according to the season. With cooler, shorter autumn days, plants require less water, even if it isn't raining. Mulch your plants to keep the soil cool and reduce evaporation.
We also need to reconsider our fall watering habits. It used to be possible to stop watering trees by late August and many other plants by mid-September. With the change in climate, you now need to continue to water until the rains finally arrive. Also consider our fall heat and low-humidity periods. Look for signs that your plants need water. Drooping leaves and/or dull leaves are two primary indicators. Get to know how your plants show they are thirsty.
How much and how often should you water with this new climate? For annual plants, simply test the soil with your finger. If the soil feels moist one to two inches down, you do not need to water yet. Keep checking and you'll soon have a sense how much water your plants need in this cooler season and how quickly they dry out when we get Diablo winds.
For trees, you can either dig down six inches to see if the soil is dry (this is the best way to check), or simply extend the time between watering. If you were watering your trees once a month in the summer, you might wait five to six weeks for the next round, and then six to seven weeks (mid- to late November) for the next round. Still no rain by New Year's? It might be time to water again! Even our native and other drought-tolerant plants may need supplemental water when rains are delayed.
More frequent heavy rains are another outcome of climate change. We will need to be able manage more rainfall on our properties. Heavy rain can damage soil structure, wash away topsoil and produce standing water in low or poor-drainage areas. You can protect your soil structure by mulching. (Yet another benefit of mulching.) Observe how water flows on your property during a heavy rain. Your goal is to slow down the flow, which you can do by spreading it out, and also by including areas where you intentionally allow the water to pool and infiltrate. Overall, the better your soil, the more rainfall it can absorb and the more water it can hold. Organic mulches do wonders to improve your soil – so, yes, keep mulching.
After a heavy rain, you may see water pooling in areas where you don't want it. In that case, you need to improve the drainage in that area. The best approach is to divert water from that area and to create additional opportunities for water to drain away. You can raise the soil level, dig small swales or create shallow berms. Small changes can make a big difference. You may also find, as I have, that as you improve the soil, your standing-water problem will diminish and eventually disappear.
Gardeners are a resilient and persistent bunch. With preparation, we can manage some of these climate-change challenges.
The UC Master Gardeners of Napa County are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.
By Corinne Yoshihara
This article is a summary of a seminar conducted by Susanne von Rosenberg, U. C. Master Gardener of Napa County. on gardening in an age of climate change.
Greenhouse gases (GHGs) are the major human-influenced cause of climate change. GHGs warm the earth's surface by trapping heat in the atmosphere. Carbon dioxide and methane are the most important of the common GHGs in influencing climate change.
In 2016, California achieved its goal of reducing its GHG emissions to below 1990 levels. California is home to almost 13 percent of the U.S. population but produces only 6.6 percent of the country's carbon dioxide emissions. The U.S. as a whole is not doing as well. Until recently, the U.S had the highest total emissions worldwide, but China has overtaken us. The United States represents 4.4 percent of global population but 15 percent of the worldwide total of emissions.
Scientists consider four primary scenarios when projecting climate change: GHG emissions peak by 2020 and decline thereafter; GHG emissions peak by 2040 and decline thereafter; GHG emissions peak by 2080 and decline thereafter; and GHG emissions continue to increase throughout the 21st century. If we meet the goals of the second scenario, we may be able to keep global temperature rise below 2°C, the target of the Paris Climate Accord.
Today, worldwide, there is “more energy in the atmosphere, rising air and ocean temperatures, sea level rise, reduction of icepack, ocean acidification and biological change,” says von Rosenberg. In California, “Each of the three past decades has been hotter than the one before.” The year 2014 was the warmest on record, followed by 2015, 2017 and 2016. Most notably, says von Rosenberg, “Temperatures at night have increased more than during the day.”
In the Bay Area, the sea level is rising 3 millimeters per year and that rise is accelerating. This increase in the rate of change is mainly due to the increased rate of melting of Greenland and Antarctic ice. There is also a greater loss of snowpack in the Sierra Nevada and increased runoff.
There are also biological changes occurring due to climate change. Humans are experiencing more heat-related illness and mortality and more health issues related to air quality. Recent droughts and wildfires have killed trees and wildlife. Species distribution is changing. Animal and plant behaviors, such as bird migration patterns and fruit-tree maturation, are also changing.
These changes will affect us adversely. We will experience more intense storms, greater potential for floods and droughts, reduction in sea ice and effects on infrastructure and property value, not to mention loss of vegetation and wildlife.
Gardeners will have to grapple with higher overall temperatures, higher night-time temperatures, longer and more frequent extreme weather events and increased precipitation variability. Higher overall temperatures will mean higher water needs, earlier bloom times and increased insect activity. Higher night-time temperatures will result in more humid nights and potentially faster growth or fruit production. Excess heat over a long period can reduce yields. Extreme weather events mean more drought and fewer, more intense periods of rain.
What can we do? We can reduce our GHG footprint, advocate for renewable energy and educate others. In our own gardens we can conserve and manage water, be flexible, be fire-wise, be proactive with insect and disease control, pay attention to microclimates, plant the right plant in the right place and reduce our garden's carbon footprint. (Removing lawn is one place to start.) Whether we are gardeners or non-gardeners, we can all help.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
By David Layland, U. C. Master Gardener of Napa County
Climate change, also called global warming, has been in the news lately because of the devastating wildfires in Northern and Southern California. Climate change refers to the rise in average surface temperatures and is due primarily to the use of fossil fuels which releases carbon dioxide and other greenhouse gases into the air.
The gases trap heat within the atmosphere, which can have a range of effects on the environment including rising sea levels, severe weather events, and droughts that render landscapes more susceptible to wildfires.
There are two ways to mitigate the environmental damage done by fossil fuels. The most common way is to reduce the use of fossil fuels—by driving a hybrid or electric car, for example, or using solar or wind power. The second way, carbon sequestration, involves pulling carbon out of the air and storing it in the ground.
I don't drive a hybrid or electric car but I do have solar power. It provides 90 percent of my electricity at home so I've done something toward lowering emissions.
Carbon sequestration is new to me. In researching what I could do to help pull carbon out of the air, I discovered that I'm already using several carbon-sequestration practices in my garden. To some extent, these practices are what organic gardeners have been doing for a long time.
Make compost: One of the primary differences between organic and conventional gardening can be boiled down to a simple change in perspective: Instead of worrying about feeding the plants, we should worry first about feeding the soil. Take care of the soil and the plants will take care of themselves.
By composting all of our food scraps and garden waste, we aren't just providing valuable nutrients for plants. We are providing food for a huge ecosystem of bacteria, fungi and insects, all of which help to absorb carbon from the environment and keep it locked up in the soil. You can add cardboard and other paper-based waste to your compost, too. High-fiber composting works, and it's another way to lock up some CO2.
Don't dig: Many old-school gardeners may scoff at the idea of no-dig gardening, but there are good reasons to abandon the rototiller and dig only when necessary. No-dig gardening could have a significant impact on preserving soil carbon.
By slowing down the rate of decomposition in the soil, you help increase soil carbon and save yourself some labor. More than 15 years ago I purchased a rototiller because I thought I “needed” one for my garden and vineyard. I used it for a few years, until I realized I didn't need it. It sat under a tarp for a few more years until I found a new home for it.
That was an expensive lesson. Not using a gas-powered rototiller also means you are not using fossil fuels and are not spewing pollutants into the atmosphere. And you're not killing the hard-working earthworms that are improving your soil health.
When you refrain from tilling, you avoid exposing the soil to excess oxygen and sunlight. You can achieve the same thing by mulching, but an even better way is to plant cover crops, or so-called green manures, which can later be hoed in or mowed down. Doing so will add carbon to the soil while helping the root system keep soil in place. Cover crops also provide a habitat for soil life when you don't have edible crops.
Lose the lawn: This recommendation was easy for me. Before my wife and I moved to Napa, we had a lawn that was more than an acre and, of course, we had a riding lawnmower. After four years of mowing this lawn I never wanted to have another one.
The standard lawn requires a considerable amount of costly maintenance, water and chemicals if you want that green carpet to look perfect. There are many environmentally-friendly alternatives to a lawn. In Napa, I opted for decomposed granite. There's no maintenance and the permeable surface allows water to reach the soil. I added a few drought-tolerant plants for color and trees to shade the house. And I'm saving fossil fuels by not using a gas-powered lawnmower.
Grow lots of stuff (except a lawn): To store the maximum carbon, always keep the soil surface covered with growing things such as trees, turf, vegetables, flowers and cover crops. The more variety, the better. Grow plants with deep, extensive root systems and coarse, woody roots; shallow, fine roots decompose too easily. If I had it to do over again, I might not use as much decomposed granite as I did. At the time, I was focused on lawn alternatives, not on carbon sequestration.
So there you have some tools for carbon sequestration at home. Now go out there and do your part to fight climate change.
Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Rose Pruning” on Saturday, January 13, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Why do we prune roses? Is winter the only time to do it? What will happen if we don't? Should hybrid teas be pruned differently from floribundas? Join the Master Gardener Rose Team at this popular forum where resident experts will answer your questions about basic rose pruning fundamentals with research-based information. Topics include rose types, how and when to prune, what tools to use and how to care for them, safety and sanitation. No doubt each Master Gardener will have some suggestions for new plantings, too. Online registration (credit card only);Mail-in/Walk-in registration(check only or drop off cash payment).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
