- Author: Amy Breschini
It's always in the summertime that we get inundated in calls at the Helpline about dying redwoods. I was just going through my archives and found a great answer to an incoming email about dying redwoods. Because water is such a valuable resource, I won't just hint around about it, but redwoods are native to areas of California that have about 40 inches of rainfall per year, mild weather and heavy amounts of fog. Average rainfall in Paso Robles is about 15 inches, low humidity and often has very sandy/silt soil that drains quickly.
Here's the question:
Dear Mary,
We are still trying to find a solution to our dying redwood trees. The irrigation schedule is now 2 gals per tree, per day, 4 days a week. The trees were shipped in 15 gallon plastic containers. The trees were planted with sufficient room for root growth and to allow for the planting mix to be placed at the base of the hole, as well as around the tree. The planting mix was approx. 20% compost, 80% natural soil. We have had some hot weather lately. What effect can this heat have on these trees? I appreciate your feedback.
Thank you,
C
Answer:
There are procedures for determining the water needs of plants in a landscape. Your particular situation on the edge of the Nipomo Mesa in a coastal area means that exposure is going to bring up the water needs of the plants. Additionally, redwoods are high water demand plants and obtain much of their needed water from fog drip. Somewhat more limited in your exposure.
We can estimate these conditions numerically, and what those calculations indicate is that your redwood trees will use about 3/4 of the water that a lawn planted on the same total area would use. Now we do have good data on the water needs of a clipped grass lawn in these coastal areas, and the requirements are about 4.6 inches of water during July. So your trees are need about 3.5 inches of water. Think of it like a rain gauge but upside down. That's a tough concept to convert to how long to run your drip system.
You can calculate the area for each tree, and we know that it takes a little over 27,000 gallons of water to cover an area 209' by 209' (an acre). If you convert that 3.5 inches of water, corrected for the efficiency of the irrigation system and for the spacing of your trees, that means each tree is using about 10 gallons of water per day. Yes, per day.
Your weekly irrigation amounts are 8 gallons per tree per week, but the tree needs 70 gallons per week. For a period of time, the tree will be able to use water that is stored in the soil from winter rainfall. We know that in most sandy soils, there is about 1 gallon of water per cubic foot of soil. The later the spring rains and the greater the number of foggy days, the less water you need to apply with the drip system. We did have some later spring rains, but it has been clear and hot most of June and July.
Redwoods benefit from less frequent deeper water than will be supplied with short irrigations. So having said all of this, here is my recommendation.
1) Identify 2 trees - one that is doing well, and one that is just starting to look like it's suffering. Don't pick a 'dying' tree because it's likely already gone.
2) Run your irrigation system for the normal two hour set. Wait until the next day before going to step 3.
3) Start about 2 foot from the edge of the canopy of both trees and dig a trench towards the trunk that goes down at least 2 feet if not more. Look for moist soil and roots. If there is adequate soil moisture, you will be able to form a ball with the soil when you hold it in your hand. If the soil moisture is low, then you won't be able to form a ball. You should find roots from the tree throughout the trench. Fill in the trenches.
4) Next, run your irrigation system for 6 hours and repeat the above on the other sides of the same trees on the day following the irrigation. Look to see how much more water movement you've gotten from this longer irrigation. This irrigation would be supplying enough water for the tree for one day.
Let me know what you find, and if you can send pictures that'd be great!
Mary B.
- Author: Terri Sonleitner Law
Master Gardeners Offer Workshop on Fire Safe Landscaping
by Terri Sonleitner Law
UC Master Gardener
Q. What can I do in my landscape to make my home less vulnerable to
wildfires? John B., Paso Robles
A. That’s a timely question. Wildfires can be threatening, but with proper
planning you can have a beautiful landscape and create a Fire Safe Zone
around your home.
Begin by creating and maintaining a defensible space of 100 feet around
your home that includes a lean, clean and green zone of 30
feet, plus a reduced fuel zone of 70 feet. Greater defensive zones are
necessary if your home is on a steep slope or in a windswept area. Here’s
a closer look:
Green zone: Remove flammable vegetation and combustible materials
within 30 feet immediately surrounding your home. This includes keeping
trees trimmed, removing needles and leaves from roof and gutters, and
removing dead or dying plants, leaves and debris. Increase spacing
between plants, and use fire resistant plants. Regular maintenance like
pruning, weed control and adequate irrigation is necessary to maintain the
fire resistance of your landscape.
Reduced fuel zone: Create this next to the green zone, extending out
an additional 70 feet, or to your property line. Open space between plants
improves chances of stopping a wildfire. Either create greater horizontal
and vertical spacing between plants, or if you have trees, remove plants
growing beneath the trees that are greater than 4 inches in height. Remove
lower limbs of trees to at least 6 feet, and remove one-third of branches on
any smaller trees.
The Master Gardeners, with assistance from the Fire Safe Council, San
Luis Obispo County, installed a new Fire Safe Landscape display in our
demonstration garden. Our free July workshop will focus on Fire Safe
Landscaping this Saturday from 10 a.m. to noon in the Garden of the
Seven Sisters, 2156 Sierra Way in San Luis Obispo. Parking is free in the
adjacent parking lot. Additional information on Fire Safe Landscaping is available from the Fire
Safe Council: http://www.fscslo.org/Solutions.html# and from University of
California
publications:http://firecenter.berkeley.edu/docs/CeMasterGardener8322.pdf
Have a Gardening Question?
Contact the University of California Cooperative Extension Master
Gardeners: at 781-5939 from 1 to 5 p.m. on Monday and Thursday; at 473-
7190 from 10 to 12 p.m. on Wednesday in Arroyo Grande; and at 434-4105
from 9 to 12 p.m. on Wednesday in Templeton. Visit the UCCE Master
Gardeners Web site athttp://ucanr.org/sites/mgslo/ or e-mail
mgsanluisobispo@ucdavis.edu
- Author: Tami Reece
- Editor: Noni Todd
Horticulture at the Paso Robles Mid State Fair
By Tami Reece
Master Gardener
In July, if you are a gardener in San Luis Obispo County, you look forward to fresh picked corn, juicy ripe tomatoes, crunchy cucumbers and the Paso Robles Mid State Fair. The fair started in 1945 and for more than 66 years San Luis Obispo County gardeners have proudly showed their gardening skills to their family, friends and the community at large. Entries will include locally grown produce and can only be current season crops. Did you know that the produce divisions are divided into two shows, allowing the exhibits to remain fresh throughout the fair? There will be an assortment of citrus fruits, stone fruits, apples, herbs, nuts, vine crops and every vegetable that will be in season during the summer months. If you are an especially talented gardener, you can enter a Harvest Basket which includes only produce, herbs, and fruit grown by you.
Floriculture is also a popular exhibit at the fair. With many beautiful flowers being exhibited, Dahlias are always a show stopper. Joe and Jill Sabol have been growing Dahlias for over 12 years and receive numerous awards each year at the fair. Joe has stated the Dahlia shows have significantly improved over the years, mainly due to the two outstanding judges, Kevin Larkin and Karen Zydner, who travel from south of Santa Cruz each year to judge at the fair. After judging the exhibits, the two judges will return in the afternoon to help the exhibitors grow better flowers by covering many aspects of propagation and cultivation of prize winning Dahlias. The San Luis Obispo Dahlia community is very appreciative of these two judges.
If you have traveled throughout the state, you will also realize the Paso Robles Mid State Fair has one of the most beautiful fair grounds in California, offering spectacular flower beds, a wonderfully landscaped rock mountain with waterfall and even a small vineyard. As you wonder through the many exhibits at the fair don’t miss the prize winning horticulture and floriculture exhibits!
The photo below was taken by Master Gardener Joe Sabol of exhibit judge Kevin Larkin with exhibitor Betty Cook.
- Author: Jim Borland
Everybody knows that plants can die of thirst, but don't forget you can
also send them to an early grave by overwatering. When we overwater,
the soil becomes saturated and forces out vital oxygen, and we literally
drown our plants. So then how do we know when to water our plants?
Here are some simple and useful methods that should help.
First thing to do is make a close observation of your landscape plants.
A plant's stress symptoms which indicate it is too dry include wilting
or folded leaves, dull or gray-green foliage, leaf drop, and new leaves
smaller than normal. These symptoms often first appear during the
hottest time of the day, but before you automatically add water, check the soil moisture first!
The soil can be checked by the "feel" test where you dig down 6 to 8 inches
in your garden, grab a handful of soil from that depth and squeeze it in
your hand. Moist soil will feel very cool to the touch.
Both the tactile sensation and your analysis will vary for
different soil types, but we can summarize by considering two broad
categories: sandy loam and clay soil. Sandy loam has poor moisture retention characteristics, so if you squeeze that soil and have some moisture on your hand, and if the dirt forms a weak ball, there is a good amount of moisture available for your plants. Clay soil, on the other hand, is excellent at retaining moisture so it will form a tight ball and feel slick when there is an adequate amount of moisture present.
You can also purchase small, portable soil moisture meters for
determining when to water, which cost pennies and are available at local garden centers. There's new technology in irrigation controllers, referred to as "Smart" controllers which use current weather conditions being delivered from nearby weather stations and adjust automatically. They also have the capability of having underground probes buried at root depth, to signal the controller to begin an irrigation cycle. This is not only helpful in giving your plants the optimum water, but helps to conserve water during the rainy season.
Determining whether a plant needs water is always a judgment call. With practice and good observation skills you can have a healthy, properly watered garden.
- Author: Andrea Peck
What should I be doing in my garden during July?
Leo P.
Fireworks and socializing may dominate the calendar for July, but whether you plan to prepare for revelers or escape the hubbub, there are plenty of chores to enjoy in the garden.
Guests and plants are hungry during this festive month; feed warm-season annuals and lawns, subtropicals and summer vegetables at this time. Hold off on feeding tomatoes, however, excess nitrogen impedes fruiting. Baby your melons by placing an aluminum pie tin underneath growing fruit. The reflected heat improves growth, while the tin keeps sensitive fruit off moist soil. Once 3 to 4 fruits have established themselves, remove new blossoms. You may have a smaller harvest, but fruit will taste more flavorful and grow larger. Similarly, wood chips or Styrofoam placed underneath pumpkins, squash and gourds prevents rotting.
Time to pinch and prune! Pinch leggy petunias and fuchsia seed pods. Fertilize and pinch Chrysanthemums for a final time. Prune wisteria for the last time and poinsettias by 15%. Deadheading flowering plants keeps them at their blooming best.
Hopefully your hard work has paid off and your harvest is bountiful this year. Pick fruit regularly and discard any that has fallen on the ground. Sanitary practices prevent a host of furry visitors. Gophers, always on the unwanted list, are best controlled by trapping. A weed-free strip or buffer around your garden deters voles (meadow mice) and moles. Prepare for the heat by covering the soil with mulch.
If you’re looking for summer color, verbena, zinnia and petunia don’t disappoint. Impatiens brightens shady areas. Divide bearded iris clumps every three years. It’s not too late to plant summer squash inland or corn on the coast.
Get a leg up on spring perennials. Biennial seeds should sprout by September. Plant seeds in pots and transplant seedlings into the garden when they reach 4-5 inches. Canterbury bells, foxglove and hollyhocks are pretty garden choices.
Keep fire safety in mind by removing dead limbs and leaves. Long grass, weeds and shrubs, especially near the home, are hazardous. Finally, sit back with a snack and enjoy your efforts. 
Contact the University of California Cooperative Extension Master Gardeners: at 781-5939 from 1 to 5 p.m. on Monday and Thursday; at 473-7190 from 10 a.m. to noon on Wednesday in Arroyo Grande; and at 434-4105 from 9 a.m. to noon on Wednesday in Templeton. Visit the UCCE Master Gardeners Web site at http://ucanr.org/sites/mgslo/or e-mail mgsanluisobispo@ucdavis.edu
