 Laguna Hills Nursery |
|
|
|
Garden Check List for Early Fall
|
|
|
|
|
|
Greetings!
Local nurseries always promote fall as a great time to plant. The days are getting shorter and cooler, therefore there is less stress on newly installed plants. The soil is still warm, so roots will grow fast. Just watch out for Santa Ana winds. A strong warm wind with zero humidity is just about the worst stress a plant can get. Make certain new trees are staked very securely. Even then, every single leaf can be torn off.
The summer that just ended was about as cool a summer I can remember. 1996 was cool also. Contrast this summer with a year ago when we had 4 weeks in a span of 5 that were all above 95 degrees.
In about a week the soil should stay cool enough to plant your fall annuals. Peas, broad beans, carrots, radishes, beets, cilantro, lettuce, chard, and cabbage are edibles to plant. Cyclamen, Iceland poppies, pansies and violas, lobelia, nemesia, and primroses are annuals to plant. Don't forget bulbs like daffodils, narcissus, freesias, ranunculus, sparaxis, and leucojum. Tulips and hyacinth are a lot of work for just a few weeks of color.
The remainder of this newsletter will discuss current problems in the garden.
|
LAWN PROBLEMS
 The vast majority of lawn problems are due to lack of moisture, although not necessarily a lack of irrigation. During the heat of summer, grass needs about 40 minutes of watering per week to stay green. The biggest problem is that local soil will only absorb about 4 minutes of watering per hour. This means that if your lawn isn't totally flat, when you water it for a period of 10 minutes most of that water is wasted as it runs off your property. It is ideal to water your lawn for 4 minutes at a time, 2-4 times (at least 1 hour apart) during the day you water your lawn. During the hottest weather you would water every 2 days. (If the day tops 100 degrees, you may need to water every day.) For most of summer you would water every 3 days. During fall you would average about twice per week and winter, about once per week.
How wet does the soil need to be? The soil for grass to remain green (actively growing) needs to be moist at least 12 inches deep. You can push a rod (made of wood, metal or fiberglass) through moist soil of any type (except when rocks or big tree roots are in the way). I use and recommend a 4' long piece of metal rebar. If I can push it into the lawn at least 12 inches using the strength of my arm, the soil moisture is adequate. In my observations the grass starts looking stressed at 8". At 6" the blades roll up and become dull. At 4" the tips dry up and turn white or tan. At this point the grass plants can go dormant and the lawn will be mostly brown, or even become patches of bare soil!
Once the lawn turns brown, I've seen a lot of homeowners then reseed and start over. When lawns go brown or bare they are still alive for at least 3 months. This means that in most cases reseeding is not necessary. All the homeowner has to do is restore 12" of moisture and the dormant grass starts growing.
During the summer of 2009 I had a sprinkler head that got clogged. By the time I got around to fixing it we had about 100 square feet of brown grass. It was several months before I got it fixed. Within a month of repairing the sprinkler about 80% of the area recovered and just a patch about 2 square feet remained bare after several months.
The goal is to maintain the moisture at 12" all year. Some wet years (like 1998 or 2005) the soil moisture reached about 4' deep! The lawn looked great! Keep checking the depth with a rod. The water district gives us recommendations based on average weather conditions, but weather is rarely average and the microclimates in your garden affect water usage tremendously.
My other goal is to not let a single drop of irrigation water make it to the street in front of my house. Water flowing into the gutter is totally wasted.
This summer I only had to water about 6 times per week (4 minutes per cycle).
I have heard that St. Augustine grass prefers 18" of moisture, but I've not owned a St. Augustine lawn and haven't checked.
A few decades ago, one of the larger sod suppliers, I believe it was Pacific Sod, tested all the different grasses they grew to see how long they could stay alive with no irrigation during the dry seasons. They found that all grasses they trialed could stay brown and dormant for at least 3 months and recover completely. This is something to remember in case we have a year of severe drought and water restrictions. Just turn off the water for the summer. If your homeowners association sends you letters, just paint your brown grass with green dye. When fall comes revive your lawn with normal irrigation. Most other common garden plants will not tolerate a dry summer.
I know there are some new native western grasses that are being promoted for requiring less irrigation. I don't know if they still require 12" and just use less moisture (so less frequent irrigation is needed) or if they can tolerate drier soils, or both. The latest is a type of Buffalo Grass that is adapted to warm winter climates. Regular Buffalo grass goes dormant in winter and has trouble waking up in the spring.
Many "experts" will tell you that brown areas are caused by fungus or insects. I do see lawns that are less than 2 years old being attacked by caterpillars. Older lawn are rarely attacked. We do get fungus spots when the summers are hot and humid (definitely not this year).
When I was in high school (back in the early 1970"s) my father was selling hundreds of gallons, perhaps thousands of gallons of lawn insecticide every summer. People with brown patches would swear that if they applied it every week, the grass was greener. What they were actually doing, was watering more effectively. The insecticide wasn't necessary. The instructions on the product said to water deeply first. Wait one hour. Apply the poison through a hose end sprayer with more water. Wait a few minutes. Water everything in. That much water one day a week was making a visible difference.
I haven't treated my lawn for insects for nearly 2 decades. I do find it rather interesting that young lawns attract caterpillars (webworms and cutworms). A few years ago my neighbor decided to redo her front lawn. All the lawns on our street are identical (Tall Fescue). The first summer after she replaced her lawn you could walk up to it and grab handfuls of caterpillars feasting on it. The older lawns on either side weren't infested at all. Be aware that insects don't make the lawn turn brown. They just eat the blades and leaves thin or bare patches.
I am seeing many lawns being overcome by crabgrass. It is nearly too late to kill it this year. Crabgrass is one weed that can kill off the desirable grass if not treated by pulling or spraying, or preventing. Crabgrass would actually make a decent lawn if it didn't totally die every winter. It survives winter as seed.
I had a customer complain one December that the lawn he started with seed purchased at our store kept dying every winter. He was tired of reseeding every spring. He thought there was something wrong with the grass we were selling him. I told him to bring me the remnant of his lawn. He brought me dead crabgrass. Apparently the seed came up fine but crabgrass took over the lawn during the summer (it is a bit difficult to tell the difference between crabgrass and tall fescue), killed the fescue he had planted, then died off during fall. I told him how to fix the problem and I never heard that complaint again.
October is the best month to replace or install a lawn. For most purposes the Tall Fescue lawns (like Marathon, Medallion, Bonsai, and Triple Crown) are the easiest grasses to grow. All other lawns require annual removal of thatch.
If you want a perfect lawn, don't hire a gardener. Or if you do, make him (or her) use your mower, not his. A gardener's mower is the #1 way to get infestations of crabgrass and devil's grass (bermuda). Mowers transfer weed seeds (it takes just one) and viable clippings of bermuda and other nearly uncontrollable running grass weeds.
|
Sharpshooter Still Causing Tree Deaths
 Back in the 1980's a bug called the GLASSY-WINGED SHARPSHOOTER made it to California. This bug is native to the Southern US. It is like a disease carrying mosquito. It can suck right through the stems of many plants and trees and transfer diseases.
Currently it is quite common, you can find at least one on any large shrub or vine in the garden. They are about the length of a fingernail with a lizard-like head. They have good vision and will hide when you approach by moving to the backside of the stem. At dusk, in the setting sun, you might notice tiny drops of water streaming from the tree or vine above. This is the sharpshooter's trademark excrement raining down.
One type of disease that it can carry is a bacterial infection called Bacterial Scorch. It made headlines when the disease started killing grape vines in Temecula This bug could cause the demise of the Wine Industry in California and Oregon. The goal at the moment is to not let this bug get north of the mountains that separate Southern California from the Central Valley.
Researchers are trying different ways to control it.
The natural predator has been introduced. This can keep the population small, but can't eliminate it.
Researchers are developing grapes that are immune to the disease that can be used to make wine. UC Riverside is also working on a immunization treatment.
At present, the main way to stop the bug is to treat the vineyard (at least the outer portions) with a systemic insecticide. Anytime this bugs sucks on the sap of the vine, it will get a lethal dose. Apparently, none of the insecticide gets into the fruit.
In our own gardens, this bug is killing other plants also. There are many strains of the Scorch disease. Each strain can kill one or more types of plants. The biggest problem is that the disease can exist in many plants with no symptoms or effects. Just imagine if every plant in your garden harbored diseases that could spread to you! This is the main problem with this disease. It can exist in a multitude of hosts.
In one African country the Citrus orchards were infested with a certain virus specific to Citrus. To stop the disease they burned all the Citrus and didn't replant for 5 years. Without a host the disease disappeared.
With Bacterial Scorch diseases this strategy won't work.
In the 1990's we saw the quick decline of the majority of Oleander bushes in central Orange County. The disease didn't kill the roots, but any new growth that emerged was attacked again. We stopped selling Oleander plants around 1992.
Subsequent research has suggested that Bacterial Scorch is responsible for disfiguring and killing many other plants.
OLIVE TREES
PURPLE-LEAF ORNAMENTAL PLUMS
LIQUIDAMBER (SWEETGUM)
MULBERRY
NANDINA HEAVENLY BAMBOO
CRAPE MYRTLE TREES
ALMOND TREES
The disease usually starts by causing one branch to turn scorched, brown, or become leafless. Soon after, other branches also die, until the entire tree is affected.
I really feel badly about the Olive trees. They are one of the signature trees of Mediterranean landscapes. We are not certain that just treating one tree with a systemic will keep it from getting infected. You probably have to treat a whole neighborhood.
Purple-Leafed Plums are interesting. The disease does not affect green-leafed plums. I saw a whole street of about 40 purple-leafed plum trees die, but one that still exists was a green-leafed sucker that was trained into tree form. I do think we are loosing a lot of fruiting peach trees to a similar Scorch disease.
We are seeing Liquidambers with a lot of dead branches.
I'm not yet certain if local Crape Myrtles, Mulberries or Heavenly Bamboo are being affected.
Most of the ugly Crape Myrtle trees seen in neighborhoods are just specimens that were originally grown in an organic based soil. These trees have only a few, unhealthy roots and their leaves look scorched all summer and fall. They don't die, but may take decades to overcome the grower's mistake.
|
|
|
|
 Citrus Problems
You are probably aware that Citrus trees are threatened by a new bug called an Asian Citrus Psyllid. Hopefully, you'll never see this bug (it is the size of an aphid) or the disease it can spread. So far, only a few specimens have been discovered in Orange County, but the CDFA is hoping that it can be totally eliminated. (The Sharpshooter, on the other hand is well established and here to stay.) The psyllid does little damage but can spread a disease called Citrus Greening Disease. This is a virus that slowly kills the tree. Florida is currently having major problems battling the bug and the disease. Florida made the mistake of allowing the psyllid to get established. It came before any sign of the disease, but when the disease arrived decades later the bugs spread it very quickly.
The relatively new Citrus pest that causes trouble in most gardens (mostly on newly planted trees) is the Citrus Leaf Miner. From July-October this caterpillar will cause all of the new growth to curl up with silvery trails. When heavily infested the new foliage dies back. Mature orange, grapefruit and tangerine orchards are not being treated. The trees look bad but the bugs don't affect the spring bloom or the developing fruit. Lemons and limes can suffer the loss of some crop as these will bloom in the fall also. Spinosad is an organic insecticide that will kill the leaf miners for a period of 2 weeks. Supposedly there are native predator insects that will feed on this pest and will eventually make treatments unnecessary.
Actually the biggest problem I see with Citrus trees (especially those purchased within the last 20 years) is the same as with the Crape Myrtles trees mentioned above. All retail citrus trees are grown in containers in a sawdust(compost)-based soil. Sawdust, or any compost, will eventually rot the Citrus roots, unless the soil the tree is planted in is fast draining and sandy. To make retail Citrus survive you can do 2 things:
(1) Purchase a 5-gallon or smaller tree and wash off half the soil that comes with the tree. Wash away the outer few inches of compost and expose some of the roots. Do not wash all of it off. Usually the center of the rootball doesn't have sawdust in it. The growers use better materials when the trees are in their starter pots. If you only wash off half the soil, the tree won't go into shock. If you do take off all the soil, you then need to remove all the leaves.
(2) Make a large hole and mix all the soil you take out with an equal part of sand. Plant the tree in this mound of sandy soil that you just created. With the extra aeration that sand provides, the compost should not cause problems. Water immediately and frequently.
Without rotting sawdust surrounding the roots, the tree can be irrigated without much chance of root rot.
|
26285 Verona Place
Mission Viejo, California 92692
|
|
|
|
|
|
|
