By Yvonne Rasmussen, U. C. Master Gardener

This time of year, as the weather starts to cool and we get a little more moisture in the air, we start to see some fungi in the garden. These might be mushrooms growing in the lawn or at the base of a tree, or conks growing out from the trunk. Other smaller fungi can produce white, black or orange spots, fuzzy material or residue on leaves. Still others make strange forms we might not recognize as fungi, such as puff balls, earth stars, galls or masses on branches or soil.

Some of these peculiar protuberances are caused by the closely related slime molds, such as the so-called “dog vomit” slime mold seen in the spring. This mold produces a bright yellow, frothy-looking growth on soil, often near the base of trees or other plants.

Fungi play an important role in the environment. They help decompose plant material that cannot easily break down otherwise.

But they can also cause plant diseases and problems in the garden. Fungi generally need moisture for reproducing, which they do by means of spores. Generally spread by wind or water, spores are a little like tiny seeds. The powdery substance you feel on the underside of a rose leaf  infected with rust is the rust spores. You can sometimes see spores on the underside of a mushroom, or in the smoky substance from a puffball.

Althought some fungi are edible, others are deadly poisonous and some are major allergens.

In the fall, powdery mildew often develops on the leaves of vegetables and ornamentals. It may look like white spots or a dusty coating on the leaves. Leaves infected with powdery mildew will eventually turn yellow, die and fall off.

Powdery mildew prefers cool, moist places. It does not do well in full sun and heat, so it appears first on plants in shady areas.

To avoid powdery mildew, plant in sunny locations and provide good air circulation. Keep plants pruned properly to encourage air circulation and don’t over fertilize. Too much fertilizer promotes fast, weak, leafy growth that will need more water. Excess nitrogen in the soil—what the plants can’t use—washed into our waterways and promotes algae growth.

For many vegetable crops and deciduous plants, there’s no good reason to treat for powdery mildew since the plants will soon be removed or go dormant. Most treatments can prevent the fungus, but they don’t cure it. This means you need to treat before you see symptoms.

Treatments need to thoroughly cover all susceptible plant parts. Mild to moderate symptoms can be treated with horticultural oils or plant-based oils. Follow package directions carefully. These oils can damage plants if used within two weeks of a sulfur application, or when temperatures are high, or if plants are drought stressed.

University of  California Cooperative Extension has three free “Pest Note” publications related to controlling powdery mildew. You can read these publications online or pick them up in the Napa County Master Gardener office (address below).

Mushroom are generally beneficial in the garden because they break down organic matter. They grow on buried wood, dead roots and other plant debris. Removing the mushrooms will not remove the fungi from your yard because most of the fungus is actually underground or in the plant tissue. The mushroom is only the fruiting body.

It’s like harvesting an apple from a tree. You remove the seeds but the tree lives on. For fungi, spores are the equivalent of seeds. They can travel great distances on the wind.

Because some mushrooms are toxic, you may want to remove them to keep them from being eaten by small children or pets.  If you suspect mushroom poisoning, contact California Poison Control at 800-222-1222. If possible, keep a piece of the suspect mushroom or take a photo of it so you can accurately describe it to poison-control or medical personnel.  If you suspect your pet has eaten a toxic mushroom, contact your veterinarian.

University of California Master Gardeners do not identify mushrooms, nor can we determine if they are edible or not. But we do have Pest Notes available on mushroom control.

To learn more about the biology of mushrooms and other fungi,  consult the websites of the Mycological Society of San Francisco (http://www.mssf.org), the Bay Area Mycological Society (http://www.bayareamushrooms.org) or the Sonoma County Mycological Association (http://www.somamushrooms.org).

By Sue Hurley, U. C. Master Gardener

The first time I gazed upon a dahlia I was with my father, driving up the Arlington Circle in Berkeley. I spotted a driveway filled with black pots and tall plants that had dinner-plate size flowers.  I had never seen anything like them.

Dahlias are a perennial that grows from tuberous roots and blooms from mid- to late summer until first frost. I must warn you now: Collecting them can be addicting.

I love them because they make wonderful cut flowers and last a  long time. The best dahlias for cutting are those with multi-petaled medium to small flowers. Large dahlia blossoms can be floated in a bowl.

Dahlia blossoms range in size from two inches in diameter to dinner plate size. They come in 15 hues and may be a solid color, bicolored or multicolored. There are 19 different shapes, including single, cactus, ball, informal and formal decorative, and pompon types. Dahlias range in height from 12-inch dwarfs to 8-foot giants.

Wait until after the last spring frost to plant them. The soil should be warm enough by mid May. Dahlias love full sun and do well in our Mediterranean climate; they will tolerate light afternoon shade in very hot areas.

Dig a hole one-foot square. Work some peat moss or steer manure into the soil. I also work a small handful of bone meal into the bottom of the hole. Plant the tuber horizontally four to six inches deep.

Drive a stake of appropriate size into the ground now so that you don’t damage the roots later on. Dahlia tubers have small “eyes,” which are the growing points of the plant. Place the stake a couple of inches from the eye so you can easily tie the stems to the stake for support.

Now cover the tuber with soil and water well. Snails love the new sprouts so scatter some snail bait. After they sprout, dahlias will need deep watering two to three times a week, and more often in  warm weather.

Dahlias like low-nitrogen fertilizers such as those used for vegetables. Give them the first feeding a month after planting, and another feeding three to four weeks later. High-nitrogen fertilizer can produce small blooms, no blooms or weak stems, and cause the tubers to rot or shrivel during winter storage.

In the fall, dig up your dahlias two weeks after a killing frost. They will be brown then. If you dig too early, the tubers will not store well. Cut the foliage to about four inches and lift the plant out with a spading fork. Wash the dirt off and let them dry overnight in a protected area. Tubers should be stored for winter in cardboard boxes.  Layer with sawdust or peat moss using newspapers to separate layers, and store in your garage.  Write the name, color, and size on each tuber with a black marker.

In spring, a few weeks before planting time, you can divide the tubers by cutting the stalks with a sharp knife. Leave one inch of stalk for each tuber, which in turn needs at least one eye or bud to enable a new plant to form.  Place the tubers in a tray of wet sand to encourage new sprouts, or sprinkle occasionally with water until it is time to plant.

Would you believe that there are even “tree dahlias” that can grow to 20 feet?  They are multi stemmed and grow each year from permanent roots.

I decided to try my luck with one that a fellow gardener was trying to get rid of. I must say that I had a very hard time trying to get a piece of the root using a pickax. So be cautious when planting a tree dahlia because it might be hard to move or remove.

The flowers bloom in late fall on branch ends and are four to eight inches wide. Cut the tree to the ground after frost. Plant them in full sun or part shade. They will grow from cuttings.

Tree dahlias can be dug in the fall or left in the ground over the winter. Nurseries rarely sell them because they are short lived, but their fall flowers may take your breath away.

Free Workshop: Early winter is the best time to plant bare-root fruit trees, the least expensive way to purchase them. Napa County Master Gardeners will hold a free workshop called “All About Fruit Trees: Selection and Planting” on Saturday, November 7, from 9:30 a.m. to 11:30 a.m., at Napa Valley College’s Upper Valley Campus, 1088 College Avenue, in St. Helena. The workshop will be repeated on Saturday, November 14, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. You will learn planting techniques, what to look for at the nursery, and what characteristics to consider in your decision. This workshop is the first in a three-part series. Reservations are recommended; call 707-253-4221.

By Bill Silfvast, U. C. Master Gardener

Do you have cute little animals in your backyard that you enjoy watching as they chase each other around the tree branches and hop along the fence, occasionally sitting up to look around at their beautiful environment? You might even get the urge to cuddle them since they appear so lovable.

Or do you have awful little pests that eat your homegrown fruit, including figs, grapes, walnuts, persimmons, kiwi, cucumbers and tomatoes? Do they dig holes in the ground to store nuts, eat all of your bird seed, make messes on your patio, eat through the roof of your garden shed to gain access to some bird seed, or generally just make nuisances of themselves?

Both descriptions apply to the same creature: the squirrel.

Although we don’t like to think of them as such, squirrels are members of the rodent family. Perhaps it’s the fluffy, bushy tail that allows us to distinguish them in our minds from rats and mice. The word squirrel comes from the Greek word for shadow tailed, because squirrels use their tails to shade their bodies.

Squirrels cannot digest plant cellulose, so their diet consists mainly of foods high in protein, carbohydrate and fat. Nuts are an ideal food for them. But once their buried nuts begin to sprout in the spring and are no longer tasty, these creatures have a difficult time finding food. They will then resort to eating the buds of trees and plants.

As you may have noticed in your own garden, squirrels typically consume a wide variety of foods, including nuts, seeds, fruits, fungi and some types of green vegetation. They have also been known to eat insects, small birds, young snakes and smaller rodents if they get hungry enough.

Their cleverness is readily apparent. They dig holes in planting pots to reach the bulbs they love to chew on. They steal the seed out of bird feeders. They bury food in the ground, or find crevices in roof eaves to store food. Their sharp teeth provide access to many places that we might normally consider “squirrel proof.” They will even chew on the insulation of wiring as a food source.

Carefully sealing your shed, garage or house will usually keep them out, but check regularly for chewing marks if you have a squirrel problem.

The female squirrel typically has one litter a year, consisting of three to four young. One aspect of the mating ritual, which you may have observed, is an extended chase, mostly among tree branches. The young are born in around 40 days, and they reach full body size in about four months.

If you consider squirrels a pest on your property, you may want to investigate methods for control. Some people resort to shooting them or putting out rat poison. But there are more humane approaches.

One idea is to contact a humane animal removal company. They set traps and remove the squirrels to a remote location. You can find these companies online or in a telephone directory.

Another method is to use a safe repellent. The squirrel’s most feared enemy is the fox. So fox urine makes a great deterrent. Sprays or bottles of the urine can be disbursed in your garden, or pellets containing the urine can be buried in the ground. Check hardware stores or online sources for these products.

Whether you enjoy watching squirrels or prefer to bid them good riddance, you’ll have to admit that they are cute little creatures. If only we could figure out how to have them around without having to tolerate their bad behavior. 

Free Workshop: Early winter is the best time to plant bare-root fruit trees, the least expensive way to purchase them. Napa County Master Gardeners will hold a free workshop called “All About Fruit Trees: Selection and Planting” on Saturday, November 7, from 9:30 a.m. to 11:30 a.m., at Napa Valley College’s Upper Valley Campus, 1088 College Avenue, St. Helena. The workshop will be repeated on Saturday, November 14, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension , 1710 Soscol Avenue , Napa . You will learn planting techniques, what to look for at the nursery, and what characteristics to consider in your decision. This workshop is the first in a three-part series. Reservations are recommended; call 707-253-4221.

by Penny Pawl, U. C. Master Gardener

Swales are ditches or trenches that catch rainwater for the purpose of conserving it in the soil. And if you top the swale with compost, you will gradually improve the water-holding capacity of the soil underneath.

Most swales are created on hillsides to keep rainwater from washing downhill, but mine are on the Napa Valley floor. They are not straight but rather bend around the plants already in the area. They are about two feet wide and 12 to 15 inches deep. Compost was spread on top of the soil including inside the swale.

Last winter, rains filled the swales up three or four times. Each time, it took about three days for the water to be absorbed and stored under the swale. I have been planting a dry habitat garden in this area. Eventually, these drought-tolerant Mediterranean plants, which have been in the ground only one to two years, will be on their own, with no additional water.

Because my plants were young, I watered every few weeks this past summer. A slow-growing Hollywood juniper that had been in the ground for a long time, with no water, doubled in size this past  year. I can only presume it is because of the additional moisture provided by the swale.

As the roots of the plants go deeper and I continue to add compost on the surface, the water-holding capacity of this area should increase.

Last winter I placed a couple of garbage cans under downspouts, covering the cans between rains. I used this water on potted plants throughout the winter. Since then I have acquired two 300-gallon plastic containers. They rest on a raised platform under rain gutters, so after they fill, I can attach a hose and get some water pressure.

Because of the West’s growing water shortage, people are devising more ways to save rainwater. Some methods are elaborate, while others, like mine, are simple and inexpensive.

You can buy adapters to cut into gutters to direct the water and flat-sided tanks that butt up against the side of your house. These tanks are lidded and usually made of dark plastic so that light does not get inside. If kept covered, the water stays clean and free of mosquito larvae.

So how much rainwater can you glean from your roof? Most roofs are pitched, so a 1500-square-foot house may have a roof with double that surface area. In that example, an inch of rain will produce 1000 gallons.

To see how much rainwater you can save, check the chart at www.rainwater-green.com/RainfallCharts.pdf.  Driveways, parking lots and streets also displace rainwater. In our area, any water not retained likely ends up in the river and bay

Some states do not allow collection of rainwater. Others allow limited collection to protect the interest of those downstream. California does not restrict rainwater collection, so you may harvest what you can.

Of course you can also save on water use by selecting plants that tolerate our dry-summer climate. When choosing plants, check their water requirements. You can also make plans to start eliminating lawn as that patch of grass is the biggest water user you have.