Organic mulch in garden

Do you have an area in your yard where you just can't get anything to grow? Have you struggled repeatedly with a prized plant or tree that just won't thrive? If you know what type of soil you have and are watering properly, it may be time to dig a little deeper to find out what's going on.

Check your soil texture. It dictates the way your soil drains and the amount of nutrients available to your plants. Providing the appropriate amount of water across the entire bed and at the right time also is of utmost importance.

Soil compaction is the next thing to look for. When soil is compacted, the air pockets are compressed, making it harder for roots to expand and grow and therefore harder for the plant to take up water and nutrients. Soil becomes compacted by foot traffic, use of heavy machinery, working the soil in overly wet conditions or when proper amendments — organic matter — haven't been added.

To improve your soil, apply a 2- to 4-inch layer of compost once or twice a year.

Aerating, especially in lawn areas, also can be helpful.

Soil pH is another important factor; it determines how acidic or alkaline the soil is, which affects plant growth, soil bacteria, availability of essential nutrients and soil structure as well.

Acidic soil has a low pH, and extremely low levels can cause a plant to become stunted or die. Plants that thrive in acidic soil include blueberries, azaleas, rhododendrons, hydrangeas, gardenias, camellias, crepe myrtles and pine trees. Adding soil sulfur, peat moss or iron sulfate will decrease the pH level.

Alkaline soil is high in pH and is generally deficient in nitrogen and other important minerals. A high-alkaline soil has higher levels of sodium that may be toxic to plants. Plants that grow in alkaline soil include clematis, heuchera, delphinium and dianthus.

If your plants have pale green or yellowing leaves, that may be a sign of nitrogen deficiency. Plants may be stunted or have much smaller leaves than normal. To increase nitrogen, add good-quality compost; grow cover crops, such as fava beans, borage and vetch, in the offseason; or add coffee grounds to the soil.

The amount of soil organic matter — decomposed plant and animal residues -- really does matter. It has been called the most complex and least understood component of soils. High levels of soil organic matter improve water and nutrient retention; help fend off compaction and erosion; balance pH levels; and even bind harmful pesticides and trace elements, keeping them from polluting our watersheds.

To increase soil organic matter, apply compost and mulch, reduce tillage, leave grass clippings on the lawn and rotate crops in your garden.

Earthworms are an excellent and essential indicator of healthy soil. They create burrows in the soil, allowing water to move through the soil and roots to more easily expand and grow. Dig out about 6 inches of soil and count the number of worms you find. Three to five is a good indication of a healthy soil. If you don't see any, your soil is lacking in organic matter.

By UC Master Gardener Rebecca Jepsen

This article first appeared in the July 20 issue of the San Jose Mercury News.

by UC Master Gardener Rebecca Jepsen

Knowing soil types and water requirements may help us grow healthy vegetable gardens and flowers, but it is also vital when it comes to trees.

Igor Lacan, environmental horticulture adviser for UC Cooperative Extension, says as we move toward warmer temperatures with less predictable annual rainfall, we will need to make smart choices about our landscapes.

“Even in a drought, it is essential to prioritize your trees,” Lacan says. “Trees not only support our native birds, bees and wildlife, they provide major ecosystem services to us as well. Urban trees lower the ambient temperature, thereby reducing the need for air conditioning, sequester carbon from the atmosphere, provide stormwater capture, decrease pollution and enhance the property value and aesthetics of your home.”

Start with soil
In order to practice responsible irrigation — using enough water to keep a plant alive and no more — knowing your soil type really does matter.

Soil type, or texture, refers to the proportions of sand, silt and clay particles in its makeup. Sandy soils are coarse and drain quickly. Plants in sandy soil need frequent watering and may need fertilizer.

Clay particles are very fine and become glued together when wet, and although clay soil can be slow to drain, it retains moisture and minerals, requiring little to no fertilizers.

The roots of newly planted plants may have a harder time getting started if the soil is hard and dense, but once established, plants tend to thrive in clay soils.

Silty soil is found along our riverbeds, lakes and other riparian areas. Particles are smaller than sand but not as fine as clay. It drains well and has good nutrient retention.

Loam represents a combination of sand, silt and clay and most of the Bay Area has clay or loam soil.

To tell what kind of soil you have, moisten a handful of it and give it a firm squeeze. If it holds its shape but crumbles when you give it a poke, you have loam. If it holds its shape without crumbling, you have clay. If it falls apart as soon as you open your hand, you have sandy soil.

Knowing your soil type will guide you in how much water to apply and how often.

To gage soil moisture levels, you will need to dig down to the root level. For trees, use a shovel or an auger to get 12-18 inches below the surface. After watering to this depth, soil should be moist but not drenched.

For mature trees, deep water infrequently, about once a month. Imagine refilling a 12- to 18-inch deep water reservoir around the tree's roots.

It's important to water beneath the entire canopy. Installing a Tree Ring Irrigation Contraption (TRIC) is a great way to accomplish this.

Newly planted trees may need only 10-15 gallons per week, but they may need additional water in extremely hot weather.

In all cases, a good rule of thumb is to water deeply and observe your tree. If the tips of the leaves and branches start to droop, it's time to water again.

You will then be able to properly set up your automated irrigations systems. But remember, they need to be changed seasonally as the weather and temperature fluctuate. Online watering calculators can also be helpful.

This article first appeared in the June 26 issue of the San Jose Mercury News.

by UC Master Gardener Rebecca Jepsen

Reports of Africanized bees in Contra Costa County, which turned out to be ordinary European honeybees, has people thinking a lot about bees and their place in our gardens.

Bees are responsible for pollinating nearly 30 percent of all the food we eat. Their cross-pollination also is crucial for the survival of most of our native plants.

"The diversity and abundance of bees in your backyard varies greatly on the diversity of flowers available," says Robbin Thorp, entomology professor emeritus at UC Davis. "Help encourage bees into your backyard and garden with a variety that blooms all year long."

Thorp recommends growing lavenders, rosemary, salvias, ceanothus, ribes, lupines and California poppies. For pops of color add asters, sunflowers, cosmos, penstemon, cuphea and nepetas. Plant herbs that both you and your bees will enjoy such as parsley, chives, dill, basil, borage, mint and fennel.

Here are some of the more common bees you'll likely find in your yard.

Honeybees, which are ¾-inch and can vary in color from blonde to black, represent only a small fraction of the total bee population but they play a critical role in pollinating more than 40 varieties of fruit, nut, vegetable and seed crops valued at more than $1.5 billion per year.

Bumblebees are up to 1-inch long. They are more round, and are black or yellow with white or orange bands. Bumblebees are social and, although similar to honeybees, generally have much smaller colonies. They produce only enough honey to provide for themselves and are not used for commercial production.

Carpenter bees are shiny, black and as large as a bumblebee. They drill into wood, a trait that gives them their name, to create tunnels where they breed and raise their young. Although you might see carpenter bees drilling into the side of your home or other wood structure, they will seldom do significant damage. Make sure all surfaces and your siding are painted as they prefer untreated wood. However, if you suspect they are doing significant damage, you can treat the holes with insecticidal spray or dust. Wait two to three days, make sure the holes are empty, and then plug them with steel wool and caulking.

Leafcutter bees are small, smoke-colored bees with pale abdominal bands. They are productive pollinators, often doing 20 times more pollinating than honeybees. They are passive, solitary bees that need bare ground in order to nest and lay their eggs. For this reason, don't practice wall-to-wall mulching. Leave some bare spots for the bees.

While some may be upset by seeing a bee swarm, Elina Niño with the Honey Bee Research Facility at UC Davis, urges people to remain calm.

"If you see a swarm or nest of bees, don't panic," she says. "Just move away as quickly as you can and call your local extension office or beekeeping association. Don't swat or try to kill them; a dead bee can release an alarm pheromone that could mark you as a potential threat to other honey bees."

This article first appeared in the May 29 issue of the San Jose Mercury News.

Remove all lower leaves, keeping just the top two to three sets. Allow the wounds to heal for a few days, then plant in a deep hole or sideways in a trench so that only the remaining leaves are above the soil. Roots will form where the leaf nodes were, resulting in a stronger, more stable plant as it grows.

Prepare your soil by mixing in 2 to 3 inches of compost. Add in some organic fertilizer if your soil is lacking in nutrients. For raised beds or containers, add in some fresh potting soil and slow-release organic fertilizer to ensure plants have the nutrition they need to grow and produce.

Choose an area that gets 6 to 8 hours of sunlight a day.

To avoid problems with fungus and disease, don't plant in an area where in the past three years you have grown tomatoes or plants from the same family, including eggplants and peppers.

Rotating your crops will help to avoid fusarium wilt and verticillium wilt, two common fungal diseases that affect tomatoes.

Fusarium wilt invades the plant through its roots. It is a serious problem that causes branches and leaves to become yellow and wilt; infected plants usually die. Look for plants labeled "F," which means they are resistant to fusarium.

Verticillium wilt causes leaves to yellow and turn brown before dropping off. The infection usually appears in a V-shaped pattern. Although it is seldom fatal, it reduces vigor and yield. Due to significant leaf drop, sun damage to the fruit also may occur. Buy plants labeled "V" or "VF."

Blossom end rot is caused by a calcium deficiency, often a result of irregular watering as well as a lack of calcium in the soil. Symptoms first appear as a water-soaked spot near the blossom end of the fruit. The spot will become brown, leathery and sunken, and may cover half of the fruit's surface. It's unsightly, but the fruit is still edible -- just cut off the damage and enjoy the rest. Avoid blossom end rot with regular and deep irrigation.

Another common tomato ailment is tobacco mosaic virus. It causes light green, yellow or white mottling on leaves, which may become stringy or distorted. It is usually caused by contact with tobacco products. Don't smoke or allow tobacco in or near your garden. Look for disease-resistant plants labeled "T."

Tomato and tobacco hornworms cause extensive damage to both plant and fruit. Look for black droppings or eggs on the leaves. It is best to hand-pick and discard them. If necessary, spray with Bacillus thuringiensis.

Russet mites are minute pests that can't be seen by the naked eye. Use a hand lens to identify their yellowish, conical-shaped bodies. They feed on leaves, stems and fruit, and if not controlled they will usually kill the plant. Apply sulfur dust or spray to young plants, and avoid planting near petunias, potatoes or other solanaceous plants that are often a host for the pest.

Blossom drop is caused by environmental issues. Insufficient pollination, lack of water, extremely high or low temperatures, and even smog -- all conditions we can't control -- are to blame.

by UC Master Gardener Rebecca Jepsen

This article first appeared in the May 1 issue of the San Jose Mercury News.