Restoring Soil

Several people commented on last week’s column on the carbon cycle. All endorsed the concept of restoring garden soil, to support its natural ability to sequester carbon.

One reader had questions about how to go about restoring garden soil. This is a Big Topic and you, good reader, might have your own questions, but you also might share his interests. My brief responses are below. Visit gardening.com for more details, including plant suggestions.

Q. Plow the grass under?

A. Losing the thirsty lawn is a good first step, because such monocultures are not appealing to wildlife. Plowing, however, could both promote re-growth of the grass and bring dormant weed seeds to the surface. A better approach is to kill the grass over several sunny weeks by covering it with clear plastic (solarization), or with newspaper or cardboard (smothering).

For information on Soil Solarization for Gardens & Landscapes, visit the University of California’s Integrated Pest Management webpage on the topic. The presentation emphasizes pest control; in this context, unwanted turf grass amounts to a pest.

The California Native Plant Society has Detailed lawn removal advice.

Q. Plant different grass?

A. Yes! California native grasses can provide the basis of an attractive meadow, which is more casual than a manicured carpet of turf grass. A meadow has unique aesthetic appeal; supports a variety of wildflowers and wildlife; requires little water, infrequent mowing, and no chemicals; and helps to restore the soil.

Kids on Native Grass Lawn
JACQUELINE RAMSEYER —
BAY AREA NEWS GROUP

Lily Baker’s front yard in San Jose
features a native grass lawn.
California native grasses help restore the soil.

For information on several California native grasses, visit the Tree of Life Nursery’s web page, “Masses of Grasses.”

A very good book by Carol Bornstein, David Fross, and Bart O’Brien is Reimagining the California Lawn: Water-conserving Plants, Practices, and Designs (2011).

Q. Grow more trees?

A. Absolutely! Trees and large shrubs are attractive additions to the landscape, valuable participants in the carbon cycle, and welcomed by all forms of wildlife. Invest a little research to select trees will thrive in your climate, and grow to an appropriate size for your landscape. Again, California natives are good choices.

A good introduction to California native trees and larger shrubs is available from the non-profit Nipomo Native Garden, which has produced a web page, “Native Trees for Landscaping and Wildlife.”

Q. Eliminate ground cover in favor of something with deeper roots?

A. Ground covers are any plants that hug surface or rise to any height up to four feet. Most importantly, they protect soil and soil microbiota from baking in the sun, or eroding. During the fall and winter, plant seasonal cover crops that draw nitrogen from the air and store it in their roots. Examples of such “nitrogen-fixing” plants include peas, beans, and clover. In the spring, before your cover crop sets seed, till the plants under to decompose and release their nitrogen into the soil to support the growth of other plants.

Deeper roots mean better drought-tolerance: deep-rooted plant can find moisture far below the surface. Such plants are generally preferable in the landscape, all other factors being equal.

The depth of roots varies among plants, reflecting adaptation to the plant’s environment. Among weedy grasses, for example, Annual Bluegrass (Poa annua) has roots only about right inches deep, while Bermudagrass (Cynodon dactylon) can grow to 60 inches deep in search of water.

Infrequent, deep irrigation encourages all plants to develop deep roots and drought tolerance. A common error with automatic irrigation systems is to schedule frequent, brief periods of watering. This practice encourages shallow roots, ultimately increases overall water usage and leaves plants vulnerable to dry periods.

Q. Shallower roots?

A. The advantage of shallower roots is that plants growing in arid climates have immediate access to occasional rains. Succulent plants have adapted to such conditions by developing shallow roots and the ability to store scarce moisture in their leaves, stems or roots. For this reason, gardeners often appreciate succulent plants for both drought tolerance and landscape appeal.

The New California Garden, which we envision here, features meadow grasses and succulent plants: a good time to start is now.

Rain Gardens – Advanced Water Conservation

Most gardeners have learned that large percentages of residential water usage occur outdoors, mostly as a result of irrigating lawn grass and other plants, and have adopted water-saving practices: replacing thirsty lawn grass with naturally drought resistant perennial plants, especially California native plants, using efficient drip irrigation, and mulch. These strategies involve relatively low expense, depending on implementation.

Some gardeners have gone to the next stage of water conservation, which includes water catchment and grey water recycling. These strategies require equipment, and its installation, both of which could lead to some initial expenses. A 5,000-gallon water tank, for example, would be a substantial investment, but one pays off through long-term water savings or even fire protection.

Today’s column introduces percolation ponds as another stage of water conservation.

When we are fortunate enough to have rain, much of the water from roofs and paved areas runs to storm drains, which in the Monterey Bay area lead eventually to the sea. An efficient storm drain system avoids flooding, but often delivers pollutants into the ocean. A better approach is to direct the runoff to the soil, which filters the pollutants and leads the water into the aquifer.

This approach involves the development of a percolation pond, which is simply a low area that collects and holds runoff so that it percolates into the ground.

The principal objectives for percolation ponds are to filter runoff to minimize pollution, recharge local groundwater, and conserve water.

To include a percolation pond in your garden, find a naturally occurring low area (or create one) that is at least ten feet away from your home and any existing septic field. This separation is needed to avoid having water migrate towards your foundation, or to interfere with any utilities close to the house.

Rain Garden - Sentinel

A rain garden by a driveway in Pacific Grove. Credit Dona Johnsen Landscape Archietcture

 

gi_raingarden

A rain garden away from the (east coast?) residence. Credit: EPA:gov

 

The percolation pond should have good drainage, so that it holds water for no more than forty-eight hours. A retention pond, by contrast, holds water for longer periods, and could be designed as a water garden or bog garden.

Determine the surface area of the percolation pond to reflect the surface area of the capture area and the soil type. For example, multiple the surface area of your roof by 20% for sandy soil, 33& for loamy soil, and 45-60% for clayey soil. If you are creating a percolation pond, the bottom layer ideally should consist of about 60% sand, 20% compost and 20% topsoil. This composition would provide effective filtering of the runoff.

Then, adjust downspouts or a sump pump outlet to direct the water into the percolation pond. Depending on the situation, a bioswale could be used to direct the runoff to the percolation pond. A bioswale is a drainage course with gently sloped sides (less than six percent) and filled with vegetation, compost and/or riprap.

In areas that receive regular rainfall, the upper layer of the percolation pond can be planted with deep-rooted perennials, which can flourish under occasional deep soaking, followed by relatively dry periods. These features are called “rain gardens.”

In California, where we need to protect and restore our aquifers, and have current drought conditions, the upper layer might emphasize decorative stones, which can slow the flow of water that might otherwise overflow, and promote percolation. California native plants, once established, would do well in a percolation pond, and also provide both an attractive appearance and environmental benefits. Continue reading

Gardening Close Up

 

We garden on different perspectives: specific when studying individual plants, and general when designing a landscape. We can regard gardening as a continuum with many points between its ends. This range of possible perspectives deepens our interest in gardening.

With all that in mind, where does the survey of a genus belong on this continuum? That thought came to mind during a recent talk by Brian Kemble, Curator of The Ruth Bancroft Garden in Walnut Creek, specializing in succulent plants.

Ruth Bancroft established this extraordinary garden in 1972 as her private collection. It was the first garden supported by the Garden Conservancy, and in fact inspired the formation of that nation-wide organization. The garden was opened to the public in the early 1990s and soon became managed by a non-profit corporation.

Brian Kemble 3-2015

Brian Kemble, Cactus & Succulent Horticulturist

Kemble has been involved with the garden continuously since 1980, and has brought his considerable knowledge of horticulture and his expertise in succulent plants to the cultivation and development of the garden. Ms. Bancroft, now 106 years of age, maintains her interest in the collection.

Kemble spoke to the Monterey Bay Area Cactus and Succulent Society, in Watsonville. His talk focused on the genus Gasteria, a South African member of the Aloaceae plant family, which includes other popular genera: Aloe, Bulbine, Haworthia and others.

The name of the genus Gasteria reflects its flowers, which to some observers are stomach-shaped (“gaster” is Latin for “stomach). The flowers hang from inclined long racemes, which can includes clusters of 100 or more flowers. The flowers range in color from pink to vermillion with yellow-green tips.

The genus includes 22 species, with rosettes ranging in size from the diameter of a nickel coin, to those with leaves a meter long.

Gasteria acinacifolia

This is a Scimitar-leaved Gasteria (G. acinacifolia), displayed at the meeting of the Monterey Bay Cactus & Succulent Society, as part of the monthly mini-show. (It won a prize in its category!)  This is the tallest of the Gasteria species, native to the Eastern Cape of South Africa.

Kemble showed examples of several Gasteria species, each of which is native to a specific area of South Africa. He also showed several hybrid forms, including at least one that he developed himself.

Gasterias are relatively easy to propagate from seeds, divisions or leaf sections. They are also readily crossed with other plants in the Aloaceae family, so we have cultivars called xGasteraloe or xGasterhaworthia.

Kemble provided an expert overview of this interesting genus Gasteria. Some members of his audience might have been inspired to collect different species of the genus, but others most likely learned about how any given Gasteria fits into the larger botanical context. This knowledge adds in subtle ways to the enjoyment of gardening.

To learn more about Gasterias and other succulent plants, visit the web site of the Monterey Bay Cactus & Succulent Society, and click on
Specific Resources. Gasterias, as you will recall, are in the plant family Aloaceae.

 

Bare Root Trees and Shrubs

One of the best bargains in gardening is planting bare root trees and shrubs. And now is the time to do just that.

Bare root trees are dormant, by definition, and not attractive in the usual way, but they are excellent candidates for addition to your garden.

Bare Root Tree

Click to Enlarge

I have often written of the advantages of buying mail order plants, to draw from a wider selection than local garden centers can offer. That’s still a good practice for many plants, although there are drawbacks, as well: mail order buyers need to confirm that the plant of interest is right for their garden, particularly in terms of winter temperatures. Some tropical plants will not survive even the moderate winters of the Monterey Bay area, and some require more winter chill than they will receive in our climate, and will not blossom or fruit well here.

Years ago, eager to start a small orchard of antique varieties of apple and pear trees, I ordered ten bare root plants from a mid-west nursery, only to watch them struggle and eventually fail for lack of winter chill. Purely by chance, one tree, a Cox’s Orange Pippin, managed to survive my garden’s USDA zone and is producing very tasty apples to this year. That tree stands to remind me to do my homework before ordering mail order plants.

The hazards of selection are less important during bare root season because local garden centers are able to stock very good inventories of bare root trees and shrubs that are right for the local climate.

Despite the best efforts of garden centers, the economics of stocking containerized plants limit inventories of plants in pots: they cost more to ship and require more space, and offered at twice the price of the same plant in bare root.

Conversely, mail order suppliers (which still might offer a greater range of choices) can ship wholesale orders of bare root plants efficiently to garden centers, but have to recover the greater costs of shipping small quantities of plants to retail purchasers. So, for individual gardeners, the mail order price could be higher than the garden center price.

Additional benefits of buying bare root plants include larger root mass, according to researchers, easier to move and plant without soil and container, and faster growth because they adapt easily to local soil as they come out of dormancy.

The range of options at a garden center could include ornamentals, fruit trees, roses and berries. Many other shrubs could be offered in bare root form, as well, with the same advantages, but I have seen little development of that market.

When selecting an ornamental or fruit tree, look for a straight trunk, evenly spaced branches (if any), good spread of healthy-looking roots that have been kept moist, and a complete lack of any wounds or disease.

Many garden centers also offer espaliered fruit trees that have been developed by grafting branches in the right places, rather than by the time- and labor-consuming process of training. Some espaliered dwarf apple trees include grafts of several apple varieties, to produce a healthy young tree that will both fit a tight space in the garden and produce a selection of applies that ripen at different times during the season.

It is important to plant bare root specimens before bud break, so there is a small window of opportunity for the lowest prices. Don’t delay!

Roses for Foggy Areas

Q. Are there any hardy roses you would suggest I could plant that will survive Pacific Grove’s sandy soil and fog?

I enjoy your column.

December 2013

A. In December, it’s appropriate to strip leaves from roses to encourage dormancy. Just pull them off by hand and rake up under the rose bush to minimize any disease and over-wintering pests.

Treat the sandy soil and fog as two different issues. (They are both manageable.)

Sand in the soil helps drainage (which roses and most other plants appreciate), but there can be too much of a good thing. The sand content of your soil should be between 10% and 30%. I recommend analyzing soil texture so that you will know what you have. Here is a link to Fine Gardening magazine article, “How is Your Soil Texture?” that describes a simple procedures that you can do in a few minutes and without cost.

If this test shows an excess of sand, add compost or other organic material to improve the mix. During January or February, you could lift the rose, dig a hole about twice the size of the root ball, fill the hole with a mixture of garden soil, sand and compost, replant the rose, and water in. There is no correct mixture, but you might try for something like 70% soil, 20% sand and 10% organic material.

When lifting the rose, first use a shovel to cut the roots to about six inches around the plant. You could lift the plant without soil around the roots, but keep the roots moist (or at least out of the sun) until replanting.

A foggy environment has good and bad effects. Fog will help to keep the rose from drying out, but it will also promote various diseases, e.g., mildew, black spot, rust. The best strategy lis to select disease-resistant roses. Here’s a link to a Sunset magazine article, “Roses for Foggy Coasts,” with a list of rose recommendations.

The article recommends seeking advice from members of the local rose society. The Monterey Bay Rose Society has several members who are qualified Consulting Rosarians, and generous with their expertise.

Lose the Lawn

One the best gardening strategies to prepare for future droughts—and achieve additional benefits—is to replace your lawn with any of several landscape designs.

Lawns, and especially front yard lawns, began as a mark of affluence, because mowing a lawn was once a labor-intensive (and therefore costly) session with a scythe. A skilled scythe-wielding worker can be impressively efficient, but for most workers, including the homeowner with an up-to-date lawnmower, mowing a lawn is a tedious and repetitious task. The homeowner’s reward for a well-maintained lawn can include pride of ownership.

A lawn does more than display the homeowner’s wealth. It also serves as the base for widely accepted front-yard designs, the principal one of which has been called the Contractor’s Landscape. This consists of a shallow bed of reliable small shrubs next to the house, followed by turf grass to the curb. This design is quick and cheap to install, and inoffensive.

From an aesthetic viewpoint, the lawn provides a resting place for the eye as the viewer focuses on individual trees, shrubs and blossoms. The lawn is a neutral swatch of greenery, contrasting carpet-like with the relatively busy landscape.

But consider the negative aspects of the lawn.

  • Maintaining a good-looking lawn requires much more effort, water, chemical fertilizers and herbicides than alternative landscapes.
  • Two-cycle lawnmowers pollute the air about ten times as much as a car, and add noise pollution as well. Electric mowers are better, but they also impact the environment. Push mowers are best for the environment, the lawn and the homeowner.
  • Lawns are the homeowner’s version of monoculture, growing just one crop over an area. This practice might seem efficient, but to the wildlife, it’s a wasteland with very little food or water and no shelter at all.
  • Lawns might be valued for recreation, but in reality often have minimal use (except for maintenance). Other landscape designs could be more inviting and supportive of outdoor activities.

If these factors encourage you to consider losing your lawn, it’s time to look into the many possible alternatives. Begin with Sunset magazine’s “21 Inspiring Lawn-free Yards” <www.sunset.com/garden/earth-friendly/lose-the-lawn-low-water-landscaping>. This webpage offers a slideshow of attractive options to contemplate.

For more in-depth information, visit Evelyn J. Hadden’s extensive website, “Less Lawn, More Life,” or look for her book, “Beautiful No-Mow Lawns: 50 Amazing Lawn Alternatives’ (Timber Press, 2012).

Another fine resource on this topic is book by Carol Bornstein, David Fross and Bart O’Brien: Reimagining the California Lawn: Water-conserving Plants, Practices andDesigns (

Another helpful resource is the Lawn Reform Coalition, which is “all about reducing or replacing lawn, water-wise lawn species and eco-friendly care for all lawns.” Visit the Coalition’s website for information on all aspects of lawn alternatives.

“Lose the lawn” emphasizes the loss of a familiar element of the landscape. “Lawn alternatives” suggests a more appealing idea, one that opens our thinking about creative approaches to the landscape and new resources in the home environment.

Think of the possibilities!

Rain at Last

As an impressionistic meteorologist, I’m very pleased with our recent rains and even more so with the promise of more rain in the near future. Some areas of northern and central California could actually reach normal levels of annual precipitation. The Santa Cruz area is during fairly well, but this happy future might not extend throughout the area: portions of Monterey County are receiving lighter precipitation.

What have we learned?

My first reaction to the overdue rain is that we can now anticipate fresh new stems and leaves and a great floral display in the spring. Our plants are responding to the moisture by extending their roots and drawing in nutrients, preparing for a new season of growth.

Then, I flashed on the idea that the drought is over for good, and we’re back to the Monterey Bay area’s historical weather pattern, with a dry summer and the onset of the rainy season around mid-October. This thought didn’t last long. Realistically, our climate is changing in ways that will change our gardening—and our lives—in significant ways.

This change is happening at a fast rate, not with the very slow arrival of the Ice Age (approximately 110,000 to 12,000 years ago or the Little Ice Age (1550 to 1850), which developed relatively more quickly, over a period of about 200 years.

Politicians are debating a range of responses to today’s emerging problem. Clearly this is a global issue that requires global action, but as individuals, we can respond in small ways. The most constructive action for individuals is to elect those who accept the reality of climate change and support long-term solutions.

As gardeners, we can pursue three basic strategies:

First, retire plants that require summer irrigation and that suffer under drought conditions. The single most widespread plant in this category is lawn grass, which achieves it aesthetic potential only with frequent irrigation, applications of nitrogen fertilizers and broadleaf herbicides, and regular cultivation, including mowing, aeration and pest control.

In a future column, I will describe alternatives to traditional turf grasses.

Tropical-climate plants compirse another category to avoid for drought-tolerant gardens. Examples include the hibiscus (H. syriacus is the most popular ornamental species) and the banana (Musa acuminata, M. balbisiana and others). In general, avoid plants with large glossy dark leaves, which tend to absorb more heat, require a lot of water and transpire a lot of water.

For the water needs of specific plants, Sunset’s Western Garden Book provides useful guidelines, with briefly descriptive terms from “ample water” to “little to moderate water.”

The second basic strategy is to favor plants that will survive in your garden under drought conditions. Generally, as often mentioned in the column, these are plants that are native to coastal California and other Mediterranean (or “summer-dry”) climates. These plants will do better with a little moisture during a prolonged drought, but they have evolved to withstand dry periods, using such methods as growing small leaves, that minimize water loss.

Succulents are another category of drought-tolerant plants, which have developed structures for storing water in their leaves, stems or roots.

The third strategy for drought-tolerant gardening is to use water wisely, through drip irrigation and regular mulching. These water-conservation methods complement the two preceding strategies for plant selection, and help the gardener to cope with water restrictions.

Use the next clear days to assess your garden for drought-tolerance. However much we enjoy the current rains, preparing for future droughts requires long-term planning..

Summer Pruning of Apple Trees

Do you have one or more apple trees that have vigorous new upright growth, like the shoots, often called water sprouts, shown in the picture? This photo shows new growth on an espaliered Gala apple in my garden, before and after pruning (click to enlarge).

BEFORE PRUNING

Water Sprouts - vert

AFTER PRUNINGWater Sprouts - pruned

Those shoots, usually at least one foot in length, are the tree’s response to heavy pruning during the dormant season, and represent an effort to restore the balance between the canopy and the root system.

Water sprouts are unlikely ever to bear fruit. Instead, they sap the tree’s energy and shade the interior of the tree, slowing the development of vertical growth, and the time for dealing that problem begins now. The period from early August to mid-September is the ideal time for summer pruning, after the new branches have set their terminal buds. This means that the branch has stopped growing for the season, so pruning will not stimulate additional growth. The best practice is to remove the water sprouts with their terminal buds.

Note that some new shoots will be shorter, and horizontal or nearly horizontal. Horizontal shoots (properly called “laterals”) are more likely eventually to bear fruit, so they are treated differently from the vertical or near-vertical shoots.

First, consider training these laterals to close to horizontal, using string or V=notched spreaders, to support fruiting.

Then the recommended treatment is to prune these laterals back to three buds of new growth after the cluster of leaves at its base. This will stimulate the formation of fruiting buds.

Oren Martin, the gardening guru at UC Santa Cruz’s Farm & Garden, says this three-bud pruning system is based on the advice of Louise Lorette a French orchardist of the early 20th century.

Pruning your apple tree’s water sprouts and laterals in this manner can be a repetitious and fussy detailed task, but it really will not take long and will contribute significantly to your tree’s vigor and productivity.

My practice is to listen to National Public Radio on a portable radio while pursuing repetitious tasks like pruning or weeding. That way I can feel like both a conscientious gardener and an informed citizen.

Summer pruning of apple trees is distinctly different from winter pruning, which should focus on the tree’s structure and overall form. Summer pruning, by contrast, emphasizes the tree’s details, keeps sunlight flowing to the interior and supports fruit production

The time for structural pruning of an apple tree is late winter while the tree is dormant and leafless. Winter pruning can stimulate the growth of water sprouts, which are pruned in summer when the tree is not producing new growth. This practice results in less pruning down the line.

When the dormant season comes again, we’ll review the art of winter pruning. Now, during the summer months, pick up your clippers and snip away at those water sprouts.