Gardener’s Gold

Posted on November 24, 2012 by tomkarwin

If you have deciduous trees in your garden, you might be fretting these days over the task of raking and disposing of the fallen leaves. You might instead welcome this form of nature’s bounty, because your trees have contributed the raw material for an excellent natural resource for your garden: leaf mold.

Leaf mold, which is simply partially decomposed leaves, can be used as a mulch to discourage weeds, retain moisture and insulate the roots of plants from the coldest weather. It can also be used as a pH-neutral soil amendment, like compost, to retain moisture, improve soil texture, add nutrients and support the growth of beneficial soil organisms of all kinds.

The question, then, is how to convert the fallen leaves to leaf mold.

The raking can’t be avoided, but the rest of the task could take any of several forms, depending on the gardener’s patience and available space, and the kind of leaves. Some leaves, including oak and holly, contain relatively high levels of cellulose and are slower to break down.

The easiest conversion of leaves to leaf mold is to pile the leaves in an out-of-the-way location and let them decompose on their own schedule. This process could require a year or more, but could be hastened in several ways, singly or in combinations.

Leave your leaf pile in a shaded location, or cover it with a plastic tarp. This helps to retain moisture, which supports the decomposition process, which depends upon the work of fungi.
Water the leaf pile occasionally, to maintain a damp (not soggy) condition.
Turn the pile occasionally, to expose the contents to oxygen.
Shred the leaves. Smaller pieces have greater exposure to the air and moisture, and therefore break down faster. Run over the leaves with a lawn mower—almost any kind would do—or put them through an electric leaf shredder or leaf blower-vacuum. My American Sycamore’s big leave tend to block my blower-vacuum, so they have to be roughly shredded first with the mower. For smaller quantities, place the leaves in a trashcan and shred them with a weed whacker. n order to keep your yard in tip-top shape and to protect your lawn from succumbing to the cold snow, you need to ensure that you take the proper steps to ensure that your lawn can spring back in the spring! Consider shoppok – cyclone rake the cost of this product in this site is better than other places.
Add nitrogen. Old dry leaves are almost all carbon, so the addition of nitrogen will speed their breakdown. Add green vegetation or nitrogen-rich fertilizer. Dry chicken manure has twice the nitrogen content as horse or steer manure.

The leaf mold is ready when it has become soft and crumbly. Use it to mulch your plant, spreading it about three inches deep (not too close to the base of the plant). Or dig a similar amount into the soil; this could be easiest when preparing a new bed, and is particularly helpful for improving soil that contains an excess of clay or sand. Leaf mold also could be included in containers to lighten their weight.

Enjoy gardener’s gold in your garden!

Growing Terrestrial Orchids

Posted on November 17, 2012 by tomkarwin

Most orchids are epiphytes, meaning that they grow on another plant. Epiphytes are not parasites, which are plants that scrounge nutrients from another plant. An epiphyte attaches itself to another plant (a tree, usually) and gets moisture and nutrients from the air and rain and sometimes from debris accumulating around it.

To grow an epiphytic orchid, the gardener must reproduce the temperature, humidity and light level that the plant has evolved to require. This is true for all plants, to be sure, but these orchids have become accustomed to very particular environment that can be difficult for the gardener to provide.

Experienced orchid growers claim that success with epiphytic orchids requires only creating the plant’s preferred conditions. This typically includes planting the plant in coarse bark chips to provide ample access to air.

Without denying the accomplishments of amateur orchid growers, I confess to having killed more than my share of epiphytic orchids.

Given that sad history, I am delighted to have discovered hardy terrestrial orchids. These are plants that thrive in well-drained soil and within a moderate climate like that of the Monterey Bay area. Some terrestrial orchids will even take freezing temperatures.

Terrestrial orchids that are popular for home gardens have been described in three groups according to water needs:

Upland species include Lady’s Slipper (Cypripedium), Chinese Ground Orchid or Hyacinth Orchid (Bletilla) and Hardy Calanthe (Calanthe);
Transitional species include Grass Pink (Calopogon), Marsh or Spotted Orchid (Dactylorhiza), Egret Flower (Habenaria), Fringed Orchid (Platanthera), Fragrant Ladies’ Tresses (Spiranthes), and Helleborine (Epipactis);
Wetland species include Rose Pogonia (Pogonia).

Three years ago, I acquired a small Lavender Chinese Orchid (Bletilla striata), which is widely available, and planted it in semi-shade, assuming that all orchids want shade. Although I never watered or fertilized the plant, it grew well but produced only occasional blossoms. This was disappointing because Bletillas often will have as many as 20 flowers on a single spike.

Then I learned that this plant prefers full sun exposure. I lifted it and discovered it had developed about twenty pseudobulbs, which are storage organs (like tubers) that some orchids produce. These can be planted six inches apart, about three inches deep, so I should have several patches of these plants in bloom in the spring.

Terrestrial orchids can provide an exotic display in the garden without requiring extraordinary care. The Chinese Ground Orchid is particularly easy to grow, and the Lady’s Slipper and Hardy Calanthe are also good choices for most gardens. The Transitional and Wetland species require more moisture, making them inconsistent with water conservation goals, but a small display would be tolerable.

If you enjoy the unique beauty of orchids, but have had poor experiences with epiphytic species, growing terrestrial orchids could be an appealing option.

Here are current books about the cultivation of hardy orchids.My principal reference for this column was the Mathis book, but other books listed offer additional information and other perspectives.

The Orchid Manual: For the Cultivation of Stove, Greenhouse, and Hardy Orchids, With a Calendar of Monthly Operations, and Classified Lists of Species, by Thomas Appleby. Forgotten Books (June 23, 2012) (Note: this is a reprint of a classic book published in 1845.
Growing Hardy Orchids, by Philip Seaton, Phillip Cribb, Margaret Ramsay and John Haggar. Royal Botanic Gardens, Kew; Original edition (March 15, 2012)
Growing Hardy Orchids, by John Tullock. Timber Press (September 15, 2005)
The Gardener’s Guide to Growing Hardy Perennial Orchids, by William D. Mathis. The Wild Orchid Company (2005)
Hardy Orchids, by Phillip Cribb and Christopher Bailes. American Orchid Society (December 1989)
Hardy Terrestrial Orchids for Perennial Gardens with a focus on Bletilla, Calanthe, and Spiranthes – Excluding Cypripedium, by Dennis Carey & Tony Avent. Plant Delights Nursery Inc.

Selected sources of hardy terrestrial orchids:

Wild Orchid Company, Carversville, Pennsylvania
Poplar Hills Nursery, Alexandria, Virginia
Fraser’s Thimble Farms, Salt Spring Island, British Columbia, Canada
Brent and Becky’s Bulbs, Gloucester, Virginia

Small Gardening

Posted on November 10, 2012 by tomkarwin

The gardening world has been buzzing about small gardens. The current interest in this topic might reflect a trend toward small-scale properties or growing desire among gardeners to limit the time and energy they commit to gardening.

A small garden could be the entirety of a small property or an area within a large property. A large property might include several small gardens (sometimes called “rooms”) or one small garden plus undeveloped space, or something between those extremes.

In either case, the goal for small gardening should be quality gardening.

“We would do well to follow a common rule for our daily lives—do less, and do it better.” (Dale E. Turner)

When developing a small garden, all the usual criteria for plant selection and cultivation are applicable. Ensure that the soil is fertile, friable and well drained, and choose plants that are appropriate for the climate, sun exposure and prevailing winds of the garden.

In addition, three broad guidelines come to mind.

First, specify a theme beyond “small size.” The garden might focus on a genus (rose, iris, clematis, etc.), a category of plants (succulents, white blossoms, herbs), a plant community (California natives, African bulbs, aquatic plants) or any other theme of interest. A theme provides coherence to the garden and a rational approach to plant selection.

Second, provide a story line for visitors. The garden planner could guide a visitor’s attention by establishing a focal point: a well-placed, exceptional plant, a piece of garden art, or a water feature, etc. After that initial impression, the gardener or discrete signs might encourage a visitor to examine a series of specimen plants. A rose garden, for example, might showcase several hybrid teas or species roses for comparison.

Finally, plan the maintenance of the small garden for close inspection. No garden looks good when unkempt, but a neglected small garden can be particularly unsatisfying to both the gardener and the visitor. While fallen leaves, a forgotten watering hose and a few weeds can be tolerated in a large, sprawling garden, a small garden should be raked and pruned and tidied regularly. By virtue of being small, it should also be manageable.

The small garden is to a large garden as a sonnet is to free verse.

Here is a link to an article with additional thoughts about small gardening: “Big Help for Small Gardens.”

Sharing Plants

Posted on October 27, 2012 by tomkarwin

The fall season is both the best time for planting, and an excellent time for gardeners to share plants.

Plant and cutting exchanges, which are popular in the Monterey Bay area, invite gardeners to bring plants or cuttings from their garden to swap for plants or cuttings offered by another gardener.

That seems like a fair trade, but because plants vary greatly in size, condition and desirability, a really balanced exchange would be difficult to achieve.

Still, these exchanges often succeed without even requiring a contribution. They work because plants propagate naturally on their own: the gardener does not incur a significant cost, and still reaps the satisfaction of giving something of value to another gardener.

Cheap thrills!

Propagating plants for sharing require a significant investment of time: growing plants from seeds or cuttings and then giving them away could amount to a generous gift of the gardener’s time. However, opportunities exist for sharing plants with little effort.

For example, if your daffodils or irises need dividing, you could very well end up with a surplus of bulbs or rhizomes that you could share.

Another example: plants might self-propagate in your garden to the point that you have more than you want, and would prefer to reclaim the space for other plants.

In my garden, Pig’s Ear (Cotyledon orbiculata) and Japanese Anemone (Anemone hupehensis) had grown too large. With the help of a friend, we uprooted dozens of each plant for others to propagate.

Succulent Cotyledons can be propagated most easily from tip cuttings.

Japanese Anemones are best propagated from root cuttings taken in the late fall or early winter. We lifted them rather early, but we saw vigorous new white shoots on the roots, and felt that they would re-root quickly in a new environment. This plant produces beautiful pink or white blossoms, and grows so readily that it’s almost invasive.

Plant society sales offer another sharing opportunity. While these are not free exchanges, they typically offer plants at below-market prices. And the gardeners who grow these plants gain satisfaction from sharing both their plants and their enthusiasms.

Watch for opportunities to share plants with your friends and neighbors. You will both grow from the experience.

The Web has very helpful information resources for plant propagation.

Wikipedia – Plant Propagation (often my first stop)

Plant Propagation.com

Stover’s Nursery

North Carolina State University

YouTube also offers several short video recordings (often simply produced) on aspects of plant propagation.

Cacti of the Sonoran Deseert

Posted on October 20, 2012 by tomkarwin

After a few days in the Sonoran Desert, my head is filled with thoughts of cacti.

I attended the annual meeting of the Garden Writers Association, attended by writers from many parts of the United States. This year’s meeting convened in Tucson, Arizona, which is within the upper part of the Sonoran Desert’s 120,000 square mile area, most which is in Mexico.

We locate Tucson in our southwest; Mexicans see it in their northwest.

The meeting included talks to inspire writing or teach up-to-date written and multimedia communication, numerous awards for outstanding writing, photography, videography and graphics, many exhibits by garden-related vendors, and bus trips to twelve public and private gardens in the Tucson area. Visit ongardening.com for more of my travel notes and photos.

For me, the primary effect of this occasion was exposure to the distinctive plant life of the area, especially the Cactus family, almost all members of which are native to the Americas.

The most prominent local cactus is the stately Saguaro (Carnegiea gigantea), which grows in the wild only in the Sonoran Desert. I saw specimens of about thirty feet high, but it can reach up to fifty or seventy feet.

Other cacti widespread in the area include the Cholla (Cylindropuntia spp.), Beavertail (Opuntia basilaris), Hedgehog (Echinocereus spp.), Fishhook (Ferocactus wislizeni), Prickly Pear (Opuntia spp.), Night-blooming Cereus (Peniocereus spp.), and Organ Pipe (Stenocereus thurberi).

According to Sunset’s Western Garden Book, these cacti could be grown in the Monterey Bay area, but we see them infrequently. This presumably reflects local gardeners’ preferences: with such a wide range of plants that thrive in our moderate climate, gardeners have many spineless horticultural options.

There are, however, important environmental conditions other than temperature that affect the growth of plants. Plants that grow in the harsh conditions of the Sonoran Desert have evolved to adapt to the desert climate, characterized by a biseasonal rainfall pattern (late summer and early winter), and daily temperature ranges of about thirty degrees.

The Sonoran Desert also includes plants from the Agave, Palm, and Legume and other families. The large Legume family includes many varieties of peas and beans, plus alfalfa, clover, lentils, lupins, mesquite, carob, soy peanuts, Locust trees, wisteria and the green-trunked Palo Verde (Parkinsonia aculeate), which grows throughout the Tucson area.

I have had no cacti in my garden, but the friends who hosted my visit gave me two specimens: a hybrid Echinopsis ‘Los Angeles’, which will grow to about eighteen inches, and produce pink flowers in late spring and early summer, and a Echinocereus morricalii, which also will grow to about eighteen inches and blossom in May in bright magenta.

Many cacti would not fit easily in my garden, but these small plants will fit fine and provide gorgeous flowers. Travel could broaden our gardening tastes!

More coming soon

Interesting Weeds

Posted on October 6, 2012 by tomkarwin

Yes, even weeds can be interesting. Here are two examples.

First, I’ve written about the “weed seed bank” that exists in all gardens. This inventory of dormant seeds lurks in the top few inches of soil, waiting for life-giving sunlight, air and moisture.

The weed seed bank results from earlier generations of weeds that dropped their seeds under the plant, projected them a few feet away or cast them to the winds for wider distribution. Such seeds might also be brought to the garden as the undigested part of a bird’s meal, tracked in on a visitor’s clothing, or imported with a plant from a friend or the local nursery. Whatever the source, they are part of every garden.

The weed seed bank might be called simply the seed bank, because it includes wildflowers and other garden-worthy plants as well as weeds. Abandoned gardens eventually sprout their hidden wealth of weeds and wildflowers.

Weed seeds can remain in the soil, ready for germination, for several years. Gardeners are wise to use mulch to discourage the germination of weeds and help realize “low maintenance” gardening.

Dormant seeds can be amazingly long-lived under the right conditions. Earlier this year, Russian scientists reported their discovery in Siberia of seeds that a squirrel had buried in the Early Pleistocene era, about 31,800 years ago. The seeds soon were frozen in permafrost and didn’t thaw until retrieved by the research team. With great care, scientist Svetlana Yashina cared for the seeds, which germinated and produced a flowering plant and a new generation of seeds.

The plant is the Narrow-leaved Campion (Silene stenophylla), once known by mammoths and wooly rhinos. An evolved form of this plant grows today in Arctic regions. The genus Silene includes many species, including several wildflowers of Europe and elsewhere in the Northern Hemisphere.

The story of bringing this prehistoric plant into blossom raises the possibility that more plants could be recovered from frozen seeds in Siberia, the Arctic and the Yukon, and the intriguing prospect for the gardeners to grow prehistoric weeds and other plants. Examples of other specimens include the Sago Cycad (Cycas revoluta) and the Maidenhair Tree (Ginkgo biloba). Both of these plants, which are distant relatives, have fossil histories from more than 250 million years ago, and are available today as young plants.

***

A second example of interest in these lowly plants involves harvesting them for the dinner table. Dandelions and purslanes are only a beginning. A new cookbook, Foraged Flavor: Finding Fabulous Ingredients in Your Backyard or Farmer’s Market, by Tama Matsuoka Wong, with chef Eddy Leroux, describes many culinary and nutritional benefits of several common weeds. Ms. Wong’s website, Meadows and More, offers more details and an extensive weed identification section.

For more about the prehistoric Narrow-leaved Campion (Silene stenophylla), including pictures, browse to the article in Discover magazine.

Another interesting ancient plant is the Amborella trichopoda (no common name), which has been called “the most primitive living flowering plant.” It may be the earliest of the angiosperms: flowering plants that emerged about 130,000,000 years ago. A useful article about this plant is available on Wikipedia. This Arboretum at the University of California, Santa Cruz is the only place in the United States that is growing this plant for botanical study. For a 1999 article on the Arboretum’s work with this plant, click here.

For more information on the book, Foraged Flavor, browse to the New York Times article.

Ms. Wong’s website, Meadows and More, has a wealth of information on culinary uses of common weeds, and an extensive series of weed photographs, with expert identifications.

For identification of weeds that are common in California, visit the Weed Photo Gallery on the University of California’s Integrated Pest Management website.

Coming to Grips with Thrips

Posted on September 29, 2012 by tomkarwin

Happily, several years have passed since I’ve noticed thrips in my garden, but they are back!

Thrips are flying insects that are less than 1/20 of an inch long and eager to suck juices from plants. There are over 500 genera and 5,000 species of thrips, some of which are beneficial predators of mites, scales and even other thrips. Others feed on fungal spores or pollen, and some feed only on favored plants, such as avocados, citrus, blueberries, or various others.

My garden’s visitors almost certainly are Western Garden Thrips (Franklinia occidentalis), which attack a wide range of herbaceous ornamentals, vegetables, fruits and some shrubs and trees, including roses and stone fruits.

Thrips are poor flyers but can find juicy plants and infest all of a large shrub or a good-sized bed of a plant that they find tasty.

In my garden, they found a 200 sq. ft. bed of Bergenias (an unidentified cultivar of the popular species, Bergenia crassifolia). This plant from central Asia has numerous common names: Elephant Ears, Pig Squeak, Large Rockfoil, etc. It is an attractive groundcover plant, growing one-to-two feet high, with clusters of small, bell-shaped pink flowers on stems that rise above the foliage in early spring.

Bergenias are generally free of pests, at least until thrips discover them.

Thrips might make only limited damage to ornamental plants and could be ignored. When conditions are favorable, however, they can cause great cosmetic damage.

When thrips attacked my Bergenia bed, nearly all the leaves, each about four by six inches, became discolored and distorted, and their upper surfaces turned silvery gray, the result of losing their waxy surface. The leaves also were stippled with black specks of the thrips’ fecal matter.

The normal growth of Bergenias has new leaves emerging above older leaves that turn brown without dropping off. New leaves cover the old leaves, but removing the dead leaves improves the plant’s appearance. In this instance, the action of the thrips revealed the dead leaves, and the entire bed was devastated.

The damage was limited to the leaves. The stems and roots of the plants were alive and well, and able to produce new leaves. Our treatment was to remove all living and dead leaves, using garden clippers, and then spray the plants with Spinosad, an organic pesticide that kills insects both by direct contact and by ingestion.

I used a Spinosad-based product, Captain Jack’s Deadbug Brew, in a container designed conveniently as a hose-end sprayer. Despite its promising name, the spray doesn’t guarantee success: a follow-up spray might be needed to control the newest of up to eight generations of thrips for the year.

Thrips are members of the order Thysanoptera. The earliest fossils of thrips date to the Permian Period, 250 to 299 million years ago. This period was the last part of the Paleozoic Era, which ended with the largest mass extinction in Earth’s history, when nearly 90% of marine species and 70% of terrestrial species died out.

That thrips were among the survivors of that period suggests the difficulty of eliminating them from our gardens.

When the gardener suspects that thrips are present, they can be detected either by close examination of the underside of affected leaves, or by beating or shaking a branch or flower onto a sheet of paper. Yellow sticky traps also can be used to monitor their presence.

The most important way to encourage biological control of pest thrips is to conserve naturally occurring populations of beneficial insects, e.g., predatory thrips, minute pirate bugs, predaceous mites, and green lacewings . This can be done by controlling dust and avoiding the use of persistent pesticides in the garden.

For other control, see the University of California’s Integrated Pest Management information page on How to Manage Pests—Thrips.

Gopher Overview

Posted on September 23, 2012 by tomkarwin

Most of these columns are on current priorities in my own garden. The premise of course is that many gardeners could be dealing with the same issues at any given time.

Recently, when we listened to those people who always seem to know what’s going at, we learned that 2012 is a big year for gophers.

In the past, I have relied on two visiting cats to keep my garden gopher-free. (I don’t know where else they get their food, so they probably are feral felines.) The result of their advancing age plus a peak in the local gopher birth rate is a record number of gopher mounds.

It might be possible to avoid gopher problems entirely by limiting the garden to plants that gophers do not enjoy. This approach limits the gardening experience severely and still might not succeed: hungry gophers don’t always follow the rules.

The first step toward “control” (the polite term) is to confirm that you have gophers, rather than relatively harmless moles. Gophers are herbivores; moles are omnivores, but mostly eat earthworms and insects. Gopher mounds are crescent or horseshoe shaped when viewed from above. The hole, off to one side of the mound, usually is plugged. Mole mounds are more circular and volcano-shaped when viewed from the side.

One gopher can create and abandon several mounds in day, so the gardener’s challenge is to find the gopher’s main burrow, which will be six-to-twelve inches deep and connected to a mound. When you see a fresh-looking mound, poke around with a stick or metal probe until you feel a drop of about two inches, indicating that the probe has entered the burrow. This might be the main burrow, where you should set your traps.

Use a shovel to expose the burrow enough to set your traps. The popular Cinch Trap, available at most garden centers, comes in small, medium and large sizes. Use the size that fits snugly in the burrow you found. Set two traps according to instructions (watch your fingers!) and place them in opposite directions in the burrow, to trap the gopher coming from either direction.

Baiting the traps is optional. Fruits, vegetables or peanut butter are good choices. You could also use toxic baits, but that is personal choice and probably not ecologically wise.

Connect the traps to stakes with baling wire or light chain, for easy removal. Cover the excavation with dirt clods, wood, cardboard or anything else to exclude light.

Check the traps regularly and reset them as needed. If you haven’t caught a gopher in three days, try a different location.

Benjamin Franklin probably wasn’t thinking about garden pests when he said, “Energy and persistence conquer all things,” but that’s good advice for gopher hunters.

Growing Gorgeous Geophytes

Posted on September 15, 2012 by tomkarwin

The fall season invites gardeners to plant bulbs to blossom in the spring and create bright swaths of color for the new gardening year.

Right now is an excellent time to design bulb bed(s) and select spring bulbs for the garden. There is a lot to consider.

One strategy is to favor the most familiar bulbs, choosing either old favorites or recent introductions. The most popular bulbs include Daffodils (Narcissus), Tulips (Tulipa), Hyacinths (Hyacinthus) and Dutch Crocuses (Crocus vernus). Garden centers offer many varieties of these plants: the long popularity of daffodils and tulips in particular has motivated hybridizers to develop a range of colors and interesting forms.

The next most familiar bulbous plants include Lilies of the Valley (Convallaria, from rhizomes), Spanish Bluebells (Scillas), Grecian Windflowers (Anemones, from tubers), Snowdrops (Galanthus), Dwarf Irises (Iris reticulata, from bulbs), and Grape Hyacinths (Muscari). There are many appealing options within these genera, as well.

Adventuresome gardeners can explore a long list of less familiar bulbs, each of which brings unique characteristics. Visit my website, ongardening.com, for links to additional options.

A different group of geophytes are summer-bloomers. This group includes Gladioli, Calla Lilies, Dahlias, Tuberous Begonias, and Crocosmias. They are planted in the early spring about the same time we plant tomato seedlings.

Other geophytes we enjoy are fall-bloomers, which are planted in the late summer: Autumn Crocus, Winter Daffodil, Guernsey Lily, Saffron Crocus, and some species of Snowdrops.

With planning, you could enjoy glamorous geophytes during much of the gardening year.

Some spring-blooming bulbs need a chilling period to bloom their best. Winter in the Monterey Bay area rarely provides a chill that is long enough and cold enough for these plants, so schedule six weeks of cold storage. The kitchen refrigerator will suffice except for larger projects, when gardeners will appreciate the luxury of a second refrigerator. Consider organizing a chilling co-op with gardening friends.

Many mail order bulb sellers offer pre-chilled bulbs to be shipped at the right time for local planting. A welcome service!

Here are the basics of planting bulbs. Choose a site that receives all-day sun, and drains well. Select larger bulbs of the preferred genus. Plant the bulbs at a depth that is about three times the bulb’s diameter, and take care to position them with the pointed end up.

Bulbs can be planted very close together and may be arranged in either formal or informal patterns. Fertilizers are not required, but a small amount of bone meal in the planting hole could help. For clay soil, add compost to improve drainage. Water to settle the soil then let the seasonal rains take over.

Prepare now for a spectacular spring.

More.

Information About Uncommon Geophytes

North Carolina State University

The Plant Expert

Pacific Bulb Society Wiki

Mail-order Suppliers of Uncommon Geophytes

Brent and Beck’s Bulbs

Mulch for Much Easier Gardening

Posted on September 8, 2012 by tomkarwin

Mulching represents a gardener’s not-so-secret strategy for achieving the universal objective: a low-maintenance garden.

If your garden is time-consuming, frustrating and disappointing, it probably needs mulching.

Several other possible causes should be considered: nutrient-poor soil, lack of irrigation, inappropriate plant selection, etc., but let’s focus for the moment on mulching.

A three-inch deep layer of an organic mulch between plants discourages weed growth, conserves water and, in time, breaks down to add nutrients and texture to garden soil.

We should not ignore the downsides of mulching. For example, a larger garden will require several cubic yards of organic mulch, leading to significant charges from a landscape supply company for the material and its delivery. In addition, distributing the mulch within the garden, while not difficult, consumes time and energy.

One more downside: organic mulches decompose in time, so the time and expense will have to be incurred again. Finer mulch materials break down faster than coarse materials.

Some organic mulch is free, e.g., disease-free wood chips that tree services will dump on your property, upon request (to avoid landfill charges), or seaweed harvested during low tide. Wood chips might be regarded as less attractive than finer mulches, and seaweed, although excellent in nutrient content, often is troublesome to gather, buddy and smelly.

A landscape supply company will offer a variety of organic mulches in bulk, e.g., redwood sawdust, shredded cedar, fir bark and gorilla hair (shredded redwood bark, really), in a range of sizes and prices.

Another option is cocoa shell mulch, which is available in bags of two cubic feet for about $5.00. This material looks good, emits a nice fragrance and breaks down slowly, but contains theobromine, a natural compound that if eaten is highly toxic to dogs and cats.

The gardener could consider each of the available options, and perhaps try a sample bag in the garden.

Home supply stores offer organic mulches in bags of two cubic feet of material. These can be appropriate for smaller beds, but for larger projects will be more expensive than bulk materials. To move one or two yards of mulch, it’s good to have a friend with a pickup truck.

Gravel mulch might be preferred for a rock garden or succulent garden. For a rock garden in particular, gravel mulch simulates scree, the debris of broken rock seen on mountain slopes.

Like organic mulches, gravel mulch discourages weeds, conserves moisture and looks better than bare soil. Gravel is much more expensive per cubic yard than organic mulches, but a one-inch layer should be enough and gravel doesn’t decompose. Gravel mulch is difficult to remove, so for practical purposes treat the installation as permanent.

Enjoy your mulched garden.

Estimating Mulch Needs

To decide how much material you will need, estimate the surface area of the garden bed(s) to be mulched: length times width (in feet). Multiple by the intended depth of the mulch layer: for a three-inch layer, multiply by .25. Finally, convert cubic feet to cubic yards by dividing by 27.

Example: a 12 feet x 18 feet garden bed has a surface area of 216 square feet. For a three-inch layer of mulch, .25 x 216 yields 54 cubic feet. Divide by 27 to determine a need for two yards of mulch.

Seaweed Mulch

An interesting article, How to Use Seaweed to Mulch Your Garden, is available on the website for Eartheasy: Solutions for Sustainable Living. Gardeners who live close to the beach might wish to try this mulch material, but it seems too smelly and buggy for my taste. It also decomposes into slime rather quickly.