Gardening in July

During this hot and dry month, the avid gardener should pursue seasonal tasks to keep the garden looking good and prepare for the change of seasons.

Irrigation should be a high priority to sustain plants that must have a ration of water during the drought. Pass by Mediterranean climate plants, which are accustomed to dry summers. A little moisture will perk up even these rugged individuals and extend their best days, but a better use of scarce water resources would target the garden’s thirstier specimens.

Roses, for example, could produce another bloom cycle during July if treated to a balanced fertilizer and watered deeply. Other candidates for regular watering are plants in containers, which can dry out fast.  First confirm that your water usage is within current restrictions.

If your garden consists mostly of Mediterranean climate and succulent plants, this year’s drought should not cause alarm. On the other hand, if you have a thirsty lawn, consider replacing it with plants of the summer-dry persuasion. The same strategy would be appropriate for plants from tropical, riparian or boggy areas.

Blossoms to enjoy in July include gladiolus, agapanthus and fuchsia, and fragrant Oriental hybrid lilies, e.g., pure white ‘Casablanca’.

Casablanca Lily

I am also enjoying blossoms of Chitalpa tashkentensis ‘Pink Dawn’ trees, which are crosses of catalpa and desert willow. They put on a show reliably around Independence Day, but opened a little earlier this year.

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The Corsican hellebores (H. argutifolius) have finished their winter-to-spring display, and leaned down their bloom stalks to drop seeds all around. The seasonal task is to cut stalks to their bases to make room for the new growth, which has already started.

The tall bearded irises also have finished blooming for this year. They will look best after the flower stalks are cut down, the leaves fade, and the rhizomes enter dormancy. Every four years, during the period from mid-July to mid-September, dig and divide the rhizomes to promote blooming for net spring.

In July and August, plant autumn-blooming blubs, e.g., autumn crocus (C. speciosus and C. sativus), meadow saffron (Colchicum autumnale), and spider lilies: Lycoris squamigera with lilac or rose pink blooms and L. radiata with orange-red blooms.

Control cool-season annual weeds, currently going to seed: bindweed, chickweed, crab grass, knotweed, lambs-quarters, mallow, pigweed, purple deadnettle, groundsel, nettle, purslane, speedwell and spurge, as well as field grasses. Dispose of seeds in the green waste not in the compost bin! The invasive cheery yellow Bermuda buttercup (Oxalis pes-caprae) has already faded, leaving clusters of bulbs to sprout next spring.

Renovating the Garden – More Planning

Gardening and landscaping involves planning before getting your hands in the soil.

Last week’s column, which was about renovating a garden, recommended four preparatory actions:

  1. Draw a Diagram of the Property
  2. Decide on Basic Design Concepts
  3. Establish Objectives for the Finished Landscape
  4. Set Priorities for Development

Once the gardener has completed those actions, he or she still has to additional tasks to complete. Those tasks are the focus of this week’s column.

Remove Unwanted Plants

A neglected garden probably motivated the landscape renovation project. Neglect often includes trees and woody shrubs that have outgrown their space, lack a role in the new design, or are unhealthy. In some cases, this task will require contracting with an arborist or laborers. Check local ordinances before removing trees.

All herbaceous plants that are unwanted are defined as weeds. These include garden plants and grasses as well as common weeds. Pull or dig larger plants, then remove grasses and weeds efficiently with chemical-free solarization. This method covers the target area with clear plastic so that the sun raises the temperature of the soil, killing weeds, pathogens, nematodes, and insects. For details, see the University of California’s free online publication “Soil Solarization for Gardens & Landscapes.”

Removing weed plants with a do-it-yourself approach could be time-consuming and frustrating. Consider contracted services to get the job done quickly and thoroughly.

Remove Unwanted Hardscape

If your garden includes paving, e.g., sidewalk, patio, walls or outbuildings that are not included in the new design, remove them to free your progress. Again, consider contracted services to speed the work. This would be a good time to invite a disinterested friend to comment on your garden accessory collection, and to remove items that are no longer assets.

Analyze Soil Structure

The gardener should know the structure of the garden’s soil. An ideal soil would have 45% minerals (sand, clay, silt), 5% organic material (plant and animal), 25% air and 25% water.

Click to Enlarge

Soil Textural Triangle

The Soil Texture Triangle illustrates various combinations of sand, clay and silt that might be found in a garden. The mineral content of ideal garden soil, called loam, should be about 40% sand, 40% silt and 20% clay. A simple method to analyze your garden’s soil texture, involves placing a sample of your soil in a jar with water, shaking  and then letting it settle into density layers. Here are Organic Gardening’s brief instructions for a soil texture test.  Also, check out this helpful article by the Marin Master Gardeners.

Notice that these preparations do not include buying plants! For many gardeners, the primary strategy for improving the landscape is to buy plants. That approach, without an overall plan, weakens the landscape design and wastes time and money.

Enjoy your preparation! The fun stuff (selecting and installing plants) comes next.

Gardening Ideas for Fall

Recently, we have considered seasonal projects: harvesting annual seeds for planting and planting bulbs. Here are more timely garden projects.

More about bulbs: gophers avoid daffodils, which are toxic to them, so encircle a favored bed with daffodils to produce both a gopher barrier and a pleasing display for the spring. This project works best with island beds and costs least with wholesale prices (as little as 30¢ per bulb). A good source for daffodils by the hundred: Van Engelen, Inc., at www.vanengelen.com or (860) 567-8734.

Renovating Garden Beds

The fall is the ideal time to renovate a bed that has become neglected, overgrown or plain boring. First, clean out everything unwanted, reserving plants small enough to be relocated or given to friends.

Every three years, divide plants with rhizomes, tubers or bulbs. Divide overgrown plants by cutting their root balls into two or more segments, and replant.

Then, add compost, cultivate, and add fertilizer.

If the bed is larger than four feet in any dimension, install narrow paths to provide access to the plants without compressing the soil or stepping on plants.

Then, select plants that are right for your climate and the bed’s sun exposure, and that will grow to appropriate sizes. Also, choose plants that will combine well and please your eye.

Finally, plant, mulch and water. Keep watering until the rains take over.

Controlling Weeds

The early fall is also time to control both annual and perennial weeds.

Annual weeds include bindweed, chickweed, crab grass, knotweed, lambs-quarters, mallow, pigweed, purple deadnettle, groundsel, nettle (common), purslane, speedwell, spurge and yellow oxalis.

Perennial weeds include bindweed, burdock, dandelion, dock, ground ivy, horsetail, Japanese knotweed, plantain, poison ivy, purslane, quackgrass, thistle, ragweed and anything else you might have.

The primary strategy for organic weed control is to remove weed seeds before they mature and are dispersed. Hoeing weeds before they set seed can be effective with annual weeds.

This method certainly helps to reduce the spread of perennial weeds, but it leaves behind root segments that could re-grow. For this reason, perennial weed control includes removing the entire root system by pulling or digging. Persistence is the gardener’s friend!

Other organic approaches to weed control include providing a three-to-four inch layer of mulch between plants, to deny weed seeds the light and air they need to grow. Dense spacing of desirable plants also can crowd out weeds.

Finally, drip irrigation systems deliver water to desired plants and deny water to weeds.

Enjoy gardening in the fall!

More

A helpful resource for organic weed control is the website, Pests in Gardens and Landscapes: Weeds, maintained by the University of California’s Integrated Pest Management Program. This site includes weed photos, articles and fact sheets in individual weeds that are common in California gardens and landscapes.

A Seasonal Pest

For the past several days, I have been pulling oxalis seedlings from my garden. There are 800 species of oxalis, some of which are desirable ornamental plants, but the species in my garden is no prize.

The pest in my garden is Oxalis pes-caprae (Bermuda Buttercup or Sour Grass), a South African plant that has naturalized in the Monterey Bay area’s similar climate. The plant has clover-like leaves and a bright yellow flower. It’s not unattractive, but it reproduces rapidly and could take over the entire garden in time.

Leaves, root, bulblets

Ocalis-pes-caprae

It reproduces by multiplying its small bulbs, which are around one-quarter inch in diameter. One bulb can produce ten in a single season.

It’s theoretically possible to excavate 100% of the bulbs, but this is time-consuming and unlikely to be successful.

The most effective approach is “old bulb exhaustion,” which involves removing the top growth before it can flower. In this area, flowering occurs in February, with sunnier spots blossoming earlier than shadier spots. The idea is to deprive the old bulb of nutrients that would be provided by the leafy growth above ground, so that the new bulbs will die off.

It is best also to disrupt the new bulbs by cultivation, but this might be difficult if the pest has started close to desirable plants.

In any event, this process requires tilling to remove any new growth that appears in about two weeks. A Dutch hoe, which is good for shallow cultivation, would make short work of the new growth.

Several products are marketed as controls for this pest and other broadleaf plants: Weed-B-Gon Chickweed, Clover & Oxalis Weed Killer, Roundup, Finale, Oxalis X, etc. I do not use synthetic chemicals in my garden, because of concerns that they will harm plants, beneficial insects, microorganisms and perhaps myself and other mammals, in addition to the plants or pests they are intended to control.

There are less toxic concoctions for controlling this plant. For example, one foliar spray recipe calls for two cups of white vinegar, one teaspoon of baking soda, and one teaspoon of liquid detergent. Reportedly, this spray will kill the oxalis plant’s top growth but not the bulbs. It should not be sprayed on desirable plants.

Another control strategy is let chickens snack on this weed. Reportedly, they like it a lot.

The gardener engaged in weed control adventures can find confidence in the knowledge that no plant will survive the persistent removal of its top growth.

Finally, a frustrating encounter with Oxalis pes-caprae should not bias the gardener against less invasive species from the wood sorrel family. One of my favorite nurseries, Annie’s Annuals and Perennials, lists seven Oxalis species as desirable garden plants.

Enjoy your weed-free garden.

More

More information on this weed from the California Invasive Plant Council.

 

Interesting Weeds

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.

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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.

More

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.