Wednesday, April 2, 2014

Late rains bring flowers and weeds

Although my own garden is not short on weeds - and being on the Theodore Payne Native Plant Garden Tour this Sunday, it really should be - I spent much of the day bashing, scything, pruning, pulling, wrestling, and cursing the weeds at the nature park. The late rains have brought more wildflowers, lovely clouds, even a rainbow over the Angeles, but also lots of weeds to the park. The plants we planted on February 1 are doing very well, also thanks to the extra moisture.

Rainbow over Angeles National Forest. It was much more vivid and striking than picture shows.
 So if you have a spare moment, go on down to the park, and be sure to pull a few weeds.

Sunday, March 23, 2014

Colors in the nature park

It has been more than month and a half since I last posted. Though my electronic mouth has been silent -  if you don't count a few murmurs on Facebook, Twitter and Instagram - much has been happening in the nature park and my own garden.

Following the only significant rain of the year, the weeds in both places have been having a party. I have spent more time at the nature park than I should given that my house is on the Theodore Payne Native Plant Garden Tour again this year. So if you visit Wild Suburbia on April 6, please forgive me the "occasional" garden spurge, knowing that the time was spent pulling mustard, radish, tocalote, horehound, etc. etc. in the nature park. Weeding there means that seedlings of California buckwheat, sage, sagebrush and annual amsinckia will have a chance to take hold, tipping the balance from weedy lot to coastal sage scrub habitat.

And of course, there are the grandchildren. Much more important to watch them grow then pull a few weeds. If, however, you can get them to pull a few, then each slow day now is leveraged for the future.

Wish I could bend like this while weeding. Ahhh, to be young!

This album includes pictures of some of the plants blooming in the park. I will try to post more flower pictures so people can look for these beauties themselves.

Here's a slideshow of the February 1, 2014 MLK Service Day Planting Party. I have been trying to keep these new plants watered. Oh, to have another rainfall!

Thursday, January 30, 2014

Working with clay soil

There is much debate about the best way to garden with clay soil. Growing native plants is very different than cycling through annual vegetables and herbs, and so recommendations for edible gardens usually do not apply to natives. The best approach to native plant gardening with clay soil, as long as weeds or other plants have been able to grow in the area, is to select plants that do not require excellent or good drainage. There are lists of native plants that do well in clay soil (see below) but each garden is different and so gardeners should be adventurous - within reason!

If nothing grows
In the rare case where nothing is found growing in the soil, one needs to enlist professional assistance to determine the problem and the appropriate solution. Causes may include chemical imbalances, the presence of toxic chemicals, high salinity, or the absence of microorganisms, among other things. There is no way forward without knowing precisely what the problems are.

Texture and structure
This, however, is not a common in most residential yards. Usually, although we are unable to grow some of the plants we prefer, weeds seem to like the soil just fine. Beside selecting plants that can grow in heavier soil, certain gardening practices will improve your success. With clay soil one must be very careful to avoid compaction. The term clay soil refers to the texture of the soil, that is the preponderance of very, very small particles. Sandy soil, in contrast, has an abundance of large-sized particles. The tiny clay particles are typically flat in shape, like small flakes. The flakes can easily stick to each other and other particles resulting in compacted brick-like soil (think clay bricks!). So the best advice is to avoid digging, walking, driving or dragging a wheelbarrow across wet, clay soil.

In addition to texture, soil also has structure. This term refers to the arrangement of soil particles into clumps or aggregates. Clay soil with good structure has gaps, pores, and small cracks throughout the soil that improve infiltration, drainage, and aeration. Rototilling and cultivation destroy soil structure - and set the stage for a healthy crop of weeds. Working wet clay soil, as noted above, damages  soil structure, resulting in compacted, often impenetrable soil. Cultivating dry, clay soil, also, damages its structure, and so it is best to garden when the soil is moderately wet. You can tell the moisture is correct if a small ball of soil falls apart when handled. Dry, clay soil will hold together until it breaks, while wet, clay soil will just, well act like clay.

Amending soil
Amending clay soil is difficult to do properly, and if done incorrectly, can exacerbate the problem. Since clay soil has a high percentage of very small particles, one would think that adding sand would improve drainage and aeration. However, if too little sand is added to clay soil, the result is pretty much the same as creating concrete - clay plus sand. The grains of sand migrate to the small pores in the soil where clay particles surround and stick to them. It is generally recommended that coarse sand in the amount of 50% or more by volume is required to improve drainage. Organic material can be added to the mix, though clay soil itself is fairly rich in nutrients. The organics will decompose over time.

"Soil conditioners" are often recommended for the improvement of heavy soils. They are only helpful, however, if they correct chemical problems. Gypsum, calcium sulfate, may be recommended to improve drainage in clay soils. However, its real purpose is to replace sodium in saline or sodic soils with calcium. If it is determined through a soil test that there is too much sodium, then the soil chemistry needs to be corrected, either through leaching or the addition of gypsum. However, it has not been shown that gypsum improves soil fertility, structure or pH for other soils (The Myth of Gypsum Magic, Linda Chalker-Scott). Lime, another commonly recommended amendment, is made from limestone and contains calcium carbonate and sometimes magnesium carbonate. It is used to raise soil pH, meaning it decreases soil acidity. Western soils are usually fairly alkaline to start with, and so, in addition to adding calcium and magnesium, which may not be needed, it also increases alkalinity. Chemical soil conditioners should only be applied when called for by a soil test.

When amending clay soil one needs to consider what happens at the boundary between the amended soil and the native soil. Water can collect there leading to root problems down the line. Even if water is prevented from collecting, plant roots may not be able to penetrate the harder clay soil, limiting the size and form of the root system.

What to do
I can hear the frustrated gardener say: Okay, I won't amend the soil, I won't work it or walk on it when it is saturated, I will limit myself to plants that do not require great drainage, but you have not seen my soil. It is terrible. Can't I do something to improve it?

Many gardeners have found that applying a thick layer of coarse mulch, approximately 2 - 5 inches, works wonders. The mulch protects the soil from compaction, and over a short period of time worms and other insects and microorganisms do much to improve soil structure. I would suggest, though, that if you are planning a desert garden, inorganic mulch is more appropriate since you do not want to further increase soil fertility. In this case, the mulch can still protect the soil, but you will have to be patient as it can take much longer for desert soils to improve. 

When planting in clay soil, dig the hole wider but not deeper than the root ball. Roughen sides of the planting hole. Backfill with native soil, do not add amendment to the planting hole. I would also suggest that you remove as much of the potting mix as you can without damaging the root ball. Leaving the container soil on the roots creates conditions similar to adding amended soil to the planting hole. Since water cannot easily move into the surrounding clay soil, the roots may rot in the wet planting hole.

Irrigate slowly to allow water to penetrate with no runoff.  On/off cycling allows time for deeper water infiltration. Check for moisture several inches below the surface. Do not water again until soil is moderately dry.

Try growing some durable wildflowers like California poppies to begin the process of developing good soil structure. A layer of coarse gravel mulch may help the seedlings germinate and penetrate the soil.

To increase variety in your garden, grow some plants in containers or raised beds (at least two feet deep, and prepared so water does not accumulate at interface) where you can easily modify soil conditions. Remember that plant roots may be unable to penetrate the soil beneath and around a raised bed and select smaller plants that can grow in the confined space.

And most importantly, be patient. As plants start to grow in your clay soil, root growth and other biological activity will gradually improve the soil structure. The garden will settle in, you will learn what works and what doesn't work, and your patience will be rewarded.

Growing natives in clay soil. Wild Suburbia how-to sheet.
Horticultural Myths by Linda Chalker-Scott, Washington State University, Extension Urban Horticulture
Improving Clay Soils, by Keith Baldwin, Fine Gardening.
Native Plants Tolerant of Clay Soils. Leaflets of the Santa Barbara Botanic Garden. Vol. 1, No. 12, 1969. pp. 125-126.
Soil Science & Management, 3rd Edition, by Edward J. Plaster. 1997. Delmar Publishers.
Working with Clay Soil. Bachman's.

California Native Plants Suitable for Clay Soils in San Francisco Bay Area Gardens, Gardening With Native, CNPS – Santa Clara Valley Chapter.
Clay Tolerant Native Plants, Yerba Buena Nursery.
Plants for Clay Soil, Weeding Wild Suburbia.

Saturday, January 25, 2014

Why we weed in the park

The green arrow points to a sagebrush seedling, the progeny of native sagebrush that was planted in the nature park to re-create coastal sage scrub habitat. The rest of the seedlings (red arrows) are non-native weeds that would outgrow this and other native seedlings if left to their own devices. This is why we spend time carefully hand-weeding neighborhood bullies.

Non-native mallow, mustard and horehound will claim the nature park as their territory unless we take action.
Howie, the horse, does a neat, clean job of weeding out the non-native, annual grasses. Thanks, Howie.

Monday, January 20, 2014


Just thought I'd upload some pictures of gardens that are based on coastal sage scrub and chaparral plant communities. Naturalistic paths and boulders help define the space in a pleasing way.
The gardens shown are:

Maloof Garden
Eaton Canyon Nature Center
South Pasadena Nature Park


140120_ScrubChaparral, a set on Flickr.