LynnAnnRose and I have a plot at our neighborhood community garden. After removing the drip irrigation tubing and raking back last year’s straw mulch, we prepared the soil and planted some pre-sprouted sugar snap peas and radishes so far. The soil is sandy, in contrast to the compacted, silty soil in Flagstaff; it required very little loosening. We had to buy some compost to spread on top since we don’t have our own compost bin yet. Compost works to improve all types of soil. We added plenty of new straw mulch on top to prevent soil water evaporation. The tomato cages on top are preventing the mulch from blowing away.
We bought the pea and radish seeds and other heirloom seeds from Native Seed/SEARCH, including one of LynnAnnRose’s favorite foods, Chimayo chiles. Chimayo is a small village not far from Santa Fe. The chiles have been grown for centuries by Hispanic farmers in the region. We also have some purchased seedlings of vegetables and herbs that will be planted mostly in out back and front yards. We plan to save the seeds from the open-pollinated varieties.
Native Seed/SEARCH is a regional seed bank for Native American and Southwest Hispanic seed varieties. Limited quantities of these seeds are available for purchase.
Mulch is happening. My leafy greens bed has been doing quite well with cold-tolerant species like self-seeded arugula, dandelions, and orach, a perennial related to spinach. The cold season herbs are still leafy, too. The Chinese garlic chives are self-seeding around the apple trees. The weather is supposed to turn colder this week. And we are supposed to have our first hard freeze tonight in Flagstaff, Arizona. I expect the perennial greens and herbs will go dormant.
Dan sifted 18 gallons of compost at Juniper Street community garden. We deposit all of our food scraps at this community composting site. Dan has done a lot of work to maintain and improve the compost bins and turn the compost over the years. See what this dark, rich compost with composting worms looked like back in June before the monsoon rains sped up decomposition.
I spread the compost on my two apple tree beds, container gardening beds around the outside of the house, and the container beds on our balconies. I first raked back existing mulch, spread the compost, then replaced the mulch. When the apple trees’ leaves fall in a month or so, they will create a natural mulch topping for the two miniature forest gardens.
Topsoil builds slowly, more slowly in semi-arid climates than in humid temperate climates (I’m talking decades and centuries). Stable humus-rich topsoil lasts for centuries if cared for properly. The soil microbiome needs plenty of freshly-deposited organic matter on the surface for food and to create a spongy mulch layer. Fertilize from the top down, as happens in wild ecosystems. Plant trees and other perennials to create stable microclimates that protect soil.
Focus your soil-improvement labor, time and money on beds for intensive annual vegetable and herb growing and on tree planting sites if your yard is not very large. Apply compost in the fall at a minimum of a half-inch thick layer. Add two to three inches if you have enough to go around. The compost can be half-finished. Add more, optionally, in the spring; spring compost must be fully finished. If you are using the cool compost method, you can build a frame with a wire-mesh bottom (quarter-inch holes) for sifting out un-composted material. Hardware stores sell mesh with quarter-inch or half-inch spacing, depending on how fine you like your finished soil.
Dan’s father, and his father’s wife, came to visit. We took them on a tour of Wupatki and Sunset Crater National Monuments, which are right next to one another northeast of Flagstaff.
We stopped at Wukoki Ruin, my favorite pueblo in Wupatki National Monument. You can see a light dusting of volcanic cinders around the ruin from Sunset Crater. The cinders used to be deeper in this area but have eroded away over the last 1000 years.
Sunset Crater, today a 1000-foot-high cinder cone, probably erupted in the 1080s. We walked up to the Bonito Lava Flow, which erupted from the base of the cinder cone. I told them to smell the ponderosa pine bark, which smells like butterscotch, and Dan’s father decided to become a tree hugger.
A thick layer of ash and cinders piled up for miles around Sunset Crater. The Ancestral Puebloans, which here included the ancestors of some Hopi clans, called the Sinagua by archeologists, noticed that native plants grew bigger and faster in areas with roughly one to four inches of cinders (deeper cinder deposits inhibit plant growth). Farmers planted in the cinder mulch. Warm season crops like corn, beans and squash benefited from the heat-retaining cinders and extra soil moisture.
The Sinagua had previously lived in small clusters of pit houses. After the eruptions began, they built pueblos from rocks and mud plaster. At its peak, the biggest pueblo in the area, Wupatki Pueblo in Wupatki National Monument, had 100 rooms and was three stories high. It housed as many as 100 or more people. The pueblo was inhabited for 150 years, until the Great Drought of the late 1200s.
The first photo is my home rhubarb bed. It is a self-watering bed that I also water from the top. Rhubarb is a Siberian native that prefers cool air and soil temperatures and needs some shading in very sunny or arid climates. At my 7,000 foot elevation the sunlight is especially strong, with more ultraviolet wavelengths reaching the ground than in lower elevation and humid climates. The poplar trees shade the bed for much of the day in the western-facing site that would otherwise be very hot, sunny and dry at this time of year (spring is a dry season in the arid and semi-arid Southwest USA).
The second photo is my old rhubarb bed at Juniper Street Community Garden, now gardened by someone else. As you can see, the plants are going to seed. When rhubarb plants have reached five to eight years old, they need to be divided or they will go to seed. In this case, a strong contributing factor is that the plants look seriously underwatered; the leaves are small and tough-looking, rather than large and tender like the ones in my home rhubarb bed. Because rhubarb is a cool season plant, warm weather and not enough water will force the plants into setting seed because they think they might die.
My advice to this unknown gardener is to divide the crowns, cut off the flowering stalks, and keep the plants well-watered. The community garden needs more shade and wind protection as well (one of the reasons I no longer garden there; the church that owns the land is not open to permaculture site modification for better growing conditions).
Vegetables need the equivalent of one inch of water across the garden bed each week. This quantity doesn’t include water wasted through evaporation and transpiration from leaves. The amount of water needed varies according to the characteristics of the soil, use of mulch (if you live in an arid or semi-arid climate, use it liberally), shade, wind breaks, and the garden’s aspect—the direction it faces (north, south, east, west), as well as a few other factors. For example, soil high in organic matter holds much more moisture than poorer soil.
These are my two self-watering raised beds on the western side of my house. They are partially shaded in summer by the poplar trees that help cool the house. I use these beds to grow cool season crops (leafy greens, rhubarb, etc.) that wither in too much Arizona heat and sunlight. I live in a neighborhood with a Homeowners’ Association. The HOA board had to approve of my beds, which are in the common area owned by everyone in the townhome complex, so I chose these beds made of recycled plastic to blend into the color scheme. The hoses distribute both greywater and roofwater to the poplar trees. The beds are surrounded by barberry shrubs (Oregon grape).
Raised beds are a traditional annual gardening method. Permaculture rainwater harvesting enthusiasts prefer sunken rain gardens with their surfaces below the ground surface. Swales have both a raised berm and a sunken water catchment area. Neither raised nor sunken beds are “better” than the other. The choice depends on what you want to grow, where, and when, as well as other concerns like physical ability. The two types of beds create different microclimates. In temperate climates the following points hold true:
Raised beds & berm tops Sunken beds, swales, waffle gardens
Warm up faster in spring Warm up slower in spring
Hotter during the summer Cooler during the summer
Warm season crops Cool season crops during the summer
Stay warmer into the fall Cool down faster in the fall
Raise plants above cold air Cool air flows into sunken beds at night
Less frost exposure Plants are more susceptible to frost
More evapotranspiration Conserve moisture in soil and leaves
Soil drains faster Soil drains more slowly
Require extra irrigation Collect rainwater runoff passively
Raised beds also:
make it easier for handicapped people to garden.
can be built easily atop bedrock or hardpan soils or existing lawns.
These amazing drawings of rhubarb and beet roots are from the book Dry-Farming: a System of Agriculture for Countries Under a Low Rainfall, John Widtsoe, originally published in 1911. The book is available free online. Researchers carefully excavated real plant roots in ideal Midwestern USA loam topsoil that was more than 10 feet thick and drew what they saw.
Ideal garden loam is approximately 40 percent sand, 40 percent silt, and 20 percent clay. Half the soil volume is composed of solids composed of weathered bedrock (mineral soil) plus decayed organic matter. The other half is pore space (soil particles aggregate together, which creates air spaces in between the particles). The coarser the soil particles are, the faster water drains out of the soil; the finer the particles, the slower the drainage. Poor drainage caused by high clay composition or compacted silt causes waterlogging. Organic matter improves the texture and other characteristics of all soil types, slowly turning them into perfect garden loam.
Loam topsoil is well-aerated, allowing plant roots and soil organisms to breathe properly. After loam soil has been wetted and free drainage has stopped, half of the pore space will be filled with water. Soil that is high in organic matter will hold water without waterlogging as clay soil does, or draining excessively beyond the root zone as in sand and volcanic cinder soils. Water that drains below plant roots is no longer available to plants.
Fully-formed humus is called stable humus. In topsoil with excellent structure, soil particles group together into large granules called aggregates. The glue-like gels that hold the humus and mineral soil particles together are produced by bacteria and fungi (the gels are colloidal starches, i.e., carbohydrates suspended in water to form gums, like starch-thickened gravy). Microbes (mostly bacteria and protozoa) live within the gel coating because they must stay immersed in water. The soil aggregates are held together in larger masses by plant roots and fungal hyphae. The pores between aggregates provide passageways for oxygen, rain and snowmelt, plant roots and tiny invertebrates. Stable humus resists further decomposition and erosion. In addition to pH buffering and its other functions, it holds water like a sponge (80–90 percent of its weight), keeps tons of carbon out of the atmosphere and chemically binds toxic heavy metals into forms that cannot harm life.
Root growth occurs at the root apex, which is protected by a root cap and lubricated by mucilage. It used to be believed that only root tips absorbed water and nutrients. It is now known the entire length of roots can absorb nitrate, ammonium (a bioavailable nitrogen compound), phosphate and potassium. Some nutrients, however, are dependent on healthy root tips for plant uptake.
“The efficiency of the root as an absorbing organ depends on its absorptive surface area relative to its volume, created by root hairs [extending beyond the roots themselves]. … It has been estimated that a 4-month-old rye plant … has a total area of over 600 square meters in contact with the soil.” [Science and the Garden, p. 35.]
Mycorrhizal fungal webs expand that surface area by several orders of magnitude.