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- Oak trees of Marin
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- Seeds hold the miracle of life, so save, swap and share them
- Sold on Salvia
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- Growing In Your Garden Now - Fava Beans
- Using water effectively in the garden
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- Growing a salad in a pot
- Rain gardens: an attractive solution to a challenging environmental problem
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- Australian plants in winter
- Get a head start on spring with cold frames
- Snails and slugs: keep them out of the garden
- Sow seeds now for flowers in spring and summer
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- Plants made for the shade
- Chinese pistache tree glows in autumn
- Attracting honey and native bees to your garden
- Sow wildflower seeds in fall for spring show
- Native shrubs create a visual anchor in landscapes - fast
- What to plant in the fall-winter veggie garden
- Proper pruning of wisteria for a plethora of blossoms
- Compost for every corner of your spring garden
- All about mushrooms
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- How to plant a fruit tree
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- What's that plant?
- Bright spots of color lift the drabness of the winter garden
- Books for Marin gardeners
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- Why bees matter, and how you can help
- Picking the Right Plant for the Right Place in Your Garden
- What's That Plant?
- Keeping Cut Flowers Fresh
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- Short on space? Containers!
- Herbs: tough, attractive, practical
- These plants are true companions
- Companion planting in the vegetable garden
- Get Grounded – Healthy Soil Does Matter
- Mushrooms on the March
- Our Gentle Winters are Good for Vegetables
- Rodents like it Warm
- Know What Makes an Invasive Species Invasive
- California Natives - Plant Like a Native
- Consider a Simple Water-Catchment System and Rain Garden/Bioswale Before Winter Rains Arrive
- Have You Scheduled a FREE Bay-Friendly Garden Walk?
- A Green Autumn
- Rx for Pests: Ants
- Fine Tune Your Garden
- Colorful Drought-Tolerant Plants Thrive in Marin
- Water Restrictions and Recognizing Signs of Water Stress
- UC Researcher Is Helping Plants Survive the Drought
- Summer Is Perfect For Peppers
- Do the Leaves on Your Trees Look Scorched?
- Fine Tune Your Garden
- How to Recognize Drought and Water Stress
- Spring is the Time for Potatoes, Asparagus and Citrus
- Don't Let Stink Bugs... Bug Your Vegetables
- Harvesting Berries
- Water Heroes
- Natural Cold Storage
- Fruit Trees; Why We Treat Them in Dormancy
- Fondness for Old Friends
- What Happens to Garden Bad Guys in Winter?
- Plants that aren't blown away by the wind
- A hill o' beans
- Fruit tree thinning
- Fragrant plants: Add some chocolate or Kool-Aid to your garden
- Top 10 resolutions for Marin gardeners
- Trees with interesting bark shine in winter
- Who says your garden has to be green?
- Plant bulbs now for spring beauty
- Gardener's checklist for fall
- Cover crops boost soil in vegetable beds
- Rx: Living with deer
- Growing berries in Marin
- How to build healthy soil
- Gardener's checklist for summer
- Water-saving tips for the home garden
- Gardener's checklist for spring
- Stop the popping - Controlling hairy bittercress
- How to control aphids
- Brightening up the winter garden
- Selecting a fruit tree
- What to plant and harvest in the winter vegetable garden
- Rain, rain, don't go away
- Gardener's checklist for winter
- Getting rid of rats
- Fall: a time for planning and planting
- Asparagus: spears for years
- Lawn: use it or lose it
- Rx for powdery mildew
- Community Outreach Projects of UC Marin Master Gardeners
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- Selecting Plants
- Marin Master Gardener Independent Journal Articles
- How to Become a Master Gardener
- UC Marin Master Gardeners Opportunity Fund: Providing for the Future
How to build healthy soil
The dirt on your soil
Soil, the loose upper six to eight inches of earth, is teeming with microorganisms (animal), the residue of live and dead plants (vegetable) and the decomposed rock from which the soil originated (mineral). Soil supplies plant roots with a source of air, water and nutrients plus insulates them from extreme changes in temperature. Topsoil is the layer most influenced by climate and most enriched by the addition of organic matter. It is the cornerstone of a healthy garden.
Here are the key components of healthy soil and the steps you can take to get there.
Soil texture and structure: working toward loam
Soil texture is grouped into three categories: coarse (sandy soils), medium (loamy soils) and fine (clay soils). Very coarse, sandy soil dries out rapidly and is difficult to maintain at a high fertility level. It feels gritty, doesn't form clods, and can appear somewhat dusty when dry. Clay soil, which is common in Marin County, retains more water, has slower air and water movement and holds more mineral nutrients than sandy soils. Clay soil feels smooth between the fingers and is sticky when wet. Clay soils amended with organic matter are some of the most productive farmland soils on earth.
Loamy soil has roughly equal proportions of sand, silt and clay. It allows roots to penetrate easily and it drains well. The majority of plants -- and gardeners -- enjoy the benefits of loamy soil.
Good-quality topsoil has a crumb-like structure. The tiny pores between soil particles allow water from the soil surface to infiltrate so water is retained but excess amounts drain down to allow space for air circulation.
Understanding soil nutrients and pH
Ideal soil contains sufficient quantities of approximately 20 essential plant nutrients. Carbon, hydrogen and oxygen are drawn from air and soil water; the other nutrients are dissolved in the soil water and absorbed by plant roots. Nitrogen (N), phosphorus (P) and potassium (K) are the elements plants need in the largest quantities.
Soil pH is a measure of the soil's acidity or alkalinity. Soil pH affects the solubility of soil minerals, the availability of nutrients to plants, and the activity of microorganisms. The midpoint of the (1 to 14 point) pH scale (7.0) is neutral. Numbers below 7 are increasingly acidic as the number decreases; numbers above 7, increasingly alkaline. Most plants prefer a pH ranging from 5.5 to 7.5 or slightly acidic to neutral, the range in which all plant nutrients are most readily available. Soil microbes are most active in this range also.
Gardener's to do list for great soil
Test. The most accurate way to determine the nutrient content, pH, structure and texture of soil is to send a sample of your soil for analysis to a soil-testing laboratory. Contact the Master Gardener Help Desk at 473-4204 for more information. Do-it-yourself soil testing kits are also available at garden centers but do not produce as detailed information.
Tread lightly. Many gardeners, anxious to get into their gardens in early spring, work their soil when it is still too wet. Soil should not be dug until it is sufficiently dry enough to crumble when worked and has reached a temperature of 50 degrees. Soils high in clay content are easily damaged if worked when wet. Foot traffic and heavy equipment crush the soil's pores, which limits plant's roots access to nutrients, air and water.
Amend. Amend soil with compost. A good rule of thumb when incorporating compost as a soil amendment is 25 percent of the planned depth, i.e., two inches of organic matter worked in to a depth of eight inches. Animal manure is another good soil amendment. Follow application instructions posted on the bag. Fresh cattle manure should be applied in fall or winter. Work the manure in right after spreading as this helps decompose the manure and lessen odors.
Mulch. After amending with compost, add a layer of approximately three inches of mulch every year. Mulching reduces moisture evaporation, suppresses weeds, moderates soil temperature and helps prevent soil compaction. In addition, mulches decompose slowly thereby adding organic matter over a longer period. Use bark in perennial beds if possible, since it decomposes more slowly.
Weed. Weeds crowd plants, compete for nutrients and moisture and often harbor pests. Eradicate as needed.
The health of your soil determines the health of your plants. The mantra of Master Gardeners -- "compost, compost, compost, mulch, mulch, mulch" -- still rings true. The best way to amend your soil's structure and to provide oxygen, moisture and nutrients is to add moderate amounts of compost and top dress with mulch. Begin by testing your soil for pH and nutrient content. Follow these recommendations and with time, your garden soil and the plants you grow will reward you with beauty and bounty.
Contributors: Marie Narlock, Martha Proctor