Tag Archives: mulching

Growing Cover Crops- Part I

Every drop of rain that hits bare soil is destructive. Over 3000 years ago the Chinese knew how to protect their soil from erosion and increase fertility by planting cover crops. Early Nile Valley inhabitants 3500 years ago also practiced this method of agriculture as did first century Romans. Lupines were planted in poor soil when no animal manure was to be had. I learned this and also how to protect and improve my soil from Orin Martin, manager of the Alan Chadwick Garden at a cover crop workshop recently on the campus.

aster_Michaelmas_daisy.2048“It’s all about the biology of the soil”, Martin said. “You grow the soil that helps you grow the plants”. A cover crop is really anything that covers the soil and protects it from rain, trapping nutrients and preventing them from leaching downward, he explained. Cover crops can increase the tilth of the soil. Quick germinating grasses easily loosen the top foot of soil with their root mass. Legumes have a tap root, a bio drill, that penetrates 30″ downward while alfalfa roots can grow even deeper.

Cover crops like bell beans, vetch and fava beans are especially valuable as they increase nitrogen levels in the soil in two ways. Atmospheric nitrogen can be “fixed” and left in the soil to fertilize subsequent crops. This is in addition to the nitrogen left from the foliage of the legume.

Cover crops are also called green manure when they are chopped up and turned into the soil in spring lettuces_after_cover_cropping.1024before going to seed. The planting of legumes like peas and beans can actually increase nutrients in your soil giving you a net gain which is needed to offset what you take out of the soil when you harvest fruits, vegetables and flowers.

From late September to the end of November is the best time to sow cover crops. You will need to irrigate lightly a couple times per week if it doesn’t rain. You can also wait to sow just before the rains start. Be careful about working overly wet soil however as you can ruin the structure of your soil.

The Chadwick Garden, Martin explained, originally was heavy red clay. 35 years of soil building with bell beans and vetch cover crops and compost have established a level of fertility that now supports several acres of vegetables, fruit trees, berries and beneficial flowering plants. Fall-sown, spring ploughed-down cover crops are the sole fertilizer used for the better part of the last decade.

Soil_builder_cover_crop_mix.1600Martin explained that recent research now recommends planting a tandem of grasses and legumes. Annual cereal grasses such as oats, rye and barley germinated quickly to hold and shield the soil until the legumes take hold. Bell beans, fava beans and vetch which are the best legumes for our area grow slowly the first 3 months then take off growing 70-80% in the last 3 months. The ratio of grass seed to legumes can vary from 10% to 30%.

There are other legumes that fix nitrogen but no where near as efficiently as bell beans.  Crimson clover seed is also more expensive, needs lots of water to sprout and competes poorly with weeds. Mustard causes competition with the fruit trees as bees will concentrate on the mustard flowers instead of the fruit tree flowers.

A question came up about using inoculants on legume seed. Martin explained that our soils have a native resident population of good bacteria that will break down the seed coat and encourage the plant roots to fix more nitrogen especially after cover cropping for a few years.

We all followed Martin out to the cover crop trial plots to see how the different types were growing. Bark chips will soon be applied to the paths. All of the gardens are mulched several times per year with wood chips. A 10 year study, Martin explained, demonstrated the amazing benefits of ramial chipped wood which is the type the tree service companies provide for free.

We watched him work the soil lightly with a metal bow rake then broadcast 8-10 seeds per square foot. Weeds were already cleared but Martin said this step doesn’t have to be perfect. Afterward the area was raked again lightly 1-2″ down and covered with 3-4″ of straw. Wood chips would be fine, too. Mulch heavier if you have bird competition. Cover crops are vigorous and will come up through just about anything, he said.  Water in lightly.

There are 3 ways to fertilize, Martin said. You can buy chemical fertilizer which is expensive and doesn’t do much for the soil. You can apply compost, which being carbon based, ramps up beneficial fungal organisms in the soil. Or you can cover crop or grow green manure which increases beneficial soil bacteria. Orin Martin has proof of the benefits of the last two methods.

Garden Tips for March

Spring is in the air. It’s always exciting to see the plants in the garden come to life. I’ve been invited to tour a  garden in Scotts Valley in April when many of the early flowering plants will be in bloom.  I’ve been to this garden before and there’s always an interesting tree, shrub or flower to enjoy.

One of my long term goals is to view the great gardens in the Santa Cruz Mountains. If you have a garden that you think others would like to hear about and you are willing to share it with me, please contact me. I’d love to spend time with you in your garden.

There’s so much to do now in the garden. If you are feeling overwhelmed here are some suggestions for the more important to-do’s.

* Check drip systems for leaks or clogged emitters. Flush sediment from filters and check screens for algae. You may need to add emitters if plants have grown significantly.

* Finish pruning and clean-up of trees, shrubs, vines and perennials. This includes fireblight die-back on pears, apples, hawthorn, pyracantha, photinia, crabapple quince and toyon., Prune out and discard diseased branches making the cut at least 6-8" below blighted tissue. Clean the pruning blades with alcohol or a 1:5 solution of household bleach to prevent spread of the disease. Also finish pruning and cutting back perennials and ornamental grasses. Go ahead and give grasses a 3-5" crewcut so fresh growth can emerge. Cut back old foliage of maiden hair ferns to allow new growth to take center stage. If you have Western sword ferns or another type that has winter or thrip damage, remove shabby looking fronds. Even if you have to cut back the entire fern it’s OK. It will regrow in just of couple of months.  Prune any other frost damaged plants when you see new growth begin.

* Spread fresh compost around all your plants. Good soil is the secret to successful gardening. The first principle of organic gardening is to feed the soil and it will feed the plant. Remember that all gardening used to be organic. Layer compost and or mulch on top of the soil and let it slowly decompose and filter down into the earth.

* As you plant new additions to the garden add organic matter to the soil. If your garden’s soil is sandy, organic matter enriches it and allows it to hold water more efficiently. If your soil tends toward clay, organic matter will loosen it up and improve drainage. In well-amended soil, plants grow deep roots, are hardier and more resistant to disease. Organic matter, such as compost, planting mix and well-rotted manure, boosts nutrition and improves soil structure.

* Fertilize if you haven’t already done so. Citrus, shrubs and fruit trees just emerging from dormancy are begging for their first meal of the season. Lawns begin their spring growth now also and benefit from a boost of nitrogen. You can also spread a thin layer of composted manure over you lawn. Leaving you grass clippings on the lawn will benefit it by shading the roots as it get warmer and as they break down they help feed it, too. Perennials benefit from both a fresh layer of compost or manure and a light application of balanced fertilizer. They respond to phosphorus especially in the spring for root growth, stem sturdiness and flower development. Wait until azaleas, camellias and rhododendron have finished blooming before feeding them.

* The most important to-do for March is to take time out and enjoy your garden and our beautiful surroundings. Those last few weeds will be there tomorrow but you’ll never get another today.

How and Why to Mulch

We never stop learning. No matter how much we think we know about a subject, there is always more to learn. 


Take mulching, for example.  Mulching is simply covering the soil around plants with a protective material, organic or inorganic.  This helps maintain moisture in the garden, decreases soil compaction, modifies soil temperatures and adds nutrients and humus to the soil as they decompose. 

It’s that time of year to mulch existing perennials, shrubs and trees. While a little chicken manure is good worked into the veggie garden, composted horse manure works better as a mulch for the rest of the garden.  Chicken manure is high in phosphates and too much can inhibit beneficial microbes in the soil.  It also feed the weeds.  They love it.  A better method would be to cover a layer of compost or  composted horse or steer manure with a thick 4" layer of wood chips.

Wood chips offer additional benefits: They’re local, free from arborists, and affordable from the transfer station in Ben Lomond  . Any disease in the chips doesn’t transfer to healthy plant roots, as long as you don’t dig the chips into the soil.  You can also buy clean chips from landscape supply yards or in convenient bags from nurseries.

To make the most of , learn what kind of soil you’re working with.  The University of Massachusetts at Amherst  ( www.umass.edu/plsoils/soiltest/ ) offers a basic standard test for $9.  It includes  pH, buffer pH, extractable nutrients (P, K, Ca, Mg, Fe, Mn, Zn, Cu, B), extractable heavy metals (Pb, Cd, Ni, Cr), and extractable aluminum, cation exchange capacity, percent base saturation. 

Our local soil testing laboratory in Watsonville, Perry Laboratory, offers a comprehensive test.  Their web site is  www.perrylaboratory.com.  The landscape package they offer includes basic fertility, micronutrients, salinity, alkalinity, texture, organic matter content and lime content. The main difference between the two labs is that Perry’s  will give you  specific recommendations based on your results to improve your soil. 

Make sure you get fresh mulch spread over your garden plants soon.  You’ll be amazed at the difference in your garden this season.  A mulched garden is a happy garden.