Why Plant Cover Crops?

Cover crop mix

Every drop of rain that hits bare soil is destructive. Over 3000 years ago the Chinese increased their soil’s fertility and protected it from erosion by planting cover crops. Early Nile Valley inhabitants 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. Planting a cover crop is another way to improve and retain your soil.

A cover crop is really anything that covers the soil and protects it from rain, trapping nutrients and preventing them from leaching downward. 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. Growing a cover crop also increases beneficial soil bacteria.

Cover crops are called green manure when they are chopped up and turned into the soil in spring before 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.

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.

Orin Martin shows the extensive root system of bell beans

Recent research now recommends planting a mixture 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 nowhere near as efficiently as bell beans. Crimson clover seed is 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.

You don?t need to use innoculants on legume seed. 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.

Work the soil lightly with a metal bow rake then broadcast 8-10 seeds per square foot. Weeds should be already cleared but this step doesn’t have to be perfect. Afterward the area should be raked again lightly 1-2 inches down and covered with 3-4 inches 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. Water in lightly.

Groundcover on Slopes

California native ceanothus goundcover

Now that we?ve had a bit of rain – and I?ll admit .37 inches is not much to write home about – it?s time to get serious about planting groundcover to protect that valuable soil on your slope.

Living ground covers add beauty to the garden while holding the soil in place and preventing erosion. They contribute to soil health by encouraging microorganisms. A garden wouldn?t thrive as well without groundcovers.

There are many attractive plants that work well for erosion control. Often they need to adapt to shallow, poor soil and cope with less than ideal conditions all while putting down dense, strong roots. California natives are among those well suited to this job.

Calycanthus occidentalis

Common native shrubs that fit the bill include ceanothus and manzanita of all types. Ceanothus maritimus, ?Heart?s Desire?, ?Valley Violet? and ?Anchor Bay? are good groundcover that are not attractive to deer. Spicebush (calycanthus occidentalis) has fragrant flowers in late spring blooming well into summer with a spicy fragrance. The foliage is aromatic when crushed and changes from a spring green color to pale golden in autumn. Decorative woody fruits last into winter making this shrub attractive year round. It thrives with infrequent to moderate watering. Combine with coffeeberry and deer grass in sunnier spots or with Douglas iris and giant chain fern in shaded spots below trees. All these plants have deep roots and control erosion.

King Edward VII Flowering Currant

Flowering Currant (ribes sanguinem) is another show stopper capable of controlling erosion. In the spring the long, flower clusters of this deciduous shrub will dominate your garden. Choose from white flowering ‘White Icicle’ or ?Barrie Coate” and ‘King Edward VII’ with spectacular deep red flower clusters. ‘Spring Showers’ has 8 inch long pink clusters. Grow in full sun to partial shade. This California native requires little water once established and is a valuable nectar source for hummingbirds.

Some other good California native shrubs for erosion control are western redbud, mountain mahogany, western mock orange, lemonade berry, toyon, matilija poppy, western elderberry (sambucus nigra and mexicana) and baccharis.

Bush poppy

Bush poppy (dendromecon rigid) is another native found right here in our area and needs no irrigation at all once established. Beautiful bright yellow, poppy-like flowers cover the plant in spring. They can be propagated from cuttings taken in summer and are pest and disease free.

Common Snowberry or Creeping Snowberry (Symphoricarpos) will hold the soil on steep banks. This native tolerates poor soil, lower light and general neglect. Evergreen Currant (ribes viburnifolium) and creeping mahonia also tolerate shady conditions.

Smaller natives that put down deep roots are yarrow, coast aster, California fuchsia, wild grape, mimulus, buckwheat, wild rose and salvias including ?Bees Bliss?.

Low water-use non-native ground covers like cistus salviifolius, grevillea lanigera, rosemany prostratus, rubus pentalabous, correa and sarcococcas are also good low-water choices.

Remember when setting plants on a steep slope to arrange them in staggered rows. Make an individual terrace for each plant and create a basin or low spot behind each one – not around the stem – to catch water. Set the crowns of the plants high so they won’t become saturated and rot after watering and make sure mulch does not build up around the stem.

It’s time to enjoy the fall weather and cover that ground before winter.

Autumnal Equinox

The autumnal equinox will arrive on Monday, September 23rd this year. It’s the official start of fall when the sun crosses the celestial equator and moves southward. The earth’s axis of rotation is perpendicular to the line connecting the centers of the earth and the sun on this day. Many people believe that the earth experiences 12 hours each of day and night on the equinox. However, this is not exactly the case.

During the equinox, the length is nearly equal but not entirely because the day is slightly longer in places that are further away from the equator – like where we live. Also the sun takes longer to rise and set in these locations as it does not set straight down but in a horizontal direction.

With the changing of the season, take advantage of fall planting weather. It was a hot summer and I?m ready for fall. This is the perfect time for transplanting or adding new plants to your garden. Why? Cooler air is kinder to plant foliage while soil temperatures are still warm creating an excellent environment for new root growth. In the fall many plants and trees, even broadleaf evergreens, are entering a period of dormancy. With no need to allocate resources into foliage, plants are transferring all their energy into roots and storing nutrients for the cool months ahead. By spring, the new root systems should be well established.

I had hoped to spend some time at the UCSC Arboretum earlier this year when the showy pincushion and leucospermum protea were flowering but I never made it. Because anytime?s a good time to visit the arboretum I dropped by recently. There is always something in bloom there and the hummingbirds know it. Here are just a few of the spectacular fall blooming plants that you might want to add to your own garden.

Leaucadendron Jester

The Leaucadendron ?Jester? (Sunshine Conebush), another type of protea, were loaded with brilliant deep wine-red bracts. This evergreen shrub grows to 5 feet tall and is very pest and disease resistant. Deer aren?t interested in the showy bright pink, cream and green foliage and it?s quite drought tolerant once established. You can cut the branches as they are prized for use in floral arrangement. People think that protea are hard to grow but really it?s a plant-it-and almost-forget-it kind of plant. They need good drainage and don?t like phosphorus fertilizer preferring poor soils with minimal care. Sounds like a winner to me.

Epilobium ‘Mattole Select’

A little further down the trail I came across another easy to care for plant. California fuchsia have undergone several name changes over the years but whether you call them epilobium or zauchneria they are in bloom now. The ‘Mattole Select’ cultivar forms tidy 6 inch high mats of beautiful silver foliage. Late summer through fall brings orangey-red tubular flowers which attract hummingbirds. Spreading by underground rhizomes, this epilobium increases size a little less vigorously than the others. It?s more shade tolerant than most California fuchsias and needs just a bit more water but it?s still quite drought tolerant. Pruning plants down to a few inches in late autumn helps rejuvenate them for the following year.

Grevillea junipera ‘Monoglo’

As I followed the hummingbirds around the arboretum I came across another groundcover that both the birds and the bees favored. Grevillea juniperina ?Molonglo? (Juniper Leafed Grevillea) blooms with a soft yellow flower unlike most grevillea. This fast growing evergreen forms a mass of dark green soft needle-like leaves and bears an extremely profuse show of light golden yellow flowers from late spring to winter. This tough hardy drought tolerant plants is the perfect groundcover for large areas and will cascade down slopes and walls.

I?m looking forward to another visit to the arboretum this winter as the Australian garden will be in full bloom then.

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