Soils

Part A

California has a wide spectrum of soil types, with soil pH in our county (SLO) alone ranging from 4 to 8.5. The highest pH we've seen in California (and tried to find plants for) was 8.9 in Tulare.

If there is a lush crop of weeds (other than mustard) and you only want a small garden, don't worry about soil. Natural soil is probably good enough for most natives as long as plants from the general habitat/community are being planted back. The soil is not wrong or bad if conifers fail in the desert or desert species fail in the forest, the wrong plants are being used.

In replacement of an established landscape that was doing fine, do not worry about the soil. Landscape soil is probably good enough for most natives. Again, if you are in Barstow, Bakersfield or Taft, use desert species, if you're planting in a pine forest, don't plant desert species and complain about the soil. Plant by plant community.

In replacement of an established landscape that was dying or dead, do worry about soil and soil pathogens. What is the problem? What killed it? Have a soil analysis done, look at the watering practices, was drip irrigation used? (that will kill most gardens in about 5 years.) Was it a rental house planted with 'normal' garden plants that needed regular watering and never was watered? Was there a timer there set at 10 minutes every day? (That, by itself, could kill the plants and alter the soil.) If everything in the garden just died, figure out why, before the next batch of plants is condemned to death.

If there are no weeds on the site or garden (and it has gone through a rainy season) have a complete soil analysis done. Please do not follow the normal advice that comes with the soil analysis. Some of them give crazy advise on things to add that in most cases will cause more problems then they solve. Just ask if there are any elements that are WAY off, or the pH is too high (8+) or too low (4-). If something is way off, then use the search engine on our front page to check our site for plants that will grow in your problem soil. Also check the advanced section.

Frost burn.

New growth too early in spring, or planting plants from early spring areas into colder areas can cause this.

This is an alkaline tolerant plant in acidic soil.

The alkaline soils are generally more fertile and the plants have not adapted good nutritional strategies, nor can they handle the higher levels of available iron and metals.

This is an acid tolerant plant in alkaline soil.

Acidic plants can't handle the higher levels of calcium, sodium, magnesium, etc., in the soil. It's like people that are not milk (lactose) tolerant, on a milk diet.

Native plants like undisturbed soil. If you are planting natives avoid tilling, ripping, trenching or otherwise tearing deeply into the soil. Cut your ditch so as to leave connecting areas between existing plants, if possible. The ditches for water, electricity, telephone, or sewer could be put together or parallel (if building codes allow it) so that the trees are not cut off by themselves from each other. (If the garden is in a new subdivision or other site with no viable native ecosystem you can ignore the previous paragraph.)

Some plants care about their soil. Some do not. Grow Ceanothus hearstiorum does well on clay but hates sand. In a Cambria garden in sand, only a few miles from where it was native, it failed. This Ceanothus has been successful in interior gardens as long as it is in good-draining clay or clay-loam. Most native plants do not care about soil as long as they are growing with their associated plants.

PLANT

Plant likes less than 1 meter of soil

Plant likes 1-3 meters of soil(tolerates deeper soils)

Plant likes deep soils

vegetables

X

rushes and sedges

X

X

X

wildflowers

X

X

X

most native grasses

X

X

most Sages

X

X

most Penstemons

X

X

most Buckwheats

X

X

X

most Ceanothus

X

most Manzanitas

X

X

most pines

X

most Oaks

X

Part B - Soil Amendments and Mulch

Soil amendments usually make the problem worse. The only amendment that can sometimes help is liquid lime-sulfur (Calcium polysulfates) or gypsum watered in on poorly draining sites or sites with a high sodium/low calcium balance. Gypsum only helps for a few years, the plants have to be close to the right plant community if the soils is 'bad'.

Don't try to improve your soil by adding mushroom compost. It is a little manure, straw and sand that is amended with clay soil to make adobe bricks! Sand added to clay makes a nice patio as it approaches concrete in texture! If your soil is bad enough to think about amending you should be thinking about what plant material will work in it, not what amendment to add to it. In most cases the soil consistency isn't the problem but what it contains. Just because it is hard as a rock ( break the shovel handel off ?)doesn't mean you have bad soil.

Why do people move to the redwoods and try to replace the soil to plant tomatoes? Why do people move to Barstow and try to replace the soil to plant pine trees or blueberries? There is more soil under the stuff you are amending than you can amend. Dig a 3' deep by 2' wide and 5' long hole for a series of rose bushes to try and overcome the alkaline clay soil in the garden. Replace the soil, do it for each bush, and all the roses will still be yellow from lime within 6 months. If you work amendments only into the planting hole, you've made a sump hole in the winter (water drains into it from the surrounding areas. When you pull the dead plant out it will go 'sucky-slurpy'. Amended soil also forms a soil inversion layer that will drive you crazy.(The plants and their fungal helpers 'see' a amendment-soil line as a 'rock' or hardpan and cannot go through it.). Soil hardpan occurs in all soil types, some of which you'd never guess. In one place along the coast in pure beach sand the planting hole had been amended with a sewage- based product at planting time. A 5 gallon plant was set out in that hole that eventually died of drought. When pulled up, what roots it had, had coiled up against the shovel line where the soil had been amended. No, that's right, no roots had passed that soil line after 5 years. This same effect is one of the reasons a gallon-sized plant will consistently grow bigger than a 24" boxed plant after about 5-10 years if the two plants are planted at the same time.(Look at the plant size section.) Lawns, perennials, shrubs and even trees do the same thing vertically. They 'see' soil lines we would not think about. It is really weird to see a 30' tree blow over and only have a 12" deep root system.

When we lived on adobe soils in San Luis Obispo and tried to grow carrots we discovered the soil effect . On the clay by itself the carrots literally grew above the ground. We put a raised planter in and filled it with sand and planted in it. Our carrots grew down to the clay and back up, making upside down ????s. (Try grating those for a salad!) Take that money and buy mulch, you get more for the money and cause long-term soil improvement Three inches of mulch on top does more than six inches tilled in over a 5 year period to improve the soil's health. On sites with compacted soil the texture, drainage and fertility of the soil was is completly changed after mulching heavily (it took a couple of months for the worms, fungi and microfauna to start working). The great thing about this is it does not limit the root system, and the plants go crazy. Again, a point to make clear, the mulch goes on top, not worked into the soil.

Mulch can greatly suppress the great weed invasion (it will supress the vegetables too). I briefly ran out and made a list of our local weeds that are growing on the nursery site and the effect that mulch has on them:

S= Strong Weed Control Strong weed control on our site meant we had 1-5 weeds per 20' circle.

M= moderate weed control Moderate meant we had 5-30 weeds in a 20' circle.

W= weak weed control Weak meant we had 30+ weeds in the 20' circle.

Control = areas with no mulch in the nursery are a carpet of weeds!

Both mulches had a strong positive effect. It is important that the mulch slowly break down and it should not have fertilizer in it. It also needs to be at least 2" thick in wet or cool climates, and 3-4" thick in hot, dry climates. If you are planting shrubs you can go to 6-12" deep with mulch as long as it is fluffy, allowing air to the roots. In wet summer climates you may want to leave a circle of bare soil extending 2-3" away from the trunk around the plant to keep the crown dry. Mulches suppress the weeds in part by providing an environment for weed killing pathogens that attack the weeds as they emerge, and for little weed-eating insects, and by shading those weeds that need sunlight to germinate.

The Efectivness of Mulch on Weed Supresion

Weed

Rock Mulch

Wood Mulch

Chickweed, Mouse ear

S

S

Mustards

S

S

Clover

M

S

Nettles

S

S

Filaree

S

S

Oxalis

S

S

Goosefoot

S

S

Petty Spurge

S

M

Grasses, annual

S

M

Pimpernel

M

M

Grasses, perennial

S

S

Pineapple Weed

S

S

Groundsel

M

S

Shepard's Purse

W

S

Henbit

S

S

Spurge, Spotted

M

M

Horehound

S

S

Thistle, Sow

S

S

Mallow

S

W

A Garden Mulch Table

Mulches (arranged by initial cost, cheapest first) (From Vandenberg AFB Landscape Ordinance, ©1995 Las Pilitas)

Best use

Possible Problems

Sources

Life?

Lawn clippings

compost pile for vegetable garden

Lots of weeds in it eg. Bermuda grass, plant diseases

maintenance

3 months

Manure

Vegetable garden

Salt burn, too much fertility for natives

Any Garden center

1-3 months

'Green waste'

Conventional flower beds

weed seeds, shrub and tree seeds

Recycling programs

1-3 years

Arborist's chippings

natives, drought tolerants and conifers

few but, may contain eucaliptus or walnut clipings some tree and shrub seeds

Arborists

5 years

Fir bark, Pine bark, Redwood bark

conifers, most others ok

floats and moves off of site, doesn't provide full groundcover so more weeds present

Bulk distributors, Garden centers

7-10 years

Shredded redwood bark

the best mulch (when combined with boulders) for Coastal Sage Scrub and Chaparral natives

very few

Bulk distributors

7-10 years

Boulders, rock

Desert plants or combined with other mulch

very few (don't put the rocks on top of the plant)

bulk distributors, some General Engineering contractors

20+

NONE

Lawns, walkways, parking lots, areas of flowing or standing water

topsoil loss, erosion, dust

n.a.

generally covered with weeds in a few months

It is important to recognize that desert and prairie plants want rock or boulder mulch, chaparral and woodland plants want tree mulch mixed with boulders (or large rocks), and conifers want tree mulch. Veggies and English-Garden-type plants hate mulch but love manure worked into the soil.

When in doubt, Mulch!

Part C - Fertilizer

Do not use any fertilizer unless you have a minor problem, such as a minor deficiency, that is corrected long-term with one application or so. Also, sometimes lime-sulfur (calcium-polysulphates) can be useful to help mitigate high pH and sodium problems (see soils). Nitrogen, Phosphorus, and Potassium fertilizers have killed more native plants than they have helped. Fertilizers do not seem to hurt ruderal (weedy or vegetable) plants. Circumventor plants will survive the fertilizer but will not have a normal lifespan. They will grow big and fast but die fast. For natives, fertilizers are like steroids. (Stress tolerant plants usually will just die after being fertilized.) The Ceanothus spp. die in three years, when overwatered and fertilized. In the wild they will last 100-150 years plus. Fertilizer can only be used if a soil analysis has shown the soil has a deficiency of a minor element.

One fertilizer application is enough to kill!!!!! Do not fudge unless you know which plants will tolerate it and how much. "The plant died with 'just a little' fertilizer" is common with natives.

View your whole site as a living body. Fertilizer behaves as salt does. You may be putting it in one area but it is affecting the whole body. If you change the biological balance by adding fertilizer you will also favor weeds, snails, rats and bad bugs.

Part D - Landscape drainage

Most California native plants need good drainage. Fair to Good drainage means that if you dig a shovel sized hole and fill it with water it will drain in an hour or two. Some of our chaparral plants need excellent drainage. If you fill a shovel-sized hole the water should drain out in less than ten minutes (good-excellent drainage). If the garden does not have good drainage, and you want to plant stuff that likes good drainage, try using large raised beds or planting on a slope. If water stands for periods of time, abandon the drought tolerant plants and use seasonal riparian (river, meadow or creek) species.

Amending the soil to make better drainage is almost always a disaster. It just makes a mess. A combination of the correct plants and the right mulch are both much better at improving the soil.

When you walk on healthy soil in a native habitat you leave a footprint. The soil is light and fluffy. Even rocky terrain is light and fluffy between the rocks! Hopefully in your life time you'll restore a viable garden or ecosystem and remove a footprint!