Why your weeds keep coming back

Have you noticed an abundant crop of weeds this spring?  One reason – the heavy rains of last fall and winter may have awakened long-dormant seeds.  Does it feel like the long rainy winter just erased all the backbreaking work you did last year?  Our guide to weeds includes the why what and how of managing weeds. 
Plus our guide to weeds is downloadable.  See link below.

Why do they reappear?

  • Weeds produce thousands of seeds.  Those seeds are stubborn and can be viable for years, even decades.
  • They are transported by weather, especially wind. Also by animals, humans, and water. Mulches and soil can also harbor weed seeds.
  • Even after weeding, their seeds will remain in the soil and may be dormant for years.
  • Perennial seeds are the hardiest.  Their roots are alive for many years and harder to kill than annual weeds.
  • An example of a perennial weed is a dandelion.  Just one dandelion puffball carries as many as 100 seeds!

Understanding is the key to managing weeds

They are tough and relentless. Weeds can thrive in the most unsavory environmental conditions. Drought, fire and even herbicide applications don’t kill all weeds.  And, they will outcompete with desired plants for sunlight, water, nutrients, and space. 

Weeds offer some benefits

  • Protect bare soil from erosion.
  • Improve the soil by imparting organic matter.
  • Absorb carbon dioxide from the atmosphere.
  • Can provide habitat for birds, worms, and beneficial insects.
  • And – some have powerful medicinal properties (and are edible)

Weeds are a problem when

  • They overpower desired plants and deplete the soil of nutrients and moisture.
  • Their unattractive appearance, texture, color and growth habit detracts from your garden or landscape.
  • They harbor disease-carrying insects that spread to desired plants.
  • Poisonous weeds can be dangerous to you and your pets.
  • Invasive weeds take over your garden in a single growing season.

Two types of weeds – what makes them different

Annual Weeds
Warm weather annual weeds grow only from seeds every spring.  Cool weather weeds germinate in late summer or fall. Their roots are shallow as compared to perennial weeds (see below). For this reason, they are easier to pull.  Some die out after flowering.

Perennial Weeds
These weeds reproduce year after year from roots and seeds.  Because of their tenacious roots and seeds that can live for years, they are much more difficult to control.  Two common perennial weeds in the San Francisco Bay area are dandelions and oxalis.

Tips for Managing Weeds

The harsh truth is that you can never completely eliminate weeds, but effective management will help control them. 
Your first step is prevention.

Tips on Weed Prevention

Plant Choices
The right plant in the right place sounds simple but makes all the difference.  Healthy vigorous plants have the best chance of out-competing weeds.  
Healthy Soil
Make sure that plants are healthy by feeding the soil with organic products including mulch and compost.
Mulching and Sheet Mulching
Mulch keeps the soil cool and moist.  It deprives weeds of light.  Organic mulches enhance soil structure and host insects can devour weeds.  Sheet mulching is layering of cardboard, newsletter or fabric.  It serves as a weed barrier.
Proper irrigation is critical
We recommend drip because the water goes directly to the root of the plant, not in between them. Spray irrigation can encourage weed growth.  
Pre-emergent Herbicides
There are products that range from natural to chemicals whose purpose is to control the germination of weed seeds. This product will not impact weeds that have already grown.  An herbicide is a barrier so it needs to thoroughly cover an area for maximum effectiveness.

 

How to get rid of them?

Gardeners’ Guild’s philosophy is to use the least toxic practices. We recommend a combination of prevention, mechanical, biological, and chemical means only when necessary.  

Hand Pulling
This works best when weeds are small and before they flower.  Once they flower, seeds will be spread.
String Trimming
This works best for annual weeds.  It is used for the top growth control of broadleaf weeds.
Mowing
For a heavily weeded area, mowing helps prevent broadleaf weed seeds from spreading but cutting off flower heads.
Flaming
Less effective for deep-rooted (perennial) weeds. This method requires a propane burner which burns cell walls of the seeds.
Post-emergent Herbicides
Their purpose is to kill weeds once they appear. This product will either target foliage and/or weed roots. Take precautions when using and be aware of any community regulations against them. 

 

Weed Types Common to SF Bay area

Below is a list of common San Francisco Bay area weeds.  Some are invasive and fire hazards.  Invasive weeds will damage our ecosystems by displacing native species, increase fire and flood danger and consume valuable water.
 
Ice plants – Invasive
They compete with native plants. Seeds are carried from landscape settings to natural areas. Pieces of the plant can be washed into storm drains. They grow in natural areas and along freeways. Remove by hand pulling, mechanical methods.  Glyphosate is effective but only as a last resort.
Oxalis/Wood Sorrel
Grows in lawns; flower beds.  Blooms in spring. Spreads rapidly by their many persistent bulbs. Very competitive. Remove root bulbs before they bloom.  Sheet mulching or post-emergent treatments are used.
Dandelion
Perennial. Seeds spread in wind. Leaches nutrients from the soil of desired plants. Prevention is key. Hand weeding and fabric mulching can work.  Herbicides if necessary.
Periwinkle/Vinca Major – Invasive
Their aggressive stems root wherever they touch the soil.  Spreads rapidly in shady creeks, drainage areas and chokes native plants. Vinca minor is okay.  Removal by hand pulling.  Rake the area to loosen the soil. Or, brushcut and cover area with cardboard for at least a year.
Licorice Plants – Invasive
Seeds spread by wind.  Spreading branches root wherever they make contact.  They can and do displace native plants in coastal areas. Hand pulling is effective for small infestations.  for larger areas, herbicides are used.
English Ivy – Invasive
Distinguishing them from less invasive ivy is difficult.  Invasive ivy will smother understory vegetation, wrap around trees and harbor non-native rats and snails.  Removal – wear protective clothing. Dig down 8-10 feet should get at their roots. Dispose of plants. A large expanse of ivy can be rolled like a carpet.
 

Download our report on Weed Management

 

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Coreopsis Perennial

Above: Coreopsis – a perennial and native to North America


8 Easy Drought Tolerant Plants for Your SF Bay Area Climate. And, how to care for them.

These plants are beautiful and tough. They will save water and add color to your garden.

One of these 8 plants will work for your SF Bay Area climate.  Whether you live in the hottest inland part of the San Francisco Bay Area or on the coast.

Get the printable version of our report below
Download the Report

 
Lantana
Lantana, a non-native perennial
Attributes Non-native
They come back, year after year. In an array of colors.
Colors Pink, purple, yellow, red and orange
Bloom times  Spring, summer and fall
Light Requirements  Full sun
Water Drought tolerant
Maintenance Easy; deer resistant
Notes Bees and butterflies love them
They like well-draining soil


Salvia Leucantha (Common Name Mexican Sage)

Salvia Leucantha, a drought tolerant perennial
Attributes From Mexico; one of numerous varieties of Salvia
Colors This variety is purple
Bloom times  Late summer to early frost
Light Requirements  Full sun; will tolerate some shade
Water Drought tolerant
Maintenance Easy to grow
Notes Butterflies and hummingbirds love them
Hardiness to 15 degrees; tolerates windy conditions


Achillea Moonshine (Common Name Yarrow)

Achillea Moonshine or Yarrow is a drought tolerant perennial
Attributes Native. Showy flowers that can be dried; fragrant
Colors This yarrow flowers are yellow.
Bloom times  Early to late summer
Light Requirements  Full sun
Water Drought tolerant
Maintenance Easy; deer resistant
Notes Attracts bees, butterflies and other beneficial insects
Hardiness Heat tolerant



Dietes (Common Name Fortnight Lily)

Dietes, a perennial that adapts to wind and fog
Attributes From Africa, from the Iris family
Colors White, yellow or pink flowers
Bloom times  Spring to fall
Light Requirements  Full sun to partial shade
Water Drought tolerant
Maintenance Needs regular pruning and deadheading
Hardiness Adapts to wind and fog

Ceanothus Diamond Heights

Ceanothus Diamond Heights, native ground cover
Attributes Native ground cover or shrub
Colors Yellow chartreuse and variegated foliage
Bloom times  Spring has pale blue flowers
Light Requirements  Shade to part sun
Water Drought tolerant
Maintenance Easy; deer resistant, pruning not necessary.
Hardiness Likes coastal temperatures. 
Hardy to 20 degrees


Cistus x purpureus (Common Name Rock Rose)

Cistus x purpureus or Rock Rose, a hardy shrub
Attributes Non-native, fire-resistant, tolerates neglect
Colors Bright pink almost purple showy flowers
Bloom times  Spring, and summer
Light Requirements  Full sun
Water Drought tolerant
Maintenance Easy; deer resistant
Notes White (salvifolius) or light pink (xskanbergii) are adaptable to fog and wind
Hardiness Tolerates heat



Arctostaphylos Emerald Carpet (Carpet Manzanita)

Arctostaphylos Emerald Carpet, drought tolerant ground cover
Attributes Native ground cover or shrub; evergreen
Colors Deep green foliage, white flowers
Bloom times  Winter to spring
Light Requirements  Full sun, partial shade
Water Drought tolerant
Maintenance Easy; deer resistant
Notes Bees and butterflies love them
Hardiness to 15-20 degrees


Penstemon Carillo Red

Penstemon Carillo Red, native great for cut flowers


Attributes Native, makes beautiful cut flowers
Colors Red tubular-shaped flowers
Bloom times  Early to late summer, blooms for 4 weeks or more
Light Requirements  Full sun to mostly sunny
Water Drought tolerant
Maintenance Deer resistant
Notes Attracts pollinators
Hardiness Tolerates hot dry climates

 

 

 

 

 

 

 

bullthistle


Prevention and Control of Top 7 Invasive Weeds Using the Least Toxic Practices

Our report on the top 7 invasive weeds in the SF Bay Area was re-worked from one I posted in 2016 weeds typical in the San Francisco Bay Area including the most invasive weeds.

The top 7 invasive weeds is focused on the worst for good reason. This summer promises to be hot. Some of the top 7 are highly flammable.  Our treatment options for getting rid of the top 7 emphasize the least toxic solutions. Hand pulling or mechanical means for some, at the right time, can be effective.

Our Recommendations

We suggest a combination of prevention, mechanical or biological means. 
Sometimes a chemical solution is necessary, but only that is so.
The results of 2018’s on and off rainfall and intermittent heat waves have seen a prolific  crop of bull thistle (pictured above) and oxalis.

See the full report on managing weeds. It includes 13 weed types, prevention and control.

Download

Prevention – the First Line of Defense

Plant Choices
The right plant in the right place sounds simple but makes all the difference. 
Healthy vigorous plants have the best chance of out-competing weeds.  
Healthy Soil
Make sure that plants are healthy by feeding the soil with organic products including mulch and compost.
Mulching and Sheet Mulching
Mulch keeps soil cool and moist.  It deprives weeds of light.  Organic mulches enhance soil structure and host insects which will devour weeds.  Sheet mulching is layering of cardboard, newsletter or fabric.  It serves as a weed barrier.  Water Management
Proper irrigation is critical.
We recommend drip because the water goes directly to the root of the plant, not in between them. Spray irrigation can encourage weed growth.  

The Most Invasive Weed Types

Source: California Invasive Plant Council

Remove these plants from your garden! 
They damage our ecosystems by leaching nutrients from native species.
Some are highly flammable and at the same time consume valuable water.

Broom Species (French & Scotch)

Plentiful in forests or wooded areas. They spread along roads and appear like small trees.
Despite their pretty flowers they are toxic to humans and animals.
BEWARE. They are fire hazards. With a hot dry summer coming , get rid of these.
Crowds out desirable species by leaching nutrients.
Seeds spread by wind
Treatment Options
Hand pull between January-May

Cut to just above ground
Cut and treat with an herbicide

Fennel or Licorice Plant

Seeds spread by wind and competes with other plants for nutrients.
They will displace native plants in coastal areas.
BEWARE – This plant is also considered a fire hazard.
Treatment options
Hand pull when soil still wet.
Dig out as much of the root as possible with shovels, hand picks.
Mowing needs to be done at the right time or will encourage seed growth.

 

Bull Thistle

Showy purple blooms and sharp needle-like leaves.
Grows where soil is disturbed. Spreads rapidly.
Leaches nutrients from desired plants.
Treatment Options
Hand pull and step on stem before pulling
Mow before they flower
Herbicides

Cape Ivy

Forms a dense blanket over desired plants.
Distinguishing from less invasive ivy is difficult.
They choke off nutrients from understory vegetation, kill trees, harbor rats and snails.

Treatment Options
Requires precision as every stem must be removed.
Removing around the perimeter of a patch.
Because removal is complex cutting and using herbicide may be advised.

Himalaya Blackberry

Don’t confuse this with native blackberries!  Natives are smaller and don’t tangle and sprawl.
The
Himalayan Blackberry grows in dense thickets, covered in thorns. 
Highly invasive and difficult to
control.
They leach out nutrients from desired plants and shade out light.
BEWARE they are also a fire hazard
Treatment options
Mechanical – digging up root tall
Burning of mature plants only with consultation with a professional
Unfortunately, treating with concentrated herbicide is one of the best ways.

Periwinkle or Vinca Major

Vinca Minor is okay! The two types look a little different
Vinca Major leaves are broader, larger; heart shaped.
Vinca Minor leaves are smaller, elongated.
Major is a pest. They root wherever their stems touch soil.
They spread rapidly in shady creeks; drainage areas.  And, they choke off natives.
Treatment Options
Hand pulling will work if roots are not deep, soil is loose and moist. (put plants in plastic bag & destroy)
Mechanical means (put plants in plastic bag and destroy)
Foliar spray can work
Cutting and treating with an herbicide is effective if all else fails.

Ice Plants

Competes with native plants.
Seeds are prolific. They move from landscaped areas to natural areas.
Pieces of the plant can be washed into storm drains.
They form a dense mat which can harbor rats and contribute to soil erosion.
Research has shown that where they root, ice plants make long term changes to the soil.
A snippet from one study found that when the ice plant was removed both native and exotic plant
species returned.  But natives were less abundant.
Treatment Options
Hand puling is effective, just do it early.

 

 

 

 

 

 

 

landscape drain

I’ve updated our post about drainage from March of this year.
We talk again about solutions to landscape drainage problems.
There is additional detail added including graphics that describe the drainage problems and solutions.
One of the solutions described below is a dry creek bed. It was a project of Gardeners’ Guild at Spring Lake Village.

1. Hardscape with Standing Water

Example of drain pipe clogged with tree roots

Includes patios, pavers, driveways, parking lots and steps.
If these areas have had standing water for some time it could be due to these issues listed below

Improper grading
Your hardscape may not have the proper slope and is directing water toward the building foundation. 

Blocked drains
Tree roots, leaves, mulch and other debris can blow into the drain from winds and rain

Corroded pipes
Over time, your drainage pipes deteriorate and will eventually collapse.

The Risks
Water can put your structure’s foundation at risk.
Storm water carries with it chemicals, debris, dirt, pesticides and other toxins.


Solutions for Standing Water 
Regrading.  Over time a property will settle.
Clear out drain grates and pipes (make a plan for their regular future maintenance)
Arrange gravel around the perimeter of drain grate to deter debris from blowing in.
On larger hardscaped commercial property areas more drains may be required.

2. Flooded Turf

Aeration process illustration

Above illustrates what aeration does

The culprit can be grading but a more likely offender is compacted soil.
Summer drought conditions and degraded soil will shrink pore space that normally accepts water and nutrients.
High foot traffic will also contribute to soil compaction. You can identify it by its hard surface.

Soil texture needs to be loose enough to allow water to pass through. Clay soil, common in the San Francisco Bay Area is the opposite!

The Risks
When water pools on top for a prolonged period, turfgrass will decline and rot.
You can observe it by smell – foul odor. 
You will also notice grey, red or orange spots and insects.

Solutions for Flooded Turf
Re-grading
Aeration. The soil is perforated which opens up its pores to allow nutrients and moisture. (See graphic above)
Build a dry creek bed.  It is a gully or a trench usually lined with stones and edged with plants to mimic the look of a stream.  They are beautiful and will help with drainage. See example below.

GGI dry creek bed project at Spring Lake Village, Santa Rosa

Dry creek bed under construction at Spring Lake Village Santa Rosa

3. Flooded Planter bed and other planted areas

 Example of flooded planter bed

A planted area or bed should be designed to allow the water to flow out and be distributed to other areas.  A proper slope needs to be calculated with a site level during the design process.

The Risk

Plant root damage will occur if soil is saturated for a prolonged period. When soil’s abililty to absorb water is tapped out it is considered saturated.

Solutions for Flooded Planter Beds

Re-grading will help with slope problem. Correcting this involves directing surface water to the lowest spot on the property which will empty into a drainage ditch, catch basin or well.
Good options include:
Creed beds (illustration above)
French drains
Bioswales. Increasingly popular and effective.  They are constructed to slow, collect infiltrate and filter stormwater.  They include a permeable storm bed. (See graphic below)

Bioswale illustration

4. Flooding Around Down Spouts

Solution to flooding around down spout

Example of re-directing down spout and into creek bed

This is a common problem.  In heavy rain down spouts can empty rainwater into the landscape.

The Risk

Your building’s foundation
Plant root damage, erosion and hardscape deterioration.

The Solution

A professional can re-direct the downspout.  A dry creek bed is an additional step to drive moisture away from your building.

Highway 37 and US 101 February 2017

The photo above is breathtaking reminder of the toll our rainy season has taken on San Francisco Bay Area residents.  El Niño surprised us with a ferocious encore performance. Many of our properties, roads and highways are still recovering.

Highway 37 is an extreme example of what happens when drainage fails.

Five feet of water flooded a 3-mile stretch of the highway after the heavy storms this winter.

Ditches on either side of the highway act effectively as drains, keeping water from flooding the road in a typical rainy season. But, this year, back to back storms prevented them from draining. Having no place to drain the overflow, efforts by Caltrans to pump the water out were stymied.    

An emergency solution included raising a portion of the roadway and fixing the drainage system by installing larger pipes, giving it greater capacity for moisture.  It seems to have worked. No unexpected weather has tested it yet, though.

Does your property have any areas of standing water, mulch that is washing away, soggy grass or mosquito problems? If so you probably have poor drainage that winter storms have exposed.

 


hardscape with standing water

Area 1

Hardscape

Includes patios, pavers, driveways, parking lots and steps.

If your hardscape has had standing water for sometime it could be due to these issues.

Improper grading. The photo on the right is an example of pooling water showing improper grading.

Blocked Drains  Debris, mulch or plant material could have gotten in from winds and rain.

The Risk

If the drainage problem is not resolved your structure’s foundation can be at risk.

Solution

  • Re-grading. Over time a property will settle.
  • Clear out drain grates and pipes. They should be maintained consistently. Laying down gravel around the perimeter of the drain grate can help in its maintenance.
  • Retaining wall. This can also resolve a slope problem.

 

Area 2

Turf

It can be also be improper grading.

But more likely it is compacted soil.

Previous drought conditions and/or degraded soil will shrink its pore space that normally allows water and nutrients. You can tell if soil is compacted because its surface is hardened.

Soil texture needs to be loose enough to allow water to pass through.  Clay soil, common in the San Francisco Bay Area, is the opposite.

The Risk

Water will pool on top and you will have soggy mess of plant material.  This is true of all plants.  They will decline and rot. 
You can observe this problem by its smell – foul odors.
By sight – grey, red or orange spots and insects.  

 

flooded turf

Solution

  • Re-grading can also help.
  • Aeration.  This is perforating the soil opening up its pores to allow nutrients and moisture.
  • Creek beds are another good solution.

Area 3

Planter Beds and All Planted Areas

A planted area should be designed to allow the water to flow out and be distributed to other areas.  Consider natural water flow.

A proper slope needs to be calculated with a site level during the design process.

The Risk

Plant root damage will occur if soil is saturated for a prolonged period. Soil is saturated when its ability to absorb is tapped out. 

flooded planter beds

Solution

  • If it is a slope problem, regrading will help.  Correcting a slope problem involves directing surface water to the lowest spot on the property which will empty into a drainage ditch, catch basin or well.
  • Creek beds, french drains and bioswales are great options!

Area 4

Gutter Spouts

A common problem.  If gutter down spouts are not properly installed they can empty rainwater into the landscape it will damage plant material and your hardscape.

The Risk

Your structure’s foundationPlant root damage, erosion and hardscape will be degraded.

flooded planter beds

Solution

  • Hire a professional to re-direct the spouts so the water goes downhill.

Hire a Professional

At the very least call one and discuss your drainage problems with them. 
Your plant material, trees, hardscape including driveways and your building’s foundation are too important.
Gardeners’ Guild has a construction division with many years of experience resolving all kinds of drainage problems.

Learn More About Drainage Systems

Descriptions of 5 Types of Drainage Systems

Pervious Paving – Pavers that will help with drainage and are sustainable!