bullthistle


Prevention and Control of Top 7 Invasive Weeds

The top 7 invasive weeds that we highlight this month are predators that will leach water and nutrients from your desired plants.  Some of them are highly flammable.  Our treatment recommendations for getting rid of the top 7 emphasize the least toxic practices.

Getting rid of these weeds is a combination of mechanical or biological means. 
Although Integrated Pest Management (Best Practices) sometimes requires a chemical solution.  Seriously, they are tough t to control.  Consult a professional if possible.

Because the weather is already warming and experts forecast a dry spring, this is the time to remove them. Fire district warnings may come sooner than expected.

What are invasive weeds?

This definition is based on their real threat to native plant and animal communities.  Their impact includes the risk of fire, flooding, and the potential to lower land value.

What are noxious weeds?

One weed on our list is considered noxious.  This term is a legal one used by state regulatory agencies.  A weed is categorized as such if it poses a threat to agriculture or plants and enables the agencies to ban, quarantine, or eradicate them.

The First Line of Defense is Maintenance (Prevention)


The Top 7 Invasive Weed Types

You may notice some weeds entangling their branches around your desired plants, or growing in the middle of them. It may take time to trace their branches to get to their roots. 

Some are flammable – noted in red below.

Broom Species (French & Scotch) Fire Hazard

French or Scotch Broom

French or Scotch Broom


Plentiful in forests, wooded areas, and roadsides. They spread along roads and appear like small trees.
Despite pretty flowers, they are toxic to humans and animals.
Crowds out desirable species by leaching nutrients.
Seeds spread by wind.

With a hot dry summer forecasted, get rid of these now.
Treatment Options
Hand pull between January-May

Cut and treat with an herbicide


Fennel or Licorice Plan – Fire Hazard

Fennel

Fennel


Seeds spread by wind and compete with other plants for nutrients.
They will displace native plants in coastal areas.

Treatment options
Hand pull when soil is 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
Bull Thistle

Bull Thistle


A noxious weed.  Toxic and difficult to control once established.
Showy purple blooms and sharp needle-like leaves.
Grows where the soil is disturbed. Spreads rapidly up to 6 feet.
Aggressively leaches nutrients from desired plants.

Treatment Options
Dig out with a shovel making to get the root before pulling.
Mow before they flower.
California Invasive Plant Council says herbicides are effective.

Cape Ivy
Cape Ivy

Cape Ivy


Poisonous, toxic, and aggressive.  Will reduce habitats for pollinators.
Forms a dense blanket over desired plants. Its weight can cause a tree to fail.
Distinguishing from less invasive ivy is difficult. 
They choke off nutrients from understory vegetation, 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.

It may also require multiple treatments.
Best to use a professional.

Himalayan Blackberry – Fire Hazard
Himalayan Blackberry

Himalayan Blackberry


Don’t confuse this with native blackberries!  Natives are smaller and don’t tangle and sprawl.
The
Himalayan Blackberry grows relentlessly in dense thickets, covered in thorns. 
Highly aggressive, invasive, and difficult to
control. Displaces native species.
They leach out nutrients from desired plants, their thickets can block the sunlight they need.

Treatment options
Mechanical – dig up by root ball.
Burning of mature plants only with consultation with a professional.
Unfortunately, treating with concentrated herbicide is one of the most effective options.

Periwinkle or Vinca Major

Vinca Major

Vinca Major


Vinca Minor is okay! The two types look a little different.
Vinca Major leaves are broader, larger; heart-shaped.
Major is considered invasive because it is aggressive and outcompetes natives, leaching soil nutrients.
It spreads rapidly in shady creeks; drainage areas. 


Treatment Options
Hand pulling will work if roots are not deep and soil is loose and moist. (Then put plants in a plastic bag & destroy)
Mechanical means (put plants in a plastic bag and destroy).
Foliar spray can work.
Cutting and treating with an herbicide is effective if all else fails.



Ice Plants

Ice Plant

Ice Plant


When established, they form a dense mat that can choke out natives and destroy soil chemistry.

This mat can harbor rats and accelerate erosion.
Seeds are prolific. They move from landscaped to natural areas and devastate their ecosystem.
Pieces of the plant can be washed into storm drains.
One study found that when an ice plant was removed, both native and exotic plant species returned.
However, the natives were less abundant.

Treatment Options
Having shallow roots, hand pulling is effective, just do it early.

Closing Note

California Invasive Plant Council has taken the lead on public and professional education, and the eradication of invasive plants. 
They developed a comprehensive inventory of these plants and have initiated multiple plant control projects throughout the state. 
As they are a non-profit they rely on funding and volunteers for them. 
Their website is a great resource if you want to learn more.

Sources and Resources

California Invasive Plant Council (Cal-IPC)

UC Master Gardeners

California Native Plant Society (CNPS)

 

 

 

 

 

Plants that attract pollinators

What’s Unique about Gardening for Pollinators in the Bay Area

Most important is plant types.  Because of the bay area microclimates, planting in the right environment is critical.  Plant vigor will be impacted by sun exposure, fog, heat, soil type and wind.  Learn about pollination in a stunning video (below) that catches them in the act.  Also below is an update on the status of our pollinators which explains why gardening for pollinators is so important now.

Below is a downloadable list of 9 plants for a pollinator-friendly garden.  The list shows their preferences for sun, soil, water; the pollinators they will attract, and bloom seasons.

Why Gardening for pollinators will help sustain our food supply

We depend on pollinators

Plants that produce seeds, flowers, fruits and vegetables depend on animals who perform the magic of moving the [male] pollen from one part of a plant to the [female] part. Thousands of pollinators exist, but the most common ones include bees, butterflies, hummingbirds, wasps, beetles, and wasps. 

Consider the Bumblebee.  They are lured by the scent of nectar and the color of an apple tree’s blossoms.  Flying from flower to flower, they find nectar to feed on. While enroute, pollen from the male part of the flower sticks to their body, signaling it’s time to move on and deliver their powdery stash to the female part of the flower.  That, in a nutshell, is fertilization!  Not exactly romantic, but, now the tree can produce fruit – and that’s pretty cool.

Pollinators are declining

The reason, is pollution, the loss of their natural habitat, and poisoning from pesticides.
Habitat loss happens as an outcome of urban and suburban development.  Read about the status of our most popular pollinators.

Bees
You’ve probably heard about the decline of Honeybees.  They are most prominent of all pollinators and integral to food production. Their loss has an impact on our supply. 

Native bees’ decline, however, is lesser known and has more severe implications.  As documented by the Center for Biological Diversity,  nearly 1 in 4 are at risk.  Moreover, the Center describes native bees as having a “crucial ecological role by pollinating wild plants and providing more than $3 billion in fruit-pollination services each year in the United States.”

The Monarch Butterfly (See our report on the Monarch below)
From 2017 to 2018 the Monarch’s
population plunged dramatically – by 86 percent, according to a report by the Xerces Society, a non-profit dedicated to protecting pollinators and their habitats.  Their analysis shows that the decline has been consistent since the 1980s.  The once 4.5 million population dipped to 1 million by 1997.  

Other Pollinators are in trouble
The Center for Biological Diversity report found that globally, more than 40 percent of insect pollinators are at risk. 

Gardening for Pollinators will Help Reverse this Trend

You can help sustain our world’s food supply by creating a pollinator-friendly garden.  No matter your outdoor environment – rural, suburban, or urban area – you can create a habitat garden.  Besides the satisfaction of giving back, it will increase carbon sequestration and help prevent soil erosion.  If you plant edibles, you’ll reap the benefits of growing your own food!

Why Pollinators Like Native Plants Best 

They are undemanding and best adapted to your local climate.  The pollinators are well-acquainted with them, also.  Non-natives might not have sufficient nectar or pollen.  In fact, a UC Berkeley study found that 80 percent of natives attracted bees versus 8 percent non-natives.

Pollination in action – Captured on Video

Watch this gorgeous four-minute clip below.  It was shown at a TED conference in 2011.  Created by filmmaker Louie Schwartzberg, it documents the romance of pollinators and pollen.  See Louie Schwartzberg’s website.

9 Plants that SF Bay Area Pollinators Love

The graphic below is a link to a plant list pollinators love plus their needs for water, soil, and light. 

UC Davis also has a comprehensive plant list.

 

See Our Report on the Monarch Butterfly

The button below is a link to the report. It’s packed with information. Learn about the caterpillar’s essential food.

Download Button Saving the Monarch

Essential Planting Tips

Know the right plants for your environment.  If you live in the city you can grow a pollinator garden in containers.  All you need the right soil, plants and a plan for watering.  Either irrigation or hand-watering.  Keep in mind, effective hand-watering is time consuming.

The

Use these planting tips below.  They were adapted from an article written by Melissa Womack, a Master Gardener

  • Plant in clumps instead of singely.  This will help pollinators find your garden.
  • Plant multiple varieties of plants.
  • Design a garden with structure.  This means simply arranging with the tallest plants in the back, the smallest in the front.
  • Pollinators prefer the sun, so aim for areas with full sun. (6 hours)
  • Reduce of eliminate pesticide use in the landscape.  Beneficial insects are an alternative and effective pest management method.
  • Tips for nurturing your pollinators: provide a hummingbird feeder, clean water in a shallow dish or bowl and dead branches for bees and beetles to nest.

Sources for this post:

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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.