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Post-Fire Invasive Plants


Invasive plants are those species that spread rapidly and grow so dominant that they change the landscape.



·Their ability to aggressively reproduce, spread, and out-compete cultivated or native plants.

·Thrive and well-adapted to disturbed soil and they come from fire-adapted climates.

Interact With Wildfires

·Some facilitate the spread and/or severity of wildfires.

·They become much more vulnerable to fire, and some are highly flammable (ignite easily and burn intensely).

·Act as ladder fuel into tree canopy.

Take Advantage of Disturbance

·Spread across larger areas and in higher densities.

·Vigorous growth because more sunlight, less thatch (biomass), and fewer competitors.

Manage Their Spread

·Limited-time opportunity to start control (cut, pull, herbicide) and support cultivated and native species return. 

·Avoid disturbing the soil as much as possible.


Common Post-fire Invaders Grizzly Flats Area?

French Broom 

Italian Thistle 

Perennial Field Pea 

Rush Skeletonweed

Scotch Broom 


Tall Whitetop  


White Sweetclover 

Yellow Starthistle 

Invasive Annual Grasses

Barbed Goat Grass 


Italian Ryegrass 

Johnson Grass 


Wild Oats 

List prepared By Native Plant Society & Master Graders


May contain: plant, vegetable, food, and produce

Barbed Goatgrass

Found primarily in northern California Central Valley foothills and woodlands on disturbed and undisturbed soils, and along roadsides.

Barbed goatgrass grows up to 20 inches tall with few to many rigids, loosely erect aerial stems.

In late spring the plant produces rigid flower spikes consisting of three to six spikelets bearing long barbed bristle like appendages. 

Seedheads are 1 to 2.5 inches long.

When mature, plants turn reddish-purple and then dry to straw color.

Barb goatgrass go to seed in late spring to early summer, seeds germinate in fall and winter. 

How to get rid of it:

·    Hand pulling or hoeing small infestations is effective. Pulled roots should be air-dried before disposal.  

·    Mowing can reduce seed production, by mowing after flowering, but before seeds develops.  


May contain: grass, plant, vegetation, and bush

Cheatgrass (Downy brome)

Cheatgrass rapidly occupies areas that have been disturbed by fire, construction actives. 

Cheatgrass is an annual plant. The plant grows in spring and dies by early summer. 

Cheatgrass can be several inches to more than 18 inches tall.  

The leaves are bright green and typically covered with short, soft hair but can sometimes be hairless. However, they quickly dry out and straw color as the summer progresses.

Flowers occur in loose, bending downward branches 2 to 9 inches long.  The bristles are long, stiff and course. Flowering occurs in early spring and can often be identified as they mature and turn reddish-brown.  

It has seed head that resembles a shepherd’s crook.  There is often a tinge of red or purple in the leaves. 

How to get rid of it:

·    In the spring or fall, hoeing and pulling young plants before seed heads turn purple and repeat when new plants appear are formed. 

·    Mowing during flowering, if too early result in vigorous resprouts.


May contain: plant, flower, blossom, petal, and leaf

French Broom

French broom is well-adapted to open, sunny, well-drained sites and is mostly likely to negatively impact open habitats.  French broom can invade a wide range of habitats including roadsides, fields, and logged areas.

Woody shrubs with grow up to 10 feet tall.  Older stems are brown and round; younger silvery hairs stems are dark green, ridged and very leafy.  

Branches have small oval leaves in groups of three. Leaves have silvery hairs.

Abundant pea-type flowers are bright yellow, in clusters of 4-10 at branch tips.  

Seeds are produced in pods 0.4 to 1.2 inches long, dark brown when mature and covered with silky hairs.

French broom has a large taproot.

French broom is the only invasive that is evergreen. 

How to get rid of it:

·    Hand pulling is effective on seedlings and small plants.  Larger plants require a more concerted effort with shovel, pick, or brush grubber. 

·    Lopping when plants are stressed can provide some control.


May contain: plant, flower, and blossom


Erect annual 6 to 24 inches tall.  Leaves are alternate on the stem and are sparsely covered with hair. 

Plants produce white flowers in umbrella-like cluster, 2-3 inches across.  

Each flower produces an oblong seed that is covered in minutely barbed, hook-tipped bristle. Bristly seed burs stick to many different surfaces.

Germinates with the first fall rains and its lacy green foliage often makes the plant inconspicuous amongst grasses and herbs. 

How to get rid of it:

·    Hand pulling is effective on seedlings and small plants.  

·    If plants have gone to seed, deposit the plants carefully into paper bags so seeds don’t disperse.

·    Mowing plants just before flowing can prevent seed production and may kill plants.


May contain: grass, plant, lawn, and agropyron

Italian Ryegrass (Annual ryegrass)

Italian ryegrass prefers areas with fertile, well-drained soils, including woodlands, roadsides, and disturbed sites. 

Italian ray annual or perennial ryegrass grows to 3 feet tall.  

Stems are round and hollow with swollen nodes.

Leaves are hairless and glossy green.  Leaf blade is narrow and long, 2-8 inches long by 0.2-0.4 inch wide.

Flowers consist of a terminal spike-like panicle up to 12 inches long.  

The root system produces rhizomes.  


How to get rid of it:

·    Hand pulling or hoeing small infestations is effective. 

·    Mowing is generally not effective.


May contain: plant, flower, blossom, and thistle

Italian Thistle 

It favors woodlands (especially oak woodlands), disturbed open sites, and roadsides. 

A winter annual, stems range from 8 inches to 6.6 feet, and are smooth surface completely devoid of hair to slightly wooly. Steams are winged and spiny.  The multiple stems plant grows in a rosettes of 10–14 inches in diameter, with four to ten lobed basal leaves that are 4–6 inches long.

The leaves are white-woolly below and hairless-green above. Leaves are deeply lobed and spiny.  

Flower heads are 2-5 per cluster and are small ½ to 1 inch, pink to purple and covered with dense hairs.  Flower heads are densely matted with cobwebby hairs at the base of the flower and spiny towards the tips. Whorls of leaf like structure immediately below a flower head.

The fruits are brown to gold, with a bristly, minutely barbed appendages.

How to get rid of it:

·    Tillage, hoeing, and hand pulling are effective if they are done before flowering to prevent seed production.  

·    Any treatment that severs the roots below the soil surface is very effective.

·    Mowing is most effective when plants are just beginning to flower.


May contain: bush, plant, vegetation, grass, tree, and conifer


Johnsongrass habitat in disturbed sites, roadsides, field, and riparian areas.  Johnsongrass found in the Sierra Nevada foothills to about 2600ft. 

Johnsongrass, a course and generally clumping grass.  Steams stand erect, from 6 to 7 feet tall, and are unbranched. 

The leaf blade is flat, hairless to sparsely hairy.  It has wide leaves with a prominent whitish midvein. 

In the vegetative grow stage, there are relatively large, jagged-edged, thin outgrowth at the junction of leaf and leafstalk.

The flower head is large, open, well opened branched structure and has an overall pyramid outline, 4 to 20 inches long.  Flowers are initially green, but often mature to dark reddish- or purplish-brown.

The branches support thousands of spikelets from which seeds are produced.  Initially it is green or greenish violet.  

At maturity it becomes a dark reddish or purplish brown. Mature Johnsongrass grows in spreading, leafy tufts with shoots sprouting from the base.  

Underground stems (rhizomes) are thick, segmented, and several feet in length.  Rhizomes are extensive and are produced in the top 10 inches of soil. Roots and shoots can sprout from these segments. 

Seedling resembles a young corn plant.   

How to get rid of it:

·    Hoeing or pulling young plants before they develop a root system and rhizomes.

·    Older plants remove the entire root system.

·    Mowing can slow plant growth; often doesn’t kill plant.


May contain: grass, plant, vegetation, and lawn

Medusahead (Medusahead Wildrye)

Medusahead is a very effective colonizer of fire-denuded and disturbance of soil.

Medusahead is a winter annual grass germinates in the fall and it overwinters as a seedling.

Leaves are bright green and upright. 

It is typically 6 to 20 inches tall with distinct bristly seed heads. Multiple stems can emerge from the base of the plant, each producing a single seed head.  

Each seed head may contain 20 or more seeds.  Seed head produce two, spike-type bristles which are upward and outward, with a twisting appearance.  

Medusahead has a shallow root system.

How to get rid of it:

·    Hoeing and pulling must sever the roots before the plants flower thus preventing seed production.

·    Mowing Medusahead in the early flowering stage before viable seed can be produced can reduce seed production.


May contain: plant, flower, blossom, soil, and petal

 Perennial Pea (Wild Sweet Pea)

Species escaped cultivation and is found along roadsides, and old properties. Plants favors sites in full to partial sun that have well-drained soil.

The plants are quite vigorous (vines can grow to 6 feet in a season) and can from dense colonies covering large areas.

Stems are without hairs or projections and winged.

Alternate compound leaves consist of a leaflet pair and winged petiole.  Leaflets are ovate to oblong with pointed tips and entire margins and up to 3-inches long and 1-inch across.  A tendril for climbing grows from the leaflet base. 

Perennial pea blooms are pink or white or maybe other colors.  Short racemes of 4 to 10 flowers arise from the leaf axils. Individual scentless flowers up to 1-inch wide consist of five petals.

Seedpods are hairless, flattened, and about 2 inches long by ½ inch wide. They progress from green to brown at maturity.  

The long-lived vine arises from a taproot and rhizome root system each year 

How to get rid of it:

·    Digging or hand pulling young plants before flowering.

·    Complete mowing and cutting before flowering because the viney stems are difficult to cut in the late growing season.

·    Repeated tilling of the rhizomes control plants.


May contain: plant, flower, blossom, dandelion, and anther

 Rush Skeletonweed  

It thrives in sunny areas with dry, sandy to gravelly soils.

Highly branched perennial or biennial that grows 1 to 4 feet tall.    Plant is wiry with few leaves.  The lower 4-6 inches of the stem often has course reddish hairs that bend downward. 

Leaves at the base of the plant are sharply toothed and wither as stem develops.  On the stem, the small narrow leaves are smooth edge lobed, fuzzy-textured, and have spines on the edge.

Flowers are scattered on branches, less than 1 inch in diameter and yellow, strap-shaped petals have five distinct teeth on the end.  

Seeds have fluffy white hairs that disperse by wind 

Rush skeletonweed taproots can grow over eight feet deep, making it difficult to remove.  Roots pieces as small as 1-inch and buried 3 feet in the soil can produce viable plants.  Lateral-growing roots that can sprout new plants. 

Leafless branching stems emerging from dandelion-like rosettes of leaves.

The plant exudes milky white sap from stems and roots. 

How to get rid of it:

·    Hoeing or pulling young plants before they develop a root system and rhizomes.

·    Older plants remove the entire root system.


May contain: plant, flower, blossom, petal, and leaf

Scotch Broom

Scotch broom flourishes in full sunlight in dry, sandy soils. However, it does not tend to survive in very arid or cold areas. Scotch broom invades dry hillsides, forest clearings, dry scrublands, and riparian woodlands. 

Woody shrubs which grow up to 10 feet tall typically grows 3-6 feet tall.  Stems are 5-angled with green ridges, or star shaped in cross-section. Stems are hairy when young and without hairs as they mature.

Branches are dark green with small leaves occur in groups of three. Each leaf is oblong and pointed at both ends.

Abundant flowers are bright yellow, pea-shaped and occur singular or in pairs, not in clusters. Each flower is usually located in the space between the leaf stem and the branch.

Seed pods are flattened, dark brown or black, contain 5-9 seeds and have hairs only along the margin. The seeds inside the pod are shiny and greenish-brown to black in color.

Similar Specie: French broom can be distinguished from Scotch broom by its brown stems, leaves always in threes (some Scotch broom leaves are single), smaller flowers, and seed pods entirely covered by hairs (Scotch broom pods are only hairy on the edges).

Scotch broom has a relatively deep root system and can reproduce by leaving rootstalks that may resprout.

How to get rid of it:

·    Hand pulling is effective on seedlings and small plants.  

·    Weed eating can give partial control; plants can grow from remaining lower branches.  

·    Lopping when plants are stressed can provide some control.

·    Controlled by digging 6 inches or deeper around the plant to get as much of the root system close to the soil surface as possible. Plants should be bagged and taken off site or burned.  It is easiest to remove plants in early spring or late fall when the soil is moist, and roots can be dislodged. Grubbing when the soil is dry and hard usually will break off the stems. 


May contain: plant, asteraceae, flower, blossom, aster, vegetation, daisy, and daisies


Found in disturbed soils of roadsides, wasteland, riparian woodlands, and other habitats.  Thrives in areas with hot, dry summers with well-drained soils.

Stinkwort is an erect, annual growing up to 3ft tall, pyramid- or sphere-shaped plant with sticky, glandular-hairy and strongly aromatic foliage.

Its leaves are narrow to lance-shaped, typically 0.5 to 1inch long.

It flowers are small yellow flowerheads around 0.25-inch diameter, turning reddish with age. 

Stinkwort seeds germinates during winter but remains small until spring. Stinkwort has a relatively shallow root system.

Protect skin surfaces to minimize exposure to the irritating oils.

How to get rid of it:

·    Hoeing or pulling young plants before they develop a root system.

·    Once stinkwort goes to flower, plants should be bagged because seeds may ripen on the cut plants and taken off site or burned.

·    Mowing can give partial control; plants can grow from remaining lower branches.  


May contain: plant, flower, blossom, apiaceae, and lilac

 Tall Whitetop (Perennial Pepperweed)

Tall whitetop is found in wetland, meadows, riparian zones, and roadsides.

The mature plant grows rigidly erect about 11 to 38 inches tall (may grow to a height of 6 1/2 feet) with multiple woody branches.   

The waxy leaves range from lance to football shaped to oblong and are hairless, green to gray green, and alternate along the stem. Basal leaves are larger and wider than the stem leaves up to 12 inches long and 3 ⅕ inches wide with toothed edges on the stalk about 1 ⅕ to 6inches long.

Flower bloom from May through September.  Small, white flowers with 4 white spoon-shaped petals about 1/16-inch-long form dense clusters arranged in branches at the tip of each stem.

Young plants form a basal rosette and grow from perennial rootstock.

Tall whitetop has extensive creeping roots. Plants can reproduce from root fragments and rootstock, and creeping roots. It is nearly impossible to cut the roots fine enough to prevent the sprouting of buds that form new plants. 

How to get rid of it:

·    Hoeing or pulling young plants before they develop a root system. 

·    May be possible repeated mowing can suppress perennial plants.


May contain: plant, flower, and blossom

 White Sweetclover

Habitat preference for full sun, slightly moist to day conditions, in disturbed sites, meadows, and riparian areas.

White sweetclover is an annual or biennial legume that can reach 8 feet in height.  The light green stems are round or slightly furrowed on all sides, smooth and often branched.  Stems are woody at the base.

The 0.5 to 2 inches long alternate leaves consist of three leaflets and sparsely distributed along the stem and alternate in arrangement. 

The upper stems terminate in narrow of white or yellow pea-like flowers about 2 to 6 inches long that tend to hang downward on short stalks.  Each flower is about 1/3 inch long, consisting of five small white floppy petals.  Flowers are sweetly fragrant. Plants generally flower and die during the second year of growth.   

Seed pods on stalks that bend down-ward containing 1-2 seeds.

Taproot tough or woody, slender to thick, typically deep, with fibrous lateral roots.

How to get rid of it:

·    Hand pulling is effective on seedlings and small plants.  

·    Mowing plants just before flowing can prevent seed production and may kill plants. Cutting second-year (flowering) plants at 1 inch or less in height would provide effective control. If first-year plants are cut, they will resprout in the same year.


May contain: grass, plant, lawn, and leaf

 Wild Oats

Disturbed or degraded sites, and woodland communities, and roadsides within elevations that generally range from 2,500 to 7,200 feet.

Wild oat is an erect, cool-season annual grass with open branches. Mature plants are study and can grow to 4 feet tall. Stems are round in cross-section, hairless, or nearly so. 

Leaves are flat bladed, rolled in the bud and grow to 8 inches in length and 2 to 8 inches wide.  Oats have a large membranous thin leaf collar scalelike appendage.

The nodding flower clusters are typically large and loose and bear minute flowers. Flowers is a panicle, 2 ¾ to 16 inches long; bracted spikes ¾ to 1 ¼ inches long. 

The seed is characteristically hairy and feature long bristles. Mature bracted spikes are bell-shaped, with bent slender bristle like projections.

It does not have creeping stolons or rhizomes; however, it has an extensive fibrous root system. A single plant can produce ¼ mile of roots.

They resemble cultivated oats but have finer stems and a smaller grain.

How to get rid of it:

·    In the spring or fall, hoeing and pulling young plants before seed heads turn purple and repeat when new plants appear are formed. 

·    Mowing before or during flowering.


May contain: plant, grass, flower, and blossom

 Yellow Starthistle 

A long-lived winter annual that matures in late summer.  

Grows to heights varying from 6 inches to 5 feet.  Stem of mature plants are rigid, spreading and typically branch from the base in open areas. Stems and leaves are blue-green, covered with loose, cottony wool that gives them a whitish appearance.

Has bright, thistle-like yellow flowers with sharp spines surrounding the base.  

Seed germinates from fall through spring. Produces a deep taproot. 

How to get rid of it:

•     Before plants flower:  plowing, hoeing, hand pulling can all work, especially if root below surface is severed.  Flowering plants will go to seed even after being cut, which is why this must be done before they flower. 

•     Mowing can be effective when beginning to flower, but only if most flowers have not matured. 

•     Any treatment that severs the root below the soil surface is very effective.