Weeds that establish or increase after fire will compete with desirable plants for water, nutrients, and sunlight, inhibiting successful revegetation or natural recovery after fire.

Effects of Fire That Favor Weed Invasion or Increase • Fire exposes and disturbs soil • Fire reduces shade and competition • Fire creates a flush of nutrients in the soil • Fire creates conditions for water runoff, flooding and

mudflows

Factors That Influence Weed Invasion or Increase After Fire • Condition of plant community before the fire • Severity of fire in the area – bare ground and disturbance • Presence of weed seed sources in or near the burned area • Seed dispersal potential into or within burned area • Flooding or mudflow potential in the area

Create a Weed Management Plan • Determine if revegetation will be needed by assessing factors

that influence weed invasion • High severity + poor community condition pre-fire =

revegetation likely needed • Low severity + good community condition = natural

recovery may be sufficient • Monitor burned area for the presence of weeds, be especially

vigilant in areas of: • Soil disturbance by vehicles , animals or erosion • Receding flood water or mudflows

• Control weeds mechanically or with herbicides • Eradicate smaller patches of new weeds • Control by containing and reducing large populations

Weedy species that are likely to invade or persist and increase after fire have effective seed dispersal mechanisms, persistent crowns, or perennial rhizomes and root systems.

Russian knapweed persists by root buds, seed may move in flood waters

Canada thistle has wind blown seed, persistent perennial roots and rhizomes

Diffuse knapweed is easily dispersed by vehicles and animals

Dalmation toadflax persists from perennial roots and rhizomes, seed production increases

Hawkweed survives by crown and root buds, long distance dispersal of seeds from off site

Rush skeletonweed has deep perennial root buds, wind blown seed may infest burned areas

Yellow starthistle is dispersed by human activity, in straw, hay and seed, fire stimulates germination

Class A noxious weeds that can be introduced as contaminants in straw and seed – eradication required

Buffalobur Velvetleaf

Noxious Weeds After The Burn Chelan County Noxious Weed Department