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Growth of mullein with respect to soil composition and exposure to sunlight

Iesha Brooks and Grace Harsha

Introduction

Mullein is biennial weedy plant introduced from Europe.  The plant forms a rosette during the first year.  During the second year, it forms a tall flowering stalk.  The plant has a restricted dispersal pattern. Thousands of seeds are dispersed over a few yards.  Seeds have a slim chance of survival.  Most seeds become dormant and germinate when conditions are better (usually after a disturbance).

Hypothesis

Mullein grows in shady areas of mixed gravel and soil next to trails.

Methods

Measured plant abundance at 12 locations
Rated health of adult and juvenile plants
Collected soil samples
Separated soil samples using sieves
Estimated canopy cover using a densiometer 

results

Abundance of adult and juvenile plants at twelve locations

Health of adult and juvenile plants

Soil composition for locations with high abundance of mullein.  1 = coarse soil, 2 = medium soil, 3 = fine soil.

Discussion

Germination of mullein seeds is a function of environmental conditions.  Soil composition affects mullein abundance and colonization success.  Mullein grows better in areas where there is protection from high temperatures and high sunlight, and grows better in areas where soil has a higher composition of medium-sized soil particles.

references

Gross, K. L.  1980.  Colonization by Verbascum thapsus in an old field in Michigan: experiments on the effects of vegetation.  Journal of Ecology 68:  919.

Semenza, R. J., et al.  1978.  Influence of light and temperature on the germination and seedbed ecology of common mullein (Verbascum thapsus).  Weed Science 26:  577-581.

U.S. National Park Service.  2009.  PCA alien plant working group. 

U.S. Forest Service.  Verbascum thapsus.