1. Field bindweed  Scientific name: Convolvulus arvensis  Family: Convolvulaceae (Morning Glory family)  Life cycle: Perennial  Where found: Range, Cropland  Physical description:  Seed: dark grey to reddish brown, three-sided  Cotyledon: linear to oblong  True leaves heart-shaped becoming arrowhead- shaped  Often confused with wild buckwheat  Similar leaf shape, arrangement alternate, petiolate leaves  Nodes of wild buckwheat have papery sheath, absent on field bindweed  Wild buckwheat has inconspicuous flowers, field bindweed has large white-pink, funnel-shaped flowers  Wild buckwheat leaf bases point in, field bindweed bases point outward  Growth habit: climbing/creeping, rhizomatous  Interesting facts:  Will host viruses affecting potatoes and tomatoes Wild buckwheat Field bindweed

2. Weed life cycles

3.  Vegetative reproduction  Production of new plants from vegetative structures  Clones=daughter plants=ramets  Genetically identical to the parent plant  Sexual reproduction  Production of new plants from seeds  Allows for genetic mixing/diversity in offspring (genets) Types of reproduction in plants

4.  Summer annual  Germinate in spring and summer and mature before winter  Problems in spring and early summer planted crops, open sites, winter cereal crops, edges of natural areas  Lambsquarter, redroot pigweed, bedstraw, wild buckwheat, green foxtail, wild oat  Winter annual  Germinate in the late summer, fall, and winter (in warmer regions)  Mature in spring or early summer  Problems in late summer and fall planted crops, open sites, bare spots in pastures  In colder regions, winter annuals may be summer annuals  Shepherd’s purse, field pennycress, downy brome Five life cycle categories for weeds

5.  Biennial  Live for two growing seasons  Seeds germinate and plants grow vegetatively as rosettes the first year  Exposure to cold in winter causes the rosette to bolt in the spring  The biennial then flowers, matures its seed, and dies during the summer or fall of the second growing season  Usually a problem in perennial fields; not in fields that are disturbed in fall  Henbit, houndstongue  Perennial  Survive indefinitely (3+ years)  Flowering doesn’t trigger senescence  Underground structures continue to live Five life cycle categories for weeds

6.  Simple perennials  Start from seed, grow vegetatively  Form a crown of tissue at or below the soil surface on the upper end of a taproot  Root and crown survive indefinitely  Shoots periodically produce flowers and seeds  What is the purpose of seeds?  Found in perennial crops, undisturbed areas, no-till fields  Spotted knapweed  Creeping perennials  Reproduce from vegetative structures and seed  Vegetative reproductive structures are the major means of localized spread, competition, and survival  Creeping roots, rhizomes, stolons, bulbs, tubers  Have large amounts of stored food and numerous buds  Field bindweed, quackgrass, Canada thistle Five life cycle categories for weeds

7. Vegetative reproductive structures  Rhizomes  Elongated horizontal underground stems with nodes, internodes, and modified leaves  Root and new shoot growth always originates from buds at the nodes  Tubers  Thickened underground stems borne on rhizomes  Internodes are shorter than those on a rhizome  Root and new shoot growth always originates from buds at the nodes

8. Vegetative reproductive structures  Bulbs  Modified leaf tissue borne on a small stem plate  Roots and new bulbs develop from this stem plate  Stolons  Horizontal aboveground stems  Leaves produced at the nodes are green  Food storage not a major function

9. Vegetative reproductive structures  Creeping roots  No leaves, nodes, or internodes  Can grow downward and horizontally  Can produce shoots along their length  Tend to penetrate deeper than other vegetative reproductive structures and are harder to control

10. Shoot Regeneration in Weed Species

11. Shoot regeneration  All plants have a growing point from which they can regenerate shoots  Any practice that destroys the plant below the lowest growing point will kill the plant  The position of shoot regeneration on a plant and the resistance of a plant to destruction depends on the life cycle  Annuals  Broadleaves  The bud in the axil of the cotyledons in the lowest point from which an annual broadleaf can regenerate a new shoot  Any action that destroys the weed below that point should kill it  Grasses  The growing point, or crown, is just below the soil surface  Annual grasses need to be damaged under the soil surface for complete kill

12. Shoot regeneration  Biennials  Rosette stage difficult to control  As the seed stalk begins to elongate (bolt) the meristems raise aboveground  Simple Perennials  Crown is 1 to several inches below soil surface  Crown and taproot survive and generate new shoots even after substantial damage  How would you go about trying to control a simple perennial (mechanically?)  Creeping Perennials  Numerous well-protected buds capable of generating new shoots  Large amounts of stored food and many buds  Usually 6 in belowground, sometimes several feet  Severe disturbance usually helps them regenerate  Need repeated action to deplete the plant of energy reserves

14. Questions! 1. Summer and winter annuals germinate in spring and summer and mature before winter. True or False? 2. _______________ weeds are most troublesome in perennial and no-till cropping systems. a. Perennial b. Annual c. Biennial d. Centennial 3. What stage of a biennial weed is most difficult to control? Why?