Specialized mechanisms of some weed species to bury themselves: wild oat hygroscopic awns that twist themselves into the soil (self-seeding)
-ones with hard gizzards that destroy seeds;
-soft gizzards that pass on viable seed
Wind dispersal of weed seed is a function of:
-how fast seed falls: weight, density, ability to float in air
-height of release: may be most important factor in distance spread; mullein seed
-speed, direction and turbulence of wind between release point and ground
-very light, dust-like seed (poppies; fungal spores)
-species with specialized wind dispersal mechanisms generally don’t colonize as a horizon but as isolated individuals over a greater distance
Differences in time:
-seed ripens on parent plant
-seed retained on parent before its dispersed (seed shattering)
-example: weeds with long flowering period and corresponding long period of ripening and release: seed shatters immediately after ripening on parent
-example: weeds flowering and seed production in narrower time period, often require harvesting activity to release seed: evolved with crop, maximize chance of dispersal with crop
Poverty of seed fall in the immediate neighborhood of the parent characteristic of of plants in isolation; e.g. mullein, musk thistle is pasture
"Tumble Weeds: movement of parent plant (with seeds) on ground after dispersal, -blow with wind;
-seeds dispersed in rolling action;
-examples: kochia on mother plant, forms rolling ball;
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Throughout the growing season, take notice of unwanted plants in your garden or yard and remove them immediately. After all, an amazing adaptation of weeds is that they produce many seeds. For example, one common mullein plant can produce at least 200,000 seeds, and one purslane plant can produce two million seeds! No wonder it may seem like you can never get rid of them. Many seeds can live for years within the soil in what is called the seed bank, so it is not only the current year but also past year’s practice that plays a role in how many weed seeds are present. For more reading, MSU research explains “Weed Seedbank Dynamics.”
Many gardeners are calling the Michigan State University Extension Lawn and Garden Hotline and uploading photos to our Ask an Expert resource wanting to know if what they’re trying to identify is a weed. A weed is a subjective human classification usually indicating a plant out of place, but identifying a plant you see as a problem is a great first step in finding the right solution for your yard or garden.
Weeds have multiple survival tactics
Do not dispose these vegetative parts in your compost pile, as they can resprout and be reintroduced back into your garden. Also, try to avoid placing any weed seeds back into your compost. Unless you are actively managing your pile at temperatures of greater than 140 degrees, they may survive and be reintroduced back into your garden.
Reproduction may also occur vegetatively for some, which means if you leave a portion of a root or rhizome or stolon (i.e., below and aboveground creeping stems, respectively) in contact with the ground, this part will continue to live and regrow. Dandelion, Canada thistle and creeping bentgrass, respectively, are examples with these survival tactics.
Weeds can be frustrating, but by better understanding their specific life cycles and adaptations, you are better armed to defend your garden and landscape against them. Be mindful that many of what we term “weeds” were actually brought here because they had useful properties that served human civilization over time, such as food sources, nutrients and medicinal properties.
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