Weed Life Cycles

Learn the life cycle of weeds.
Weed Life Cycles - Videos

Instructors

Bill Riden

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- [Bill] When we try to control weeds, it's very important to understand the life cycle of the weed we're trying to control.

In this video we're gonna take a look at the life cycles of weeds and point out when they're vulnerable, when they are not.

There's actually three different life stages we're gonna take a look at, one we break into two separate parts.

So, we're gonna start with the annual life cycle.

This is the one we break into summer annuals and then also winter annuals.

But the annual life cycle, as annual implies, the plant's only gonna live one year.

So, let's start with the summer annual, and you can see across the top we have the months of the year going from January through December.

And in the spring, the summer annual will germinate from seed, and you can see the nice supply of weed seeds, annual seed there in the soil.

So, it would germinate.

It's gonna keep growing.

And then it's gonna mature.

It's gonna shoot up a seed stalk to produce seeds, and the seeds are the primary principle for the annual to survive and to reproduce to guarantee future generations.

So, it's gonna set seed.

Those seeds will fall to the ground when they mature, and then they'll be there in the soil, actually for years and years to come.

Now, they don't all germinate at the same time.

So, after the seed, and we get the first hard frost in the fall, the summer annual is gonna die.

Again, an annual only lives one year.

Its main function is to grow, produce seed, and it's done.

Now, when we go to the winter annual, please note at the top our months of year are different.

We go from July to June, so we're picking up really the start of the winter annual in the fall of the year.

Again, we have seeds in the soil that are just waiting to germinate.

But the main thing here is the winter annual is germinate sometime in the fall.

Now, even though my arrow points to September/October, this can actually happen as early as August through that fall period.

The key thing is they're gonna germinate in the fall and they're gonna grow.

And, again, their main function is to grow and eventually produce seed.

Now, at the end of the year, the growing season, the cold weather will not kill the winter annual.

It may die back, but it's not gonna kill it.

It's gonna survive.

Come early spring, oftentimes very early before anything else starts growing, the winter annual will start growing.

And, again, its main function is to grow, produce seed, and then it's gonna die.

So, it's actually the warmer weather that's gonna kill the winter annual.

It has matured, it's done its thing, it's produced its seed, and now its life cycle is over.

The next one I wanna talk about is the biennial life cycle.

Bi meaning two, so this particular life cycle, the plant lives for two years.

The first year, it's really a vegetative life cycle.

You're gonna see we're gonna get germination from the seeds, again, it's gonna grow, and it's gonna produce what they call a rosette of low-growing foliage, if you will.

It's not gonna produce much height in the first year.

Now, one of the things you'll see is it's developing a very sound root system.

In this particular case, this is wild carrot, and it's producing this underground tuber that's growing in size, and it's gonna provide a storehouse of energy.

So, come the second year, it's gonna have energy to start growing.

And that's what we see here in the second year.

The second year is really the reproductive year versus the year one that was mainly vegetative.

So, it's gonna grow, but now it's gearing up to start producing seed.

So, you're gonna get much higher growth, it's gonna shoot up, and it's gonna flower and seed at the end of year two.

After it's produced seed, basically the two-year life cycle is over, and it's gonna die.

Regardless of the weather conditions, it's only gonna live two years.

But you can see it's produced lots of seeds.

You have a seed bank with lots of soil that will germinate, depending on the climatic conditions.

The last life cycle I wanna look at is the perennial, perennial meaning more than two years.

And in fact, some perennials can live for a long time.

Eight, 10, 15, 20 years is not uncommon.

Perennial means it's gonna live year after year.

So, the first year, we get seed germination, although they can also sprout from plant parts if you go on in and let's say cut some of the plant parts trying to maybe cultivate your garden or the farm field.

Those plant parts can take root and sprout.

Anyhow, the first year, you're gonna get development.

They're gonna grow.

The key thing to keep in mind with the perennial is they typically have a very extensive root system.

You can see here in year one we have the root system, but as we go into year two, it's gonna really take off.

There you see the root system, and the other thing you'll see is it'll send up new plants from that root system.

So, as it spreads, you'll see more above ground plants appearing.

So, then we move to year two, and now we're gonna start seeing production of seed.

If not in year two, the following years.

You have a mature plant.

We have a very extensive root system.

We're seeing how it's spreading by producing more plants coming up through the soil from the root system.

So, now you have a real mess.

You have a plant that's very difficult to control because it has a massive root system.

We can sometimes kill the top growth, but if you don't kill the roots, it's gonna come back on you.

So, again, you see a very difficult to control weed.

So, there you have it, the four life cycles of weeds.

The summer annual, the winter annual, the biennial, and the perennial.

I should mention that the biennial that takes two years, only broadleaf weeds exhibit the biennial life cycle.

The other ones, annuals and the perennials, we can see that with not only broadleaf, but also in the grasses as well.

Okay, I hope that helps you understand the different life cycles of weeds.

Now please contact us at Pesticide Education if you have any additional questions.

Thank you.

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