Identifying weeds is the first step toward controlling them. There are many ways to identify and classify weeds, and one of these is by their life cycle. Like all plants, weeds can be annual, perennial, or biennial. The ways to control annual vs. perennial weeds are quite different, which is why correct identification is so important.
In general, annual weeds are much easier to control, and weed control methods that work for them may not be effective on perennial weeds. Let’s learn more about the difference between annual and perennial weeds and how to adjust your weed control accordingly.
What are annual weeds?
Annual weeds are simply unwanted plants that only last a single growing season (roughly 12 months) but never beyond that. This means they’ll sprout, grow, flower, produce seeds, and die within 12 months. Since they live such short lifespans, annual weeds usually have showier flowers that last much longer than their perennial counterparts.
Annual weeds can be further divided into two categories depending on their growing season: summer annuals and winter annuals.
Also known as warm-season annual weeds, these weeds germinate in the spring and grow, bloom, and make seeds throughout summer. Summer annuals are more cold-sensitive, dying by the time the first frost comes.
Here are some common summer annual weeds:
- Prostrate knotweed
- Southern sandbur
In contrast to summer annuals, winter annuals are more sensitive to heat. Also known as cool-season annual weeds, they sprout from late summer to early fall when temperatures start to cool down. They grow throughout fall, lay dormant in winter, and reemerge in spring. They then bloom from spring to summer before dying.
Here’s a list of some common winter annual weeds:
- Annual bluegrass
- Common chickweed
What are perennial weeds?
Unlike annual weeds, perennial weeds live for multiple years and become dormant during the winter. They usually last three or more growing seasons, blooming year after year.
Perennial weeds are able to live as long as they can because of their hardy root systems, which can store energy that keeps them chugging through the winter. These root systems — typically with a central taproot — also make perennial weeds very difficult to get rid of. Perennial weeds can regrow from root fragments, so you need to take out the whole root system in one go to keep them out of your lawn for good.
Methods to kill weeds permanently from the root include herbicides, hand-pulling, weed-burning, smothering, and natural remedies like salt, vinegar, or boiling water. However, these methods can be tricky, because most of them will kill your grass along with the weeds. That’s part of what makes perennial weeds so hard to get rid of.
Perennial weeds can be further classified into simple perennials and spreading perennials.
Simple perennials are perennial plants that spread only through seeds. They grow alone. Single perennials that grow near each other are separate plants rather than one big plant. Because of this, they’re also called solitary perennials.
Here are some examples of simple perennial weeds:
Unlike simple perennials, spreading perennials spread through more than just seeds. They have special structures like rhizomes (underground stems) or stolons (above-ground stems) that spread horizontally, sprouting new — but identical — plants. This process is called vegetative reproduction, and it produces clones of the parent plant.
Also called creeping perennial weeds, they can take over an entire lawn or garden within a few years if left unchecked
Some of the most notoriously difficult to eradicate weeds are spreading perennials, including:
- Ground ivy (creeping Charlie)
- Poison ivy
- White clover (and other types of clover)
- Oxalis (however, it can also act as an annual depending on the climate)
How to control annual vs. perennial weeds
Annual weeds are much easier to control than perennial weeds, but perennial weeds are typically easier to keep out of your yard in the first place because they don’t reseed themselves like annuals. Let’s see how different weed control measures stack up against annual and perennial weeds.
|Weed control method
|Effective, just make sure to grab part of the roots. You might need to hand-pull weekly as more weeds pop up
|Effective only if you dig up the whole root system; ineffective otherwise
|Reactive: Post-emergent weed killers
|Both contact and systemic herbicides are very effective
Systemic: Very effective
|Effective, but not as much as for annuals
|Preventative: Pre-emergent weed killers
|Very effective, but you have to apply at the right time
|Not as effective
|Preventative and reactive: Good lawn management
|Effective, especially against grassy annuals
|Effective, especially against grassy perennials; a healthy lawn can outcompete broadleaf perennials
|Preventative and reactive: Mowing
|Not very effective but can keep seed production at bay
Although you may need to pull the weeds weekly, it’s much easier to eradicate annual weeds through hand-pulling compared to perennial weeds. This is because perennial plants can regrow from root fragments.
If you want to hand-pull perennial weeds, you’ll need to dig deep and carefully pull up the plant and its entire root system. This may not be an option for perennials in lawns unless you’re willing to overseed the bare patches that will be left afterward.
Post-emergent weed killers
There are two types of post-emergent herbicides: contact herbicides and systemic herbicides. Contact herbicides only kill the parts of the plant they come into contact with. In contrast, systemic herbicides travel through the whole plant, killing it completely.
Post-emergent weed killers are very effective against both annual and perennial weeds. However, contact weed killers are less effective — often ineffective — against perennial weeds because they don’t kill the roots.
Laying down mulch can be an effective way to prevent weeds from sprouting in your yard. Mulch blocks weed seeds from sunlight, making it harder for them to germinate. It’s more effective against annual weeds, as it does nothing against established perennials.
Pre-emergent weed killers
If you want to prevent weeds from germinating, using a pre-emergent herbicide is one of the most effective ways to do so. Pre-emergents are especially effective against annual weeds since they tend to self-seed. However, it’s important to apply these weed killers at the right time. If you already see weeds, then it’s too late.
For summer annuals, you’ll need to apply a pre-emergent herbicide in the spring; then, treat your lawn in the fall to ward off winter annuals. Pre-emergent herbicides might be a little less effective on winter annuals, though. This is because winter annuals have varied sprouting periods – some may sprout after the pre-emergent herbicide has lost its effectiveness.
Good lawn management
If you’re worried about lawn weeds in particular, you might be pleased to find out that one of the best ways to deal with them is by keeping a healthy lawn through good lawn care practices. Lush, green turf will outcompete most weeds, especially grassy weeds like crabgrass.
Healthy turfgrass also leaves no space for weeds to germinate. Properly mowed lawns – not too short and definitely not scalped – may help prevent weeds from sprouting, too, as they can block out the sun.
Mowing by itself won’t eradicate weeds, but it does help with weed control. Mowing the lawn can help make weeds more susceptible to herbicides. Aside from that, repeatedly mowing your lawn (and, by extension, the weeds) will injure unwanted plants and keep them from growing to their full potential.
This is quite important for annual weeds, as mowing prevents seed production because their flowers never get a chance to grow. Once they die, it’ll be curtains for those weeds if they never get to set seeds. Perennial weeds aren’t really affected by mowing, but mowing can help prevent their seed production, too. Mowing won’t do anything if you’re dealing with spreading perennials, though.
Weed control FAQs
1. What are biennial weeds?
Biennial weeds are unwanted plants that live for two growing seasons (roughly two years). In the first year, they sprout and dedicate their time and energy to growing. They usually grow low to the ground during this time. In their second year, they develop a flowering stalk and bloom. After that, they die.
Many wildflowers, like Queen Anne’s lace, burdock, and thistles, are biennials. They’re often mistaken for perennials, especially since quite a few of them have large taproots. However, they almost never spread through vegetative reproduction. They only spread through seed.
Getting rid of biennial weeds is similar to the methods used to eradicate perennial weeds. Make sure to target their whole root system to kill them completely.
2. Are grassy and broadleaf weeds perennial or annual?
Grassy and broadleaf weeds can be annuals or perennials. These categories aren’t mutually exclusive. Grassy weeds and broadleaf weeds are just different classifications of weeds that are either grass-like or not. You can learn more about the differences in our article on telling broadleaf and grassy weeds apart.
3. Are all annuals and perennials weeds?
Definitely not! Annual, perennial, and biennial are just descriptions of a plant’s life cycle. All plants fall into one of these categories – even grasses and ornamentals.
4. What are some other ways to control weeds?
If you’re not a fan of herbicides, there are some non-toxic weed control methods that you can use. We’ve already shared some of them (mulching and hand-pulling), but vinegar and flame weeders are another way to keep weeds at bay. You can even rent goats to munch on the weeds for you!
When to call professional weed control services
Properly identifying what type of weed is invading your yard is the first step toward creating an effective weed control program. After all, using the wrong method – like a contact herbicide on a perennial – probably won’t do much. So, what should you do if you can’t figure out what type of weed is growing on your lawn?
Homeowners like you can turn to a professional weed control service for help, and Lawn Love can lead you to the right pro for the job. We can connect you to local weed control pros in your neighborhood who have the knowledge, skills, and tools to get rid of weeds once and for all.