Annual Weeds

Posted by Kara Harders, Regional Small Acreage Management Specialist, Peaks and Plains Region

Cheat grass, gone to seed

 Getting rid of weeds sounds like a simple idea but most of us know it is easier said than done. This post talks about controlling annual weeds, not perennials. Always try to identify the weeds you are dealing with so you can plan the most effective attack plan.

As I take my socially distanced walks around the neighborhood I am always disheartened at the sheer volume of annual weeds I see taking over peoples yards, gardens, rocked areas, and flower beds. It isn’t that I think my neighbors don’t care, I think many of them do, it is just such a hard problem to cure.

The annual weeds are some of the worst because they come up in the spring when we are all dying to see green. They give us hope that the dead patch in the back alley or next to the driveway is finally filling in with the grass we want, and just a few months later we are irritated by the nasty seed heads stuck in our socks and pet’s fur or the dead brown patch they become.

Often times killing the annual weeds (be it Blue Mustard, Yellow Mustard, Cheat grass, Green Foxtail, Henbit, Kochia, Russian Thistle, or others) won’t do anything in the overall control of the weeds. Annuals are the quick and dirty plants of the world because they go to seed so quickly, often before we really have the chance to find and identify them all.

Foxtail, gone to seed

Instead of having it in your mind to kill annual weeds, have it in your mind to keep them from spreading seed. Since an annual weed only lives for a year and then dies, it’s entire specie depends on producing enough seeds to repopulate next year. This can be achieved (or at least attempted) in several ways.

Weed Early: If you can pull or otherwise root up the weeds when they are very small (less than 3 inches, and no sign of seed heads) they will likely die without reproducing (win!). If you don’t mind the look of little weed bodies all over, you can even leave them on the ground. No bagging for you! Herbicides are also an effective choice at this point (always read the label on herbicides! The Label is the Law).

Weed Often: Sometimes with cold and warm weeks and spring rains we will have “flushes” of new weeds coming up. So take a walk around your yard or property fairly frequently, it’s good for your health and also lets you keep on top of what is sprouting up.

You say you see weeds with seeds? It is easy to fall behind on weed watching. I know it happened to me this year. If you start seeing taller weeds or weeds with seed heads you know you have missed the easy window. I really am sorry for you because things get a little more labor intensive now.

Herbicides: If you were all for using herbicides, that window has closed, put down the sprayer. If you kill a happy green weed with seeds you will have the satisfaction of seeing it get sad and brown and die, but the seeds will survive your chemical assault and next year you will be back where you started.

Don't leave a pile of weeds with seeds!

Pulling: Pulling is a solid option. Annual weeds are usually easy to pull up and can be bagged and thrown away. Since the seeds exist try not to shake the pulled plants too much. You have to bag and throw them away at this point.

Mowing with a bag: If you just can’t possibly pull all the weeds consider using a lawn mower with a bag to collect your cuttings (and throw the mowed contents away). This method is sloppier than hand pulling and bagging but will collect more weed seeds than doing nothing. This works from some weeds but less on others, Kochia for example will just grow lower to the ground and form a mat of seed producing weeds.

Keep Weeding: You will likely need to do some level of weed control every year. Seeds from deeper underground will start to grow, wind will bring seeds from your neighbors, a rogue Kochia tumble weed will make its home in a corner of your fence and rain seeds on the ground, the possibilities are endless. But keep your head up, after the first year or two of keeping the seeds at bay you will probably see a good reduction in the weeds that come up, and after that hopefully you can work proper weed management into your schedule.

For more information and links to fact sheets visit: https://planttalk.colostate.edu/topics/weeds-cultural-problems/2117-landscape-weeds-control/

Blue Mustard with seeds

Young Kochia, not seeded yet

Young Cheatgrass, not seeded yet

Tansey or Yellow Mustard with seeds

Prickly lettuce, no seeds

The Gift of Gardening

Posted by: Deryn Davidson, CSU Extension Boulder County

It is no secret that time spent in the garden has myriad benefits to our health and well-being. It can provide stress relief, mental clarity and moderate (or depending on the task at hand, intense) physical activity. This holds true under normal circumstances and it may prove to be even more important during this time of uncertainty as we all learn to navigate the new reality of social distancing and COVID-19. An experiment published in the Journal of Health Psychology looked at gardening versus reading as stress-relieving activities. The study found that both reading and gardening decreased stress, however, the decreases were significantly stronger in the gardening group. In the coming weeks as public events are being cancelled and gathering spaces are being closed, people will be looking for a multitude of activities to pass the time. For me, it’s a comfort to know that we can still get outside to connect with nature.

Now, given that this is springtime in Colorado and it is quite possible, quite likely in fact, that we will still get at least one or two good snow storms along with plummeting temperatures, what are our gardening options?? It’s a great time to tackle those winter annual weeds. Since we’ve been getting moisture here and there, it is easy to pull them up by hand. These are plants that germinate in the fall and winter and grow actively in the spring. They are the ones that seem to pop-up overnight and create a carpet of green in your garden. After they bloom in the spring, they will drop their seeds and die. The trick is getting them out of the ground before they set seed which will germinate the following fall or winter. A few of our more common winter annual weeds are prickly lettuce, henbit, cheatgrass, redstem filaree and any of the mustards (e.g., blue, flixweed). Spring pruning should be on your list too. If you have fruit trees that need to be pruned, now is the time to get that task done while they are still dormant. Pruning fruit trees is different than pruning shade trees and there are great CSU Extension resources online to guide you through that process (including the very informative blog post just before this one!). You can also prune shrubs that flower in the summer or fall. If you prune spring blooming shrubs now, such as lilac, you will prune off those buds so pay close attention to the bloom time of your plants. If you have a vegetable garden, you can be planting peas, spinach and other cool-season crops. You can also take some of your gardening inside and get seeds started for those warm-season crops like tomatoes, squash and melons.

Photos taken one day apart in spring 2017

Now, what if you don’t have a garden? Or what do you do when the inevitable spring snow hits? While it’s not quite the same, there are online resources to take advantage of. Many public gardens are closed to the public right now, but they are staying connected with visitors virtually. Check out your favorite local or even international botanic gardens on their websites, FaceBook and Instagram accounts. You can peruse photos of their gardens and daydream about warmer days to come. Another great option if you can’t get into the garden is paying attention to your houseplants. Check them for insect pests, clean-up old leaves and give them a little extra attention. By working with your houseplants, you will still reap some of the same benefits as going outside.

Gardening is a simple, and meaningful way to connect with the larger world around you. The opportunity to commune with the plants, bees, birds, and other animals that are benefiting from your efforts is truly a gift that I hope will benefit you over the coming weeks, months and years.

What is in your toolbox for Weeds?

By Susan Carter, Horticulture and Natural Resources, CSU Extension, Tri River Area

Spring is here especially in the valleys.  I manage 4.5 acres at our Mesa County Extension office and the weeds are off to the races for growing.  So how do we manage weeds?  First and most important is to identify the weeds or at least figure out what growth type they have such as annual, biennial, winter annual or perennial.  This will help you to come up with the best plan of attack or tool to use.

Dandelion-A perennial Photo By Susan Carter

So let’s start with the annuals.  They are plants that come up from seed from the previous year and complete their life cycle in one year or less.  Depending on the species, they may come up in early spring or they may be warmer season and come up later.  For example, there are many mustard plants that come up very early such as flixweed and blue mustard.  Mustards or plants in the Brassicaceae Family (Cruciferous was the old family name) have four petals arranged in a cross or crucifer shape.  Their seed pod is also very unique and is either a silique or silicle.  The silique faces upwards or downwards and is a long and thin.  The silicle can be heart shaped and is wider than long.  Some mustard plants are edible and others are the opposite so identification and knowing what parts to eat is very important.  These mustards set seed almost immediately.  Since they are annuals they are easy to pull, hoe or till.  But if you do not catch them right away or if you have too large an area, you could use a pre-emergent herbicide.  Pre-emergent target seeds when they are germinating.  They need to be applied prior to any germination.  So I missed the boat for the flixweed and blue mustard for pre-emergent this year so we will be pulling or hoeing or using a post emergent herbicide in large areas. 

Flixweed, an annual in the Mustard Family- Photo by Susan Carter

I should have applied the chemical in early March or even late February since winter was so warm and plants are growing in the Grand Valley.  Make sure to always read the label and follow the instructions, it is the law.   The instructions are written to have the most success so if it says apply a certain amount or to water in, follow the instructions.  Also make sure the weed you are trying to control is listed on the label as being controlled by that specific chemical.  Or if allowable in your area, you could flame the weeds.

Biennials are plants that come up from seed the first year and form a rosette or basal foliage (low to the ground).  The second year they sprout upward, flowering and going to seed.  Then the whole process starts again.  Many people don’t notice some of this type of plants till their second year.  An example of this would be prickly lettuce as in my picture below.  Ideally if you can remove or kill biennials the first year, then you are preventing more seeds from entering your soil and build that seed bank.  Certainly using a hand tool to remove the first year would be good.  Pre-emergent chemicals will also work to prevent seed germination.  And post emergent non-selective or broad leaf killers can be used.  Again, match the chemical to the specific plant being controlled.  And I must admit I hate when people spray really tall weeds.  Then you just have tall big brown dead weeds.  Mowing may slow flowering but many plants will just try to flower again by pushing a new flower head or may flower very low close to the ground.

Winter annuals like Cheatgrass (Downey Broome), Storksbill (Redstem Filaree), prickly lettuce all germinate late summer to early fall, sit there over winter, then take advantage of winter moisture and early warm temperatures and off to an early start they go.  They are among the first to go to seed.  And some like Cheatgrass become fire hazards because they dry out totally by mid-summer.  Cheatgrass is a noxious weed in all 50 states and alone has changed the fire cycle in the West.  Typical sagebrush land prior to cheatgrass would burn about every 75 years.  This interval has been shortened to as little as 5-7 years.  Much work is being done to find a control of this noxious weed.  I have had great success applying a pre-emergent in early August prior to germination, pulling when young in flower beds and using my D hoe to disturb in small patches.  Here is a factsheet on cheatgrass: http://extension.colostate.edu/topic-areas/natural-resources/cheatgrass-and-wildfire-6-310/

Cheatgrass aka Downy Broome - Photo by Susan Carter

Perennial weeds come back from the roots.  They may keep foliage above ground over winter or may die back to the ground and sprout up again from the root.  There are some beneficial insects that slow these plants down.  Bindweed mites can actually get rid of the bindweed if in unirrigated areas.  If watered, the mites cannot keep up with the growth of the plants.  Visit the Palisade Insectary website for more beneficial insects for specific weeds: https://www.colorado.gov/pacific/agconservation/biocontrol

Bindweed Photo by Susan Carter

Other tools that can help include flaming if allowed in your area.  Best not to do in very dry areas.  I believe whenever possible good old fashion labor is a great way to remove weeds.  Digging can work on some species.  But there are some weeds that have roots to China and pulling or digging can make the situation worse.  There are organic labelled herbicides like 20% vinegar, but though organic, it is still an acid and is not cheap.  It works by burning off the tops of the plant so a good control for annuals that do not return from their roots.  Another tool is to out compete the weeds which work well in lawns.  See our lawn care sheet. http://extension.colostate.edu/topic-areas/yard-garden/lawn-care-7-202/

There are also some new zappers that use LED lights on the market.  Tony, our turf specialist, said he was going to try it.  So Tony, we will wait for your review.

So in summary, get to know the bad guys in your garden and make informed decisions based on the type of weed, the amount of weed, the timing of the year and what you personally can handle or afford.  We have many more ways of tackling the weeds than mom and dad did.  And get those weeds when they are small and manageable.

Blue Mustard, an early spring Annual- Photo by Susan Carter

The Annual Weeds of Summer

Posted by: Alison O'Connor, Larimer County Extension

Though we're approaching the end of the gardening season (I know...I don't want to think about it either!), most of us are still battling the sea of weeds on our gardens. As I was walking Maple the other day, I took photos of a few persistent and common annual weeds that we see in our gardens, lawns and landscapes.

It's important to note these are annual weeds and germinate in spring and complete their lifecycle in one growing season (just like petunias or geraniums). Most summer annual weeds will germinate after soil temperatures warm to above 60 degrees. This year, we had a slow start to spring...and our soils stayed cool, so we didn't see weed growth as early as normal. But once temperatures heated up--BAM! Weeds. Everywhere.

There's a few approaches to weed control. One is to pull the weeds. Persistent and regular pulling will prevent the weeds from going to flower and seed (very important) and help keep the weed seed bank at bay. I'm sure most gardeners do their share of pulling weeds throughout the year. Another control option is to use an organic mulch (wood chips, grass clippings, leaves). Granted, this isn't possible in all areas of the landscape, but a thick layer of mulch in planting beds and vegetable gardens does wonders to prevent weed growth. Most weed seeds need light and exposed soil to germinate. Take away these two things and you'll have fewer weeds.

Using chemical options is also an option. For post-emergence weeds (those that have germinated), there are only a few options in our landscape areas (far more in lawns). These options include glyphosate and some organic products (like acetic acid (vingear) and oils). These tend to be non-selective products. Glyphosate is absorbed via the foliage, which does kill the root of the plant. Acetic acid and oils are burn-down products, which means that the foliage dies back. It also means that repeat applications may be necessary.

There are pre-emergence herbicides that you can use in the early spring, such as treflan (sold in Preen), isoxaben (sold in Ferti-Lome Broadleaf Weed Control with Gallery) and corn gluten meal. All  of these products can work, but may need to be reapplied. Always follow the label on the product you plan to use. And a note about corn gluten meal: While it has VERY LIMITED, SHORT-TERM weed control capabilities, it has proven, by research, to be a much better fertilizer than herbicide.

So let's look at the Weeds of Summer:

Crabgrass (Digitaria sanguinalis)

Large crabgrass

Good ol' crabgrass. Here it is in all its glory. Other plants get called "crabgrass" but this is the one and only. Crabgrass won't germinate until soil temps are above 60 degrees. In a lawn, the best defense against crabgrass is to keep the lawn healthy (well-watered and fertilized). In this situation, crabgrass found a great place to grow in rock mulch along the sidewalk. It's nice and hot and ideal for growth. Crabgrass has a very distinct seedhead, which is finger-like (hence the genus Digitaria).

Finger-like seedhead of crabgrass.

Prostrate spurge (Euphorbia maculata)

Prostrate spurge

Prostrate spurge has had a very good summer. It's everywhere. This mat-forming weed can reach impressive size by late summer if left uncontrolled. Fortunately, it's easy to pull. The one caution is that like other plants in the Euphorbia genus, the plant has a milky sap, which oozes when stems are broken. The sap can be caustic and an irritant. If you have sensitive skin, wear gloves and be sure to wash your hands following weeding.

White latex sap of prostrate spurge

Close up of prostrate spurge...you can make out the teeny-tiny flowers, which all form viable seeds!

Purslane (Portulaca oleracea)

Purslane is a pretty mild weed...it's edible, after all! And I haven't seen as much purslane this summer, but I might not be looking that hard. Purslane can be confused with spurge, but there is no milky sap...and this weed has thick, red stems. It's a succulent, so it can tolerate dry conditions with occasional moisture. I see it most often in my vegetable garden, near the drip irrigation lines.

A very mature purslane plant.

Puncturevine (Goatheads) (Tribulus terrestris)

Ugh! By far the WORST of the summer annuals. This beastly plant is just nasty and mean. If you aren't familiar with puncturevine, consider yourself lucky. The seedheads can pop bicycle tires, injure dogs' paws and wreck havoc on bare feet. This is one weed that you should 100% remove and prevent from growing. It can reach widths of feet if left to grow undisturbed...yikes!

One (yes one!) puncturevine plant.

That same plant pulled from the ground.

Puncturevine has yellow flowers and the seedheads start off green, hardening into sharp, pointed, vicious seedheads by late summer.

Yellow flowers of puncturevine.

Nasty, mean and cruel seedheads. The plant is called "goathead" because the seedhead resembles a goat's head.

And poor Maple, my faithful beagle pal and gardening buddy, was afflicted by a stray puncturevine seed on our walk. Poor thing hobbled for a few feet before sitting down, lifting her paw in the air. It's because of this that I just despise this weed. So pull it already!

Maple's paw with puncturevine seed stuck in the pad.

There are many other weeds of summer that I didn't mention, like kochia, but we can cover those another time. Happy late summer weeding, folks!