CO-Horts Blog

Friday, June 28, 2013

Plant This Not That: Arborvitae Edition

Arborvitae (Thuja occidentalis) are evergreen trees which are prized by many homeowners for their deep green color, refined-soft texture and value as a year round screen plants.  However, this year the weather we experienced along the Front Range (which has been discussed here and here) exposed one of their weaknesses.  In our dry climate with its fluctuating and inconsistent temperatures in the spring they are borderline cold hardy.  

Arborvitae damaged by cold temperatures this spring
While you can get away with planting Arborvitae in the right protected microclimate I thought I might highlight a few more reliable substitutes for them in the landscape.
Cooke Peak Arizona Cypress (Cupressus arizonica 'Cooke Peak')

This evergreen plant has a nice texture and attractive and aromatic spearmint green foliage color.  This selection is drought tolerant and reliably cold hardy along the Front Range.   The habits of individual plants can vary somewhat. 
 Two examples of Cooke Peak Arizona Cypress growning in Fort Collins. 

Close up of foliage of Arizona Cypress

Pinion Pine (Pinus edulis)

Pinion Pine is a native evergreen which is smaller in stature and not as dense as Arborvitae.  However, it is very drought tolerant once established and does add winter interest to a landscape.  Pinions sited in more moist sites such as irrigated turf grass may struggle.

Young Pinion Pine in the Adams County Colorado Master Gardener Demonstration

Rocky Mountain Junipers (Juniperus scopulorum various cultivars)

Woodward Rocky Mountain Juniper

There are many clones of Rocky Mountain Juniper which are suitable for use as screen plants, very drought tolerant once established and reliably cold hardy.  While they do lack the smoother more refined texture of arborvitae they offer a wider range of foliage colors.  The cultivar ‘Woodward’ is upright selection with dull green foliage which has a strong central leader and is less prone to damage from snow loading than other upright cultivars.  It may be difficult to find but it’s worth the search.    Selections such a “Gray Gleam”, “Cologreen” and “Moonglow” all have more gray-green or blue-green foliage and are more commonly available at nurseries and garden centers.   All three earned good ratings on the Front Range Tree Recommendation List.
Upright Oaks (Quercus various cultivars and crosses)

I know this seems like a stretch but hear me out.  While they are not evergreen most of the upright oaks are dense enough to provide some screening even in the winter.  Many of them also have attractive deep green foliage and some even get reddish fall color.  Most are narrow enough to fit in smaller yards of many new homes.  Crimson Spire Oak® (Quercus alba x robur 'Crimschmidt')is one upright hybrid with very attractive fall color.  Columnar English Oak (Quercus robur 'Fastigiata') and the other upright English Oak cultivars often exhibit juvenility, retaining dead leaves on their branches thoughout the winter.   Some people find this unattractive and it can increase snow loading, however, it does add extra screening value in the winter.
Columnar English Oak

While no plant is bulletproof these can fill many of the roles of Arborvitae in Front Range landscapes and are generally much more reliable.  Does anyone else have any favorite recommendations for Arborvitae’s niche?

Wednesday, June 26, 2013

Wine Bottle Art In the Garden

By Greg Nolan, Colorado Master Gardener and Native Plant Master,Pueblo County, Colorado.
Posted by Linda McMulkin, CSU Extension-Pueblo County.

Every year, tons and tons of glass bottles are put into our landfills. In places like the arid southwest, those bottles may last thousands of years. Chances are you just might be a wine drinker; chances are you throw your wine bottles into the trash. Chances are an archeologist a thousand years from now will determine that you drank too much. Well, we can mess with the minds of the archeologist of the future.

A local gardener has been adding
bottle trees for color in his
new landscape.  Wine trees grow
faster than pinon pine.

Start recycling your bottles into yard art. You can make wire trees and adorn the branches with wine bottles. You can take dead trees and adorn the branches with wine bottles; heck, you can even incorporate wine bottles into your living trees to add color. How about a wine bottle holiday tree? When people ask where you got your wine, you can simply say; from that tree over yonder.

You can incorporate wine bottles into the paths of your yard. Simply partially bury the wine bottle, mouth down. Using this method you can line the paths and gardens of your yard with wine bottles. This adds definition and character to your garden.  If you want to get more ambitious, using the same method you can make an entire path out of wine bottles. If you are really ambitious, you can encase the bottles in concrete for  a more permanent path. These paths add great color and interest to your yard. Use your imagination.

This short wooden fence on a corner lot became more private by additional height.  And it catches the sun in the late afternoon, adding flashes of color!

          How about adding color to a chain-link fence?  This can be a great backdrop for a young shrub border or the vegetable garden.  Or increase the privacy of your four-foot wooden or picket fence by adding some tall support posts and attach chicken wire and multi-colored bottles. 
If you want something to cool all the wine you will be drinking, consider removing a slat from your deck and suspending a piece of home guttering in its place. You can fill the gutter with ice and add your wine bottles.
Perhaps the best part of any wine bottle yard adventure is the planning. For this you will need a warm summer evening, a bottle of cold rose, something light to eat, a significant other, a comfortable seat in your yard, and a dream. 

Friday, June 21, 2013

Gatsby Gardens

Posted by: Alexis Alvey, Horticulture Agent in Denver County

I'll admit that I am a dork at heart.  But unlike most of my colleagues, I don't just geek-out about plants - books and American literature will induce the same type of nerdy enthusiasm.  (And don't even get me started on plant books!)  So when I found out that a new film was being made about The Great Gatsby, a book that I've read not once, not twice, but three times, I pretty much flipped-out.  (And Leonard DiCaprio as Jay Gatsby was a huge bonus!)  I was super-excited to see Gatsby's enchanted gardens, where "men and girls came and went like moths, among the whispering and the champagne and the stars" on the big screen.  Did the exquisite gardens live up to the magnitude of greatness I had created in my head?  Well, unlike the critics, I thought Baz Luhrmann's over-the-top directing did a great job of conveying the splendors and excesses of New York during the Roaring Twenties.
Being that Colorado is a tinderbox and entrenched in wildfires at the moment, I thought I'd use this blog post to provide a brief reprieve by describing some of the lush, green, Gatsby-esque gardens I've had the pleasure of visiting on Long Island, NY.

The front entrance to the Old Westbury Gardens mansion
The Long Island Gold Coast, which encompasses Gatsby's legendary West and East Eggs, occupies the North Shore of Nassau County, from Great Neck to Huntington.  Over a dozen estates, once owned by some of the most famous people of NY, have been converted to public use.  Most of these mansions were built from 1890 to 1925, and they were the playgrounds of the great barons of the Industrial Revolution, including the Vanderbilts, Roosevelts, Whitneys, Pratts, Morgans, and Woolworths.
Old Westbury Gardens is one of my favorites.  Located in Old Westbury, it was the home of John S. Phipps, his wife, Margarita Grace Phipps, and their four children.  John’s father was Andrew Carnegie’s business partner, and as such, he was heir to the US Steel fortune.  Completed in 1906, the magnificent Charles II-style mansion sits amid 200 acres of formal gardens, landscaped grounds, woodlands, and ponds.  It has been open to the public since 1959.  Perhaps you have seen it yourself, because it has been the site of many films, including Cruel Intentions, Hitch, and Gossip Girl.

Old Westbury Gardens
One of the key questions that Old Westbury Gardens wrestles with, is how do you maintain a historic landscape in the modern age that is for public use?  What happens when old, magnificent trees start to decline and invasive pests come in?  Old Westbury Gardens has invested great amounts of time, effort, and financial resources for tree preservation.  There is an old allee of European Lindens (Tilia x europaea) that traverses the property from the ornate entrance gate to the mansion.  If one tree goes, the whole effect of the allee is compromised.  These trees are routinely pruned for deadwood, and an integrated pest management program has been created for them, which focuses on improving the soil environment.

Another former Gold Coast mansion and now public garden has taken a different approach to a similar problem.  Planting Fields Arboretum is located in Oyster Bay on Long Island and was the "country cottage" of William Robertson Coe and Mai Rogers Coe.  William made his fortune in marine insurance and Mai was the daughter of one of the partners of Standard Oil. 
Planting Fields Arboretum pool
Their 65 room Tudor Revival cottage, Coe Hall, was completed in 1921.  The arboretum is comprised of 409 acres of greenhouses, rolling lawns, formal gardens, woodland paths, and plant collections.  At the time, the grounds were landscaped by the famed Olmsted Brothers. 

As a child growing up in Fairhaven, Massachusetts, Mai Coe was particularly fond of two European purple beech trees (Fagus sylvatica) on the grounds of her home.  So, when she moved to Long Island, she decided to bring them with her.  In December 1915, the two trees were moved by barge across the Long Island Sound to Oyster Bay, where they were dragged on skids by teams of horses and a steam roller.  Each tree was about sixty feet in height and about forty feet wide, and each weighed more than 28 tons.  Only one of the trees survived the transplanting.  For ninety years, the one purple beech tree towered majestically in front of Coe Hall, cooling the building in summer and tempting visiting children to climb it's enormous branches.  Then, in about 2005, the tree finally succumbed to disease and had to be removed.  But before it was cut down, the foresighted Arboretum Director, took a cutting from the original tree.  The cutting now stands about twenty feet tall, and in a few decades will become the majestic tree that its parent once was. 
Planting Fields beech tree cutting
Perhaps The Great Gatsby will inspire you to someday visit the gardens of Long Island's Gold Coast.  But in the meantime, we can focus on our own backyards and dream of the grandeur that once was.  Personally, I'm just glad I will never have to orchestrate the moving of a 28 ton tree!

Wednesday, June 19, 2013

Is that your Ascochyta or mine?

Posted by: Tony Koski, Extension Turfgrass Specialist

Wait...lemme guess…you’ve got brown spots in your lawn.  Well, the good news is you’re not alone, nor do you need to panic. You’ve probably got Ascochyta (ass-co-kite-a) leaf blight.  And it’s caused by drought stress or an inefficient irrigation system.  Whoa Nelly!  You think we’ve had lots of rain?  Unfortunately, that was weeks ago and our soils were so dry that the moisture was used or lost to the atmosphere almost immediately.
Ascochyta everywhere!
What is Ascochyta?  Technically, it’s a fungus.  But before you go reaching for those fungicides, first take a look at the cultural conditions in your lawn.  No, the fungus was not brought to your lawn by the mowing company…or moved in your lawn by your mower. The straw-colored wheel track patterns occur when drought-stressed turf is mowed – essentially bruising the turf leaf blades. Unfortunately, this bruising kills the leaf blade – often all the way to the ground. Fortunately, the actual grass plants aren’t dead—with a little time and patience (and regular water) the lawn will recover in a few weeks.

But I’m confusing disease versus stress. Let’s go back:

Classic Ascochyta symptom--withered leaf tip
Ascochyta is a fungus that lives on the leaf blade.  The fungus enters the leaf blade through the cut end (when you mow).  It causes the blade to turn a straw-color and wither to a point.  Why the fungus happens or how it works is not well understood by researchers.  It does seem to coincide with periods of cool weather followed by hot, dry weather….in other words, your normal, typical Colorado spring.
Looks like the mower did it...
but really, it's because of drought-stressed turf.
Stress in the lawn (from poor or lack-of irrigation coverage, mowing equipment or heavy foot traffic) encourages the fungi. Wilty, bruised leaves are tasty hosts for the fungi.   And then you have a hot mess on your hands…your lawn looks dead, BUT the crowns and roots of your grass plants are still alive. We are seeing this mostly on bluegrass lawns, but any turf variety (tall fescue, fine fescue) can get Ascochyta.

Don’t go to the store and reach for the “lawn disease control” products.  They will not cure the problem or hasten the recovery.  You’ll spend a lot of money for nothing (and you won’t get your chicks for free).
Instead, focus efforts on your irrigation system. Look for broken or tilted heads and fix them. Adjust the spray/arc of your sprinkler stream to get more uniform coverage between heads. And water appropriately—your goal is to water as deeply but infrequently as possible. Under current conditions, for a bluegrass lawn, this will be about 1.5” water/week. But make sure you have an idea of how much water you’re putting on by collecting water in cups during an irrigation cycle.

Mow as normal, but time mowing a day or two after irrigation and do the deed during cool parts of the day—early morning or late evening. Keep your mower height at 2-3” tall and keep the blades nice and sharp.  Leave the grass clippings on the lawn (to recycle your fertilizer) or if you collect them, it’s ok to use them in compost or in your vegetable bed.  Remember, this is a lawn disease and will not spread to veggies or flowers. 
While patience may not be your virtue, keep in mind that this disease usually disappears by mid-summer. And if your entire lawn has this, with regular irrigation and hopefully some natural precipitation, the lawn will recover to its former glory.

For more information on Ascochyta, read CSU Extension FactSheet #2.901.
It looks worse than it is. After a little irrigation
and a little time, the turf will recover nicely.

Monday, June 10, 2013

Edible flowers jazz up summer dishes

By Carol O'Meara, Horticulture Agent, Boulder County

The bravest man I know shudders at the thought of dining at my house during summer.  Not because I’m a terrible cook or my food might lead to hospitalization – these risks he faced in World War II and Korea.  No, the reason my father fears my table is because the meals I serve blossom with edible flowers.

Stuffed nasturtium
You might think it silly for a person to hesitate over eating a flower; after all, nasturtiums, squash blossoms and chives have been mainstream in culinary creations for years.  But if you think these are the limit of floral flair, you’re missing out on a decorative way to spice up your dining. 
Delicious, cucumber-like Borage (Borago officinalis) popped into salads or dips, sauteed Daylily buds (Hemerocallis fulva), cheerful pansies (Viola x. Wittrockiana) in festive salads, or Scarlet Runner Bean blossoms (Phaseolus coccineus) highlighting steamed green beans all have a place on the summertime table. 

Finding flowers for cooking may mean growing them yourself.  If you do, treat them as you would any vegetable and grow them organically, following the five rules for eating flowers:

1. Be absolutely positive about identification - not all are edible, and some can be harmful.  Know beyond doubt what you have before eating it.

2.  Common names are misleading, so don’t pick a flower based on its moniker.  Sweet peas, for example, are poisonous, while yucca is tasty.

3.  Many greenhouses and florists spray plants; these flowers are not suitable for eating.  Use only those picked from your garden or from a reputable, food-grade source. 

4.  Flowers may cause allergic reaction in some people with asthma or hay fever, or give you a digestive malfunction.  Start slowly, and eat only small amounts of them at first.

5.  Many chefs garnish with flowers that aren’t edible.  Check with the kitchen before eating them.

Deviled eggs with marigolds
Flowers degrade faster than herbs, so plan to use them within a few hours.  Keep them fresh by storing in the refrigerator.  Pick flowers on cool mornings, choosing those that are just becoming fully open and avoiding those that are wilted or starting to fade.  Pinch, don’t pull flowers from the stem.

Different growing conditions effect flavors; be sure you like what you’re harvesting.  To avoid bitter meals, taste the flower before spending a lot of time picking them.  Remember, they’re delicate, so wash flowers with a fine spray of water just before using them. Try these: 

Daylilies: Packed with vitamin A and C, these flowers also have three grams of protein in every bud.  Harvest buds when they’re one-and-a-half to two inches long; larger than this and they’re bitter. 

Pansies: Harvest by picking the stem all the way to the plant, keeping the flower intact.
Pop petals into ice cube trays, fill with water and freeze for an elegant touch in drinks, or use fresh in salads.

Roses (Rosa spp.):  Pull or snip petals from the bud. The white inner portion of the petal is bitter, so snip it off before using.  A rose’s perfume gives a clue to its flavor, and varieties that have a stronger scent generally taste better.  Look for those that smell like food; you’ll find roses can be citrusy to spicy, sweet to mild.

Lavender (Lavandula angustifolia): Pull the petals from the bud and pinch off the tiny white ends.  Lavender can turn bitter when dry; use them fresh for sweetest flavor.  Because the taste is bold, a little goes a long way - use petals sparingly.

With many flowers, such as roses, tulips, and lavender, only the petals are edible.  Remove the stamens, styles and pistils from inside the flowers, and snip off the outer, green sepals.  If the flower is tiny, gently pull the petals from the bud to use.  Others, like runner beans, honeysuckle, and pansies may be eaten whole.

Friday, June 7, 2013

Defoliation Leads to Refoliation: What it Means to Trees

By: Alison O’Connor, Horticulture Agent, Larimer County

Unless you’ve been vacationing in southern France for the past few weeks, you know that Colorado has had an interesting spring.  I’m on a listserv that includes people from every facet of the Green Industry and there is a lot of chatter about various subjects, but talk lately is about our trees.  Contributor Dan Staley said it best, “We’ll look back and sigh…’Oh yes, 2013...’”. 

Our trees have had a tough few months.  Heck, you could argue that their entire lives have been difficult—they are growing in Colorado after all.  But this spring has been a doozy.  The hottest summer on record (2012) was followed by a cold, windy, dry winter and then a wet spring and hard freezes through early May.  It’s a wonder our trees have leaves and that the lilacs have bloomed.  But if you stop and think about it—trees are pretty incredible.  They stand the test of time.

If you’ve looked closely at our ash trees, you may notice that they look a little different this year.  At least in the Fort Collins area, most of the terminal buds were killed by frost, so the tree pushed leaves at the side buds (adventitious buds).  In some species, entire trees may have had to re-leaf—some more successfully than others.  So how does the tree do this?  Does it hurt the tree?  What can we expect next year?

Many ash trees' terminal buds froze;
adventitious buds pushed leaf growth
The act of refoliation, whether from spring frosts or insect damage, is a part of the tree’s genetic make-up.  If the tree doesn’t leaf, it cannot photosynthesize and produce food for the tree…so the tree will do everything it can to push new leaves.  Repeated defoliations and stress can lead to depletion of storage reserves and eventually the tree just gives up.  All those dead trees in landscapes are probably not just because of this winter—it’s a cumulative effect (this year’s winter/spring, 2012’s hottest summer on record…and so on).

Fortunately, trees are great at storing energy and food from previous years.  If the tree is healthy, then having to re-leaf once will use up some reserves, but the tree should “grow through” the damage.  The adventitious buds formed tend to mask the damage and the tree looks normal.  But this all depends on several conditions the tree faces: severity (number of buds and/or leaves lost), frequency (how often this happens), timing (when did the injury occur), weather and other cultural conditions, tree vigor and secondary organisms that can move in and attack when a tree is stressed. 

Studies have shown (Wargo et al., 1972; Heichel and Turner, 1976) that trees can lose up to 50% of their leaves in one season and not be adversely affected.  That’s good news!  BUT, if refoliation must occur that same year, the tree’s physiology is altered significantly (Wargo et al., 1972; Wargo, 1972); the tree uses food reserves to maintain living tissues until new leaves can be formed.  So, the fact that our trees lost buds (and subsequently, leaves) early in the season and had to push new leaves is not a good thing.  If a tree loses leaves from insects or disease in August, this is less stressful to the tree, since it worked all summer to build food reserves.  It also depends on the time of year—producing new leaves and buds in late spring or early summer is stressful, since days are hotter and it tends to be drier. 

Campbell and Valentine (1972) found that even the healthiest tree that has repeat defoliations for two or three seasons in succession can die.  A tree that defoliates and refoliates in the same season will have reduced food reserves, and its leaves will produce less chlorophyll and be nutrient deficient.  If defoliation doesn’t kill the entire tree, crown and branch dieback can occur (which we can attest to) and tree vigor declines.  A healthy tree can turn into a dying tree within a couple growing seasons. 

While this ash doesn't look too bad, a few years ago, 12" of rock was dumped on its roots.  It's been declining over time and will likely eventually become mulch.

There are other effects of a severe spring defoliation to consider. We may see less leaf tissue—either a reduction in total canopy or smaller leaves.  Trees know what they can “spare” in food reserves and may produce smaller leaves as a result.  We may also continue to see branch dieback.  If terminal twigs (or buds) die, then lateral buds grow and the tree takes on a new shape.  Trees may also be slow to respond to trunk or branch injury, even from proper pruning; wounds may stay open longer, and be more susceptible to insect, disease and decay.  Also, don’t forget about the roots. “Feeder” roots (those less than 2 mm in diameter) may die, because fewer leaves in the canopy means less energy/food for the roots. But fewer, less healthy roots means that there may be less water and nutrient uptake, affecting leaf production. 

Fortunately for us (I try to stay positive), the earlier the defoliation or damage occurs in the season means the trees have a longer time to recover.  But this means that regular water and TLC becomes even more important.  Focus on proper watering.   As trees push new growth, water is imperative.  Adequate water promotes proper leaf development—larger leaves produce more food.  Try to avoid fertilizing during the growing season and fertilize only if necessary in the fall.  Fertilizing trees will not “correct” or “save” stressed trees.  Carefully monitor trees for signs of secondary organisms, like insects and disease.   

Finally, realize that this too shall pass.  Yes, we may have to replant some trees, but this is a great way to diversify our urban forest.  Maybe try planting something atypical…my ginkgo is thriving!

References cited (oldies but goodies):

Campbell, R.W. and H.T. Valentine. 1972. Tree condition and mortality following defoliation. U.S. Dept. of Agric. For. Serv. Res. Pap. NE-236. 

Heichel, G.H. and N.C. Turner. 1976. Phenology and leaf growth of defoliated hardwood trees. In Perspectives in Forest Entomology. J. Anderson and H. Kaya, eds. p. 31-40. Academic Press, New York.

Wargo, P.M. 1972. Defoliation-induced chemical changes in sugar maple roots stimulate growth of Armillaria mellea. Phytopathology. 62: 1278-1283.

Wargo, P.M, J. Parker and D.R. Houston. 1972. Starch content in roots of defoliated sugar maple. For. Science. 18(3): 203-204.

Monday, June 3, 2013

Roundup is Roundup…Right?

Tony Koski, Extension Turf Specialist
Which one do I use? They both say  Roundup!
If you are reading this in hopes that the turf specialist has seen the light and jumped on the Occupy Monsanto bandwagon, well…you can stop reading now. Glyphosate/Roundup is still, in my opinion, one of the most effective, inexpensive, easy-to-use and safest herbicides available to the home gardener – and to professional weed managers as well. But a stroll through the pesticide aisle of any hardware store or big box garden center can present to even the sharpest of gardeners a somewhat bewildering selection of Roundup products from which to choose…Roundup Concentrate…Roundup Concentrate Plus…Roundup Extended Control. The various Roundups entice you with promises like “Results in 12 hours” (faster is always better…right?) or “Controls weeds for up to 4 months” (longer is always better…right?). And then there is yet another glyphosate-containing product, ominously named GroundClear, which provides one year or more of weed control (REALLY longer is BEST…right?). It’s easy to understand the confusion when asking oneself “Which one do I buy?”. And I suppose it’s somewhat easy to understand when consumers (professional applicators don’t get a break here) misuse these products in the landscape – although a thorough reading of the label would, in most cases, prevent some damn dumb mistakes. (What? Read a label? Ain’t nobody got time for that!). Sooo….how different are these Roundup products? Can they be used interchangeably? Is one better than the others? Are all of them “safe” for home landscapes?

First, the traditional verbiage – to protect my you know what – whenever we Extension types write about pesticides: READ THE LABEL before purchasing, much less using, any of these products! A reading of the ingredients section of the various Roundup products demonstrates that they aren’t the same. And while the "where to use/not to use" instructions aren’t always the most clearly written, a close reading (ok, maybe 2 or 3 times…) of the label will help prevent misuse of these products. 

Roundup Super Concentrate (white bottle…purple cap) is your good ol’ pure and simple glyphosate.  Use it wherever (wherever the label allows, that is…yes, READ THE LABEL!) you need non-selective control of weeds in your landscape. It is taken up only by leaves and other above-ground green plant tissue. No soil residual. No root uptake. No extended control.  This Roundup can be safely used: on your driveway or sidewalk or patio…on mulch circles around trees (but don’t spray the trunk, or surface roots, or suckers)…to renovate your lawn…or to kill a section of your lawn and replace it with a flowerbed or veggie garden. This is the slowest acting Roundup product, taking anywhere from 5-10 days before you begin seeing symptoms that the weeds are dying. But because we are so impatient (we “need” FASTER internet… FAST food…RAPID transit…INSTANT mashed potatoes), a couple of other Roundup products were developed to satisfy consumer demand for more rapid weed kill. Enter Roundup Plus…

Faster Roundup is better....isn't it?
Roundup Concentrate Plus (white bottle…red cap) contains glyphosate and another herbicide called diquat dibromide. The diquat is added to give a more rapid burndown of weeds that have been sprayed. Other than providing the more rapid (within about 12 hours during hot weather) visual symptoms that the weeds have been sprayed, this Roundup product works the same way as the basic concentrate. All foliar absorption, no root uptake or soil residual. No extended control. 

Roundup Ready-to-Use Plus (blue and white bottle) contains glyphosate and pelargonic acid. The pelargonic acid makes this Roundup product work even more quickly than the Roundup Concentrate Plus – you may see wilting within 3 hours on a hot, sunny day. So, for the VERY impatient, this Roundup product works even more quickly than the Concentrate Plus product – but is otherwise the same: all foliar uptake, no root uptake, no soil residual, no extended control. Use it the same way you would the above two Roundup products.

Roundup Extended Control (gray bottle) contains pelargonic acid (for rapid burn down) and a herbicide called imazapic. Imazapic is added to provide the “extended control”. It works as a preemergence herbicide to provide 3-4 months of weed control by killing germinating seeds/seedling weeds. However, imazapic also is somewhat root active and can provide postemergence control of some weeds as well. This is where things get tricky. Imazapic is fairly water soluble, so it can move in soil. This means it can move to parts of the landscape where you haven’t sprayed it (down slopes, for example…or when sprayed on gravel-covered plastic). And because of the long soil residual, don’t use this product where you may want to plant something in the near future (so this one is a no-no for lawn renovation, nor should it be used where you plan to plant a veggie or flower garden in the future…or trees or shrubs).  The label does allow use over the root zone of trees and shrubs (established ones…not newly planted), including on mulch circles around trees. However, imazapic has been shown to cause injury to a

few tree species which are sensitive to it: lindens, green ash, and cherry trees. Soooo….while it is generally safe to use in those parts of the landscape where you need control of existing weeds AND desire some long term weed control/prevention, you have to recognize the potential for this stuff to “move” in the landscape. Use the same precautions that you would with any Roundup product…and maybe consider if you REALLY need to use this over the root zone of your trees? 

And then there is GroundClear….While it doesn’t have Roundup prominently displayed on the label, this is another Roundup product. It is aggressively marketed on the radio and in the aisles of big box stores. Who wouldn’t want weed control for a year - or longer? This is the one where the “Keep out of reach of children” line on the label maybe should read “Keep out of reach of adults who don’t read a label”. This Roundup product contains imazapyr (a close relative of imazapic…see above), which is a VERY long-lasting, soil/root-active herbicide. Imazapyr can last a year or longer in soil, depending on soil type and how much moisture the soil receives. It is non-selective, can move with water in soil, and is easily taken up by roots of trees (yours or your neighbor’s), shrubs, vines, flowers, veggie plants, turf….you get the idea. As the name would imply, this product really does “clear the ground” on which it is applied. In my opinion, there are few places in a home landscape where this product could be safely used. I doubt that there is a driveway, patio, or fence line in any urban landscape that doesn’t have a tree or shrub root growing under it. Unfortunately, the promise of long-term weed control is so irresistible, it is bought and used in places where there is significant potential for damage to trees and other desirable landscape plants. This is one that you want to avoid using in your landscape, unless you REALLY, REALLY know what you are doing – and even then I would be hesitant to use it.  I have visited landscapes where professional applicators (who should know better…and who violated the label by using it where they shouldn’t have) have killed or injured dozens of trees using this and similar products for mulch circle weed control.

Trees killed by improper use of herbicide
containing imazapyr.
Like most things in life - when preventible, bad things happen - you can only blame yourself for not reading (or following) instructions and heeding warnings.  When you purchase any pesticide, you enter into a legal agreement that you will use it as the label instructs. Your trees and turf can’t read the label…they trust that you will.