CO-Horts Blog

Monday, August 29, 2016

Fall is Coming!

Rudbeckia triloba, Tri River Gardens, Photo by SL Carter

To some people, fall might be a four letter but to me it’s one of my favorite times of the year.  Those tomato plants are finally producing, mornings are cool and crisp, Grand Junction is rarely hitting 90 degrees and lots of yellow and purple late blooming plants are blooming.  This is also a time when a lot is going on under the ground.  Cool season turf has perked up, trees are starting to grow more roots and all perennial plants (trees included) are being like chipmunks and storing up food to make it through the winter.  Here is a wonderful handout called healthy roots, healthy trees:

So what can you do to help your plants make it through winter?  Well, for one, since the nights are getting longer and the days cooler, hopefully you have adjusted how much you are watering.  We need to help slow down plants so they can harden off for winter.  If you keep giving frequent water, they will continue to grow.  So slowly start reducing the times you water but you may need to increase the length of time you are watering.  The best way to check is to use a screwdriver from the drip edge out on trees to see if it easily slides into the soil to a depth of 6-8”.  If it only gets a couple of inches down, you definitely need to water deeper.  If it comes out all muddy, you have over-watered.  Ideally, you should be checking your lawn and garden this way thru and season and adjusting the irrigation; once a month is a good rule to follow.
Lawn at Mesa County Fairgrounds, Photo by SL Carter
As the weather cools, cool season grasses (Kentucky bluegrass, tall fescue and perennial ryegrass) will begin to grow faster.  Mowing will be needed more often to ensure that the grass is not stressed.  No more than one-third of the grass blade should be removed at each mowing. Continue to maintain the grass at the same cutting height as during the summer.  Even though lawns grow faster in the fall they will need less water than during the summer.  Adjust your lawn watering accordingly.   Here is a handout on watering established lawns:

This is a good time to install sod.  Preparing the soil properly is critical to success. Contact your local extension office for suggestions.  Do not apply weed killers to newly seeded lawns; wait until the new grass has been mowed at least twice before spraying for weeds.  Sodded lawns can be treated for weeds as soon as the weeds are noticed. And speaking of herbicides, one of our agents did some work the last two falls spraying bindweed with glyphosate, and does it work well.  Targeting certain perennial weeds in fall with the appropriate chemical allows the chemical to be pulled into the roots as the weed is trying to store energy.  Always read the label and follow the instructions.  It is best to make sure what you are using is appropriate for what you are controlling.  If you only have to do it once, it will save you money too.

At lower/warmer elevations, now is a good time to plant some cool season greens to get a last batch before winter gets here.  I will say, I hate when winter gets here and there is no more fresh veggies.  So for now I’ll enjoy the cool morning that still brings abundance. Enjoy!

By Susan L Carter, Horticulture Agent, CSU Extension, Tri River Area

Thursday, August 25, 2016

A Tale of Two Honey Locusts

Posted by: Mary Small, CSU Extension State Master Gardener Coordinator
One troubled Honey Locust!
Trekking across campus I came upon these two honey locust trees. They represent the kind of question I really dislike answering - especially when you can’t actually see the plants in question. Why does one look great and the other one, well - awful? They were planted at the same time. They were purchased from the same company. They both looked good the first few years. And so on…..

So let’s go see what’s wrong with the tree in question, even though I want to shout “Hello, it’s trying to grow in a parking lot!”

First I found weak-looking leaves that were minimal in number. Twig growth increments aren’t (and haven't been) very long either, telling me that the plant hasn't been growing well. It makes sense – few leaves produce few carbohydrates resulting in little growth. On top of that, since mid-August, the tree has been experiencing “early fall”. Another bad sign, indicating some kind of stress that has caused photosynthesis to slow or cease.
Gummosis - not good

Uh-oh – there’s some gumming on the trunk and many of the larger branches I can see. Not a good sign. Right off the bat, it means the tree is stressed. The stressors include but are not limited to drought, sunscald, canker diseases and collar rot. 

The lower trunk has no flare and is flattened on a couple sides.  You can see one of those sides in the photo below. That signals girdling roots, so it’s time to do some excavating. Having only a twig for digging, I find one root just under the soil. Although I couldn’t dig deep enough, with the appropriate tools, I’m pretty sure I would have found more girdling roots.
Flat side and sprinkler too close to trunk

Girdling root

I will admit to not being astute when it comes to automatic tree irrigation, but I have a hard time understanding how one emitter adequately irrigates a tree of this size. Having it so close to the trunk of a honey locust can invite root collar rot infection, too, by keeping the collar area moist and conducive to pathogen growth and development. 
Narrowing trunk and slightly excavated trunk flare (right)
I was able to find only the beginning of the trunk flare and it’s at least 3 inches too deep. It's just showing there on the right side of the photo.  This tells me the root system is also planted too deep. Roots need oxygen to carry on various processes and when they can't get the oxygen they need, processes slow or shut down. They can't resist pathogen infection well or at all, either. 

For fun, compare this deeply planted trunk to the healthier tree’s trunk (below)– it has a comparatively good flare. And you can see it without any excavation.
Better trunk flare of healthier tree

So why does the one tree look healthy and the other awful? The nearly dead tree was planted too deep, causing oxygen starvation and a slow decline. I strongly suspect girdling roots, which would restrict water, nutrient and carbohydrate movement, are also at work here. The heat generated by the asphalt parking lot isn’t helping things, either.  Poor tree!

Sunday, August 21, 2016

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 can make out the teeny-tiny flowers, which all form viable seeds!
Purslane (Portulaca oleracea)

Purslane is a pretty mild'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!

Thursday, August 11, 2016

The Power of Plants!!

Posted by: Deryn Davidson, Boulder County Extension 

The power of plants. We eat leafy greens packed with vitamins and minerals to fuel a healthy body. We use their fiber for clothing and building materials. We use the shade of trees to cool ourselves and our homes and we search seas of parking lots looking for that sliver of shade to park our cars under. Plants prevent erosion, they clean stormwater, this list goes on and on! Given some sunshine, water and occasional feeding (if they're lucky) plants just do their thing and we reap the benefits.

So where is all of this musing about the awesomeness of plants coming from? Well, at first I was going to write this blog about all of the lovely plantings that towns along the Front Range do to pretty up their streets and make them more appealing. Fort Collins is becoming known for their lovely Old Town alleyways (when I was growing up, they were not so lovely...), Denver and Boulder put time and energy into making their public spaces planty. And Niwot, CO does a great job with this. Petunias spill out of fun and unusual containers that line the streets and a dedicated crew of folks drag a water tank around and water them regularly throughout the hot summer months.

Niwot, CO 

So, as I was thinking about all of these lovely summertime streetscapes, I started thinking about WHY towns and cities do this. It's because of the power of plants!! Plants (nature) make us feel good. Plants make a space feel more comfortable and calming and happy. Study after study shows that time spent in nature has a profoundly positive effect on us. A University of Michigan study showed that students who took a walk through the campus arboretum performed better on a short-term memory test than those who walked down a city street (I'll go ahead and assume it was an un-planty city street). Spending a brief amount of time in a natural setting can restore our mental energy know that metal foggy feeling? Research has shown that just looking at a picture of a nature can help clear that fog (looking at picture of cities did not have that effect). And we all know that gardening is a stress reliever!! 

When we go outside (or even look out a window at a bit of nature) our cortisol levels drop (the hormone associated with stress), our blood pressure drops and it can help us improve our concentration skills. Nature can even help our bodies heal. In a landmark study done in the 1980s, Roger Ulrich found that patients recovering from gallbladder surgery who had a room with a view to a small stand of deciduous trees had a shorter postoperative hospital stay, took less pain medication and had fewer post-op complication than another group whose view was to a brown brick wall. The power of plants. 

Niwot, CO
So thank you to the towns and cities who include summertime streetscaping into their budgets. Believe it or not, by bringing that little bit of nature to our daily lives as we get to work and run our errands, they are helping us all feel more calm and brightening our days! 

Thursday, August 4, 2016

Sample some Love Apples

Posted by Carol O'Meara, Boulder County Extension

  My neighbors might be catching on that living near a gardener is a good thing.  Sure, there are a few quirks to put up with, like earsplitting shrieks when squirrel damage is noticed on pumpkins or alarming noises as I rise up from crouching to weed.  But these small eccentricities fade once harvest sets in, because they know I’ll start sharing the bounty with those who wander by.
As they stroll past with their pets, I call them into the garden with friendly invitations like “you, with the Shih-Tzu, want some beans?” or “Hey, parrot-walking man!  I’ve got plenty of kale to share!”  I've contemplated tying bags of produce to cats' collars so they take them home with them, but those rascals are harder to catch than the dogs are. 

Most neighbors have gotten produce from me before and accept it with smiles, even though they know I’ll toss in a zucchini for good measure.  Right now the beans are coming in like there’s no tomorrow, but fast on their heels is a bumper crop of tomatoes.   And once they start, everyone in the neighborhood gets love apples. 

Big, little, red, yellow, purple, and orange – we’re entering tomato season with its wealth of rainbow colors.  Cherry tomatoes like Green Doctors, Isis, Sungold, and Jasper may be little in size but big in flavor.  Each of these tasty morsels is sweet enough to woo new devotees to growing them.  Matt’s Wild Cherry, a currant type, is a tiny, prolific tomato about the size of a pea. 

Salad tomatoes that shake your kitchen up with new flavors and colors are Green Zebra, Lemon Boy, or Japanese Black trifele.  Each has bold enough flavor to stand on their own, but combined in a colorful Caprese salad, they shine. 
I’m experimenting with paste tomatoes this year, because I sauce a lot of them and an Italian-American friend told me, proudly, that for real Italian sauces, you need San Marzano tomatoes.  But I love the flavor of Amish Paste and you can’t beat Roma for performance. 

Although I’m a tomato geek and love them big and small, I will admit that when the beefsteaks come in, it’s my favorite part of the summer.  Huge, brightly colored, and heavy with the promise of outstanding taste, the beefsteaks are the late season love apples that finish summer with a bang.
Of the big ones, it’s hard to beat Brandywine, but Pineapple, Amana Orange, Black Krim, Cherokee Purple, and Paul Robeson give it a run for the money.  Sweet and balanced with acid, Pineapple is a large yellow tomato streaked with red. 

Gardeners, if you’ve wondered what those tempting tomatoes taste like, but don’t have room to grow them all, head out to the Taste of Tomato in Boulder.  Sponsored by Harlequin’s Gardens and Colorado State University Extension in Boulder County, the Taste of Tomato is an opportunity to sample the love apple in its many forms - stripes, color, shape, and size.
Scheduled for Saturday, August 27, 10 am to 1 p.m. at Gateway Park 4800 N. 28th St. in Boulder, the Taste of Tomato is where gardeners can bring their tomatoes for others to try and sample the products others are growing.  Each year, tomato enthusiasts gather to taste nearly 100 varieties and vote on the tastiest of the lot. 

Entry is free if you bring three or more medium to large tomatoes or 10 cherry tomatoes of one kind, with the variety name on a card, to donate to the tasting. All entries must be home-grown.  If you have no tomatoes to bring, there will be a $5 entrance fee.