CO-Horts Blog

Sunday, November 23, 2014


Tony Koski
Extension Turf Specialist

No, Elsa, this isn’t about you..

A very frozen dandelion...still alive
Some have asked, on the heels of the recent “polar vortex” (not really…it was just a sign that winter is about that here) and temperatures hovering near zero, about how the early and abrupt cold snap might affect turf pests – weeds, fungi, and insects? The short answer (in case you want to leave now and hear Elsa sing…again) is that it likely had little effect on any turf pests – and is unlikely to affect turf pests in 2015.

There were plenty of signals (fewer hours of daylight, cooler temperatures, frost) this fall to
encourage our lawn grasses (the good ones…and the perennial weedy ones as well) to ready themselves for winter. Insects that overwinter as adults, larvae, or pupae likewise were readying themselves for diapause (insect “hibernation”). Perennial weeds like dandelion, thistle and beloved bindweed were preparing themselves for winter dormancy well before last week’s chill arrived. The spores and mycelium of fungi (it was a good fall for powdery
Knotweed (Polygonum aviculare), a summer annual,
still alive after subzero temperatures!
mildew and rust on turf) are so resistant to temperature extremes that the arrival of 0 F went unnoticed by them – so they will be back next year, without question.

Seedling downy bromegrass (aka cheatgrass) thriving in
our chilly pre-winter cold snap
Even the seedlings of our winter annual weeds - species that germinated this past late summer/fall and will complete their life cycle in the spring – appear to have been completely unaffected by the week of extreme cold. The henbit, annual bluegrass, chickweed and cheatgrass I’ve looked at in the past few days appear perfectly healthy. So, I'm sorry to dash any hopes you had about any potential benefits that the recently departed cold front might have had on the pests in your lawn. They really didn’t notice. If you had any hopes of the misnamed polar vortex eliminating some of next year's turf pests, all I can say is … let it go…let it go……..

Thursday, November 13, 2014

Aw Snap! (Cold snap, that is.)

Posted by: Alison O’Connor, Larimer County Extension

As weather forecasters were predicting our cold snap that we’re currently suffering through, I began thinking about our outdoor plants and wondering if they had hardened off. Others thought the same thing, because a recent listserv had chatter of comparing this cold snap to the Halloween Freeze of 1991. In short, the spring of 1992 proved to be fatal to many trees and shrubs, particularly Siberian elms. 
Nerd alert! Taking photos of plants in sub-zero weather.
I don’t have any elms in my landscape, but I do have many roses. And my curiosity was spurred this week by a woman who emailed asking what she could do to protect her roses. After all, ours were both still blooming and the leaves hadn’t dropped. It seems all of these things (below-normal temperatures, tender green tissue and blossoms) are pointing to one thing—likely major dieback and possibly plant death come spring 2015.

Boy howdy. That stinks. I love my roses.

I consulted with Larimer County Master Gardener and Rose Guru, Roger Heins, on his take on the subject. He expressed similar sentiments, unless people did some extra preparation (he did). I did not. But here are his recommendations for future consideration:

  1. Two or three days before the cold weather sets in (and when daytime temperatures are above freezing), deep water your roses. Actually, take the time to water all of your trees and shrubs.
  2. After the first two initial temperatures of nighttime temperatures below 30 degrees F, but before a hard freeze (<26 degrees F), pull bark chip mulch (or soil) around the base of the roses. If there is still foliage, don’t make the bark mulch too heavy…wait until leaf drop.
  3. If you have roses with long canes (one of my “shrub” roses is over 8’ tall), you can prune the canes back by 1/3 to reduce injury from snow, ice and wind.
  4. If you have blooms on the plant, remove these, as they can collect snow and ice and cause the canes to bend or break.
  5. After the roses go dormant and lose their leaves, increase the mulch depth around the base of the plants. The rule of thumb is to mulch about 6-8” up the canes. As the roses come out of dormancy in spring, remove the mulch.
  6. If you have the time and ability, you can wrap the roses in burlap.
Roses in bloom on 11/12/14.
Remember, snow isn’t a bad thing—and can act like an insulator.  But we generally can’t rely on continuous snow cover through the winter, so extra precaution is a good thing. Because my roses are an important part of my landscape, I will mulch them once I can stand to be outdoors for longer than 30 seconds. And I’ll put it on my schedule to water them once we get those glorious warm winter days. 
Snow can be a great insulator for roses.

Until then, I’ll be anxiously awaiting the arrival of spring to see how this polar vortex affects our landscapes. And keeping my fingers crossed (inside my mittens).
Not a rose! But the red arils on burning bush are beautiful.

Monday, November 10, 2014

If you can’t beat ‘em, drown ‘em

By Irene Shonle, CSU Extension in Gilpin County

Three out of my many houseplants each have mild-moderate infestations of a different insect.   My lemon verbena has spider mites, my Amazon lily has mealy bugs, and my Bay Laurel has scale.  Even though I inspected them when I bought them, it became evident in each case that the bugs were hiding in not-very-visible nooks and crannies.  And given that it wasn't that easy to find these plants, I couldn't do the sensible thing and throw them out.

While I’ve mostly kept the insect populations in check with diligent applications of neem oil spray and the occasional shower/water spray, I have never succeeded in eliminating them entirely.  I have been so frustrated that there have been times when I have sworn  to get rid of the insects even if I kill the plant doing it -- they STILL come back!   If I’m a bit negligent, the populations explode, and I have to be careful they don’t spread to my other plants (but so far, I’ve been able to quash any incipient populations on new plants). 
Frankly, I was getting sick of it! 

So, the other day, I was in the shower, and inadvertently drowned a spider.  I was astonished at how quickly it died – I had every intention of rescuing it after I dried off, but despite the fact that it was at the edge of the shower and that I take quick showers (mountain wells, you know), it still was dead when I shut the water off.   Somehow, my pre-caffeine mind made the connection between drowning spiders and drowning scales. After all,  spraying with horticultural oils works by suffocation.    I decided to submerge my whole Bay Laurel in water for a while to drown the scale insects. Since I was at the point of heaving the plant anyway, it wouldn’t be a big deal if my plant didn't survive.

I got a 5 gallon bucket, taped a plastic bag around the pot to keep the soil in, and turned in upside down in the water, submerging the entire foliage and trunk.  I left it for 24 hours, but I suspect that was overkill.  Remember - I was frustrated!

Drowned scale on bay laurel -- the whitish residue is from the dead scale.

Over the next couple of days, it became obvious that all the scale had died.  The insects scraped off easily, or even showed signs of rot (see whitish residue on picture above).  Yippee!  It’s been about a month and a half, and I still see no signs of new scale or the tell-tale sticky honey dew they leave behind.  However, I probably should have changed the potting soil (or submerged it as well), in case there were any crawlers in the soil.  If they come back, that’s what I’ll do.

After the fact, I checked to see if others recommend it, and did find it in a few places here and there, but it's surprisingly seldom mentioned, especially within Extension (for example, horticultural oils and syringing are recommended here amongst other methods, but not submerging:  Obviously, this would only work for plants small enough to submerge, and succulents might not appreciate it. Otherwise, it seems like a cheap and non-toxic method to try.

Here goes my lemon verbena - next up is the Amazon lily!

Wednesday, November 5, 2014

The Cold Frame Corner

By: Susan Perry, Colorado Master Gardener in Larimer County

Two years ago, at the end of the growing season, I had several hundred un-harvested carrots.  So I decided to try an experiment & cover them with grass clippings & leaves and see if I could harvest them all winter.  Well, I could – sort of.  They were easy to harvest & tasty until the ground froze but much harder to harvest (still tasty, however) after the ground froze.  Harvesting from frozen ground literally required a chisel & a lot of determination.  Unfortunately, things changed when we had a thaw & re-freeze, rendering the remaining carrots inedible & useful only for compost.

Last winter at the last minute, my husband Tom & I cobbled together two cold frame-like boxes, hinged on the corners for easy storage, from stackable boxes sold by Kerrie the handywoman/salvager on the main drag of Timnath.  The drawback was that while the hinges made storage easy because the boxes folded, the hinged corners weren’t “tight” (there were gaps where air could get in).  I solved that by buying foil-wrapped rigid Styrofoam insulation at Home Depot & cut to the correct height so that the entire box was lined.  The boxes were topped with two single pane glass storm windows that cost $3 each from Uncle Benny’s in Loveland.  From a temperature perspective, the inside of the boxes worked just like a cold frame – warming up enough to need venting on the morning of fall, spring, & winter days.  But I’d shot myself in the foot by using the foil-wrapped insulation because the foil foiled me, so to speak.  I had a remote wireless thermometer in the box but the foil prevented the signal from reaching the monitor inside so I could never tell the temperature inside the box.  So I just had to use an old fashioned thermometer & hope for the best on really cold nights, never really knowing.  But the goal of last year’s experiment was to use the boxes around the carrots to prevent the ground from freezing & enable an easier harvest all winter.  That goal was accomplished & we harvested our last carrots in mid-January.  But obviously, there were improvements that could be made:  the ability to know the temperature inside the box before going to bed at night on super-cold nights without having to go outside; something better than single pane glass storm windows, which ended up being nerve-wracking to handle because you didn’t want them to break (one did break when I attempted to tilt some snow off – duh); the boxes weren’t sloped to take full advantage of solar gain; and the ability to expand the crops we had all winter which also meant the ability to do more than just prevent the ground from freezing – possibly add some heat in the boxes if needed.
Figure 1 - Sloping & Notched Side of Cold Frame
Well, winter is a great time for gardeners to take stock & see what they could do differently, do additional research, etc.  One offshoot was that I learned that besides extending the fall harvest through the winter, I could also use the cold frames to get an earlier start in the spring.  So we set one carrot box out in the spring to warm the soil where we were going to plant carrots this year.  I was able to sow carrot seeds on 4-17-14 that germinated by 4-28-14.  Once this happened, my motivation really ratcheted up so I prowled the local Home Depot stores for culled wood for new, better cold frames.  Why culled wood?  Well, I view all this as an experiment and cannot bring myself to spend a fortune on something that might be a dud.  Culled wood is 70% off the normal price so I was able to get enough wood for 6 cold frames for under $10 a box.  (This took about  4 – 6 weeks of looking in the spring).  Not bad but the down side, which I knew, is that culled wood is discounted because it’s imperfect so I was buying warped or curved wood.  I just tried to pick the least warped wood possible. 

Figure 2a - Dowels in Upper Corner

Figure 2b - Corner Fits Together (Phew!)
During the 4 – 6 weeks of hunting for wood, I was able to get enough for one box and to find handy Ted, a handyman, carpenter, & otherwise talented fellow, who could cut the sides of the cold frames.  The sides have to slope down, with the “top” of the box (the part that will be on the north end) being taller than the “bottom” of the box that is located on the south end.  (FYI if you Google “cold frame diagrams”, you’ll see various diagrams that will give you the general idea).  Anyway, back to the sloping sides …. I was fortunate to find Ted the handyman because you have to be pretty comfortable with a circular saw to do the cuts on the wood that will become the sides of the box.  Ted also notched the top of each side so I could put a stabilizing bar across the box.  The box is 3’ wide by 6’ long.  Many resources on cold frames suggest making them widest from east to west and shorter from north to south.  But my beds run long north to south and I certainly didn’t plan to re-do the entire garden for this.  So just do what’s going to work in your garden.  

The prototype cold frame was where Tom & I planned to work out all the kinks – at least that’s what we told ourselves.  One thing we liked about the boxes from Kerrie was that they folded together for easy storage that didn’t take up much space.  So we wanted to figure out how we could make boxes that would be easily stored.  What follows is not for the faint of heart, especially when using culled wood … I decided we’d try to make the cold frames “knock down” which meant we’d dowel the corners so that we could knock the sides apart in the spring & stack everything in our basement.  No screws, hinges, or nails but anyone who works with wood will tell you dowels can be tough to work with.  There’s not a lot of room for error because you’re drilling holes in two pieces of wood – the holes have to match up & you stick a little piece of wood (a dowel) in them to match it all up & fit it together. 

We also decided that the wood would last longer if it wasn’t directly on the ground, so I found some 2” x 2” redwood on Craigslist for next to nothing.

Figure 3 - Redwood "Under-Frame" on Ground

We don’t have to go into all the details because if you want cold frames, you need to make it work for your situation.  Maybe you don’t know handy Ted but you have a handy neighbor or wood-working husband.  Maybe you don’t want to use culled wood because you’re just going to do one cold frame not six (or because you know that with culled wood, you might not get the corners to fit well …. I’ll get to the solution I have for that later).

So, prototype done, all wood bought & cut, but honestly then everything sat in the basement till early September – we got busy with the garden & other stuff.   
Figure 4 - The Prototype Minus Cover
To my dismay, Uncle Benny’s in Loveland did not have any storm windows so for the cover of each cold frame, we had to go with Plan B, much more expensive … twin-wall polycarbonate.  It’s what they use in greenhouses but holy cow, it ain’t cheap.  But it was cut to size so we only have to construct the remaining five boxes.  We’ve been doing that off and on for the past few weeks.  Tom has primed & painted 4 of the six boxes (bright colors because I know they will cheer up our HOA board).  Five boxes are constructed so we have one left to put together.  

Since we’re looking at some cool (30 degrees) nighttime temps in the next few days, we put up 2 boxes around the lettuce and spinach.  Of course, it was so quick to type that sentence but getting them set up took a few hours.  We have to level the ground out so the redwood would sit flush on the dirt, then set the cold frames on top of the redwood.  And that’s where we left it.  We’ll get them covered soon, either with the polycarbonate or just floating row covers, which will be fine for 30 degrees.
Figure 5 - First Two Boxes for Lettuce & Spinach

Saturday, November 1, 2014

R.I.P. 2014 Fall Color

Posted by: Eric Hammond, Adams County Extension

This fall has been spectacular.  The weather has been mild and all the warm days and cool nights have created some really beautiful color on our trees.   However, at least in my neck of the woods, most trees gave up the ghost and dropped their leaves over the last few days.   If you are interested in the science of fall color there was a post on the subject a while back which can be found here but, if  you're more in the mood for some visual stimulation, here are some pictures in tribute to the season of color that was.

Green ash (left) and white ash (right)

You really can’t recommend planting Ash right now with the green menace looming but it was a great year for fall color for both of the common ash species.
Mature Green Ash
Colorado Master Gardeners riding under a canopy of mature White Ash
I somehow missed taking a picture of aspen this fall but most of the poplars (Populus sp.) were quite showy this year.  Cottonwoods can be problem plants in many landscape settings but in a rural or more natural landscape they really can be attractive.

Volunteer cottonwood along the shore of a lake
If yellow is your color, it was also a banner year for Kentucky coffeetree (Gymnocladus dioicus) and some bur oak (Quercus macrocarpa) even had a semi-attractive fall this year.
Kentucky coffeetree
Bur oak's best effort in the fall

Callery pear (Pyrus calleryana) is one of the few species which is still showing off its leaves.  Chanticleer is probably the most common selection of this species due to its better branch structure but, there are many varieties of callery pear available and they all have nice color in the fall.

Callery pear

Autumn blaze and the other freeman type (Acer x freemanii) maples are not the best choice for the high pH soils that dominate much of the Front Range but they sure are a show stopper in the fall.
Autumn blaze maple 

Close-up of autumn blaze maple foliage
If you are looking for red fall color but want a plant better adapted to our soils, it was also a great year for some of the less well know (but probably better adapted) maples like Caddo sugar maple (Acer saccharum 'John Pair').  This is a section of sugar maple from a sub population of the species growing in Oklahoma. 
Caddo Sugar Maple

Caddo sugar maple leaf close-up

Another option might be Manzano maple (Acer grandidentatum 'Manzano').  Manzano maple is a more tree like form of bigtooth maple which can turn an attractive orange-red in the fall.
Manzano Maple
Crimson spire oak (Quercus robur x Q. alba 'Chrimshmidt') is an upright plant which is a cross between white oak and English oak.  It also has red fall color although, this year it turned more of a russet color (it also has its own Facebook page and it appears to have more friends than me... and I'm a person.  So you know it has to be a good tree) .

Crimson spire oak

Ginnala and tatarian maples (which some actually consider variations of the same species) are good examples of smaller trees that get a red to purple fall color.

Ginnala maple
Close-up of ginnala maple leaf

Let not forget about the shrubs.    All of the common species of sumac (Rhus sp.), sand cherry (Prunus besseyi), burning bush (Euonymus alatus) and many others put on a show this autumn.

Staghorn sumac
Sand cherry

Skunkbush sumac

Dwarf burning bush 

I could post more.  It really has been a fall to remember, hopefully everyone has been able to enjoy it.