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June 19, 2013

CO-Horts

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.

by CSU Hort Agents (noreply@blogger.com) at June 19, 2013 01:12 PM

Colorado Mountain Gardeners

Tips for planting on a slope by Irene Shonle

We live in the mountains. Almost by definition, that means that where we are trying to grow things involves some sort of slope. Some of them are gentle, others are steeper. This particular post will discuss planting on a gentle slope (see the article on the Mountain Gardening website on dealing with steeper slopes and planting retaining walls).

If you are planting on even a gentle slope, it is a good idea to build a shallow shelf or basin to hold water. Otherwise, most of the water goes rushing down the slope and won't penetrate to the roots.

Here's a picture of what I mean:

It's a bit hard to get a good picture here, but the slope goes down towards the right. The earth shelf or basin built up on the downhill side keeps the water and allows it to soak in. Success rates are much higher this way!

by Tina Ligon (noreply@blogger.com) at June 19, 2013 12:07 PM

June 17, 2013

Jeffco Gardeners

June Lawn Care by James Johnston

by Donna D. (noreply@blogger.com) at June 17, 2013 06:17 PM

June 16, 2013

Colorado Mountain Gardeners

An Ode to Floating Row Covers by Irene Shonle

I think I have become something of a proselytizer for floating row covers up here in the mountains.

Why?

1. You can plant earlier -- floating row covers provide anywhere from 3 to 8 degrees of frost protection, depending on the style (frost "blankets" obviously providing more protection than the thinnest "summer insect covers").

2. They keep off insects. Your arugula will be tender and free of flea-beetle damage if you keep it covered from seed. Same goes for aphids (unless you transplant them into your garden with your seedlings)

3. They keep bunnies, deer, and chipmunks out. No more buffet lunch for these critters! And if you protect your plants with a 1/4" wire mesh beneath the beds to keep out burrowing animals such as pocket gophers and voles, you're in tall cotton. Or tall lettuce. Or whatever. It's nice to see all of my seedlings growing where I planted them, rather than going out to survey the damage each morning. Makes for a much more peaceful existence!

My new garden with mesh below and floating row cover above -- I'm not battling anything!

4. You can water right through it. And it keeps moisture in for much longer, reducing watering needs. Heather, who works with me in the office, has been amazed at the difference in the soil moisture in the areas she has covered vs the areas she didn't. She said she had never really used them before, but has now become convinced of their utility. Hurray! Another convert!

5. It protects plants from the nasty drying winds we've had lately. Tender seedlings will quickly be battered to death by the powerful winds that seem to accompany the last days of May and the early part of June.

6. Lettuce and other salad greens are more tender and succulent. Maybe not quite as nice as a greenhouse, but pretty darn good!

7. Plants grow right up under the cover -- it just "floats" over them without squishing. Make sure you have some excess cover at the edges to allow for growth, otherwise as the plants gain height, the row covers will squish the plants (since the cover should be anchored down).

Tips for using floating row covers:

You can buy floating row covers at garden centers or online (big box stores usually don't carry them)
Keep the wind from ripping off your cover by using soil anchors, large rocks or lengths of rebar or fence posts. I have come to prefer the latter method the best - it's easier to lift off the posts/rebar, and voles and small chipmunks can scurry under if there are gaps (ask me how I know this!).
It is harder to water through the row covers when there are hoops holding the cover up -- it tends to just slide off to the edges. For the most part, I don't find hoops to be necessary, and the hoops raise the cover higher into the air where the wind can catch it more easily.

Give them a try, and you, too will see the light! (and no, I don't have any financial interest in any floating row companies).

by Tina Ligon (noreply@blogger.com) at June 16, 2013 11:29 AM

June 15, 2013

Jeffco Gardeners

Spider Mites - Unwelcome Visitors! by Ron Dearwater

Two Spotted Spider Mite, photo courtesy Clemson.edu

Got spider mites?
Spider mites are not insects, but are arachnids which include spiders, ticks and scorpions. They are a common pest problems on many plants, evergreens and trees in yards and gardens in Colorado. The most prevalent is the two-spotted spider mite and they are no bigger than the end of a sentence!
House plants can also be host to the spider mite. One must be persistent with the pest since eliminating them can take months. Unfortunately, you may have plants or evergreens die due to a heavy infestation.

As for biological controls, various insects and predatory mites feed on this mite. One reason the spider mite becomes a problem in yards and gardens is the use of insecticides that destroys their natural enemies. Adequate watering during dry conditions can limit the importance of drought stress on spider mite outbreaks. Periodic hosing of the plant with a forceful jet of water can physically remove and kill many mites. They spread webbing under the leaves and the water may delay egg laying.

Spraying chemicals is not recommended unless the mites are numerous and natural enemies are not present. Chemical control of spider mites generally involves pesticides that are specifically developed for spider mite control. Because most miticides do not affect eggs, a repeat application at a ten to fourteen day interval is needed for control. Horticultural oils and insecticidal soaps can be utilized but oil can suffocate the plant by covering the stoma openings that the leaves use to breathe.

As for many evergreen cultivars, the soaps and oils can remove the silvery blue-gray color from the needles. The color will return in the next year's growth in most cases. Don't use sulfur spray unless it has been shown to be safe for that plant in your locality. Sulfur is a skin irritant as well as an eye and respiratory hazard, so always wear appropriate protective clothing.

by Donna D. (noreply@blogger.com) at June 15, 2013 07:43 AM

June 14, 2013

Colorado Mountain Gardeners

Hardening off plants -- By Irene Shonle

If you live in the mountains, you surely practice what I call the "hardening off" dance.

You have houseplants like geraniums that want to spend the summer outside.
You have seeds that you started inside.

All of these plants need to be slowly acclimated from their nice pampered existence indoors to the harsh realities of the mountain climate.

Houseplants and seedlings hardening off in the shade

I recommend first putting them outside on a cloudy day or in the shade, in order to expose them to wind.
Then expose them to gradually increasing amounts of sunshine - dappled first (if you can find it), then full sun, then longer periods of full sun.

Of course, at this time of year, there's always the threat of frost, so even after the plants toughen up a bit, I watch the forecast, and bring them in if it threatens to drop below freezing. Hence "the dance".

by Tina Ligon (noreply@blogger.com) at June 14, 2013 12:07 PM

Bye-bye Juniper by Irene Shonle

Okay, confession time. Despite knowing better, I had been harboring a common juniper less than ten feet from my house (in defensible space zone 1, the most important area to mitigate that is closest to your house --see this publication for more details: http://csfs.colostate.edu/pdfs/FIRE2012_1_DspaceQuickGuide.pdf ).

Junipers are extremely flammable due to their high resin content, and should be removed from zone 1. I knew this, but I liked the way it looked in its bed, and I just couldn't bring myself to remove it.


Garden bed after the Juniper was removed. I forgot to take a before picture.

Nothing like teaching a class on fire preparedness followed by firewise landscaping to make you practice what you preach! I finally ripped it a couple days ago when the snow all melted. I'll have to review the bed once the remaining plants come in to see what I want to do with it. On the bright side, I guess it gives me a new opportunity to buy plants -- I didn't have many open spaces left in my garden.

For more information on firewise landscaping, please see this fact sheet: http://www.ext.colostate.edu/pubs/natres/06305.html

by Tina Ligon (noreply@blogger.com) at June 14, 2013 11:55 AM

Winter annual weeds - by Irene Shonle

I meant to get this post out earlier, but I just didn't have time!

Many winter annual weeds have already come up: cheatgrass, alyssum, field pennycress, and more. The key to controlling winter annual (and summer annual weeds a little bit later) is to control them before they go to seed. The trick is to get all of the seeds that germinate, and to not let any go to seed. New crops may come up from the seeds that are in the soil; get them while they're little, too. A few years of persistence, and you will find dramatically fewer weeds. But persistence is the key!

In a perfect world, you'd just hoe them all under when they look like this:

Field pennycress (Thlaspi arvense) just germinating -- so easy to hoe at this stage

Cheatgrass (Bromus tectorum) before flowering. Just hoe - no need to bag.

This is the ideal stage to control these annuals, because there are no flowers and thus no seeds, so no need to pull and bag seed heads -- a tiresome and land-fill intensive process. Also, the root system is small and fragile. It is very satisfying to go out and destroy thousands of weeds with a few whacks of the hoe. Sort of like the fairy tale of "the Valiant Little Tailor" who kills seven with one blow. This is also a good time to use an herbicide, if that's what you prefer.

Depending on where you live and the weed, it may or may not have gone to seed already (sorry I didn't get this posted sooner!).

Cheatgrass gone to seed

If it has gone to seed, you will need to pull and bag the plants and (sadly), put them in the landfill. Next year, get them sooner - less work, nothing to dispose of.

by Tina Ligon (noreply@blogger.com) at June 14, 2013 11:55 AM

The Things You Discover While Gardening.... by Irene Shonle

As I was working in our demonstration garden a couple of afternoons ago, I admired the lacy blue-green foliage and abundant yellow flowers of the golden smoke, or Corydalis aurea that had seeded its way around the garden. It is a native pioneer plant, readily colonizing disturbed, open soils. Given how the pocket gophers routinely take out parts of the garden every year, I am grateful for its willingness to fill in and cover that bare ground. It is pretty short lived, and can start to look ratty in the garden later in the season, but while it is at its prime, like it is right now, I let bloom merrily away.

Golden smoke or Corydalis aurea

This is all probably familiar to many people who grow in the mountains. What's the discovery, you say? It has an unusual, sweet smell! Somehow, I had never realized it until the other day when I was weeding. I kept smelling something sweet on the air that I couldn't recognize. I kept looking around at all the plants, but most weren't blooming yet, and most of them weren't fragrant, anyway. It finally dawned on me that it was the golden smoke, and I confirmed it by getting down on my knees and putting my nose in the plant. Who knew?

Another fun factoid about this plant with which I was already familiar is that the seeds are ant-dispersed. The seeds have a tiny little nutrient-rich appendage on it (an aril or elaiosome). Ants gather the seeds, bring them into their nests and feed the elaiosome to their larvae. The seeds are left intact (and safe from predation) to germinate later. Cool little mutualism, there.

by Tina Ligon (noreply@blogger.com) at June 14, 2013 11:55 AM

June 13, 2013

CO-Horts

Garden Companions

Posted by: Micaela Truslove, Broomfield County Extension

The practice of companion planting – interplanting crops that are mutually beneficial to increase the quality and yield of nearby plants – has been practiced for centuries. Who doesn't remember their grandparents planting marigolds in the vegetable garden to ward off insect pests? Many people have planted a Three Sisters garden at some point, which utilizes corn as a trellis for beans, beans as a nitrogen fixer for squash and nitrogen-sucking corn, and squash’s large leaves to shade out weeds. Though companion planting has long been a popular practice in the garden, there is little scientific evidence to support many of these plant associations. However, there are many beneficial ways that plants can be used to help each other out in the garden.

Zinnias attract pollinators, so are a great
companion plant for the garden. (Photo:
Micaela Truslove)

One such method is intercropping. Intercropping takes advantage of plants’ different growth rates, sizes and root depths, allowing you to plant more intensively and make the most out of the growing space. For instance, a common practice is to plant an early crop of lettuce next to tomatoes. Shallow rooted lettuce will shade out the weeds while deeper rooted tomatoes get started, and will be ready to harvest by the time the tomato vines get too big. Intensive planting in general helps to shade out weeds, but caution must be taken not to place plants too close together as this can encourage disease.

Somewhat related to intercropping is succession planting. Planting short season crops ahead of longer season crops in the same place, though not necessarily at the same time, will allow for an early harvest of spring planted vegetables before longer season vegetables are planted out. Good examples of this are spinach, radishes and peas, which can all be planted in the “shoulders” of the season (early spring and late summer). These can be succession planted before and after main season crops, such as peppers and tomatoes. Variety selection is important in succession planting. Choose varieties that mature quickly to make sure there is enough time to plant all of your successions. Another way to use succession planting is to plant crops in two or three week intervals to have a continuous harvest and to avoid a glut of any one vegetable (one can only eat or give away so many zucchini).

Trap cropping is also a useful tool in times of heavy insect infestations. For instance, in a year when flea beetles are bad, planting a sacrificial row of radishes a little way away from your other brassicas, such as broccoli, will lure flea beetles away. Eric Hammond, the Horticulture Agent for Adams County, noticed that flea beetles really loved his Basket of Gold (Aurinia saxatilis), so this might make a good trap crop for brassicas. When you notice that certain plants make good companions, write it down so you’ll remember for next year.

Yarrow (Achillea millefolium) is a great example of a flower with

shallow nectaries and small flowers which can be used in the garden

to attract beneficial insects (courtesy of Carol O'Meara, Boulder County
Extension).

Perhaps the most important way you can help your garden is to increase crop biodiversity and use plants that provide a habitat for beneficial organisms in the garden. Many people don’t want to give up valuable vegetable real estate to plant flowers, but the benefits of doing so far outweigh the space you have to sacrifice. Mixing plants of different colors, scents and ripening times and avoiding large areas of plants from the same plant family may confuse pests that are looking for a tasty meal. Herbs often have a strong aroma which may confuse insect pests, and they are also beautiful and useful for cooking.

In addition, plants with small flowers and shallow nectaries (think of your dill or fennel after they flower) often attract predators that eat other insects, including lacewings, lady beetles, assassin bugs, tiny beneficial wasps and syrphid (hover) flies. Letting some of your vegetable plants flower will give you food and the benefit of flowers that attract helpful insects. Learning what these insects look like through their various life stages will ensure that you are squashing the correct critters and leaving those that serve a beneficial purpose. Pollinators are also very important as they are the reason many of our vegetables produce fruit. Planting flowers that attract both honeybees and other bees is a great way to ensure good pollination.

Lady beetles, especially in the larval stage, are
predators of many insect pests. (Photo: Micaela
Truslove)

There are also negative plant associations. The one to avoid in the vegetable garden is planting crops from the same family in the same location year after year. Practicing crop rotation will ensure that your soil will remain healthy and disease free for the following planting season. Plant crops from the same family in a different location every year. This is often very important for tomatoes as there are many soil-borne diseases that affect tomato plants. If you are planting certain crops together to gain the benefit of the associations they form, just plant that entire block in another location the following year.

Though there is a lot of information out there about companion planting that has not been scientifically proven, there are many ways that you can use beneficial plant associations in the vegetable garden to create a healthier, more productive environment. And there is no harm in testing out the more anecdotal associations. Close observation and keeping good written records will help you identify what works best for you.

by CSU Hort Agents (noreply@blogger.com) at June 13, 2013 07:28 PM