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Master Gardening Articles 2/24/2015

Late Winter Garden and Lawn Care

By: Dick Christensen
Colorado State University Extension Master Gardener in Larimer County

Garden catalogs have arrived and gardeners are starting to get the itch to get started. The Front Range has had its share of warm days, but resist the urge to start digging in flower and garden beds too early, to avoid damage to the soil’s structure. To assess your soil, pick up a handful, it should fall apart and not stick together like glue. But mild dates in late winter can give gardeners time to get going on several important garden tasks.

Begin by planning for changes that you hope to make this year in the garden. Consider attending local garden classes. Many free or inexpensive short courses are offered at garden centers and botanical gardens.

Consult garden plans and prioritize projects for this season. If you need landscapers or designers, make calls now to get on their schedules. The calendars of lawn services also fill quickly in early spring—contact services that provide core aeration and irrigation maintenance to make a plan for your lawn this spring.

Assess the garden hardscape for winter damage. Trellises, fences, raised beds, or garden structures can be repaired on nice days throughout late winter. Make a list of damaged or missing tools. Now is a good time to clean, sharpen, and oil garden implements. Check trees and shrubs to evaluate their pruning needs. Remove broken branches or branches that cross and those that may become damaged from rubbing. Prune unwanted branches of trees and shrubs. Cut back any remaining dead perennial foliage from last season. Spring-blooming trees and shrubs (like lilac and forsythia) should not be pruned in late winter; their flower buds are ready to open as temperatures warm. Cut branches of forsythia, pussy willow, or other early- blooming shrubs and place in water indoors to force blooming and to bring some early springtime cheer to a room. During heavy snowstorms, remove snow that builds up on vulnerable limbs of trees and shrubs.

If the weather is nice, cut back perennials and grasses that were not trimmed in the fall. Add mulch to perennials beds to conserve water and to slow early spring growth. Deep water all landscape plants and turf every three to four weeks on days above freezing to help the plants survive our dry winters. Water only if the soil is dry and only when warm weather is expected for several days. Don’t forget about watering perennial and groundcover beds—especially if they are in areas void of natural precipitation or under large mature trees.

Research new varieties of favorite plants in seed catalogs and online. Shop at your local garden centers for seeds, summer bulbs, and tubers (dahlias and canna) while the selection is good. Plant pansies in your garden as early as late February if the weather is nice. Be sure to “harden off” early annual flowers by gradually introducing them to the outdoors—a week or so before transplanting into the garden, place tender plants outdoors during the day to get them used to the sun and to cooler temperatures.

February is a good time for a soil analysis in the vegetable garden or planting beds. Lawn areas can be tested too. The soil should not be wet when taking samples. A professional soil test will let you know which nutrients your soil actually needs or if the soil has too much of any particular elements. Often, gardeners tend to add too much fertilizer, compost, or organic matter; this can be as bad as adding too little. Find out more about soil testing at the CSU Plant, Soil and Water Testing Lab: www.soiltestinglab.colostate.edu.

Winter and spring lawn care

Rake the lawn to remove stray leaves, twigs, dead growth, and winter debris. This allows light and air into the soil, encouraging turf to grow. In early March, consider re-seeding bare or damaged patches of lawn. Rake bare spots firmly with a metal rake prior to seeding. Sprinkle grass seed into a bucket of soil and spread evenly over the bare spot. Keep well watered until seeds germinate and the new grass is established. Because the soil is cold, seedling germination may take several weeks. Do not apply a crabgrass preventer to the lawn if you plan to reseed in the spring.

Precipitation in Colorado is often most bountiful in spring. Delaying the start-up of your sprinkler system may save money and help conserve water. Daily watering is only necessary with new seeds or sod to help establish young roots. In all other circumstances, daily watering only encourages shallow root growth and reduces the turf’s drought tolerance. Begin mowing when your lawn reaches 3.5” high. Remember that the ideal turf-lawn height is 2.5” to 3”. To encourage lawn health and strength, try to not remove more than one third of the leaf blade with each mowing. Grass growth is vigorous in early spring, so edge flowerbeds with a sharp trench between bed and turf. If cool-season turf is in poor condition, fertilize at 0.5 – 1 pounds nitrogen per 1,000 square feet.

Aeration, or core cultivation, is standard Colorado turf care. Aerating supplies the soil with air, reduces soil compaction, helps to control thatch, and lets water and fertilizer move into the root zone. Turf can be aerated at any time when the ground is not frozen. Spring and fall are considered the best times for aeration. Aeration is most effective when actual cores or plugs of soil are pulled from the lawn. Holes should be two to three inches deep and no more than two to four inches apart. Lawns should be thoroughly watered the day before aerating so that longer plugs can be pulled more easily. To avoid damaging utilities, mark sprinkler heads, shallow irrigation lines, and cable TV lines before aerating. Leave the cores on the lawn to allow them to work back into the grass. Lawns may be fertilized and seeded immediately after aeration. Water the lawn soon after aeration. Heavy traffic areas will require aeration more frequently.

For more information on gardening in Colorado, please visit the CSU Extension website at www.ext.colostate.edu and consult with the lawn and garden Fact Sheets. Additional gardening information can be found at PlantTalk Colorado www.planttalk.org.


Western Yellowjacket Wasp – Spring Control

western yellowjacket wasp--photo by Whitney Cranshaw

By: Craig Seymour
Colorado State University Extension Master Gardener in Larimer County

The western yellowjacket wasp is deserving of its annoying reputation around backyard cookouts and picnic outings each summer. Although most victims of an insect sting blame them on bees, the western yellowjacket can claim over 90% of all “bee stings” in Colorado, followed by the European paper wasp. That leaves only a small percentage of stings actually credited to the lovable bees.

For general identification the honeybee, bumble bee and leaf cutter bees are hairy, stout bodied with muted colors of black, brown, yellow, orange and gray and usually covered in pollen. Hornets, yellowjackets and paper wasps are not hairy and have elongated bodies and bold coloring of black, yellow, orange and creamy white. Bees are beneficial pollinators. Wasps are beneficial insect predators. Bees and wasps are usually non-aggressive unless trapped or their nest is disturbed.

The western and European yellowjacket female wasps are the two notorious villains of the bees and wasps with stingers (males do not have stingers). The European yellowjacket, a relative newcomer to Colorado, is a nuisance wasp primarily because it likes to build its open paper nest in small cavities such as down spouts, grills, playground equipment, open metal tubes and similar places close to human activity. Therefore their nests are easily disturbed before we are aware of their presence, which may result in a sting.

The paper nests that are found can be controlled with any good wasp spray, usually spraying in late evening or early morning when all the wasps are on the nest and fairly inactive. If the nest is a safe distance from normal activities the nest can be left to develop, since the European yellowjacket is a beneficial insect predator.Another species of paper wasp will build a similar open paper nest but they are usually found attached to an overhang such as a deck or eve and should not be disturbed unless they are too close to human activities.

On the other hand, the deplorable western yellowjacket wasp is a scavenger of protein: dead insects, carrion, garbage, meat, sweet foods and sugary drinks. It will aggressively defend its food source. The western yellowjacket is an annual social wasp in which an overwintering fertilized queen wasp will locate a in-ground cavity in the spring, build a new nest, lay eggs and feed the first larvae until a colony of the queen (fertile female), worker wasps (infertile females) and drones (fertile males) is established.

It is that life cycle and the western yellowjackets attraction to the chemical hepytl butyrate that makes it susceptible to early control with a wasp trap. No other bees or wasps are attracted to a baited wasp trap. The western yellowjacket trap should be properly installed in late April when the queen is foraging for nesting material and protein, usually in late April and throughout May. Each western yellowjacket trapped in early spring is a queen wasp and her capture will eliminate one colony, which can produce 200 plus wasps by September.

In June, the queen stays in the colony, but the worker wasps can continue to be caught in a properly maintained trap. It may seem futile but a trap count can be an indication of the areas western yellowjacket population and give the trapper bragging rights for his effort. If the well-concealed entrance of a ground nest could be located, a repeated nighttime application of an insecticide, such as permethrin, can eventually eliminate a colony. It will take persistent applications especially late in the season.

It is important to properly identify the nesting insect because the bumblebee also has an in-ground nest that should not be destroyed regardless of its location. Even if a western yellowjacket colony is eliminated the worker wasps can travel up to 1,000 yards from their colonies in search of protein making the task of complete control improbable.

More information about bees and wasps can be found at ext.colostate.edu/pubs/insect/05525, Nuisance Wasps and Bees by W.S. Cranshaw. Colorado State University Extension supports the Colorado Master Gardener program and the information provided is a result of scientific research.

So the question becomes, “Do I live with the western yellowjacket wasp or wage war on the despicable pest?” If peaceful compliance is your choice then eliminate its food and water sources, be outdoors without food or drinks, dine out in early morning or late evenings (wasps vs. mosquitos), have a screened porch or tent for separation or retreat indoors for the summer and hope for nice late fall days to enjoy an outdoor meal.

As gardeners and consumers have become more interested in enjoying locally produced food and living within the ecological balance of nature it is important to recognize the value of bees and wasps. They are very entertaining flower pollinators and insect predators. Therefore the goal should be to eliminate only the pests that are an imminent threat and leave the rest to observe and enjoy as they go about their given tasks in nature.



The authors have received training through Colorado State University Extension’s Master Gardener program and are Master Gardener volunteer for Larimer County.

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Larimer County is a county-based outreach of Colorado State University Extension providing information you can trust to deal with current issues in agriculture, horticulture, nutrition and food safety, 4-H, small acreage, money management and parenting. For more information about CSU Extension in Larimer County, call (970) 498-6000 or visit www.larimer.org/ext


Looking for additional gardening information? Check out the CSU Extension Horticulture Agent blog at www.csuhort.blogspot.com for timely updates about gardening around the state.


Visit PlantTalk Colorado ™ for fast answers to your gardening questions! www.planttalk.org PlantTalk is a cooperation between Colorado State University Extension, GreenCo and Denver Botanic Gardens.

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