Hort Update for April 14, 2014

Hort Update for April 14, 2014

dandelion
In This Issue: 
1. Winter kill on golf courses Serious damage evident on many courses this spring
2. Overseeding Start now for earliest germination as soil warms; be careful with herbicide applications
3. Preemergence herbicide applications Professionals starting now, homeowners wait until first week in May
4. Early spring mowing Begin now to remove dead leaf tissue
5. Broadleaf weed control Wait until peak dandelion flowering for best spring control
6. Winter desiccation injury Most damage seen on white pine, arborvitae and broadleaf evergreens like holly and euonymus
7. Euonymus scale Browning of leaves; twigs covered with scales
8. Pruning shrub roses Mid- to late April is the best time
9. Cutting ornamental grasses Remove old plant material before new growth begins
10. Cutting back perennials Remove old growth before new growth begins
11. Divide perennials Divide summer and fall bloomers just as new growth begins
12. Vole damage on perennial roots Feed on tree and shrub roots, occasionally crowns of perennials
13. Soil tests Soil labs more precise; home kits provide general information
14. Planting bare root fruit trees, and container plants Proper techniques required for each
15. Preventative insect control & disease resistant varieties Preventative procedures can increase success in the vegetable garden
16. Vegetable planting dates Using average frost dates to determine planting dates
Articles
1. Winterkill on golf courses - Widespread damage from winterkill is becoming evident on many Nebraska golf courses. Windy and dry conditions this past winter caused grass plants in elevated or wind-exposed areas to die of dehydration and desiccation. Large temperature swings in January and February many have also contributed to the problem.  Mounds, greens, and bunker banks are experiencing the most damage.  Damage is extremely variable within a course, and from site to site.  Damaged areas will required overseeding.

Higher-mowed athletic fields for football, baseball and soccer do not seem to be affected.

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2. Overseeding - Spring seeding of cool season turfgrasses to repair thin or damaged area should be done as soon as possible in April. Tall fescue performs better in spring seedings than Kentucky bluegrass.  To increase success, achieve seed to soil contact. Aggressively core aerate prior to seeding. Mix the seed with fine compost, or after seeding spread a light layer of compost over the area and rake it into aeration holes. Make adjustments in spring herbicide applications. The pre-emergent herbicide siduron (Tupersan) is the only preemergent that can be applied for control of annual weeds without impacting cool season turfgrass seedlings.

Postemergence herbicides will need to be delayed until well after seedlings are established. Ideally, after the new grass been mowed two to three times. Read and follow label directions.

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3. Preemergence herbicide applications - Professionals are making applications now, but there is no rush for homeowners to make their first application.  The first week in May is the preferred time for homeowner applications in eastern Nebraska.

Spring preemergence applications are based on the germination timing for crabgrass.  Crabgrass is a warm season annual that begins germination after soil temperatures are above 50 degrees F, making late April to early May the ideal time for the first application. Two applications are usually needed for season-long control, with a second application made in early to mid-June.

Aerate lawns BEFORE preemergence application, not after. 

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4. Early spring mowing can begin now to clean up lawns and begin removing the dead tips of grass leaf blades. Grass growth comes from the base of the leaf blades, pushing last year's dead brown tissue upward.  Even through lawns still look fairly brown above, they are now becoming active and greening up at the base of the leaves.   Set a mowing height for the season, and stick with that all summer. "Set it and forget it" is the best practice. A mowing height of 3 to 3.5", and not removing more than one-third of the blade while mowing, is important for cool-season turfgrass to tolerate stress and compete with weeds.

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5. Dandelions & broadleaf weed control - Turf professionals often get requests from homeowners to control dandelions and other broadleaf weeds in spring and early summer, which is the second most effective time of year for control.  Plan applications during peak flowering of dandelions. Herbicides containing the traditional active ingredients (ai's) 2,4-D, MCPP and dicamba are effective for control of dandelions and other broadleaf weeds. Relatively "newer" ai's like carfentrazone, triclopyr, fluroxpyr, quinclorac, and sulfentrazone combined with the traditional ai's can increase the speed of burn down, expand the spectrum of weeds controlled, and/or improve overall effectiveness depending on the product used. Whenever possible, spot-apply herbicides rather than treating the entire lawn. This is expensive and can be less effective. Use caution when applying herbicides near ornamentals or trees as these are easily damaged by direct overspray or indirectly by volatilization of herbicide.

The very best time of year to control dandelions and other perennial broadleaf weeds (white clover, ground ivy, violets, and/or plantain) continues to be fall. Herbicides applied at spring flowering do not translocate as effectively and usually do not provide as effective control as when fall applied.

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6. Winter desiccation is a common type of winter injury that occurs when the amount of water lost by the foliage exceeds the amount picked up by the roots. Significant amounts of winter desiccation injury are being seen this spring on Concolor fir, white pine and broadleaf evergreens such as holly and euonymus. 

Warm, sunny days or windy conditions increase the amount of water lost from the needles or leaves. If the soil is frozen or soil moisture is low due to dry conditions, plant roots are unable to pick up enough water to meet its needs. Needles dry out and die, but often hold their green color until warmer temperatures arrive in spring, thus delaying the onset of browning symptoms.  Winter wind accompanying dry periods can accelerate water loss and damage is often more extensive on the side of the tree facing the prevailing wind. Other common terms for this type of injury are winter burn, winter drying or winter scorch.

No immediate action should be taken with evergreen plants showing winter injury other than supplemental watering if conditions are dry. Evergreen trees with a small amount of needle loss may still have live buds within the damaged branch sections. These buds will send out new growth and eventually fill in the damaged section in a few years. Evergreen shrubs, like holly and mahonia, may regenerate new leaves to replace the damaged foliage if injury was not severe enough to kill the underlying branches.

Pruning- Wait until new growth has emerged before pruning out dead branches. After the new growth has emerged, prune out any dead branches or branch tips, cutting back to 1/4" above a live bud. It is important to remove dead branches. They can provide an entryway for insects or fungi that attack the dead tissue.

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7. Euonymus scale - Infested leaves turn yellow, then die and drop off. Undersides of leaves and stems are covered with a brown or white scale. Scale insects feed from beneath a protective scale, removing plant sap from stems and leaves. Controls are most effective when the insect is in the crawler stage, usually in May to early June and late August to early September (second generation). Monitor for the presence of crawlers by wrapping a few stems with black electrical tape, with the sticky side facing out, near present scales. Crawlers are yellowish to orange. When in the crawler stage, control with insecticidal soaps. Systemic insecticides are also effective. Read and follow label directions for effective application. Prune and remove heavily infested branches to the ground.

Euonymous Scale, University of Nebraska-Lincoln Extension - IPM of Midwest Landscapes

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8. Pruning shrub roses - should be done in mid to late April, as new growth begins to remove any winter injury. Pruning of hybrid tea roses can also be used to manipulate the size, timing and number of flowers that a plant produces in the coming summer months. Prune hybrid tea roses to a height of 12-24 inches. Completely remove dead, diseased, weak or broken branches by cutting them back to the crown. Also remove branches that cross or rub each other.

On shrub roses, after eliminating any winter injury, remove up to one third of the oldest, woodiest stems each year, cutting them back to the plant's crown. This encourages the growth of new, vigorous stems from the plant crown and eliminates the development of many old, woody branches with poor flower production. It also increases air circulation through the plant, reducing potential for disease problems.

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9. Cutting back ornamental grasses - In early spring before new growth begins, remove the previous year's foliage. You can use hand clippers, a mechanical weed whip or other power equipment. Your choice depends on the toughness of the foliage, as well as the number of ornamental grasses you manage.

Grasses will begin growing earlier if foliage is removed. Also, the plant is more attractive when dead foliage is not interspersed with living tissue.

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10. Cutting back tender perennials - in spring, before new growth begins, is important to cleaning up the landscape, making room for new growth, and a sanitation practice that may help reduce pests. Last year's growth is dead and needs to be removed. It is fine to delay this practice until just before new growth begins as old growth does provide some protection from spring freezes. Delay pruning on slow to begin growth plants, such as Caryopteris and Buddleia, to better assess the amount of winter injury.

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11. Dividing perennials - is an important management practice for many species, helping to encourage vigorous growth and optimum blooming. As a rule, divide summer and fall blooming perennials during spring, beginning just before new growth begins. Many perennials benefit from division once every three to five years. Dividing is also a good way to propagate perennials. This year give special consideration to soil moisture and the possibility of dry summer conditions when deciding to divide.

Dividing Perennials, Iowa State University

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12. Vole damage on landscape plants - Usually vole damage is seen in turf areas after the snow melts.  Occasionally, though, they feed on other plants, including roots and bark of young trees and shrubs, or roots and crowns of perennials.  If the crown is destroyed, it means the plant is dead.  However, recovery can be made if damage is limited, and plants are protected from further damage.

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13. Soil tests - Soil tests are often recommended. The University of Nebraska-Lincoln no longer provides soil testing. This has led to an increase in questions regarding the use of home soil test kits. As a general rule, soil testing through a Soils Lab will provide more precise numbers, an increased amount of information, and are relatively inexpensive. Home soil tests most likely provide general ranges. For example, they may determine if a soil is acid or basic; but not what the exact pH is. For home soil testing, information needed from a test includes texture, organic matter content, pH, buffer pH, phosphorous (P) and potassium (K). Most home soil testing kits will not provide all of this information. Also, due to infrequent use of home soil test kits, reagents used in testing may become contaminated or lose effectiveness over time. For information on Soil Labs in Nebraska, contact your local Extension office. A list of labs is also available at the end of the following NebGuide.

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14. Planting bare root fruit trees & container material - Planting bare root plant material is different than planting container plant material, and homeowners are often unsure of planting techniques.  Bare root plant material is sent to the homeowner in a dormant state, looking nothing like the container grown trees and shrubs that are leafed out in the nursery, looking green and lush.  Proper planting of both types is imperative to the health of the plant, and the satisfaction of the homeowner. 

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15. Preventative pest control - Growing a vegetable garden can be a rewarding experience for the homeowner.  However, pest problems can discourage the most seasoned gardener.  People are often unaware of different options available for control of disease and insect infestations.  Rotating crops within the garden, cover crops, or planting resistant varieties are just a few techniques that greatly reduce pest populations.  Knowing which varieties are resistant to which pest is half the battle.  Understanding the life cycle of the insect or the development of disease is also an important part in proper control. 

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16. Vegetable planting dates - Planting in the vegetable garden can begin in early spring if the soil is workable.  The document below helps home gardeners know when to plant spring crops. Write the date of your area's average last frost above "00" in the table. Count backward and forward from that date to determine planting, growth, and harvest dates for each crop. 

Legend:

  • Planting time = X
  • Growing time = *
  • Harvest time = +

Last month's Hort Update included a map of Nebraska with dates for average spring frost. Download Recommended Spring Planting Dates

Chart of Recommended Spring Vegetable Planting Dates