Apply Crabgrass Preventors Now

April 19, 2015 Leave a comment


By John Wilson, Extension Educator

Usually we start talking about crabgrass preventers now, but are telling people to wait several weeks before applying them. The warm weather and dry conditions –  until about a week ago – have warmed soils faster than normal this spring.

As of April 1, soil temperatures greater than 50F at a 4 inch depth were common across the state. Soil temperatures could be even higher depending on the soil type, moisture in the soil, sun exposure, and distance to a heat sink like a sidewalk, driveway, or street.

Crabgrass will germinate when soil temperatures are sustained between 55 and 60F. So preemergence herbicides for crabgrass should be applied soon. You should delay applying preemergence products on areas that winterkilled and will need to be reseeded or on any newly seeded areas. However, preemergence products such as Tupersan (siduron) or Tenacity (mesotrione) are safe on new seeding.

Avoid using preemergence products that are combined with fertilizer. Although most preemergence products available to homeowners contain nitrogen fertilizer, the spring flush of growth that occurs naturally in early April doesn’t need encouragement from extra fertilizer. It is much easier to apply a standalone preemergence product now and a standalone fertilizer in early May than to have to mow twice a week during April.

Weed-n-feed preemergence products aren’t always as convenient as they may seem. Standalone preemergence products can be found at most garden centers. If a combination preemergence and fertilizer product has to be used, then use the product with the lowest nitrogen content. This will be the product with the smallest first number of the three on a fertilizer bag, or the highest levels of a  slow release form of nitrogen. Another advantage of a standalone preemergence is that you can treat only problem areas and skip areas that don’t have a history of crabgrass saving you money.

Since we’ve mentioned fertilization, let’s quickly recap our recommendations for fertilizing cool season turf grasses such as bluegrass or fescue. I recommend and fertilize my own lawn with a small amount, maybe a half pound of actual nitrogen per 1,000 square feet or turf, at four times throughout the growing season. The best way to remember these is to fertilize by the holidays… Arbor Day or May Day (late April to early May), Memorial Day (late May), Labor Day (early September), and Halloween (late October).

The advantage of spreading out the fertilizer applications and waiting for the first application until around the first of May is this avoids the burst of growth that follows a heavy application of fertilizer. While rapid growth in the spring seems like the sign of a healthy lawn, it can actually set the lawn up for more problems in mid-summer.

Some homeowners are not willing to fertilize four times, they only want to fertilize twice… once in the spring and once in the fall. In this situation they will still want to make their first application around May 1 and wait until Halloween for the second application.

The reason this gets trickier is turf often needs a little fertilizer in early September to help recover if it has been a particularly stressful summer, but the late October application is still the most important in the fall. If we do have a particularly stressful summer on lawns, you may be able to get by with one application this spring, but still need to split the fall application, early September and late October.

For more information on lawn care, contact your local Nebraska Extension office.

John Wilson

John Wilson

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Watering Trees and Shrubs

October 25, 2014 Leave a comment


John Wilson

John Wilson

If you had trouble with winterkill or dieback on your trees and shrubs last year, here are some suggestions on how to reduce the problem this year. If you recall, the fall a year ago was much like we are experiencing so far this year. Very little rain which was great for harvest, but not so great for trees, shrubs and perennials in your landscape.

We kind of had the “perfect storm” by having very few storms over winter. Dry soils in the fall followed by little snow cover or moisture melting into the soil caused the dieback that many people experienced last spring.

Well, my crystal ball isn’t good enough to predict what kind of winter we’re going to have, but so far our fall hasn’t put a lot of moisture around the roots of our landscape plants, so it would be a good idea to water young trees, shrubs, and evergreens before the soil freezes. It’s important for trees and shrubs to go through fall and into winter with a moist soil.

Roots do not go dormant as quick as stems and branches. While the tops of plants go dormant or stop growing sometime during fall, roots continue to grow throughout the fall and even into December if soil temperatures allow.

To encourage fall root growth, provide adequate moisture up until the soil freezes. Check the soil around your trees. If the top few inches are dry, moisture is needed. For trees and shrubs, moisten the soil to a depth of eight to 12 inches while taking care not to overwater.

Keep in mind roots are less cold hardy than stems. Roots surrounded by moist soil are less likely to suffer cold temperature injury because moist soil holds more heat than dry soil. Frost penetration is deeper and soil temperatures are colder in sandy or dry soils.

With newly planted trees, cracks in the backfill soil can allow cold air to penetrate to roots, reducing fall root growth and killing new roots. Check for soil cracks and fill these with soil. Providing adequate moisture will prevent soil cracks from forming.

When twigs and stems die in a tree or shrub, we are aware it’s happening. When roots die, we cannot see the dead roots and are not aware roots are dieing. This could be one explanation why one tree establishes quickly while another is slow to establish or dies.

Plants going into winter with adequate fall moisture are also less likely to suffer damage from winter drying. Plant tissue, particularly the green leaves of evergreens, can lose moisture during winter. Most moisture is lost on warm, sunny, and windy winter days.

Moisture lost from plants during winter cannot be replaced by the roots, either because the soil is frozen or because roots do not function at soil temperatures below 40 degrees Fahrenheit. This is why fall moisture, either from rain or irrigation, is important.

When woody plants go into winter water stressed, their tissue can be killed by winter drying. This is easy to see on evergreens whose needle tips, or entire branches turn brown in late spring. Some evergreens survive and new growth covers up the damaged growth. Other evergreens are killed by winter dessication.

The leaf and flower buds on deciduous plants, those that drop their leaves, as well as small twigs may be killed by winter dessication. This can result in sparse flowering or leafing. Plants may be forced to produce secondary buds which uses stored food within the plant and may lead to stress.

Keep the soil of trees and shrubs moist up until the soil freezes. Mulch trees and shrubs with a two to four inch layer of wood chip mulch to help conserve soil moisture. Keep the mulch one foot away from the trunk to avoid voles making a home in the mulch and gnawing on the trunk. It’s also important mulch layers are not too deep. Roots that grow into the mulch will be killed by cold winter temperatures, further stressing a tree.

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