Posts tagged herbicide

In search of grubs, and how to treat crabgrass and arborvitae

Linn County Master Gardener, Claire Smith, wrote the following about three of the most frequently asked questions to the Linn County Master Gardener Horticulture Hotline. The HortLine is available to answer questions from 9 am.. to noon and 1-4 p.m. Monday through Thursday  and  9 a.m. to noon on Fridays at (319)447-0647.

 

    One of the commonly asked questions in the spring concerns when to apply pre-emergent crabgrass killer.  Master Gardener Susan Long has this response:  Typically, the blooming of the forsythia or the redbud is a good indicator of when to apply pre-emergent crabgrass herbicide.  Pre-emergents must be applied before the crabgrass germinates. Ground temperatures must be a minimum of 50 degrees. If the material is applied too early, crabgrass seeds that germinate late in the season will not be controlled.  If applied too late, some crabgrass will have already germinated.  In central Iowa, this is usually mid-April to May 1.  However, if the weather warms up early or stays cool longer, then adjustments must be made based on the conditions.  Having a thick, healthy lawn that is fertilized, watered and mowed certainly discourages the growth of crabgrass. 

    Susan also answered a question about arborvitae having brown leaves due to winter burn and whether it will recover and/or should be pruned:  Avoid pruning browned, burned areas from evergreen trees and shrubs in the early spring since these branches may still have viable buds that will produce new foliage when growth resumes.  The brown will eventually fall off.  If the buds did not survive, then prune dead branches back to living tissue.  The affected trees and shrubs should look much better by late June or July.  There is no need to fertilize affected evergreens.  However, if the weather this spring is dry, periodically water evergreens to encourage new growth and speed their recovery.

    Another caller wondered what causes a lawn to be torn up at night.  Lawns that have grubs attract raccoons, skunks, and crows which turn over large patches of turf in search of the grubs.  The best time to treat is early in the summer when insecticides have the best changes of working.  The entire lawn may not need to be treated, rather treat grub “hot spots” determined by observation or sampling.  Presently trichlorfor (Dylox or Bayer 24-Hour Grub Control) and Sevin are the fastest-acting, most effective homeowner insecticides for curative grub control.  These must be watered in completely after application.  In many cases it may be preferable to repair the damage through seeding or sodding without treating.  If the old, loose sod is still green it may reattach with adequate watering.

Advertisements

Leave a comment »

Why aren’t you outside??

 

Another cold weekend has come and gone, but this week holds promise of spring warmth (finally!) 

The following information from Horticulturist Richard Jauron of Iowa State University Extension offers tips on spring gardening chores, now that the weather might finally cooperate:

It’s hard to beat springtime in the Midwest.  Soon the browns and grays of winter will be replaced by the greens, reds and yellows of spring. While spring is an enjoyable time, there are a number of outdoor chores that need to be done to enhance our yards and gardens. Important springtime chores include applying preemergence herbicides to lawns, dividing perennials, removing mulch from strawberries, pruning roses and many others. 

Applying Preemergence Herbicide to Lawn
The key to successful control of crabgrass in lawns is the correct timing of the preemergence herbicide application. Crabgrass seeds begin to germinate when soil temperatures reach 55 to 60 F and continue to germinate over several weeks from spring into summer. If the material is applied too early, crabgrass seeds that germinate late in the season will not be controlled. Normally, preemergence herbicides should be applied in early to mid-April in southern Iowa, mid-April to May 1 in central Iowa and late April to early May in the northern portion of the state.  The timing of the preemergence herbicide application will vary somewhat from year to year because of weather conditions. However, events in nature generally occur in a natural sequence. Preemergence herbicides should be applied when the forsythia blossoms start dropping or when redbud trees reach full bloom. Crabgrass seed germination typically begins after these events. 

Dividing Perennials
Early spring is an excellent time to divide asters, mums, hostas, daylilies, garden phlox and many other perennials. Dig up the perennials in early spring just as new growth begins to appear. Divide each plant clump into sections with a sharp knife. Each division should contain several shoots and a portion of the root system. Replant the divisions immediately. Keep the newly divided perennials well watered through spring and summer. Most newly divided perennials do not bloom well until their second growing season. 

Removing Mulch from Strawberries
To reduce the chances of frost or freeze damage, leave the mulch on as long as possible. Removing the mulch in March may encourage the plants to bloom before the danger of frost is past. Temperatures of 32 F or lower may severely damage or destroy open flowers. Since the first flowers produce the largest berries, a late spring frost or freeze can drastically reduce yields.

To determine when to remove the mulch, periodically examine the strawberry plants in spring. Remove the mulch from the strawberry planting when approximately 25 percent of the plants are producing new growth. New growth will be white or yellow in color. (If possible, the winter mulch on strawberries should remain until mid-April in central Iowa.) When removing the mulch, rake the material to the aisles between rows. If there is a threat of a frost or freeze later in spring during bloom, lightly rake the mulch over the strawberry plants.

Pruning Roses
The upper portions of modern roses, such as hybrid teas, floribundas and grandilfloras, typically winterkill due to exposure to low winter temperatures and drastic temperature changes. When the winter protection is removed from these roses in early to mid-April, gardeners should prune out the dead wood. 

Pruning roses is relatively easy. Live wood is green and has plump, healthy buds. When pruned, the center of the stem (pith) should be white. Dead wood is brown, has no live buds and has a brown or gray pith. When pruning roses, make the cuts at least 1 inch below the dead, brown-colored areas. Make slanting cuts about 1/4 inch above healthy, plump, outward facing buds; the slant being in the same direction as the bud. Remove the entire cane if there is no sign of life.  Also, remove any diseased wood. 

Because of our severe winter weather, modern roses often suffer a great deal of winter injury. Normally, the primary objective is to remove all dead and diseased wood and to save as much of the live tissue as possible. If the roses overwinter well, gardeners can prune out weak, spindly canes in the center. 

After a seemingly endless winter of shoveling snow and removing ice from sidewalks and driveways, working in the garden over the next several weeks is going to be a lot of fun.

Leave a comment »