by David Hillock

Lawn and Turf

  • Remove excessive thatch from warm-season lawns. Dethatching, if necessary, should precede crabgrass control treatment. (HLA-6604)
  • Broadleaf weeds can easily be controlled in cool-season lawns at this time with post-emergent broadleaf herbicides.
  • Pre-emergent crabgrass control chemicals can still be applied to cool- and warm-season turfgrasses. Heed label cautions when using any weed killers near or in the root zone of desirable plantings.
  • March is the second best time of the year to seed cool-season turfgrass; however, fall is the best time to plant. (HLA-6419)
  • Cool-season lawns such as bluegrass, fescue, and ryegrass may be fertilized now with the first application of the season. Usually, four applications of fertilizer are required per year, in March, May, October, and November. (HLA-6420)
  • Begin mowing cool-season grasses at 1 ½ to 3 ½ inches high. (HLA-6420)

Flowers & Vegetables

  • Cultivate annual flower and vegetable planting beds to destroy winter weeds.
  • Apply mulch to control weeds in beds. Landscape fabric barrier can reduce the amount of mulch but can dry out and prevent water penetration. Thus, organic litter makes the best mulch.
  • Prune roses just before growth starts and begin a regular disease spray program as the foliage appears on susceptible varieties. (HLA-6403 & EPP-7607)
  • Avoid excessive walking and working in the garden when foliage and soils are wet.
  • Start warm-season vegetable transplants indoors.
  • Divide and replant overcrowded, summer and fall blooming perennials. Mow or cut back old liriope and other ornamental grasses before new growth begins.
  • Your cool-season vegetables like broccoli, cabbage, carrot, lettuce, onion, peas, spinach, turnips etc. should be planted by the middle of March.
  • Watch for cutworms that girdle newly planted vegetables during the first few weeks of establishment.  Cabbage looper and cabbageworm insects should be monitored and controlled in the garden (EPP-7313).

Trees & Shrubs

  • Prune spring flowering plants, if needed, immediately following their bloom period.
  • Plant evergreen shrubs, balled and burlapped, and bare root trees and shrubs.
  • Anthracnose control on sycamore, maple, and oak should begin at bud swell. (EPP-7634).
  • Diplodia Pine Tip blight control on pines begins at bud swell.
  • Chemical and physical control of galls (swellings) on stems of trees should begin now. EPP‑7168 & EPP-7306)
  • Dormant oil can still be applied to control mites, galls, overwintering aphids, etc. (EPP-7306)
  • The first generation of Nantucket Pine Tip Moth appears at this time. Begin pesticide applications in late March. (EPP-7306)
  • Control Eastern tent caterpillars as soon as the critters appear.


  • Continue to plant strawberries, asparagus, and other small fruit crops this month.
  • Start your routine fruit tree spray schedule prior to bud break. (EPP-7319).
  • Remove winter mulch from strawberries in early March (HLA-6214).


by David Hillock

The growing season will soon be upon us and many are anxious to see the world turn green again. This will eventually lead to “yard waste.” While not a great concern everywhere, it is of concern for many landfill companies in large and small urban areas across the country, even in Oklahoma!

When properly managed, lawn clippings do not need to be caught and bagged. In fact, there are several benefits to not bagging your lawn clippings. First, experience with “Don’t Bag It” shows annual mowing time is reduced by up to one-third by not bagging clippings. Second, your mower will be easier to push with no heavy grass-filled bag attached saving energy. And third, you save money because you buy fewer garbage bags and keep your garbage bill lower; the city does not have to collect or dispose of grass clippings and this extends landfill life.

Your lawn will thank you too. Grass clippings that are returned to the lawn rapidly decompose at the grassroots level. Returning grass clippings to the lawn improves water-use efficiency, recycles plant nutrients, and gives your lawn a more uniform green color.

It is not necessary to have a mulching mower if you are mowing frequently enough that you are not removing more than one-third of the leaf blade in each mowing. However, mulching mowers can be helpful as they are designed to chop the clippings up into tiny pieces before letting them fall to the ground, which will help them break down quicker and often improves lawn appearance.

For more information on “Don’t Bag It” see our leaflet L-253 Don't Bag It: Lawn Care Plan.

Pruning Roses

by David Hillock

Rose plants need pruning to tidy up their appearance; control size; and improve their vigor, growing habits and bloom. Pruning methods vary according to the type of rose plant. To keep them in bounds, spring pruning usually is more drastic. Prune about 3 to 4 weeks before the average date of the last killing frost in your area. In most of Oklahoma that would be around the 15th of March. An exception to this rule involves climbing roses, which need to be pruned after flowering in early spring.

Probably no other aspect of growing roses has aroused as many questions as has the subject of when and how to prune roses. By following a few simple rules you can improve their appearance and vigor and control the quality and quantity of the flowers. Some fundamental practices of pruning roses correctly in all gardens, regardless of type, are: 1) remove any canes that have been damaged by insects, diseases or storms; 2) remove one of two canes which may be rubbing one another; or 3) remove canes that are spindly or smaller in diameter than the size of a pencil. After pruning, according to these general recommendations, cut hybrid teas, floribundas, grandifloras and polyanthas back to 12 inches for large flowers and 18 to 24 inches for many smaller sized flowers.

Climbing roses generally are pruned to renew plant vigor by removing the old canes since the most productive and finest blooms on climbers are produced on canes that arise from the bottom of the plant the previous year. These newer canes produce more desirable growth and flowers. Since the canes may become quite long, it is necessary to prune them back so they are maintained in the desirable area.

Old fashion or antique roses require much less pruning than modern roses. Left unpruned old fashion roses will naturally obtain a rounded shrub shape. Pruning of these roses should be confined to some shaping of the plant, removal of damaged branches, and judicious trimming back to encourage growth.

On all roses, consider the cutting of the flowers as a form of pruning. When gathering roses, always leave at least two sets of leaves on the branch from which you cut the flower to insure plant vigor. When removing faded, spent flowers, cut only as far as the first five-leaflet leaf. Make cuts on the ends of branches at 45 degree angles just slightly above an outside facing bud with the lowest point on the side opposite the bud, but not below the bud itself. Never leave stubs when removing branches, since these die and can cause problems on the plant later. Always remove branches by cutting to a lateral branch or bud, or back to the base of the rose plant.

For more information on growing roses in Oklahoma see fact sheet LA-6403 Roses in Oklahoma.

New State Fair Horticulture Class for 4H Members

by Shelley Mitchell

Thanks to the Oklahoma Pecan Growers Association, there will be a new pecan information exhibit debuting at the 2015 Tulsa and Oklahoma State Fairs. The purpose of the exhibit is to increase the public awareness of the importance and impact of the pecan industry. The educational exhibit should provide information about the pecan industry such as history, importance to Oklahoma, health benefits, uses, production, processing, or any other topics specifically focused on pecans. Any 4-H member interested in pecans or the pecan industry may prepare an exhibit, which should fit into a 3’ wide x 3’ deep area. It must be free-standing with sides attached, and include a notebook with photos. The notebook should detail any involvement the exhibitor has had with pecans, such as teaching others about pecans, giving talks or demonstrations regarding pecans, using pecans in food dishes, producing pecans, etc. The notebook may be typed or handwritten. Entries receiving first place at the state fair should be available for display at the annual OPGA meeting the following June. There are two (junior and senior) classes in this division, with ribbons to the top ten in each class. The exhibit will be judged on completeness of educational lesson (30 points), public appeal (30 points), and the notebook (40 points). Awards furnished by the Oklahoma Pecan Growers Association include cash for the top 5 entries in each class ($40, $30, $20, $10, $10).

‘Snow Sprite’ Dwarf Deodar Cedar

by David Hillock

'Snow Sprite' Dwarf Deodar CedarThis graceful evergreen is a favorite among the garden staff at Oklahoma Gardening. It is a dwarf variety of deodar cedar called ‘Snow Sprite’ (Cedrus deodora ‘Snow Sprite’). The plant holds its lovely blue-green color very well throughout the winter offering exquisite color. In spring, new growth is tinged white and warms to a creamy yellow with age.

The compact form makes ‘Snow Sprite’ very adaptable for even the smallest gardens. Plants will reach 4 to 5 feet in height over 10 years. ‘Snow Sprite’ is also available as a standard, offering an attractive option for a more formal look. Though ‘Snow Sprite’ is very drought tolerant, plants do need protection from afternoon sun and southerly winds.

New and Revised Horticulture Publications

by David Hillock

New publications include:

  • HLA-6446 Augmentation Biological Control Practices for the Home Landscape
  • HLA-6447 Conservation Biological Control for the Home Landscape

Revised publications include:

  • HLA-6434 Biological Pest Controls for the Home Landscape

The Horticulture sections of the 2015 Extension Agents’ Handbook E-832, is now available on PODS for Master Gardener groups and is listed as Horticulture Section of E-832 Ag Extension Agent's Handbook. This covers the horticulture sections beginning with Home Fruit Sprays through Vegetable Diseases, comprising pages 355-617 of the handbook. Cost of this section is $12.00.

Sweet Potato Slip Production

by Lynn Brandenberger

Sweet potato is one of a few vegetable crops that are vegetatively propagated.  Learning how to successfully grow sweet potato transplants (slips) can open up a new world to both commercial and home gardeners.   Detailed directions for slip production are in OSU Fact Sheet HLA-6022 available on-line at:  Before starting you need to understand that sweet potato is very much a warm-season crop meaning that whether we are starting slips or transplanting in the field the crop will not benefit from being planted into cold soils etc. to get a jump on the season.  Recommendations for field transplanting dates are April 20 to May 15 for southern Oklahoma and May 10 to May 20 for northern areas of the state.  That said, if soils are cooler than 72°F sweet potato won’t do much i.e. it will just sit still and wait for warm temps, bottom line. . . don’t push the limits regarding warm weather, remember “better late than early.”

Pre-sprouting seed roots prepares them for slip production and is similar to the root curing process that is done in the fall following harvest.  We normally use a room humidifier, a box-fan to keep the air moving, and an electric-heater for both curing and for pre-spouting.  Pre-spouting will shorten the amount of time required for slip production by about a week and increase the number of slips that can be produced by two or three times compared to non-pre-spouted roots.  This process should begin with sorting and culling out roots that will not be used for slip production. Eliminate roots that are cracked, show signs of rot, or those that are not of the correct size or shape.  Use seed roots that are between one inch and three inches in diameter.  Pre-sprouting requires temperatures to be maintained between 75°F and 85°F and relative humidity of 85 to 90% with good air movement provided by a small fan.  It should be started two to four weeks prior to seed roots being bedded up for slip production.  Roots are pre-spouted and ready for bedding when most roots have sprouts 1/4 inch in length.  Following pre-sprouting, conventional producers can apply a fungicide to reduce potential disease problems; see current edition of E‑832 "Extension Agents' Handbook of Insect, Plant Disease, and Weed Control" for recommendations.  However, slips can be grown without fungicides for organic production or if labeled fungicides are not available.

Varieties differ in their ability to produce slips, but generally a bushel of sweet potatoes will produce 2,000 to 2,500 slips in 2 or 3 slip harvests.  Slips can be grown in cold frames or heated beds. Allow five to six weeks for slip production in heated beds and seven to eight weeks in cold frames.  If roots have been pre-sprouted they will sprout more quickly and can be bedded up a week later than roots that are not pre-sprouted.

If roots have been pre-sprouted, place them in the plant bed with the sprouts upright; a few sprouts will be broken during handling, but this causes no noticeable reduction in slip production.  Roots that are not pre-sprouted can be planted either as fungicide-treated or non-treated roots in the plant bed.

Permanent plant production beds are a potential source of disease. If permanent beds are used, remove the old soil to a depth of twelve inches and discard. Disinfect the bed frames and covering material with a recommended disinfectant. Bring in clean top soil from an area where sweet potatoes and nematode susceptible crops have not been grown to refill the beds.  New soil can be sterilized using soil heating techniques prior to bedding roots.

Before bedding sweet potato roots for plant production, examine roots carefully and discard diseased, mutated, and bruised roots.  Separate the roots that will be bedded according to size to attain an even planting depth and uniform sprouting.  For conventional growers, seed potatoes can be treated with a recommended fungicide by dipping immediately before bedding. Dipping will help control surface infestations of black rot, scurf, and root rot organisms. Washing seed potatoes that are not pre-sprouted before fungicide treatment will remove dirt that reduces the effectiveness of the fungicide. Seed roots should not be washed unless they will be treated in a fungicide dip before bedding.

About 12 square feet of bed is needed per bushel of seed potato roots. Fertilize beds with 2 pounds per 100 square feet of bed using a complete fertilizer such as 10-10-10 or 12-12-12. The fertilizer should be mixed with the bed soil prior to bedding the roots.  Allow slip beds to warm to 80°F prior to bedding, then lower the temperature to 70°F or 75°F once sprouting begins. Place roots in the bed so they are not in contact with each other, after this cover them with two-inch mesh chicken wire followed by two inches of clean sand or sandy soil.  The mesh wire prevents roots from being pulled up when slips are pulled from the beds.

After bedding roots, sprinkle water over the bed to slightly moisten the soil but do not overwater and create a soggy wet soil.  Clear plastic can be placed directly over the plant bed surface. Remove the cover material when the slips push the covering up about two inches. Water the beds as needed to keep the soil moist. Keep the beds covered with a light-transmitting cover such as clear plastic, polycarbonate, etc. until the plants begin to emerge. Ventilate during the day to control air temperature in the beds. Air temperature in the beds should be kept under 90ׄ°F to produce good-quality plants. Pull plants when they are about eight inches tall. They should have at least five leaves, stocky stems, and a healthy root system. This type of plant is best for transplanting.  If plants must be held past the ideal size they can be cut back to six to eight inches and allowed to regrow.  This may be necessary if planting in the field or garden is delayed due to cool or wet weather.

Winter Annual Weed Control: Henbit and Carolina Geranium

by Justin Moss

Henbit (Lamium amplexicaule) is a common winter annual or biennial found throughout Oklahoma and commonly invades lawns in the late fall/winter. The most common feature that homeowners will notice are the purple flowers that appear in whorls in the axils of the upper leaves. Henbit is often confused with purple deadnettle (Lamium purpureum) which can also be found growing in Oklahoma and displays purple flowers in the late winter/early spring.

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Carolina geranium (Geranium carolinianum), also known as cranesbill, is a winter annual or biennial that is found throughout Oklahoma in the late fall/winter. The leaves are deeply lobed and with five to seven lobes per leaf. The lobed portion of the leaves are also lobed and bluntly toothed. The flowers may appear in early spring and are white to lavender colored. Carolina geranium is often confused with common mallow (Malva neglecta), another broadleaf winter annual or biennial. Common mallow does not have the deeply lobed leaves like Carolina geranium, but rather is more sharped tooth along the leaf margins. 

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Both henbit and Carolina geranium can also be confused with ground ivy (Glechoma hederacea). Ground ivy is a perennial with creeping stems which root at the nodes. Because of this characteristic, it is often called “creeping” Charlie.

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Henbit and Carolina geranium can be controlled by applying a tank mixture of glyphosate and a three-way type broadleaf herbicide containing 2,4-D, dicamba, and mecoprop (MCPP) in January or February. The three-way product can control the winter annual broadleaf weeds while the glyphosate can control both broadleaf weeds and winter annual grassy weeds. The glyphosate application is only recommended for dormant bermudagrass and is not recommended for tall fescue lawns or if the bermudagrass is beginning to green-up in the spring.  For tall fescue lawns, only apply the three-way product and do not apply glyphosate. With any product application, always read the label and only apply according to labeled directions.

Upcoming Horticulture Events

Current Challenges in Floriculture
June 11, 2015
Wes Watkins Center – Stillwater, OK

Hunger and Horticulture
July 30, 2015
Food and Agricultural Products Center – Stillwater, OK

September 26, 2015; 10 AM – 4 PM
The Botanic Garden at OSU – Stillwater, OK

Tree Care Issues Conference
October 29, 2015
Wes Watkins Center – Stillwater, OK

For more information about upcoming events, please contact Stephanie Larimer at 405-744-5404 or

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