View the February 2024 Hort tip articles below.

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Boxwood Winter Damage

Casey Hentges, Associate Extension Specialist

Bailey Singleton, Extension Assistant

 

Damage to broadleaf evergreen plants, in this case boxwoods, often occurs in the extreme winter temperatures that can happen in Oklahoma. 

 

The yellowing, and in some cases, dead foliage is a result of winter burn.  Damage can often occur on the upper part while closer to the base of the plant may not be affected.  Severe winter burn often results in dead leaves that appear yellow or white.  However, there also might be a reddish color on boxwoods, while this is also a result of exposure to extreme temperatures, these leaves will often recover.

 

Boxwoods tend to be more sensitive to cold temperatures than some other evergreens (e.g. pines or junipers) due to their leaves being broader.  The increased surface area of their leaves creates more exposure and more evaporation from the leaves.  As most people know and have greatly experienced this past year in Oklahoma, we can have incredibly strong winds and low humidity.  In winter, this only increases.  This is why it is advised not to plant new broadleaf evergreens in the fall, instead it is best to wait until spring.   

 

Once it is seen, the damage is already done. If caught before the end of winter, there are a few methods to help reduce further damage.  One way is to add some mulch around the base of the plants to help protect the roots.  Another is to place freeze cloth over the boxwoods for a little extra protection when there is a forecast of a dramatic drop in the temperatures. A sheet could alternatively be used but try to avoid using plastic, because when covering plants, the material is often resting on the plants and plastic can get colder and cause more damage to the plant tissue.  A spun material, burlap, or cotton sheets would work great.  If you have boxwoods that have been planted in a particularly windy area, such as between houses where a wind tunnel might blow over the plants, you might consider putting up a temporary burlap fence or something to help protect them from the harsh, drying winter winds.

 

As for current damage in winter, there is no need to do anything about it just yet. Instead, protect them the best you can going forward until corrective action can be taken in March.

 

2024 Pecan Pest Management Workshop 

Becky Carroll, Senior Extension Specialist, Fruit & Pecans

 

All pecan growers, with improved cultivars or native, will benefit from attending the upcoming Pecan Pest Management Workshop on February 22, 2024, at the Gordon Cooper Technology Center in Shawnee. Everyone is invited to attend the event starting with sign-in at 8:30 a.m. The event is free, but growers are required to register before the workshop. Those with pesticide applicator licenses can earn 5 CEUs in category 1A, 10 and private applicators. Attendees are encouraged to bring their applicator number. 

 

Lunch will be on their own. Refreshments will be served during breaks. 

 

Extension educators are encouraged to attend for in-service credit. 

 

Below  is the agenda with presentations and speaker information. 

• 8:30 a.m. – Registration 
• 9:00 a.m. – Welcome & Introductions – Becky Carroll & Trent Boles
• 9:15 – 10:15 a.m. – Partnership for success: Opportunities for grower-academia partnerships in managing emerging pecan disease frontiers – Mustafa Jibrin, Assistant Professor, OSU Entomology and Plant Pathology
• 10:15 – 10:30 a.m. – Break 
• 10:30 – 11:30 a.m. – Opportunities and Challenges for Microbial Biopesticides in Pecan Weevil Control – Kelly Seuhs, Associate Extension Specialist, OSU Entomology and Plant Pathology
• 11:30 a.m. – 1:00 p.m. – Lunch on your own
• 1:00 – 2:00 p.m. – Pesticide Application Safety – Kevin Shelton, State Pesticide Coordinator, Pesticide Safety Education Program, OSU Entomology & Plant Pathology
• 2:00 – 2:30 p.m. – Pesticide Storage & Disposal – Charles Luper, Extension Associate, Pesticide Safety Education, OSU Entomology & Plant Pathology
• 2:30 – 3:00 p.m. – Sprayer Tips & Information – Kenton Stanley, Savage Equipment, Inc, Madill, OK
• 3:00 – 3:15 p.m. – Break
• 3:15 – 4:15 p.m. – Controlling Weeds in the Orchard or Grove - Becky Carroll, Senior Extension Specialist, OSU Horticulture & Landscape Architecture
• 4:15 p.m. – Door prize, wrap-up and questions 

For more information, please contact Becky Carroll at becky.carroll@okstate.edu or (405) 744-6139.

 

Collecting Pecan Graftwood & Source List 

Becky Carroll

 

Using quality graftwood is key to successful grafting. If using cold-damaged or improperly stored wood for propagation, things will be much more difficult. Although grafting is done in late April through May, graftwood should be collected when fully dormant. Wood can be cut from Mid-December to early March, but January is the optimum time for collection to avoid fluctuating temperatures in the spring. 

 

One-year old vigorous wood from known cultivars work well for most grafts and some budding. Collecting various sizes will help match with different techniques. Collecting from young trees requiring pruning, or from high in treetops will provide the best vigorous growth to use for propagation wood. On large older trees, removing a large limb may encourage new vigorous growth that will be well suited for grafting. TheCollecting and Storing Pecan Propagation Wood fact sheet gives instructions on proper collection and storage for propagation wood.

 

To be able to find the cultivars that growers need, ordering from a supplier may be necessary. Getting their order in early will help the supplier to know what inventory they will need to collect and what types of cultivars are wanted. Sometimes they can collect other cultivars not listed if contacted early. Currently, we only have one supplier on our source list. Hoffman Pecan Farm, 7104 E. 32nd Ave, Stillwater, OK  74074. Their contact information is (405) 372-3583, hoffmanpecanfarm@gmail.com. Reach out to see what cultivars they have collected. Pricing for graftwood is $4.00 per 12"stick (2 grafts/stick). There is a minimum order of 5 sticks per variety. Add $10.00 for priority mail shipping. If you know of others that would like to be added to the list, please email becky.carroll@okstate.edu

 

Bring Spring Indoors

David Hillock

 

Get a jump on spring and enjoy the bright colors of spring blooming trees and shrubs indoors. Many spring flowering shrubs and trees can be forced to bloom indoors. Just cut some branches from plants like redbud, dogwood, forsythia, lilac, quince, peach, apple, plum, and weigela as their buds begin to swell and place them in your favorite vase or other container with water and watch them blossom before your eyes. 

 

Shrubs with interesting and colorful twigs and bark are also a great addition to an indoor arrangement. Red-twig dogwood produces bright red stems and some varieties also come in yellow and orange. Japanese kerria has bright green stems and produces a bright yellow flower. The Harry Lauder’s Walkingstick or contorted filbert as well as the contorted willow have unique, curly, twisty stems that are prized by florists and look awesome in a vase by themselves or in an arrangement. 

 

Control Peach and Nectarine Leaf Curl Now

David Hillock

 

It is common to get calls in early summer from homeowners wanting to know what is wrong with their peach or nectarine tree. Infected leaves pucker, become deformed, and turn yellow or reddish-brown. Unfortunately, by that time, when symptoms are most evident, it is too late to spray anything. Leaf Curl is the culprit and is one of the most encountered diseases in unsprayed orchards and home yards during cold, wet springs. Diseased leaves eventually wither and fall from the trees. Although new leaves emerge from dormant buds, their growth requirements reduce yield and may weaken the trees.

 

To prevent leaf curl disease, spray peaches and nectarines with a fungicide before bud swell (EPP-7319 Home Tree Fruit Production and Pest Management). Apply when the trees are dormant and temperatures are above 40 degrees F, usually mid-February through March depending on weather and location in the state. Bordeaux mixtures, copper flowable fungicides, chlorothalonil, and lime-sulfur sprays are commonly used for control of leaf curl.

 

Diseases in the Orchard 

David Hillock

 

Fire blight is a common disease of pome fruits, such as apples and pears. Fire blight is a bacterial disease which can severely damage apples and pears. Blossoms, fruits, fruit spurs, twigs, and branches are affected and sometimes the entire tree may be killed. The first sign of fire blight is a watery, light tan bacterial ooze that exudes from branch, twig, or trunk cankers (small to large areas of bark killed by the pathogen during previous seasons). The ooze turns dark after exposure to air, leaving dark streaks on branches or trunks. However, cankers may be inconspicuous, and infections may not be noticed until later in spring when flowers, shoots, and/or young fruit are affected. Blighted twigs and watersprouts wilt at their tips giving the appearance of a shepherd's crook. They then shrivel and turn black in color. These blackened areas appear burned and give fire blight its name.

 

Prevention is the key to managing fire blight, especially in large trees. A copper-based fungicide can be applied during the dormant season, though coverage on a large tree can be very difficult. Smaller trees are more easily managed. Affected tissue can be pruned, cutting back affected tissues to a healthy side branch. Always disinfect equipment after pruning a diseased tree to avoid spreading the disease to other plants in the landscape. In addition to pome fruits, fire blight can affect Quince (Pyracantha species), Hawthorn (Crataegus species), Spiraea, Cotoneaster, Photinia species, Juneberry or Serviceberry (Amelanchier species), Loquat, Mountain Ash (Sorbus species), and other related plants.

 

Vigorous young growth is highly susceptible to infection. Another management strategy is to limit nitrogen applications to pear trees. There are also many resistant cultivars available when selecting fruit trees for the landscape.

 

Weed and Feed Products

David Hillock

 

The concept of combining an herbicide and a fertilizer to “kill two birds with one stone” may be good in theory but may not work in every situation. Several potential problems exist when using this approach.

 

The first is that the timing for herbicide application and fertilizer application are usually not in sync. Some weed and feed products contain preemergence herbicides that control weeds as they germinate and are best applied before late February depending on weather conditions. Fertilizer applications for warm season grasses such as bermudagrass should not go on until the first of May. See the problem?! The two really need to be applied at different times; so, using a weed and feed blend on bermudagrass in late winter/early spring is not advised. 

 

Second, the selection of formulations for weed and feed blends is much more limiting than if one were choosing only a fertilizer. Fertilizer formulations are much more diverse because fertilizer companies make many more types. Most companies that produce weed and feed products only make one type, not allowing one to consider special nutrient needs that may have shown up in a soil test, i.e., a need for less or more phosphorus. Once again it is obvious that the best approach would be to apply weed killer and fertilizer separately. (Note also: Types of weed killer used in weed and feed blends is also limited compared to the many formulations available without fertilizer.)

 

Third, there is more chance of over-application or misapplication of the weed killer. Because tree and shrub roots can also absorb many of the herbicide products, care in applying the herbicide is very important. In fact, many of the herbicide products state that they should not be applied where roots of desirable trees or shrubs are growing. Research has shown that the roots of many tree species extend well beyond the dripline of a tree. So how does one apply an herbicide to turf areas with trees growing in or near them? By using separate fertilizer and herbicide products and avoiding weed and feeds. Another common problem is overthrow of the product into areas that have sensitive plants growing in them such as flower and shrub beds. This is usually a result of using the wrong equipment such as the use of a broadcast spreader rather than a drop or gravity spreader. Once again, it makes good sense to apply products separately allowing for more accurate rates and distribution.

 

And fourth and last, why treat healthy grass with something it does not need and could potentially weaken it? A weakened turfgrass is more likely to have weed problems. Spot-treat only the weed prone areas. 

 

The real way to address weed problems is to start with improving turf management. A vigorous, healthy lawn can choke out most weeds. For information on recommended turfgrass management practices see HLA-6420 Lawn Management in Oklahoma.

 

Winter Annual Weed Control: Henbit and Carolina Geranium

David Hillock

 

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 is 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.

 

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.

 

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.

 

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 that has a dense canopy 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.

 

Fruit Elimination on Ornamental Trees

David Hillock

 

Every summer we get calls from homeowners who are dealing with messy fruits from landscape trees. Unfortunately, when we receive these calls, it is usually too late to do much about it that year. Fruit control is possible, but timing is critical and must be done when flowers and fruits are forming in spring/early summer.

 

The best approach is to plant trees that don’t produce messy fruits or if you still have an appreciation for the fruiting characteristics, make sure you locate the plant in the landscape where the fruits can fall, but not be a nuisance. You could also consider planting fruitless varieties. These come as sterile forms of the tree species or in some cases as male selections. Some species produce male and female trees. The female trees have the potential for producing those unwanted fruits, the males won’t produce fruit. For example, fruitless sweetgum varieties are available like ‘Rotundiloba’ which is a sterile or near sterile variety of sweetgum. Kentucky coffeetree is an example of a species with male and female plants, the most common male selection being ‘Espresso’.

 

If you are stuck with existing trees in the landscape that produce those annoying fruits, you have some chemical options. Two types of chemical products are available for fruit control. Ethephon is a plant growth regulator that when applied to plants reacts by liberating ethylene, which interferes with the plant growth process resulting in reduction or elimination of fruit. The only product registered in Oklahoma that is packaged for the homeowner is Florel® Brand Fruit Eliminator by Monterey Lawn and Garden Products. This product should be applied to the tree when it is in mid-to full-bloom and temperatures should be between 65-95 degrees Fahrenheit. The plants should also not be under stress. Complete coverage is necessary to achieve satisfactory control. This may be a problem for the homeowner who is trying to control fruits on a large, mature shade tree such as sweetgum or sycamore, but may be an option for a smaller ornamental tree like crabapple. Most homeowners won’t have the equipment to reach high into large trees and get complete coverage, so they should hire a pesticide applicator or arborist to do the work. Drift should also be avoided as it may cause temporary modifications to plant growth of nearby plants. Of course, always be sure to read and follow all label directions!

 

The other products registered for use can only be applied by an arborist or commercial pesticide applicator. The products are applied as a trunk injection, usually at the beginning of bud break for the best results.

 

Snipper (active ingredient IBA) is a product applied as a trunk injection and should be applied by a licensed professional. The active ingredient IBA is a plant hormone, which promotes premature drop of flowers. It also must be applied at flower bud break and will have to be applied yearly to get satisfactory control.

 

Pinscher (Dikegulac-sodium) is another trunk injection product that must be applied by commercial applicators. The timing of application is different depending on the species of tree, but still must be applied annually.

 

No matter which chemical approach you choose, both will need to be repeated yearly. Remember, the best approach is to plant trees that don’t produce those annoying fruits.

 

Starting Seeds Indoors

David Hillock

 

Many gardeners choose to start their own seeds at home, rather than purchasing transplants. The advantages include savings in cost, and the availability of a much wider selection of cultivars. You can also time seed sowing according to your expected planting date so that transplants are ready when you need them. Of course, planting seeds and tending seedlings is also a great way to spend a winter day.

 

You can start seeds in flats purchased from a plant supply company or garden center, you can use expandable peat pots, or you can use a variety of household items. When selecting a container to start your seeds, consider drainage. You do not want water sitting in the bottom of the container. You also want to make sure the container holds enough media that it will not dry out too quickly and will have plenty of room for roots to develop.

 

The potting media you use is also important. Often you can find a medium labeled specifically for seeding. Look for media with both good drainage and high water-holding capacity. These things seem contradictory, but you want your soil to hold adequate moisture for seeds to germinate without drying out too quickly, but you also want excess water to freely drain from the medium.

 

Light is often a limiting factor with starting seeds indoors. To produce hardy seedlings, you need 12 to 14 hours of light per day. Natural lighting is generally not enough. Supplement natural light using a shop light with alternating cool- and warm-white, fluorescent bulbs or specially made grow lights.

 

To plant the seeds, sow in rows 2 to 3 inches apart. Use a fairly tight spacing within the row. As a rule, sow seeds to a depth of approximately 3 times the diameter of the seed. Most seeds will germinate well at a temperature around 70 degrees F held constantly during day and night. After germination, temperatures can be lowered according to the type of plant you are growing. Refer to OCES Fact Sheet HLA-6020, “Growing Vegetable Transplants” for ideal growing temperatures. For many tomatoes, a day temperature between 70 and 80 degrees F and a night temperature between 60 and 65 degrees F is ideal.

 

Managing water in seed trays can be tricky. Over-watering is a common problem. The seeds do not use much water until they have germinated, and seedlings are actively growing. However, the seeds need moisture to germinate. Misting the soil until it is thoroughly damp is a good way to provide moisture. Then, cover the seed tray loosely with plastic, checking soil moisture periodically. Remove the plastic once you see seedlings emerge.

 

Though fertilizer labels recommend weekly fertilizer applications, an application every two to three weeks is usually sufficient. The first application is not needed until seedlings are ready to be transplanted, two to three weeks after sowing.

 

Fresh Spring Vegetables

David Hillock

 

The days for fresh vegetables to be picked right from the garden are soon coming. The cold winter temperatures will soon be leaving allowing us to return to the garden and begin growing our favorite vegetables again. By February 15 many cool-season vegetables like cabbage, carrots, lettuce, peas, and potatoes can be planted (See chart below). The exact time to plant will vary slightly depending on the winter and where you live in the state. The south/southwest region could be as much as two weeks ahead of the northwest and panhandle areas of the state. The thing to remember though is that soil temperatures at planting depth should be at least 40 degrees F.

 

The ease with which one can grow plants is greatly influenced by characteristics of the soil. Modifying or improving the soil prior to and during the gardening season is important.

 

Various fertilizer elements are necessary for plant growth, and many can be easily applied. However, other aspects of soil improvement may not be as easily and readily accomplished. In a very sandy soil, the incorporation of organic matter would reduce rapid drying of the soil and improve nutrient availability. In a very heavy clay soil, organic matter would improve soil aeration, water absorption, and drainage.

 

Soil should absorb water readily, not form a crust upon drying, and drain sufficiently so that it does not become waterlogged. A porous soil contains more air, which is necessary for vigorous root growth. As organic matter decomposes, soil texture improves, and nutrient availability should increase. More information on garden soil improvement is given in fact sheet HLA-6007, Improving Garden Soil Fertility.

 

The soil must contain a supply of water and available fertilizer nutrients. Soils that produced a vegetable crop the previous year will be more easily managed than those with established grasses and weeds.

 

Additional fertilizers may be beneficial to stimulate growth and production. These might be incorporated in the soil prior to planting or applied on the soil surface later.

 

Soil Testing…the Right First Step

David Hillock

 

We all appreciate thick green lawns and lush productive gardens around the home. After all, attractive lawns and gardens add to both the aesthetic value and real value of our homes.

 

To achieve a high level of lawn quality and garden productivity, it is necessary to add fertilizer on a timely basis. When lawns and gardens don’t receive the amount of fertilizer that they need, they never achieve the quality or productivity we anticipate. When too much fertilizer is applied, nutrients are wasted and pose a threat to the environment.

 

The true value of a soil test is to help ensure that only needed nutrients are added in quantities which don’t adversely affect environmental quality.

 

The best time to test the soil is during a time when plants aren’t growing, although any time of year is satisfactory. In any case it is better to have the soil tested rather than guess which fertilizers to use and how much to apply. To make sure the test is accurate, sample the soil before fertilizer has been applied and follow proper collection procedures.

 

A soil test is only as good as the sample submitted for testing. Samples collected should represent the lawn or garden as a whole. The following steps will help in collecting good samples for submission.

 

• Scrape plant debris from the soil surface before sampling.
• Sample lawns to a depth of 3-4”. Sample gardens to a 6” depth.
• Use a clean bucket or other container and a soil probe or spade; collect cores or slices of soil from at least 15 different areas scattered throughout the lawn or garden and mix them together in the container.
• Mix soil thoroughly and fill the sample bag (bag can be obtained from your OSU County Extension Office) with a pint of the mixture.
• Submit samples and the completed information sheet to your OSU County Extension Office. They will send samples into the OSU Soil, Water, and Forage Laboratory for testing and then help you interpret the results.

Soil testing doesn’t need to be every year, every three years is often sufficient for most home gardens. The benefits of soil testing are many – it takes advantage of nutrients already in the soil, identifies nutrients that are lacking, reduces fertilizer applications, provides a proper balance of plant nutrients, allows adjustment of soil pH to an optimum level, and reduces chances of excess nutrients getting into the water sources.

 

For more information about soil testing contact your OSU County Extension Office or pick up the leaflet L-249 Soil Testing…the First Right Step.

 

2024 Oklahoma Proven Selections

David Hillock

 

Each year a set of plants is chosen by horticulturists that will help consumers choose plants appropriate for Oklahoma gardens. The program began in 1999 by selecting a tree, shrub, perennial, and annual worthy of Oklahoma landscapes. Selections for 2024 are posted on the Oklahoma Proven site. To see all the plants recommended by the Oklahoma Proven Plant Selection Program, visit the Oklahoma Proven  website.