Oklahoma State Horticultural Fact Sheets

Get the facts on gardening education, problem solving

BILL SEVIER Master Gardener

Saturday, February 25, 2017

Q: What are the fact sheets you mention in this column and how do I find them? T.S.

A: Each state has a land grant college, and each of those colleges has an extension department in each county whose goal is to educate homeowners and farmers about horticultural techniques and problem solving. Our extension office, a part of OSU, is located at 41116 E. 15th St., gate No. 6 at the Tulsa State Fairgrounds.

OSU has many hundreds of “fact sheets,” which are used for educational activities for commercial agriculture and homeowners. Each fact sheet is concerned with a specific horticultural topic.

The Master Gardener Office, which is located in the OSU Extension Building, has many of these fact sheets preprinted and available for free. You may come by the office from 9 a.m. to 4 p.m. Monday-Friday to not only get these fact sheets but also to get help with gardening problems. You may also phone (918-746-3701) or bring in a plant sample or photo relating to your problem.

The OSU Master Gardener website, tulsamastergardeners.org, has most of the commonly requested fact sheets, and those not listed may be found by using an internet search of Oklahoma State and the name, fact sheet number or topic of interest.

Below are some of the more commonly requested and most helpful fact sheets with a brief description of content:

F-6004 Oklahoma Garden Planning Guide: This lists most all of the vegetables grown in Oklahoma and describes how and when to plant, along with days to maturity. This is the most requested fact sheet in spring.

HLA-6032 Vegetable Varieties for the Home Garden In Oklahoma: Individual varieties of common vegetables that do well in our area are listed.

F-6436: Healthy Garden Soils: This is an approach to preparing soils using Organic Gardening techniques.

F-6007: Improving Garden Soil Fertility: General information about planning a garden and correcting for any nutritional deficiencies.

F-6033: Raised Bed Gardening: The best approach for gardening if you have unfavorable soils.

F-6020: Growing Vegetable Transplants: How and when to start, care for and transplant sprouts.

K-State: Top or Side Dressing Nitrogen Fertilizer for Vegetables and Ornamentals: While not an OSU document, this is a useful list on what, when and how to fertilize different vegetables.

Bermuda Maintenance Schedule and Fescue Maintenance Schedule: These two documents are available from the Master Gardener website in the turfgrass section. They have complete recommendations for lawn care — mowing, weeding, irrigation, seeding and more.

HLA-6419: Establishing a Lawn in Oklahoma: Complete details on how to seed or sod a lawn.

HLA-6608: Managing Turfgrass in the Shade in Oklahoma: This addresses the problem of growing grass in shade. It has several options and planting alternatives for an area too shady for a lawn.

These fact sheets will give you most all of the information you may need for growing vegetables, ornamentals and turfgrass in Oklahoma. Another plus is that they are totally free and are your tax dollars at work.

Garden tips

·       Finish pruning shade trees, summer flowering shrubs and hedges by the end of the month. Spring-blooming shrubs such as forsythia may be pruned immediately after flowering. Do not top trees or prune just for the sake of pruning. Get OSU fact sheet “Pruning Ornamental Trees Shrubs and Vines” for more information.

·       By Feb. 15, many cool-season vegetables like cabbage, carrots, lettuce, peas and potatoes can be planted.

·       Spray peaches and nectarines with a fungicide for prevention of peach leaf curl before bud swell.

·       Collect and store graft wood for grafting pecans later this spring.

Pruning Crapemyrtles

Don't commit 'crapemurder'

Brian Jervis: Ask a Master Gardener

Saturday, February 18, 2017

Q: When and how should I prune my crapemyrtles? E. W., Tulsa

A: Crapemyrtles, along with all trees and shrubs, should only be pruned for a reason. The best time to prune these and other trees and shrubs is late winter or early spring, before leafing out. An exception to this time are the spring-blooming shrubs, such as azaleas and forsythias, which should be pruned after blooming, if needed. Delaying pruning of spring-blooming plants is only to preserve the flower buds formed the previous year.

There is a common belief by many that crapemyrtles should be pruned back to an ugly set of horizontal nubs in the spring time. Nothing could be further from the truth about good crapemyrtle care. Crapemyrtles should be allowed to let nature have its way and to grow to their full height.

Some people think that blooming will be increased by drastic pruning (many horticulturists call this “crapemurder”), but Dr. Carl Whitcomb, a retired OSU professor and developer of crapemyrtle cultivars, cites evidence that blooming is less, not more, with drastic pruning. Light pruning of endmost 12-18 inches, back to a lower limb, can increase numbers of blossoms. However, these plants were engineered by nature to bloom profusely without this type of pruning. In summer, one can promote a second wave of blossoming by pruning off old blossoms after they fade.

Reasons to prune crapemyrtles are to confine it to the space available or to improve the shrub’s shape and structure. Removal of dead or diseased limbs and elimination of internal crossing branches should be done anytime.

For those plants that are too big for their space, rather than trimming them back each year, consider removal and planting one of the smaller crapemyrtle cultivars. There are many sizes available, ranging from 18 inches to 25 or more feet when mature.

One question that sometimes arises relates to the seed pods left over in fall after blooming is completed. The plant will remove them naturally as they have been doing for thousands of years, and they need no pruning.

Another pruning suggestion one should consider with crapemyrtles concerns those plants with a multitude of trunks. These are best reduced to three to five trunks, which will not only have more curb appeal, but also will allow more energy to be directed toward further growth and blossom formation. To further improve appearance of these shrubs, consider removing the limbs from the lower third or half of the trunks.

Crapemyrtles are notorious for sending up shoots or sprouts from the base of the plants, especially in the spring. These should be removed by pulling off if able, or clipping close to the ground, if needed.

We have an advantage over our northern neighbors in being able to grow these magnificent plants, which are the mainstay of color in Tulsa during the summer. They deserve the best care we can give them, they should not be subjected to “crapemurder.”

Garden tips

§  Now is a good time to cut back your perennial ornamental grasses, such as pampus grass. Cut back to remove the dead grass, but avoid damaging new buds and early green growth at the base.

§  Begin planting blackberries, raspberries, strawberries, grapes, asparagus and other perennial garden crops this month. Contact Tulsa Master Gardeners at 918-746-3701 for specifics about these plants.

Dormant Horticultural Oil for Crapemyrtle Scale

Treating the rapidly spreading crapemyrtle bark scale

Bill Sevier Master Gardener

Saturday, February 11, 2017

Q: I was told that a dormant oil should be used to treat scale insects, which have covered my crape myrtles. When should I do this and what should I use? Mike, Tulsa.

A: Dormant oil treatment for crape myrtle bark scale may be environmentally the safest, effective treatment available. It should be used in dormant concentrations and should be used now, before the trees come out of dormancy.

The benefit of oil for plant pest control has been known going back to the time of the Romans. To be effective, these oils must be applied directly to the insect or the insects’ eggs. The oil kills insects by blocking the insects ‘breathing passages.

In the past, oils came in two varieties, a thick heavy oil which was used as a “dormant oil” (used in late winter and early spring before bud swell and bud break). These oils, if used during the growing season, were toxic to plants. The other, thinner oil, called a “summer oil” was used safely in the growing season.

Things have changed now with what is recommended and available to treat many different pests. Most of the newer horticultural oils are petroleum-based mineral oil. They are labeled as superior, supreme or ultra-fine oils. These oils have been refined to remove undesirable compounds toxic to plants. Therefore, they may be used in winter as dormant oil and in summer as summer oils by simply changing their concentrations. The winter dormant preparations are much more concentrated and more viscous than the summer preparations but are the same oil. Most of these oils contain an “emulsifier” to help the oil mix with water.

They should only be used during outdoor temperatures of 40-90 degrees. If used in colder weather, the preparation may not mix and cover the insects well. If oils are used during high temperatures or high humidity or on drought-stressed plants, the chance of plant damage is increased.

Examples of some of the commercial brands of petroleum oils available at garden centers are Sunspray Ultra-fine, Volck Oil Spray and Bonide “All Season” oils; there are many others and are available locally.

Other than the petroleum-based preparations, there are those of vegetable origin. They are made from neem seeds, cottonseed, canola, cloves and rosemary. These are used mainly as summer oils. Neem oil is unique in that it also has effective anti-fungal activity. It is a good choice for a summer oil. However, for a dormant usage, the petroleum-based mineral oils are probably best.

These products are effective for many different types of insects. During the growing season they are used to treat scales, aphids, mites, whiteflies and others. They are used extensively by commercial fruit and nut tree farmers.

For homeowners, crape myrtle bark scale and euonymus scale are significant problems to deal with. A dormant oil applied now is more effective and safer than synthetic insecticides. As with any pesticide, one must read and follow the instructions on the label. There are some plants which are intolerant.

Garden tips

·       Most bare-rooted trees and shrubs should be planted in February or March. The roots of these plants are easily damaged and should never be left exposed to air. Plant them at the same depth as in the nursery and make sure good root and soil contact is made by gentle tamping and irrigation after planting.

·       Finish pruning shade trees, summer flowering shrubs and hedges. Spring blooming shrubs such as forsythia and azaleas may be pruned immediately after flowering. Do not top trees or prune just for the sake of pruning.

·       With our warm temperatures, applying pre-emergent herbicides earlier rather than later may be desirable to prevent crabgrass and other summer weeds.

Selecting, Planting and Caring for Blueberries

Planting a blueberry patch requires patience

Brian Jervis: Ask a Master Gardener

Saturday, February 4, 2017

Q: How do I get started making a blueberry patch? H.G., Tulsa

A: Blueberries grow well in Oklahoma as long as you have the proper soil and select the varieties that have been shown to be best for our area. You also need patience. Berry production should not be allowed until the third year after planting.

The best place to get started is by obtaining the OSU fact sheet 6248, “Blueberry Production for the Home Garden.” This may be obtained from the Master Gardener website at tulsamastergardeners.org, or from a web search of OSU fact sheets.

Plant selection is key. There are three types of blueberries that are grown in Oklahoma — Highbush, Rabbiteye and Southern Highbush. Highbush has more cold tolerance and is recommended for areas north of Interstate 40. Rabbiteye and Southern Highbush are suggested for central and southern Oklahoma. The two Highbush varieties do best with more than one cultivar for pollination.

Blueberries need full sun for best growth. Planting on a north-facing slope will help prevent early spring frost damage and will offer some wind protection in summer. The soil must drain well and be acidic. The ideal pH for blueberry growth is 4.5 to 5.2; they will not grow in higher pH soils.

Blueberries will not grow in overly wet soil; good drainage is a must. To address the drainage and pH issues, raised beds are ideal. Import soils with correct pH and high organic content. Because blueberry soil requirement is identical to azaleas, commercial azalea planting mix serves this purpose well.

These plants have shallow and inefficient roots. They must have 1-3 inches of water per week, depending on the temperature. Drip irrigation is ideal for keeping moisture levels in a desirable range. Heavy mulching will not only help with conserving water, but will also keep out weeds and moderate the extremes of temperature.

Blueberries may be planted in either spring or fall, but spring is best. Specific recommendations about how to plant and proper spacing are in the fact sheet mentioned above. Fertilization should be based on a soil test, and blueberries do best if fertilized with smaller and more frequent amounts of nitrogen than with other plants.

Pruning is best done after the spring flowering and berry production. Berries are produced in early summer in most varieties, on buds that were formed the previous growing season. Therefore, if one prunes in winter or early spring, it would remove fruit buds. Pruning is usually done to limit the size of the bushes and also to thin out limbs on the inside of the bush to improve air flow.

Blueberries take time to develop a structure and root system needed for maximum production. So for the first two years, all blossoms and fruit should be removed so that energy can be used for development. If fruit is not removed the first two years, they may not survive summer stress. They may be harvested the third year with peak production occurring in the fifth year.

Garden tips

•        Early February through March is the recommended time to plant strawberries. It is important to plant them in full sun and in well-drained soil. There are several types from which to choose. June-bearing varieties do best in our area. They have a single crop usually early May to mid-June. Ever-bearing strawberry is another variety that fruits May to June, a few during summer and again in the fall. The quality and size of this type of strawberry plant may not be as good as June-bearing varieties. For full information about plant selection, planting and care of strawberries in your garden, obtain OSU fact sheet "Growing Strawberries in the Home Garden" online or in the Master Gardener office.

•        Mid-February is a good time to begin pruning and fertilizing trees and small fruits.