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.

Non-Blooming Hydrangeas

Weather, pruning may be cause of non-blooming hydrangea

Bill Sevier, Ask a Master Gardener

Saturday, January 28, 2017

Q: I planted some mophead hydrangeas I bought from a local nursery, and they are not blooming. What could cause this? Amy, Tulsa.

A: The short answer is that the non-blooming is most likely related to pruning or weather issues, although there are other causes.

The Tulsa Master Gardeners maintain a helpline at the OSU Extension Office on 15th Street, and this is certainly in the top 10 questions called in during the growing season.

There are 23 different species of hydrangeas and five are cultivated in the U.S. These are smooth, panicle, bigleaf (mophead, lacecap), oakleaf and climbing hydrangeas, and they all share some, but not all, of the flowering habits of your hydrangeas.

In regards to blooming, the mopheads come in two general varieties. The older classic ones that just bloom in spring and the newer remontant (reblooming) varieties that bloom in spring into fall. The spring bloomers form flowers on buds developed during the previous late summer and fall. Pruning these shrubs during fall, winter or early spring will remove the flower buds with a loss of blooms for that season.

Hydrangeas in the reblooming group have last season’s buds as the others do but also form buds in the current summer, which bloom that summer and fall. If these are pruned winter or spring, the spring blooms will be lost, but the plant should still bloom in summer and fall.

Another cause of non-blooming of hydrangeas relates to the weather. Spring-blooming plants whose buds were developed the previous year may lose those buds with a late spring freeze. As it warms in early spring, the flower buds expand with water and begin to soften (bud break). As they do this, they lose their cold tolerance and a late freeze may kill them. The reblooming hydrangeas also may lose their spring flowers with a late freeze but will still bloom later in the summer. That is why this type of hydrangea is popular in the northern states.

These are the main causes of hydrangeas not blooming, but there are others.

Most varieties need about four hours of sun to bloom. If a hydrangea is planted in full or mostly shade, it will have nice green leaves, grow tall but not bloom.

Another factor to consider is that these plants need time to develop root systems and develop height before they consider blooming. Some plants may take two or more years to do this, so if everything else seems optimal and the plant doesn’t bloom, give it more time.

A last possible cause relates to most all plants in the flower or vegetable garden. If you use too much nitrogen fertilizer, plants will grow tall and green and not flower.

For a helpful review of hydrangeas and their problems, the Proven Winner website is worth reading.

Garden tips

•        Begin planting blackberries, raspberries, strawberries, grapes, asparagus and other perennial garden crops in February.

•        One can continue in the month of February spot-spraying weeds in your dormant Bermuda lawn. Use a product containing glyphosate, found in Roundup and others. Use when the temperature is above 50 degrees and always read the label carefully before using.

•        Tomato seeds are best planted into indoor flats around Valentine's Day for mid-April garden transplants. Should you decide to grow your own tomato transplants from seeds, consult OSU fact sheet “Growing Tomatoes in the Home Garden,” which can be found on the Tulsa Master Gardener website. In that same section of the website, you will find additional fact sheets on growing conditions, pests and diseases, which are helpful.

Selecting and Growing Fruit Trees

Master Gardener: Fruit trees are bountiful in Oklahoma

Brian Jervis: Ask A Master Gardener

Saturday, January 21, 2017

Q: I would like to grow some fruit trees but not sure what would be the best type to for our area. Suggestions? L.M., Tulsa

A: There are many types of fruits that may be successfully grown in Oklahoma. These include the “pome” fruits (apples and pears), the “stone” fruits (peaches, nectarines, apricots, cherries and plums), as well as other fruits such as figs, persimmons and berries.

All these fruits vary in their ease of culture; some are relatively easy to grow and others need intensive management for good fruit production. Generally, apples and pears are the easiest of the tree fruit to manage, with peaches being the most difficult. Sweet cherries do not thrive in Oklahoma, but sour cherries do well. Most of the berries require much less management and can be grown more successfully than the larger fruit.

Additional considerations, when selecting fruit trees, are varieties best for our area, as well as the pollination needs of that particular tree. OSU has a number of fact sheets available online that detail this information.

Homeowners may find a dwarf tree may be the best fit for available space and ease of harvesting. These trees are common varieties of fruit trees, which are grafted onto a hardy dwarfing root stock. The fruit is the same from full-sized and dwarf trees.

Pollination requirements are most important. If ignored, you may end up with a healthy fruit tree with bountiful spring blossoms and no fruit. Some fruit trees are self-pollinating, but the majority need another variety of the same fruit type for successful production.

After deciding on the type of fruit to grow, the choice of a growing site is also important. Remember, the fruit tree will be with you (hopefully) for many years; plan with that fact in mind.

Most all fruits need full sun, up to 8 hours per day. They also need a soil with adequate drainage. They generally will not do well in high clay soils or in areas prone to flooding. One of the challenges of growing peaches, plums and apricots is the late spring frosts that kills maturing buds. To reduce the likelihood of this, consider planting trees on a north slope or the north side of a building. This will delay spring “bud-break” and reduce spring frost damage.

For fruit trees to be most productive, they should be sprayed for insects and disease. These sprays are generally needed just before spring growth and continued up to fruit harvest. Some of these schedules are complicated, and each recommended schedule is different from fruit to fruit. The OSU Tulsa Master Gardeners website, tulsamastergardeners.org, has a wealth of information about the management of all the fruits — when and what to spray with for each type of fruit.

Growing fruits can be rewarding as a hobby, especially for children. They can see “their tree”

Garden tips

Even though there may be adequate moisture in the ground, it is normal for evergreen broadleaved shrubs to appear “wilted” during extreme cold. This is rapidly reversible after the temperatures warm. This is a way some plants deal with the cold.

Try to keep fallen leaves off newly seeded fescue. Fescue is capable of growing roots in winter unless the ground gets extremely cold. A good root system will help fescue to better tolerate the heat next summer. To grow roots, the grass needs sunlight.

Growing Blackberries

Growing raspberries and blackberries takes planning

Bill Sevier Ask a Master Gardener

Saturday, January 14, 2017

Q: Do blackberries and raspberries grow well in Oklahoma? How does one get started? M.E., Tulsa.

A: Blackberries are the easiest of all fruits to grow in Oklahoma. Raspberries are similar; the plants grow well, but the weather — spring freezes and high heat in summer — limits berry production. As a group they are called “brambles,” and the discussion below applies to both. There are hybrids between these two such as boysenberries, dewberries and others.

Although easy to do, establishing a berry patch includes more than planting a few transplants in an existing garden bed in your backyard. A good place to start planning is with OSU fact sheet HLA-6215, “Blackberry and Raspberry Culture for the Home Garden.” This document discusses the essentials, which are site selection and preparation, variety choice, propagation and planting, and general care — mulching, fertilizing, irrigation, training and pest control. The techniques of harvesting are also discussed.

The berries need at least six to eight hours of sun. They tolerate a wide range of soils if well-drained. For wet areas or heavy clay soil, use raised beds. You should perform a soil test to get an idea of what amendments are needed. Blackberries prefer a pH of 5.5 to 6.5 (slightly acidic), and all beds will benefit from composted organic material tilled into the soil.

The University of Arkansas developed most of the new productive cultivars and most are well-suited to our area. They all are named after Native American tribes and are either thorned or thornless, and they grow upright. There are other varieties of blackberries with trailing habits, which means they need trellises for support.

Blackberries usually have two types of canes. The ones produced the first year are called primocanes. Two-year canes are called floricanes.

Primocanes rise from roots and grow to full height the first year. They do not blossom or have fruit. Primocanes turn into floricanes the following year. These canes bear fruit and die. This means that normally, you must grow blackberries for two years before getting any fruit, although there are a few new varieties that produce fruit on the primocanes in the first year. This also means that the floricanes need to be pruned out at the end of the fruiting season.

Blackberries are planted as either root cuttings or plants. They may be planted anytime during the dormant season but do best if planted in February and into March. No trellis or support is needed for the erect berry plants, but all will need a thick layer of loose mulch. They all will need fertilizer, usually twice a growing season. There is some additional tip pruning needed for best production, all discussed in the above referenced fact sheet.

After planting, the blackberries will need 1 to 2 inches of water per week by irrigation or rainfall. A drip irrigation is ideal for these plants. There also are some recommended disease and insect sprays recommended for the plants.

Garden tips

·       Several early season vegetables are grown from seeds and planted as sprouts or transplants. Some examples are cabbage, cauliflower, broccoli, head lettuce, onions, tomatoes, peppers and eggplant. Most of these take 5-7 weeks from planting indoors until ready for transplanting into the garden. Onions take a little longer to grow.

·       Of these, cabbage, cauliflower, lettuce and onions sprouts should be set out from mid-February to mid-March. Plant broccoli sprouts in March. Tomatoes, peppers and eggplants need warmth and suggested planting time is mid-April, although many people take a gamble and plant earlier, depending on the weather. Look for seeds at local gardening centers or online now if you plan on growing your own transplants.