May 2014 / Volume 86        

In This Issue
May Lawn and Garden Tips
TMG Garden Tour
Effects of Drought on Insect Pests
Hydrangea Care
Ticks and Their Diseases
Ask A Master Gardener...Side Dressing

Weather Stats for Gardeners

Soil Temperature 2" below sod:   

71 degrees 


Rainfall total last 30 days:  

1.38 inches


4 Ways to Contact Us
Email us at:

See our website at: 

Call: 918-746-3701 from 9-4, M-F 
Visit us at 4116 E. 15th Street, Gate 6 at the Fairgrounds

Whether you call or bring samples of plants to the office, trained Master Gardeners will answer your gardening questions with science-based information.
Need More Information?

Click on any of the links below:


All about butterfly gardening in Tulsa County 

How to Take a Soil Test

How to collect a good sample of soil from your lawn or garden and get it tested at the OSU lab.
Understanding Your Soil Test Results
Once you have collected your soil test and gotten the results back, now what? Find out here. 
How to Plant a Tree in Oklahoma Soil
Show and tell.
Cool Season Lawn Care (Fescue)
12-month maintenance calendar.
Warm-Season Lawn Care (Bermuda)
Ditto above.
Trees for Tulsa
A list of recommended trees with descriptions.
A list of over 60, by size and color.
Demonstration Garden
Visit our demonstration garden on 
15th Street, open 7 days a week.  
Oklahoma Proven Plants
State horticulturists, nurseries and growers pick favorite plants, shrubs and trees for use in the Oklahoma landscape. See the winners for this year and years past.
Current and historical source of rainfall, air temperatures, soil temps and much more. Click on Bixby station.  

Back Issues  

Past issues of our eNewsletters can be read and downloaded.

Become a Master Gardener

Classes start in September each year. Register at our office on 15th Street for more information.

Oklahoma State University, in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Disabilities Act of 1990, and other federal laws and regulations, does not discriminate on the basis of race, color, national origin, gender, age, religion, disability, or status as a veteran in any of its policies, practices or procedures. This includes but is not limited to admissions, employment, financial aid, and educational services.

May Lawn and Garden Tips     
  • Warm season vegetables like tomatoes, squash, cucumber, pumpkins, eggplant, okra, sweet potatoes and peppers may be planted from mid April onward once soil temperatures reach 60◦. Refer to OSU fact sheet "Oklahoma Garden Planting Guide".
  • The first fruit on the strawberry plants may appear by late this month. Newly planted strawberries should have the blossoms picked off until they become well established.
  • Seeding of warm-season grasses such as Bermuda, buffalograss and zoysia is best performed in mid-May through the end of June. Soil temperatures are warm enough for germination and an adequate growing season is present to promote winter hardiness.   
  • If the weather is sunny and dry, don't neglect watering. Most flowers and shrubs, especially recently planted ones, need about an inch of water each week. 
  • Early flowering deciduous shrubs such as forsythias, weigela, and azalea may be pruned back after they have finished blooming, but only if pruning is needed.  
  • Bagworms may appear on juniper and arborvitae late in May. Pluck them off by hand and spray with an organic herbicide containing Bacillus thuringiensis (Bt). Bt is safe for people and pets. Call Master Gardeners for addition suggestions. 
  • Lace bugs may begin to feed on azalea, pryacantha and sycamore trees. Contact the OSU Master Gardeners for additional recommendations. 
  • Mophead Hydrangias may change from blue to pink blossoms depending on the soil pH (acidity). Do a soil test and add either lime or aluminum sulfate to adjust soil acidity to change colors. For more info, see article below
  • Pine needle disease treatments may be needed in mid-May. Contact Master Gardeners for recommendations. 
  • Observe roses for development of insects such as aphids and black spot disease. Spray as needed.  
  • Allow foliage of spring blooming bulbs to die back before removing. These bulbs may be dug and divided after foliage dies. 
  • Continue to plant summer annuals, summer bulbs such as cannas, dahlias, elephant ear, caladiums and gladiolus.  
  • If azaleas need fertilizing or pruning, do it now after blooming is completed.

Tulsa Master Gardeners Garden Tour 2014

The 9th Annual TULSA COUNTY MASTER GARDENER'S TOUR will take place the first weekend of June. The gardens on tour will be ones personally designed by Master Gardeners and will consist of a wide assortment of landscapes to fit the theme of "City Blocks to Country Lots".


The themes of the individual gardens are Garden Retreat, Tudor Garden, Waterfall Garden and Four Acre Garden. The tour also includes the Master Gardener's Demonstration Garden at the OSU Extension Center located at 4116 East 15th Street--gate number six into the Fairgrounds.


The tours are on Saturday June 7 from 9am to 5pm and Sunday June 8 from 11am to 5pm. The cost of advanced tickets is $5.00, those on the day of tour, $7.00.


OSU Fact sheets as well as Master Gardener volunteers will be available to provide information and tips to visitors. Don't miss the Master Gardener Garage sale in the parking lot of the Extension Center on Saturday, June 7, from 10 until 4. This sale includes objects donated by our 300+ Master Gardeners and friends. There will be bargans aplenty for everyone. You will find a wide variety of items including an assortment of houshold goods for the kitchen and elsewhere, to garden equipment, to a large number of books, to antiques and for the collector, an actual camel saddle.


Garden Tour tickets for pre-purchase will be available in early May at the OSU Extension Office. Tickets will also be available at each individual garden on tour at a slightly increased price. Dates of availability of tickets at the Extension office will be announced as soon as the plans for the tour are completed.

Effects of Drought on Insect Pests       
Eric Rebek, Extension Entomologist  
I often get asked about the effects of drought (or cold winters) on insect pests. My tongue-in-cheek response is always "Well, let me consult my crystal ball". My implied message is that forecasting pest development from one year to the next is an extremely difficult and risky endeavor. Indeed, I believe firmly that predicting the weather is an easier task, and we all know how imprecise weather forecasts can be. Long-term predictions of pest activity are risky because the livelihood of many growers is riding on my pest management recommendations. Also, I am not in the business of recommending any pest control measure that turns out to be unnecessary and potentially costly. So, I err on the side of caution and recommend a "wait-and-see" approach, which requires frequent scouting for pests and plant damage (monitoring) during critical stages of crop development. Monitoring is an essential component of integrated pest management (IPM) that should be practiced regardless of prevailing weather patterns.  


The effect of drought on all critters, not just insects, is complex and depends on many factors. These factors can be grouped into two general categories: bottom-up and top-down effects. Bottom-up effects are those resulting from aspects of the host plant that are fed upon by herbivorous insects. In general, insects that feed on plants do not fare well because their host plants become stressed, wither, and eventually die if they are not under constant care during a drought. On the other hand, stressed plants tend to be more attractive to many insect pests, so there may be an initial surge in the pest population when the effects of drought initially develop. This is well documented for wood-boring insects, for instance. And some arthropod pests such as spider mites thrive in hot, dry conditions.  


Top-down effects are those resulting from the activity of predators, parasitoids, and insect-killing pathogens (e.g., fungi) that naturally keep pest populations under control. Drought has a negative effect on these natural enemies of insect pests, leading to an increase in pest populations, at least temporarily. But insect pests themselves also are susceptible to drought, so heat and a lack of moisture can take a direct toll on pest populations.  


Let's add another layer of complexity: suppose a landscape is well tended with crops receiving enough supplemental irrigation to minimize the effects of drought. What are the effects on pest populations under this scenario? Perhaps that crop becomes an oasis, serving as a reservoir for insect pests and their natural enemies. My point is that landscape factors and crop or land management practices can mitigate (or exacerbate) the effects of drought on pest populations. Microclimatic factors also play a role in modifying the environment to favor or disfavor pests. For example, plants provide shade for both pests and their natural enemies, which seek out these favorable microclimates during the hottest part of the day.  


In conclusion, insect pests are influenced by many factors: weather, microclimate, host plants, natural enemies, and landscape-level effects among others. Thus, the effect of drought or other weather pattern on insect pests is unpredictable due to high variability in the response of pest populations to all of these factors acting simultaneously. Further, the impact of drought on insect pests is not necessarily seen immediately. It may take months or even years for an insect pest population to change or respond to a drought event.

hydrangeaHydrangea Care 
Hydrangeas uniquely contribute both color and form to our landscapes and one can hardly go wrong planting any of them. There are about 23 species of these plants, many imported from Asia, but a few are native to the Americas. Five are commonly available and used in our landscapes. Books have been written about the many hundreds of cultivars of each of these more common species.

General Care: In Oklahoma all of the hydrangeas do best with afternoon shade. It is essential for some. They also drink a lot of water in order to make those huge leaves. They will need summer irrigation in additional to our typical rainfall to remain healthy. Fertilizing with a slow released predominately nitrogen fertilizer in spring is appropriate. Fertilizer choice is always best based on a current soil test.
Pruning: Mopheads, lacecaps and oakleaf hydrangeas typically bloom on buds formed during the previous late summer and fall. If pruning is needed, do so after the flush of blooms in spring is completed.
Panicle and smooth hydrangeas bloom on current year's growth and may be pruned, if needed, late summer until early spring before new growth begins.
Any older and dense hydrangea (or any shrub) will benefit from removing 1/3 of the older stems back to the ground in winter or early spring.
Changing Blossom Color: Macrophylia hydrangeas-the mopheads and lacecaps-typically have blue to reddish to pink blossoms. The color of their blossoms depends on the amount of aluminum in the blossom. Inadequate aluminum causes them to be pink, whereas abundant aluminum produces blue petals.
Our soils generally have ample amounts of aluminum, so soil deficiency is not the problem. The limiting factor is that these hydrangeas absorb aluminum only if the soil is acidic (low pH). A pH of 5 to 5.5 is best for blue color, anything above 6 tends to produce pink.
A soil test will measure the pH or acid content and help decide what to do. In the absence of a soil test and if you wish to turn pink blossoms to blue you should acidify the soil. Aluminum sulfate adds both freely available aluminum and acidifies the soil. Use � to 1 ounce of aluminum sulfate added to a gallon of water and apply to the root zone as a drench. This may be repeated 2-3 times during the growing season. Also, the use of acidic organic material such as peat moss will help lower the PH.
If you wish to turn blue flowers to pink, reduce the acidity (increase the pH) of soil using garden grade lime. Apply one cup to the root zone twice a year during the first year and observe results. More applications may be needed, but lime raises pH very slowly (months); if overdone it can interfere with nutrient absorption.
Lastly, be aware that too much phosphorus in the soil will block aluminum absorption and produce pink flowers. In Tulsa, soil test from landscapes previously fertilized have shown that over 75% have either enough or, more often, too much phosphorus. Once excessive phosphorus is in the soil, it takes years to correct. Here you must accept that the blossoms will be pink unless you replace the soil.

Ticks and Their Diseases            
Ticks are an important pest of humans and animals that we need to be aware of. When we hear or think about ticks we think about inconvenience and disease. Their bites can cause extreme pain and discomfort in both people and animals that work or play in tick-infested areas. Ticks can also transmit several disease-causing organisms in animals and humans. Tick bites can cause dermatosis (itching, swelling, inflamed condition of the skin) on the host, and may lead to secondary bacterial infections. 

Ticks have a very hard outer skin, which makes them quite tolerant of environmental stresses. The absence of tick predators increases their ability to survive. In fact, some species have a lifespan of several years. These conditions account for the tremendously large population of ticks.  
Like many insects, ticks have four developmental stages of life: egg, larvae, nymph, and adult. Larvae are sometimes called "seed ticks" and are about the size of a pin head. But, ticks can be distinguished from insects in that their bodies are not divided into distinct segments and a distinct head is lacking. Nymphs and adults have four pairs of legs, while the larval form has six legs. The adult female will be fat and of a bluish-gray color when engorged with blood, giving an entirely different appearance from other life stages.

There are wide assortments of diseases that can be caused by some of these ticks. Rocky Mountain Spotted Fever (RMSF), also known as tick-borne typhus, is transmitted by the bite of certain ticks. It is the most common tick-borne disease in Oklahoma. Originating in the Rocky Mountains, it is now commonly found in the hill country of Missouri, Arkansas and Oklahoma. Oklahoma ranks high each year in the number of reported cases of RMSF, with most cases occurring between April and September. The American Dog Tick, which is prevalent in the eastern half of Oklahoma, is the only tick that transmits this disease. Most people come in contact with this tick in heavily wooded areas. Only a small percentage (0.1%) of these ticks actually transmit this disease after being attached for several hours. Frequent inspection and removal of all ticks at least twice per day will prevent transmission from occurring. Symptoms of this disease appear three to 14 days after the tick bite and include sudden fever, chills, muscle aches, and headaches. If this occurs, seek medical help immediately. 

Although Lyme disease has become the most common and the most rapidly spreading tick-borne disease in other parts of the country, it does not seem to be very prevalent in Oklahoma. Ticks carrying this disease favor lizards and skinks for their hosts as opposed to humans, so there are not very many cases of this disease being transmitted to humans in Oklahoma.
Less than 1% of all ticks carry infected organisms and these diseases. Also, ticks do not transmit these diseases while crawling on you. Stay away from wooded areas, wear protective clothing and use some form of tick repellent that contains the ingredient DEET. But, if you find a tick attached to you, do not panic. Use a pair of tweezers to grasp the tick at the surface of the skin and slowly pull the tick straight out with a steady pull.  

For more information on ticks and their associated diseases, see the OSU Fact Sheet EPP-7001 on ticks (Common Ticks of Oklahoma and Tick-Borne Diseases).

Question: Now that my vegetable garden is growing, what is the best fertilizer and how much should I use?

Answer: There is no "best" fertilizer for vegetables during the growing season; however, additional nutrients are usually needed. They are applied to the root zone of plants. This is called "side dressing."

The times and amounts of fertilizer to apply depends on the vegetable, type of soil and amount of rainfall. The Kansas State Extension web site has a very helpful chart of how much and when to apply different types of fertilizer as side dressing to a wide range of vegetables.

A soil test will tell you which of the three main nutrients - nitrogen, phosphorus and potassium - may be needed. If a test result is not available and the garden plot has received general fertilizer in the past, use a fertilizer containing mostly nitrogen. Rapidly growing vegetables almost always need extra nitrogen, but in sensible amounts. The other nutrients are needed as well, but previously fertilized gardens usually have ample or excessive amounts of phosphorus and potassium. Apply the fertilizer to the area of the plant's roots, but keep it away from the stems to prevent burning. Fertilizer will need to be gently washed into the soil, but do not put out before a heavy rain. Nitrogen is mobile in the soil and is easily carried beyond the plant's root zone with excessive rain, especially in porous, sandy soils. Using a fertilizer with some of the nitrogen in a slow-release form will minimize this water related loss. An example of recommended fertilizer amounts for vegetables from the Kansas State document - in this case tomatoes - is to fertilize one to two weeks before the first tomato ripens, and again two weeks after picking the first ripe tomato, then again one month later. Each time, use two tablespoons of a 16-0-0 or one tablespoon of a 27-3-3 strength fertilizer per tomato plant.

Lawn fertilizers are a good choice for fertilizing the vegetable garden. These often are mixes of quick and slow released nitrogen with little or no phosphorus. Never use a lawn fertilizer containing an herbicide such as found in "weed-and-feed" preparations.

Click here to send your question to the Tulsa Master Gardeners or see Answers to other Questions on the Web site.