August 2011 / Volume 54  

In This Issue
August Gardening Tips
Smart Watering
Fall is the Time to Divide
A Record-Breaking Summer
Ask A Master Gardener

Weather Stats for Gardeners

Soil Temperature 2" below sod:   

85 degrees 


Rainfall total last 30 days:  

0.69 inches


4 Ways to Contact Us
Email us at:

See our website at: 

Call: 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.
How to Plant a Tree in Oklahoma Soil
Show and tell.
Fescue Lawn Care
12-month maintenance calendar.
Bermuda Lawn Care
Ditto above.
Trees for Tulsa
A list of 50 recommended trees with descriptions.
Crape Myrtles
A list of over 100, by size and color.
Oklahoma Proven Plants
The new list for 2011. State horticulturists, nurseries and growers pick their favorite plants, shrubs and trees.
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. Register 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.
August Lawn and Garden Tips


  • Plants stressed from heat and drought do not tolerate fertilizers well. Fertilizer encourages new growth and adds stresses while plants are trying to survive.  
  • If water supply is a limiting factor, concentrate on watering trees, shrubs and perennials rather than lawns.   
  • Remember, mulch is your plants best friend in the heat. It can be a significant factor in survival now. The soil may be over 20 degrees cooler under a 3-4 inch layer of mulch.
  • Divide and replant spring blooming perennials including iris, peonies, and daylilies.   
  • Hedges and shrubs can be pruned as needed in mid-August. Click here for more information. Young trees and shrubs may be fertilized again.
  • Discontinue dead-heading roses by mid-August to help initiate winter hardiness. HLA-6403    


  • Lawns are suffering terribly from the heat: Bermuda will have some green if irrigated; brown, if dormant due to lack of water. It should survive in any case. 
  • Fescue, even if irrigated, often turns brown. If totally brown its likely dead from drought or disease and will need reseeding in the fall. If mostly brown but with some pale green blades mixed in, its probably dormant and will green with water and cooler weather. 
  • If your lawn is irrigated, apply 2 inches per week. Watering 2-3 times weekly early in the morning is better than every day-better for the grass and less wasteful.
  • During a drought and heat wave is a bad time to use postemergent weed killers. Weeds are not very susceptible but lawn grass may suffer from herbicides when stressed.
  • Preemergent herbicide to prevent winter weeds such as Poa annua and henbit should be applied  in late August and early September. Consider products containing one of the chemicals prodiamine, pendimethilin or dithiopyr. Water in after applying. HLA-6421 
  • Keep mower blades high. Remove only top 1/3 of grass, keeping grass 2.5 to 3 inches in length.


  • High temperatures have significant effects on vegetables-lack of fruit set on many veggies, sun scald on tomatoes and bitter cucumbers-to name a few. 
  • In addition to mulch, shade cloth over veggies and other heat-sensitive plants will help prevent damage.  
  • Monitor pests in the garden this month. Be sure to read labels on any insecticide used and note directions on last application prior to harvest. EPP-7313 
  • August is a good month to plant a fall vegetable crop. Most frost semi-tender fall vegetables should be in the ground this month. HLA-6009  
  • Spider mites love hot weather and can attack vegetables and ornamental plants. Control with a good strong spray of water every 3-5 days. Apply horticultural oil or horticultural soap if necessary.  
  • Compost needs water too! Turn the pile to generate heat for proper sanitation. 

Conserving Water
During Hot Summer Months 

Conserving water, or "Smart Watering", is on every gardener's mind this time of year. And, with this being Tulsa's 2nd hottest July on record, all of us are being challenged to keep our beautiful lawns and prized plants alive without having to take out a loan just to pay the water bill. Did you the summer, lawn, shrub, and garden watering typically accounts for 50%-80% of total home water use?

The good news is that there are some tried and true methods that will help conserve water: 

  • Water during the early morning hours when temperatures and wind speed are relatively low. The next best time to water is right after the sun sets; however, watering too late in the evening or at night can encourage the growth of fungus. Evaporation can be up to 60% higher during the heat of the day.
  • Water your lawn only when it really needs it. Water when the leaves begin to roll or show signs of wilt, when the grass does not spring back when stepped on, or when it takes on a dull, gray-green appearance. Water lawns slowly and thoroughly. Watering every day for short periods does not allow the water to soak into the ground very far. This encourages the grass roots to grow shallow and, during hot/dry periods, the roots can die quickly. Less frequent, but longer watering, encourages deep root growth, leading to more successful lawns.
  • Utilize drip irrigation systems in the flower beds and gardens. Trickle or drip irrigation systems can use 80%-90% less water than hose or sprinkler methods.
  • Condition the soil with mulch, compost, or related materials before planting to promote water penetration and retention in grass and flower beds. 

These are just a few helpful tips for water conservation. For more detailed information, click here

Fall is the Time to Divide for Spring 

The fall gardening season is the ideal time to divide spring blooming perennials such as daylilies, ornamental grasses, and hostas. This is a simple task and one that can be performed up until the first part of November. Fewer blooms, dead foliage in the center, or a plant that has simply outgrown its space in the garden are all indications that it is time to divide. To minimize the effect of shock, choose to work in the evening or on a cloudy day. Using a spade, work around the edges of the plant to loosen it from the soil, then gently lift, leaving as much of the root ball intact as possible. Shake off any loose soil and, with the spade or a sharp knife, cut the crown into smaller quart or gallon sized clumps. Discard any dead foliage and remove any damaged roots. Before replacing the mother plant, amend the soil with a small amount of compost. Water deeply and keep soil moist after planting. The remaining plants can be used elsewhere in the landscape or given away to a fellow gardener. For more information on using perennials in the landscape see Fact Sheet HLA-6410.  

A Record-Breaking Summer 

As all of us know by now, summer in Tulsa is hot, and rainfall can be hard to come by at times. This year, we seem to have taken the hot and dry to a level not seen by most of us in a long time. And, as the weather record book shows, it has been a long time since the Tulsa area has seen a summer like this one...31 years to be exact. If you lived in this area, I'm sure you fondly remember the summer of 1980!


This year, the typical summer pattern of a large, sprawling upper level ridge of high pressure over the southern United States arrived very early...about Memorial Day. Since then, it has simply refused to budge, and does not appear to be leaving us anytime soon! This persistent pattern has led to the second hottest and tenth driest June on record for Tulsa, with a record 29 days where the high temperature was 90 degrees or more. Temperatures just got hotter in July, with day after day of triple digit heat...26 days to be exact. When was the last time Tulsa saw this many days of triple-digit heat? You guessed it...1980. Overall, July was the second hottest on record in Tulsa. Number one on the list...1980! 


So, where do we stand two-thirds of the way through summer, 2011? For June and July, Tulsa broke the record for highest average temperature for that period (go ahead, guess which year held the previous record). To make matters worse, June and July have been the fourth driest such period on record in Tulsa, with Tulsa County now considered to be in a severe to extreme drought. At this point, barring a major shift in the upper level pattern, or a large tropical system in August, the hot and dry weather seems likely to continue for the remainder of the summer. Unfortunately, large scale patterns don't tend to want to shift during the there is a good chance that in the future, the summer of 2011 will have a significant place in the record books, and will come to be mentioned in the same breath as years like 1980.  


More information about the ongoing drought can be found here. Or visit the National Weather Service in Tulsa


Question: My plants are not looking good in all the heat. Would it help them to add some fertilizer when I water?  

Answer: No, now is the worst time to add fertilizer to any plant showing stress from the heat and lack of water. All plants are struggling for survival in this extremely dry and hot summer. When survival mode kicks in, most plants stop growing, flowering and producing fruit. It is not just the daytime heat that is harmful, but the nighttime highs are particularly damaging to plants. Energy is made in the leaves from the sun during the day, but not at night. Plants consume energy both day and night and the amount used is related to the temperature-the higher the temperature, the more energy used. Usually there is enough cooling at night to allow conservation of the energy produced during the day. However, with high nighttime temperatures energy use may outrun daytime production. If one adds fertilizers to a stressed plant, it forces the plant to produce new growth and this requires a lot of extra energy. This can be the "straw that breaks the camel's back" for a struggling plant. Wait until the plants and soil have cooled and water is available before fertilizing. Most plants do well with fall fertilization if they need it.

Question: Our purple coneflowers have seen their better days, how far should I cut them back?
Answer: Echinacea, or Coneflower, sometimes called purple coneflower, is a perennial that now comes in a wide array of colors including purple, purple-pink, white, yellow, red and orange...with more colors on the way! It thrives in the heat in full sun to partial shade and blooms mid-summer through fall in zones 2-10. When flowers reach their peak, the stems can be dead-headed or cut back to just above the side-shoots of new forming buds. This will guarantee continuous flowering throughout the growing season. Some gardeners prefer to cut back only some of the old blooms, allowing some seed heads to remain to provide food for the birds, mainly finches. This also allows some of the seed heads to self sow for new plants next season. Butterflies and bees enjoy new blooms all summer long. It is definitely a good idea to allow the blooms to remain in the fall for winter feeding for the birds.

Question: There are no tomatoes on my vines and the cherry tomatoes that are producing have tough skins. What am I doing wrong?
Answer: Tomatoes do not set fruit well when the overnight low temperature is above 70 degrees F, or when the daytime temperature is consistently above about 92 degrees F. When these conditions occur, flowers will drop or fruit will be misshapen. Hormone-type "blossom-set" sprays have very little effect on the set of tomatoes during hot weather. Avoid excessive nitrogen fertilization. Dry or very hot summers tend to produce thick skinned tomatoes. Even if you are watering regularly, when the air temperature is hotter, it can result in thicker skins as the plants try to conserve moisture. Inconsistent moisture levels in the soil can also contribute to the problem of tough skins. Tomatoes require two inches of water per week in July, August, and September or apply enough water to penetrate to a depth of 12 to 18 inches. Use mulch to keep the soil moisture even.  
Question: The mature trees in our yard are beginning to show stress with the leaves turning brown and curling and then falling off. What is causing this in such large trees, should I feed them?
Answer: The stresses you are describing could simply be a result of the severe drought and record high temperatures in our area. With year-to-date rainfall totals nearly ten inches below normal, even our mature trees are in need of supplemental water. If watered improperly, the tree's health will start to decline. The tree may be stressed for a long time before it begins to show symptoms such as leaf or branch drop. For most mature trees, regular monthly deep watering is recommended in the absence of soaking rain. Water when the top six inches of soil around the tree has dried out. Well-established, mature trees should receive water in several places around the tree at least half way between the trunk and edge of the canopy or drip line. Water using either a slow dripping hose or small sprinkler that can be regulated to put out an inch or two high spray. Allow the hose to remain in each location for an hour or so and do not allow water to run-off.

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