May 2012 / Volume 62         

In This Issue
May Lawn and Garden Tips
Edible Gardening
Special Thanks
Ask A Master Gardener

Weather Stats for Gardeners

Soil Temperature 2" below sod:   

73 degrees 


Rainfall total last 30 days:  

3.32 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.
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.
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 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. 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.
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. With this very warm spring all the squash etc should now be in the ground or planted soon. Click here for the 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. Click here for more information on growing strawberries. 


  • 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 azaleas need fertilizing or pruning, do it now after blooming is completed.  
  • Continue to plant summer annuals, summer bulbs such as cannas, dahlias, elephant ear, caladiums and gladiolus.
  • Allow foliage of spring blooming bulbs to die back before removing. These bulbs may be dug and divided after foliage dies. Click here for more bulb information. 
  • Mophead Hydrangeas 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.
  • 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.

  • 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.

  • 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.  

Edible Gardening - Making the Most of Your Home's Flowerbeds 

"Wow, I wish I could grow vegetables and fruit in my landscape but I only have flowerbeds and ornamentals in my yard!" If this fits you, you can grow vegetables, herbs, fruit, and edible flowers in those flowerbeds or in containers outside your front or back door.

Edible gardening is the alternative to conventional residential landscapes that are designed solely for ornamental purposes. They can be just as attractive, yet produce fruits and vegetables for home use. One can plant an entirely edible "landscape," or incorporate simple elements into existing yards and gardens. If you have planted a pot of herbs or a container with tomatoes, you have experienced "edible" gardening.


There are many advantages to incorporating edible plants into your residential landscape. An important advantage is to enjoy the freshness and flavor of home-grown, fully ripened fruits and vegetables. You can also save money by growing vegetables yourself. Another very important advantage is you can control the quantity and kind of pesticides and herbicides used on the foods you consume. In fact, mechanical control is easily used in the small garden - picking off insects, washing with strong water sprays and soaps, and using beneficial insects to control the "bad" ones. Another advantage is to grow unusual varieties not available in stores.


Edible landscaping is as old as gardening itself and has undergone a recent revival. Edible components were largely lost in residential settings over the years due to the overuse of ornamentals and trees, which provide too much shade for fruits and vegetables. A large vegetable garden did not fit in with the urban residential covenants where ornamental landscaping prevailed.


Ideas for edible landscapes include: Pots of herbs on the patio; cherry tomatoes in a container that gets plenty of sun; an arbor with grape vines; a fruit tree planted in the corner of your yard - dwarf varieties are great for a small area; rows of lettuce, spinach, or radishes planted in a flower bed before it gets too hot; blueberry bushes are beautiful ornamentals and will supply you with berries in their third year; strawberry plants make great groundcovers; herbs tucked in among your borders; many varieties of pepper are beautiful and edible too; nasturtium, violas (fall), borage, calendula flowers can be included in salad; petals of daylilies can be eaten; The general rule to follow is to have at least six hours of sun to be successful with edibles.


The possibilities for edibles in your garden are endless. By incorporating just one or many edible plants into your landscape, you can develop a new relationship with your yard and the food that you eat.


For more information, see the Oklahoma Garden Planning Guide for timing of planting or read Ohio's Extension publication on Edible Gardening.

Mulch...What, When, Why and How    

Mulching Oklahoma garden soils is one of the most valuable cultural practices of gardening. Besides giving the landscape a more natural and appealing appearance, the benefits mulch are many. First, a layer of mulch blocks sunlight from reaching the soil surface, helping keep weed seeds from germinating and minimizing weed growth, and thus, eliminating the need for cultivation. Mulch also regulates soil temperature and moisture levels, keeping it cooler in summer and warmer in winter, along with reducing water loss due to evaporation. As mulch decomposes, it adds beneficial organic matter to the soil, which helps increase water absorption and retention in the soil. Finally, mulching around the trunks of trees and shrubs protects them from lawn equipment damage.


Several materials are readily available that are suitable for use in the home garden. These include, but are not limited to: pine bark, pine straw, old hay, sawdust, cotton burrs, grass clippings, leaves (if shredded or composted), and compost. Suitable organic mulch materials include those that will decompose within a season and do not contain undesirable quantities of viable seeds and harmful disease organisms or pests. Organic materials should be dried before use. Old or composted materials are preferable as fresh or "green" materials may form molds or slime and repel water.


Mulches must be thick enough to block light to be effective. Using coarse materials (e.g. bark) requires a 3- to 4-inch layer while fine materials (e.g. grass clippings) can be applied in 1- to 2-inch layers. When mulching trees and shrubs, do not pile mulch up against the tree trunk as that can allow insects, diseases and rodents to damage the base of the tree. A desirable mulch pattern should look like a "doughnut" around the tree trunk, not a "volcano".


One final tip; as with everything else in gardening, timing is important. Mulching too early in the spring can prevent the soil from warming sufficiently for some plants. In the fall it is recommended that new mulch not be placed onto warm soil as it will delay the natural cooling and development of dormancy, potentially allowing new cold sensitive growth to occur. Ideally, mulch after the first few frosts but before a hard freeze.


Spend a little time mulching your garden and flower beds, and it will pay big dividends in return. For more information click here


 Special Thanks   

The 2012 Greater Tulsa Home and Garden Show was well attended again this year and the Tulsa Master Gardeners booth was simply outstanding. Many hours and hard work went into the design and set-up of the show booth by our own Tulsa Master Gardeners, and we thank them. But, also, we need show our appreciation to our business partners, the "Friends of the Master Gardeners" - those vendors that contributed to the success of our booth. Without them, our booth would not be possible and we sincerely appreciate their contributions. Those vendors that contributed to our booth this year include:


Colebrook's Nursery

The Garden Trug

Hardscape Materials

Kimberly Clark


Midland Vinyl Products

Midwest Block & Brick

Rocks of Character

Sander's Nursery
Southwood Landscape & Nursery

Tulsa Zoo

Whole Foods


Question: My cucumbers had powdery mildew last year. Is there any way to prevent this?       

Answer: Powdery mildew is a common plant fungus. Many varieties of vegetables, such as grapes, squash and cucumbers, are susceptible. Ornamentals commonly affected are crapemyrtles, crab apples, euonymus, lilacs, roses, photinia and zinnia.   


The fungus appears as a powdery white or gray coating on leaves and stems, hence its name. It prefers warm days and cool humid nights when dew is likely to form-conditions found in the spring and fall. PM is mostly plant specific, unlikely to spread from crapemyrtles to cucumbers.

Powdery mildew prefers to infect new growth in plants and may cause leaves and stems to twist and distort, but plants usually survive. In vegetables it reduces production and may alter the overall taste because of the stress to the plant.

The best approach to control is prevention. Many plant types at risk have PM resistant varieties that should be selected. Other ways to help prevent any fungal leaf disease is by pruning to improve air circulation. Also, if the leaves are kept dry, this discourages any fungus growth.

Water bases of plants, not leaves. It is best to water all landscape plants, including lawns, in the mornings so they will be dry by nightfall. Most fungi grow best at night. If an infection does develop, prune out and remove the infected parts from your landscape promptly.

Garden centers have many effective fungicides labeled for PM; however, they will only prevent new disease. Once the disease is established, no chemical will cause it to disappear.

Remember, you will end up eating any chemical you spray on vegetables. For your health's sake, make sure the product is labeled for vegetables if you intend it for this use.

Many garden books and Web sites mention the use of baking soda for PM. Studies have been mixed about its use and found it was best when combined with horticultural soaps or oils. Plant damage occurred when too much soda was used. So, as much as one would like to use a simple safe kitchen product, be wary of possible risks to your plant.


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