Weather Stats for Gardeners

Soil Temperature 2" below sod:   

81 degrees 

Rainfall total last 30 days:  

3.82 inches

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Butterflies

How to Take a Soil Test

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Garden  

• You have until the end of September to plant cool-season vegetables such as spinach, leaf lettuce and radishes and until the middle of September to plant rutabagas, Swiss chard, garlic and turnips. See Fall Gardening Fact Sheet HLA-6009 for more information. 

Lawn

• Now and until mid-October is still the best time to over-seed or to establish cool-season grasses like tall fescue. Use a blend of three or more fescues or a mixture of fescue blend and Kentucky bluegrass. See article below for more information. Fescue lawns should be fertilized in September after it cools and again in November.   
• Preemergent herbicide application to prevent winter weeds should be completed by mid-September. Note: Do not treat areas that will be seeded in the fall. See article below for more information.   
• Last nitrogen fertilizer application of the year on warm-season grasses should be applied no
  later than September 15. Click here for lawn maintenance schedule.
• Winter broadleaf weeds like dandelion will begin to emerge in late September, which is also the best time to control them with a 2, 4-D type herbicide.
• Continue bermudagrass spray program with glyphosate products for areas being converted over to tall fescue this fall. See Controlling Weeds in Home Lawns.

Landscape

• Spring-flowering bulbs will arrive in garden centers and nurseries during September. Select early for best choices. They can be planted in October and November. Click here for planting guidelines. 
• Fall is also a good time to plant many ornamentals. Watch for specials at your nurseries. Click here for information on training young trees and shrubs. 
• Most trees and shrubs planted in the fall will outperform those planted in the spring. Be sure to mulch. Click here for planting guidelines. 
• Before bringing houseplants indoors, reduce the amount of light they receive by placing them in shade. Inspect for pests, then hose off with water, and spray with insecticidal soap or horticulture oil such as Neem before bringing inside. Repot root-bound plants.
• Plant cool-season annuals like pansies, ornamental cabbage or kale, snapdragons and dusty miller when temperatures begin to cool.
• Now is a good time to prepare and plant a new perennial wildflower garden. After the weather cools, plant or divide peonies, daylilies and other spring blooming perennials.   
• Twig girdler insects should be controlled if large numbers of small branches of elms, pecans, or persimmons are uniformly girdled from the tree and fall to the ground.  

Fescue lawns struggle in the Oklahoma heat, especially in a summer like this one. Most homeowners will need to reseed areas which have died due to heat or disease. Mid-September through mid-October is the ideal time to do this.

The process of reseeding involves selection of seed, soil and site preparation, planting and post-establishment care. A soil test in advance of this process is strongly recommended.

Many good varieties are available, but no one variety is considered best. Rather a blend of 3 or more fescue varieties should be used either alone or mixed with 10% of a blend of Kentucky Bluegrasses. The use of several varieties of grass seed adds diversity and one grasses strength will cover another's weaknesses.

Preparing the seed bed is the greatest challenge. In a new lawn, all weeds, especially Bermuda grass, must be removed. For Bermuda this means spraying with glyphosate (found in Roundup and others) at 1-2 week intervals for 2-3 times.

After removal of weeds the soil must be cultivated either by hand or with a machine. Untilled soil has a crust that prevents root establishment of newly sprouted seeds. Machines such as a rototiller, verticutter or power rake are very useful. They may be rented.

Amendments such as organic compost and fertilizer nutrients indicated by the soil test should be added when tilling. If the soil test pH indicated a need for either lime or sulfur to adjust acidity, this is also the time to add those elements.

Sow seed according to the labeled directions on the bag. Do not develop the "more is better" philosophy; sowing too densely will prevent good growth of the seedlings. After sowing, gently rake the seeds to cover with about 1/8 inch of soil.

The planted area must be kept moist, or the seed will not germinate nor survive after germination. Water frequently and shallowly for the first 2-3 weeks, then water less frequently and deeper afterward. Try to wet the soil to 6 inches after the grass is about 2 inches tall. Mow with a sharp bladed mower when 3 inches tall, removing 1/3 of the top.

For more information , see Seeding and Reseeding Fescue Lawns and the Fescue Maintenance Calendar. 

Well, haven't the last two summers in Tulsa been a real party, with record setting heat both years PLUS a pronounced lack of moisture (in both summers as well as last winter)! Prolonged rainless spells coupled with high temperatures, intense sunlight and dry winds place severe stress on our trees. A common early symptom of stress or injury is marginal leaf burn or trees prematurely losing their leaves. While this may look like a dying tree, it may simply be the tree going dormant.

Drought or insufficient water is the most obvious cause of stress in trees. While young trees are affected quicker, recurring summer droughts can severely impact even old, long established trees. An important fact to understand is that the root system of a tree is not a mirror image of the trunk and branches. Most roots are shallow, in the upper 12 to 18 inches of the soil, especially the finer roots doing the critical work of taking up water and nutrients. This is the area that needs the most moisture and the same area that dries out quickly during the type of summer we have recently experienced.

So, what to do? First, don't immediately assume the tree is dying or dead. Premature leaf drop is a tree's defense mechanism to protect itself from further injury and it may just be going into dormancy. Bend a few smaller limbs (the size of a pencil). If they bend and flex back, the tree is still alive. Or, scratch the surface of a few limbs. If you see green, moist tissue, the tree is still alive.  

Here are a few tips to help preserve both young and older trees:

• Trees need more water than lawns. During periods of drought, occasionally supplement with deep watering at the drip line (the ends of the branches) of trees, not near the trunk.
• Protect trees from construction injury. Adding, removing or moving dirt around trees as well as driving over or near the root system can have negative long-term effects. Remember that tree roots can easily extend over twice the distance of the branch spread. Further, simply altering water drainage across the root zone can also have a negative effect.
• Be extra careful during transplanting. Root damage can easily occur. And, remember that too much water can be as damaging as too little water, suffocating the roots and preventing necessary oxygen absorption that tree roots need. The best time for transplanting is mid to late fall, as this allows time for root strengthening before next summer arrives.
• Avoid chemical damage due to careless application of weed killers.
• Deep root feeding in the fall/early winter will help to strengthen the root system over the winter and overall tree vitality. Larger trees should be treated by a certified arborist.
• Finally, select only native or proven tree species known to thrive in our region. The chances of survival increase significantly.

Click here for help identifying drought stress. If you have any questions as to the health of your trees, a call to the OSU Extension Office or to a local certified arborist is recommended. A little TLC will go a long way to preserving your trees, so keep an eye on them during these stressful times and you will reap the benefits for years to come.

  Answer: Many lawns in our area are brown due to heat and drought stress. Bermuda and zoysia lawns enter dormancy and turn brown in these conditions, if not watered (see example above). They will green up when it cools and rains. Most fescue lawns, especially those in full sun, are brown-green even if watered. They may also survive and green up as it cools. However, fescue lawns which are not irrigated and are totally brown may very well be dead and will need reseeding. Reseeding fescue is best done from mid-September to mid-October.

Preemergent herbicides are used to prevent weed growth. They are used twice yearly-in early spring to prevent crabgrass and summer weeds and from mid-August to mid-September to prevent annual winter weeds.

Three most popular and effective homeowner preemergents are dithiopyr (Dimension), pendimethilin (Halts) and prodiamine (Barricade). There are many brands that use these active ingredients and they should be available in local garden centers.

Most of these preemergents are marketed for use in the spring to prevent crabgrass, but are also effective against a host of fall germinating weeds, such as henbit and Poa annua. Henbit is the bright purple weed commonly seen in many lawns and roadsides in the spring.

These herbicides don't prevent seeds from germinating, but work by preventing new root growth in sprouting weeds. The downside to a preemergent is they may prevent new growth of the above ground stems of Bermuda and zoysia grasses. In healthy grass this is insignificant, but it may hamper full recovery of heat and drought stressed Bermuda and Zoysia after the temperature cools and water is available. Caution should be used in this situation and most labels of these products state that they should not be applied to heat stressed turf.

A "plan B" for weed control in Bermuda lawns not treated with preemergent herbicides this summer is to use glyphosate (found in Roundup and other brands), on green weeds during winter dormancy, normally in January through early March. Glyphosate cannot be used on zoysia or fescue lawns at any time.

Do not apply preemergents to fescue lawns which will need reseeding in September and October. Any preemergent applied now will prevent fescue seeds from germinating.

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