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April

Garden Tips

Vegetables

  • Wait a little longer for it to warm up before planting cucurbit crops and okra.
  • Plant vegetable crops in successive plantings to ensure a steady supply of produce rather than harvesting all at once.
  • Cover cucurbit crops with a floating row cover to keep out insect pests. Remove during bloom time.
  • Watch for cutworm damage and add flea beetle scouting to your list of activities in the vegetable garden.

planting_guide_april

Fruit and Nut

  • Don’t spray insecticides during fruit tree bloom or pollination may be affected. Disease sprays can continue according to schedule and label directions. (EPP-7319)
  • Control cedar-apple rust. When the orange jelly galls are visible on juniper (cedar), following a rain, begin treating apple and crabapple trees with a fungicide. (HLA-7319, EPP-7611)
  • Fire blight bacterial disease can be controlled at this time. Plant disease-resistant varieties to avoid diseases.
  • Continue spray schedules for disease prone fruit and pine trees.

Tree and Shrub

  • Proper watering of newly planted trees and shrubs often means the difference between success and replacement.
  • Remove any winter-damaged branches or plants that have not begun to grow. Prune spring flowering plants as soon as they are finished blooming. (HLA-6404, HLA-6409)
  • Control of powdery mildew disease can be done with early detection and regular treatment. Many new plant cultivars are resistant. (EPP-7617)
  • Leaf spot diseases can cause premature death of foliage and reduce plant vigor.

Flowers

  • Most bedding plants, summer flowering bulbs and annual flower seeds can be planted after danger of frost. This happens around mid-April in most of Oklahoma. Hold off mulching these crops until spring rains subside and soil temperatures warm up. Warm-season annuals should not be planted until soil temperatures are in the low 60s.
  • Harden off transplants outside in partial protection from sun and wind prior to planting.
  • Let spring flowering bulb foliage remain as long as possible before removing it.

Lawn

Warm-season grass lawns can be established beginning late April from sprigs, plugs or sod. (HLA-6419)

Fertilizer programs can begin for warm-season grasses in April. The following recommendations are to achieve optimum performance and appearance of commonly grown species in Oklahoma.

      - Zoysiagrass: 3 lbs N/1,000 sq. ft.

      - Bahiagrass: 3 lbs N/1,000 sq. ft.

      - Buffalograss: 2 - 3 lbs N/1,000 sq. ft.

      - Buffalograss/grama mixes: 3 lbs N/1,000 sq. ft.

      - Bermudagrass: 4-6 lbs N/1,000 sq. ft.

      - Centipedegrass: 2 lbs N/1,000 sq. ft.

      - St. Augustinegrass: 3-6 lbs N/1,000 sq. ft.

When using quick release forms of fertilizer, use one pound of actual nitrogen per 1,000 sq. ft. per application; water in nitrate fertilizers. (HLA-6420)

Mowing of warm-season lawns can begin now (HLA-6420). Cutting height for bermudagrass and zoysiagrass should be 1 to 1½ inches high, and buffalograss 1½ to 3 inches high.

Damage from Spring Dead Spot Disease (SDS) becomes visible in bermudagrass (EPP‑7665). Perform practices that promote grass recovery. Do not spray fungicides at this time for SDS control.

Grub damage can be visible in lawns at this time. Check for the presence of grubs before ever applying any insecticide treatments. Apply appropriate soil insecticide if white grubs are a problem (EPP-7306). Water product into soil.

Landscape - General

  • Hummingbirds arrive in Oklahoma in early April. Get your feeders ready using 1 part sugar to 4 parts water. Do not use red food coloring.
  • Keep the bird feeder filled during the summer and help control insects at the same time.
  • Lace bugs, aphids, spider mites, bagworms, etc. can start popping up in the landscape and garden later this month. Keep a close eye on all plants and use mechanical, cultural and biological control options first.
  • Be alert for both insect pests and predators. Some pests can be hand-picked without using a pesticide. Do not spray if predators such as lady beetles are present. Spray only when there are too few predators to be effective.
  • Schedule a group tour of The Botanic Garden at Oklahoma State University in Stillwater between the first of May and late October.

How Many Bedding Plants Do I Need?

David Hillock

Here is a simple way to avoid overbuying or underbuying the number of bedding plants you need for your flower beds. All it takes is some simple arithmetic. 

First, measure the area of your garden and calculate its square footage (width x length = square feet). If the area is irregularly shaped – oval, round or long and winding – a rough estimate is good enough.

Next, use the chart below to estimate the number of plants you will need. You will probably want to get at least a few more than you will need, just in case some are damaged by weather, animals or pests.

                        Recommended Spacing                    Number of Plants per Sq. Ft.

                                      6 inches                                                         4

                                      8 inches                                                         2.25

                                    10 inches                                                         1.44

                                    12 inches                                                         1

                                    18 inches                                                         .44

                                    24 inches                                                         .25

 

To figure out how many you actually need multiply the square footage of your bed times the number of plants per square foot based on the recommended spacing. For example, let’s say your flower bed is 125 sq. ft. and the recommended spacing for the plants you are buying is 10 inches. Multiply 125 (sq. ft.) x 1.44 (number of plants per sq. ft. for 10 in spacing) = 180. You will need to buy approximately 180 plants for your bed.

Water Test

Michael Kress and Justin Quetone Moss

Late winter and early spring is a great time to prepare for the heat of summer.  Summer in the yard means you will probably need a lot of water for your lawn and garden.  Now is the time to get your water tested.  You can take a water sample to your county extension office for irrigation testing.  The test results will explain how suitable your water is for the purpose of watering plants, and your extension personnel can explain your irrigation options.  With this information in hand you have sharpened another gardening tool in preparation for summer yard season.

The recent water problem in Flint, Michigan is a reminder that water matters.  Fortunately, your irrigation water report has some drinking water parameters.  These values are nitrate, sulfate, chloride, pH, and hardness.  Hard water can help protect water from lead.  Lead solder in the pipes of older homes becomes harmless when coated by calcium deposits from hard water.  Regardless, if you use private well water, you should get your drinking water tested for lead and fecal coliform annually.  County extension is not set up for this kind of testing; instead, contact the Oklahoma Department of Environmental Quality lab toll free at 1-866-412-3057, and they can tell you how to submit your water sample for lead and fecal coliform testing.  The cost of testing is small and helps insure a summer of fun instead of tragedy.

Lawn Fertilizer Tips

Michael Kress and Justin Quetone Moss

April should be a good lawn and garden prep month with plenty of planting, weeding, and fertilizing.  The actions you take now will pay off later for your garden and the environment.  So, when you get ready to fertilize your lawn and landcape, remember the big do’s and don’ts.

 

Don’t guess.................................................... Do soil test

Don’t use heavy fertilizer treatments............ Do split fertilizer applications

Don’t over fertilize acidic soil....................... Do lime

Don’t fertilize dormant grass......................... Do fertilize growing grass

Don’t fertilize walkways............................... Do fertilize soil

Keep fertilizer in the soil and out of waterways.  This will help minimize algal blooms later in the summer.  Enjoy your green lawn, your fruitful garden, and your clear pond.  For additional help, contact your county extension office; we’re here to help. 

Summer Weed Control:  Preventing Unnecessary Mowing

Dustin Harris and Justin Quetone Moss

Although you may have already noticed annual weeds popping up in your landscape, it is not too late to prevent the troublesome grassy weeds that cause homeowners to mow more frequently in order to maintain a manicured lawn.  Pre-emergent herbicides such as prodiamine, dithiopyr, and pendimethalin will prevent most grassy weeds from infesting lawns. Many broadleaf weeds have already emerged.  These weeds can be treated throughout the growing season with a selective herbicide.  Broadleaf herbicides often include dicamba, 2,4-D (2,4 dichlorophenoxyacetic acid or a related chemical), and/or MCPP (mecoprop).  Proper application timing is necessary to prevent slow green up of bermudagrass lawns due to herbicide injury.  As always, read the herbicide label and only apply according to directions. Grassy weeds can be more expensive and difficult to treat once emerged. Grassy summer weeds such as crabgrass and goosegrass are very difficult to control after emergence.  Furthermore, the more mature the target plants are, the more difficult they are to control.

Elimination of these weeds before they fully mature enables landscapes to be maintained less rigorously, more efficiently, and with more aesthetic value.  Save yourself from unnecessary mowing during the heat of the year by performing an easy task now.

Are My Peaches Going to Make This Year?

Becky Carroll

I often hear people say “my peach tree still has nice blooms so I think we missed the freeze damage”. Having pretty petals after a freeze event doesn’t mean that you will have pretty peaches or perhaps, any peaches.  Peaches and other stone fruits bloom early and are often susceptible to damage caused by freezing temperatures. The temperatures that the fruit can withstand is dependent on the stage of the fruit development and also the health of the tree.

A dormant peach bud is more cold hardy than a fully open bloom. A fully dormant bud can withstand 30 minutes of temperatures at -12°F and have a loss of about 10% buds; at -18°F, 90% of dormant buds will be lost. This is when the tree is healthy and going into the winter under ideal conditions. On February 10, 2011, temperatures plummeted to -13°F at the Cimarron Valley Research Station. The peach trees had been under drought conditions for 2010 and 2011 and were stressed. After the freeze event, buds were killed and the entire crop was lost.

As the buds develop, they become more sensitive to freezing temperatures. At full bloom 10% kill will occur at about 27°F; and 90% crop loss at 24°F. Average full bloom at the research station at Perkins is March 20-25. The frost free date at that location is about April 15. That is 3-4 weeks for potential damage after bloom. We’ve lost crops even into early May with an extremely late freeze event. This year, Oklahoma has experienced very warm winter and spring temperatures, advancing the bud development even earlier than the normal mid-late March timeframe. Full bloom at Perkins this year was about March 7 almost 2 full weeks ahead of schedule. This opens up the possibility for more exposure to potential damaging temperatures. Looking at Mesonet temperature data, Perkins has recorded 29°F three times since the 7th, but damage may have occurred from a low temp of 23°F in late February.

Peach trees typically set far more buds than can be produced properly. Some bud loss will benefit with the need to crop load thin, but the ability to select the number of fruit to remain on the tree is best left up to us rather than hope the freeze does a good job but not too good. A peach about every 4-6 inches or even spaced at 8-10 inches will make for a full crop of well sized peaches.

About 24 hours after a freeze event, fruit buds or blooms can be assessed for damage. If the flower bud is dissected, you can see the different parts. If any of the parts are damaged, the fruit will not produce properly. If any part of the pistil (stigma, style or ovary) or stamen (anther, filament) show browning or if the ovary is soft instead of firm, the fruit will not make. I’ve seen some with ovaries that are bright green but the stigma and style are dried up. A good indicator is by cutting the flower in half and looking at the color of the ovary. A bright green or white is good, slight browning or dark brown is bad. You can assess the damage by cutting a number of flowers and determine the percentage alive. Remember if you have 10 - 20% of the good flowers, that may be enough to have a full crop.

I’ve included a link to CRITICAL SPRING TEMPERATURES FOR TREE FRUIT BUD DEVELOPMENT STAGES - http://msue.anr.msu.edu/uploads/files/PictureTableofFruitFreezeDamageThresholds.pdf. This page shows the development stages and temperatures that are important for each growth stage for apples, pears, apricots, peaches, plums, sweet and sour cherries. This is from Michigan State and Washington State publications.

All-America Selections (2015 Regional and National Winners)

David Hillock

All-America Selections (AAS) judges have again finished a rigorous year of trialing and now the

AAS Board of Directors is pleased to announce the newest AAS Winners. A couple years ago the organization began recognizing regional performance; the entries that did well in a majority of regions are designated as traditional National Winners.

In 2016, twelve plants made it on the National Winners list with 10 vegetables and 2 flowers. Vegetable selections include a cabbage (Cabbage Katarina), kale (Prizm F1), kohlrabi (Konan F1), mizuna (Red Kingdom F1), pumpkin (Pepitas F1), two pepper varieties (Cornito Giallo F1, Escamillo F1), two tomatoes (Candyland Red, Chef’s Choice Green F1), and a strawberry (Strawberry Delizz® F1); the flowers include two geraniums (Brocade Cherry Night, Brocade Fire).

The Regional Winners include an additional six plants, four vegetables and two flowers, all of which did well in the Southeast Regional category. Winners include an onion (Bunching Warrior), pepper (Flaming Jade F1), pumpkin (Super Moon F1), and radish (Sweet Baby F1) as the vegetables and ornamental pepper (Black Hawk), and salvia (Summer Jewel™ Lavender) as the flowers.

All of these winners were trialed next to similar varieties that are currently on the market. The

AAS Judges do a side-by-side analysis of growth habit, disease resistance and more to determine if these entries were truly better than those already available to home gardeners. Only those flower entries with superior garden performance or the vegetables with superior taste and garden performance are given the AAS stamp of approval.

A complete list of trial grounds and judges can be found here: http://www.aaswinners.com/trial_grounds/index.cfm 

A complete list of all AAS Winners since 1932 can be found here: http://www.aaswinners.com/winners/index.cfm 

All-America Selections® was founded in 1932 and continues as the oldest independent testing organization in North America. Every year, new, never-before-sold varieties are trialed in our Trial Grounds and professional horticulturists determine which varieties will be deemed winners based on their garden performance. AAS relies upon a public relations program to inform gardeners about AAS Winners that are announced three times each year.

Planting Trees

David Hillock

To ensure successful tree establishment, the following planting techniques and methods should be used.

When to PlantThe best time to plant most trees is spring or fall; however, many containerized trees can be planted any time if handled properly. Plants installed during the growing season are susceptible to high transpiration rates leading to drying of plant tissues.

  • Early fall - best time for container-grown and balled & burlapped (B&B) trees.
  • Mid-February through early April - bare-root.

Handling Trees before PlantingAvoiding unnecessary damage and stress to trees prior to planting will insure better success.

  • Keep the rootball moist.
  • Handle the tree by the container, not by the trunk.

Preparing the Hole and Planting the TreePreparing the planting area properly before planting is very important.

  •  Do not apply amendments to backfill.
  • Dig the planting hole two to three times the diameter of the tree’s rootball and no deeper than the rootball itself.
  • Since most Oklahoma soils are clay, plant trees 1-3” above grade. Plant trees at original grade in sandy soil.
  • Do not put crushed stone or gravel in the bottom of the hole!
  • Remove the bag, container, and all strings and wires from the trunk! The burlap of B&B trees may be left on to decay. Be sure to lay burlap back away from trunk and cover with soil.
  • If roots are excessive and circling inner walls of the pot, score the outer edge of the rootball by slightly severing or scratching the root system. Do not cut deeply into the rootball.

Backfilling the Planting HoleFill in the planting hole (backfill) with native soil and tamp lightly. Soil amendments are not necessary and may result in further complications such as root rot.

FertilizingA new tree has a very limited capacity for utilizing fertilizer until it becomes established. Heavy fertilization is not recommended at the time of planting. Excessive fertilizer in the root zone can be damaging. If fertilizer must be used at planting or in the first growing season, apply a controlled-release or liquid fertilizer at the lowest labeled rate.

Watering the New TreeNewly planted trees should be watered well at the time of planting and during establishment. Natural rainfall is usually not adequate to provide the moisture needs of newly planted landscape trees.

Generally, young plantings need an equivalent of one inch of rain per week. Newly planted trees may need to be watered two or three times a week in extremely hot, dry, windy weather because their root systems cannot take up the amount of water needed to replenish the water lost through the leaves. Watch for signs of wilting as an indicator that the tree needs water.

Apply water slowly at the base of newly planted trees. This is especially important for container grown plants as their soilless mixes can dry while the bed or surrounding soil remains damp. If you have several young trees and shrubs, a drip irrigation system would be wise.

Be cautious not to overwater or the amount of oxygen in the soil will be lowered to a level that will damage roots. Make certain the timing and patterns of lawn watering systems are not overlapping into plant beds and too much water is being applied.

Mulching the New TreeNew trees should be mulched using an organic mulch 2‑4” deep and 5-6’ in diameter; keep mulch at least 2-4” away from trunk of tree. Do not mound mulch up against trunk of tree. The benefits of mulching are:

  • Create a weed and turf-free area.
  • Reduced plant competition for water and nutrients.
  • Regulate soil temperature and moisture.

Pruning the New TreeAvoid overpruning new trees. Leave the lower limbs intact if possible. Remove injured or diseased branches only. Overpruning may result in sunscald and inhibit tree growth.

Trunk Protective MaterialsProtective wraps provide physical protection against lawn mower and weed-eater damage.

Protective wraps also provide protection by regulating temperatures and bark moisture for thin-barked trees such as ash, birch, linden, and maple.

If misused, however, damage may occur from trunk girdling or constriction, insects, diseases and excessive moisture.

  • Protective wraps may not be necessary at planting time. Use wraps based on type of protection needed.
  • Normal application of tree trunk wraps is October – March for the first two growing seasons.
  • Remove wraps each spring prior to spring growth.
  • Wrap loosely from the base of the tree up to the first branch by overlapping for shingle effect.
  • Plastic guards should fit loosely and include holes or slits.
  • Inspect for damage and insects and spray for borers when necessary.

Staking TreesStake young trees sparingly and briefly when possible. In fact, prolonged staking can have detrimental effects on the development of the tree. Too often, staking materials end up injuring or girdling the tree.

Stake trees when top-heavy or planted in windswept areas. The material used to attach the tree to the stake should be broad, smooth and somewhat elastic. Do not stake the tree too rigidly. Always allow for sway. Tight or prolonged staking results in an overall weaker tree that is more subject to girdling. Triple staking provides more protection against strong wind and lawn mowers. Support stakes and guy wires generally should be removed after one growing season. If staking is left in place for more than two years the tree’s ability to stand alone may be reduced, and the chances of girdling injury are increased.

Bluff Creek Park Water Conservation Garden

Joshua Campbell and Justin Quetone Moss

In 2013 the Oklahoma Cooperative Extension Service and Oklahoma State University Department of Horticulture and Landscape Architecture partnered with the City of Oklahoma City Water Utilities Department to promote outdoor water conservation. Through this partnership plans to design and build outdoor water conservation demonstration landscapes were developed. These garden sites are intended to be spaces where Oklahoma City residents can visualize water conservation concepts and practices in action. Conservation garden areas and signage have been developed on the campus of OSU-Oklahoma City, at the Myriad Botanical Gardens, and at the Oklahoma City Zoo. The newest garden was installed at Bluff Creek Park in the fall of 2015. The water conservation garden at Bluff Creek Park is located in northwest Oklahoma City and a grand opening ceremony is scheduled for April 29, 2015. For more information about this project visit thinkwater.okstate.edu and watch this video:

https://youtu.be/ojD3urFvQXg?list=PLwFAYTiZB_PK1AZBLYxDbRKANCq6vgl63

Spring Water Conservation Seminars

Joshua Campbell and Justin Quetone Moss

The ThinkWater water conservation Extension program hosts water conservation workshops and seminars. This spring, ThinkWater will host a series of short seminars in Oklahoma City metro area libraries and at water conservation demonstration areas. These seminars will cover a range of topics related to landscape water conservation.

Scheduled workshops include:

Water-Wise Landscape Design – April 14, 2016

Looking to create your own water-wise landscape? Brent Wall, Professional Landscape Architect and Director of Landscape Architecture and Urban Design, will discuss proper landscape planning and design for Oklahoma. This free, one-hour class will help you learn to transform your landscape into a water conservation garden.

Water Conservation Basics – May 5, 2016

Water is an important resource. In Oklahoma we can experience both extreme rainfall and periods of drought. Because of this, it is important to understand water resources and the need to use them as efficiently as possible. Small indoor leaks can be huge water wasters and outdoor water use can account for as much as 50% of a household’s consumption. This free one-hour class will explore water saving tips to help you implement water conservation at home.

Sprinkler Systems and Lawn Watering – May 12, 2016 and May 26, 2016

Come learn the basics about automatic sprinkler systems and how to properly water your lawn. Whether you water with an irrigation system or a garden hose, we will provide helpful tips on watering efficiently. At this free one-hour class you will learn about affordable smart irrigation controllers, soil moisture sensors and rain/freeze sensors – simple technologies that can make a big difference in your water bill. You will also learn simple sprinkler repairs, the basics of controller programming –as well as all the programs offered by the City’s water conservation program and the resources available through the Oklahoma Cooperative Extension Service.

Plant talk with Oklahoma Gardening Host Casey Hentges at Bluff Creek Park – June 17, 2016

Come visit the Bluff Creek Park water conservation garden area and enjoy a picnic in the park while we discuss water conservation and drought tolerant plants with the Host of the Oklahoma Gardening television show – Casey Hentges.

To register for these free events, please visit www.thinkwater.okstate.edu and select the Workshops and Seminars tab.

Do Squash Cross Pollinate with Pumpkin?

Lynn Brandenberger

 Most years we receive questions regarding the need to keep different cucurbits separated to prevent cross-pollination.  This question has been asked by gardeners and farmers alike for decades, so much so that Dr. Dean McCraw (retired OSU horticulture specialist) wrote a Hort Tips article about it back in the 1980s.  What follows are Dr. McCraw’s responses to these on-going questions.

Information about cucurbit pollination and crossing comes from Hortus Third, Cornell University, Cucurbits.  1962.  Whitaker, T.W. and G.N. Davis.  Interscience, NY, NY.

In order to understand the genetic relationships that various cucurbits have to one another it is important to realize that this group of crops includes several subfamilies and genera with several species in a given genus.  Crosses can occur between varieties within the same species or between different species as given in the following diagram.

pumpkin_squash_crossing

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