April HortTips


David Hillock, Consumer Horticulturist

 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.  (EPP-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.


  • 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.

Landscape - General

  • Hummingbirds arrive in Oklahoma in early April. Get your bird 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.


  • 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.
  1. Zoysiagrass: 3 lbs N/1,000 sq. ft.
  2. Bahiagrass: 3 lbs N/1,000 sq. ft.
  3. Buffalograss: 2 - 3 lbs N/1,000 sq. ft.
  4. Buffalograss/grama mixes: 3 lbs N/1,000 sq. ft.
  5. Bermudagrass: 4-6 lbs N/1,000 sq. ft.
  6. Centipedegrass: 2 lbs N/1,000 sq. ft.
  7. St. Augustinegrass: 3-6 lbs N/1,000 sq. ft.

When using quick release forms of fertilizer, use 1 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.


  • 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.

 Garden Planting Guide for Warm-Season Vegetables


Time to Plant*

Days to Harvest

Method of Planting

Bean, Lima

April 15-30



Beans, Green or Wax

April 10-30



Beans, Pole

April 10-30




May 1-20


Seed or Plants


April 10-30 or later


Seed or Plants


April 10-30




April 10-30 or later




April 10-30 or later




April 10-30



Southern Pea

May 1-June 10



Squash, Summer

April 10-30 or later


Seed or Plants

Squash, Winter

May 15-June 15


Seed or Plants

Sweet Corn

Mar. 25-April 30



Sweet Potato

May 1-June 10




April 10-30




May 1-20




*These dates indicate planting times from southeast to northwest Oklahoma. Specific climate and weather may influence planting dates. For cool-season vegetables, the soil temperature at the depth where the seeds are planted should be at least 40°F.


Malarie Gotcher, Extension Associate and Justin Quetone Moss, Assistant Professor

Water issues are becoming more prevalent throughout Oklahoma. Over 30 to 50 percent of household water use is consumed outdoors and many homeowners and businesses are uncertain about how to manage water in the landscape. This Extension Educator In-Service training opportunity will provide extension educators with the tools they’ll need for homeowner education. The training will cover plant selection, irrigation and landscape maintenance, and development of municipal water conservation programs. The training will be held on April 15 from 10AM to 4PM at The Botanic Garden Educational Building in Stillwater. Contact Dr. Moss at for more information.

Malarie Gotcher and Justin Quetone Moss

Faculty and staff from the Oklahoma State University Horticulture and Landscape Architecture Department and the Oklahoma Cooperative Extension Service worked together to create a new publication titled Drought-Tolerant Plant Selections Guide (E-1037) which describes appropriate plant material selections for Oklahoma landscapes that homeowners, businesses, and educators can easily utilize. The guidebook includes color photographs of plant selections, light and soil pH requirements along with mature plant size and seasons of interest. It is available for purchase for $12 by visiting: A companion guide was created as a reference plant list for educators. Fact Sheet HLA-6444 lists the common name, scientific name, mature height and width, light requirements, season of interest and comments associated with each plant.

To help homeowners in the urban environment, A Guide to Saving Water in the Landscape (E‑1038) is also available. This guide discusses the seven principles of landscape water saving and touches on water runoff management and reuse. Additionally, for easy use at the extension office, a series of leaflets covering the seven principles of landscape water saving, landscape design examples and general lawn tips are available.

  • L-431 – Landscape Planning
  • L-432 – Seasonal Landscape Maintenance
  • L-433 – Plant Selection Factors
  • L-434 – Irrigation
  • L-435 – Improving Soil Quality
  • L-436 – All You Need to Know about Mulch
  • L-437 – Turfgrass Management in Oklahoma
  • L-438 – Water Saving Design Ideas for Oklahoma Landscapes
  • L-444 – Lawn Watering Tips


by David Hillock

Annual flowers live only one growing season, during which they grow, flower and produce seed, thereby completing their life cycle. Annuals must be set out or seeded every year since they don't persist. Some varieties will self-sow or naturally reseed themselves. This may be undesirable in most flowers because the parents of this seed are unknown and hybrid characteristics will be lost.  In addition, plants may be scattered everywhere instead of their designated spot. Examples are alyssum, petunia and impatiens. Some perennials, plants that live from year to year, are classed with annuals because they are not winter-hardy and must be set out every year; begonias and snapdragons are examples. Annuals have many positive features. They are versatile, sturdy and relatively cheap. Plant breeders have produced many new and improved varieties. Annuals are easy to grow, produce instant color, and most important, they bloom for most of the growing season.

There are a few disadvantages to annuals. They must be set out as plants or sowed from seed every year, which involves some effort and expense. Some plants require old flower heads to be removed on a regular basis to ensure continuous bloom. If they are not removed, the plants will produce seed, complete their life cycle and die. Many annuals begin to look disreputable by late summer and need to be cut back for regrowth or replaced.

Annuals offer the gardener a chance to experiment with color, height, texture and form. If a mistake is made, it's only for one growing season. Annuals are useful for filling in spaces until permanent plants are installed, acting as a temporary groundcover. Annuals can also be used to extend perennial beds and fill in holes where an earlier perennial is gone or the next one has yet to bloom and to cover areas where spring bulbs have bloomed and died back. Many annuals work well to fill planters, window boxes and hanging baskets. Many planters are moveable, providing the opportunity to move the display around the landscape if desired. A number of annuals can also be used as cut flowers, for both dried as well as live arrangements. Species like gomphrena, angelonia, celosia, and Melinus (Pink Crystals Ruby grass) are just a few of the many species that hold up well in flower arrangements.

One of the most common uses of annuals is mass plantings. Planting beds with annuals allows you to create some fantastic displays, basically a living bouquet of flowers. Use several species and cultivars to provide season long interest and genetic diversity to reduce potential pest problems when planting beds with annuals.

The best time to plant most annuals is after danger of frost has past in the spring; for most parts of Oklahoma that would be around the middle of April, but will depend on where you live and the current weather patterns. For annuals that are considered warm-season plants, such as Catharanthus or annual vinca, it is best to wait until soil temperatures reach the mid-60s before planting them; in the northern part of the state that may mean waiting until after May 1.

State Fair Horticulture Contest ID Sheet and Placing Card on Website
Shelley Mitchell, Extension Associate, 4-H Youth and Development

The updated specimen identification sheet for the annual Oklahoma State Fair Horticulture Judging Contest is now on the OSU Horticulture and Landscape Architecture Department website ( under Research and Outreach/Community and Youth/4-H Projects and Contests. The identification sheet has been modified to be less confusing to new competitors, and the list of specimens will not change for the foreseeable future. An example placing card is also posted on the same site, along with a completed example, to assist with training purposes. Training materials for the contest can be found at The 2014 Horticulture Judging Contest will take place on Saturday, September 13, 11:00 AM, at the Oklahoma County Extension Office, 930 N. Portland, with registration starting 30 minutes before the contest.

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. For the first time in AAS history, the organization is recognizing regional performance and granting an AAS Regional Winner designation to five new winners.

The Regional Winners are:

  • Penstemon ‘Arabesque Red’ F1 (Heartland, Mountain/Southwest and West/Northwest)
  • Sunflower ‘Suntastic’ F1 (Great Lakes)
  • Cucumber ‘Pick a Bushel’ F1 (Heartland and Great Lakes)
  • Pumpkin ‘Cinderella’s Carriage’ F1 (Southeast, Great Lakes and Mountain/Southwest)
  • Tomato ‘Mountain Merit’ F1 (Heartland)

 The entries that did well in a majority of regions are designated as traditional National Winners and those are:

  •  Angelonia Serenita™ Pink F1
  • Bean Mascotte
  • Gaura Sparkle White
  • Impatiens New Guinea Florific™ Sweet Orange F1
  • Ornamental Pepper NuMex Easter
  • Osteospermum Akila® Daisy White F1
  • Petunia ‘African Sunset’ F1
  • Pepper ‘Mama Mia Giallo’ F1
  • Tomato ‘Chef’s Choice Orange’ F1
  • Tomato ‘Fantastico’ F1

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: 

A complete list of all AAS Winners since 1932 can be found here: 

NEW! Website feature: AAS Winners are now sortable by either National or Regional Winners. Prior to 2014, all Winners were National Winners.

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.



Herbaceous Plant Materials Conference

  • July 17, 2014
  • Wes Watkins Center – Stillwater, OK

 Greenhouse Production Conference

  • September 11, 2014
  • Wes Watkins Center – Stillwater, OK


  • September 20, 2014; 10 AM – 4 PM
  • The Botanic Garden at OSU – Stillwater, OK

 The Botanic Garden’s Annual GardenFest brings together individuals from across the state with a common interest in gardening and sustainable living for a day of educational workshops, tours and activities for the whole family.  It is also a wonderful opportunity to view the beautiful landscapes and innovative demonstrations throughout The Botanic Garden at OSU while experts are on hand to answer questions.  Live music and vendors will be featured along with our educational programming.

 Global Horticulture Conference

  • November 6, 2014
  • Wes Watkins Center – Stillwater, OK

For more information about upcoming events, please contact Stephanie Larimer at 405-744-5404 or

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