Sunday, March 18, 2018 2 comments By: Ask A Master Gardener

Oklahoma Proven Selections for 2018

Master Gardener: Plants Proven to Grow Well in Oklahoma
Allan Robinson: Ask a Master Gardener
Sunday, March 18, 2018
Q: I want to invest in and plant plants that I know will do well in the Tulsa area, given our weather extremes. Is there a good way to know what grows well in our area? Sally M., Tulsa
A: This is a good question that many people think about. And it’s a reasonable request given the amount of labor involved in planting, as well as the cost of landscaping products these days. So, wouldn’t it be nice if someone had already done the research on which plants do best in our neck of the woods given our sometimes rather erratic weather conditions? And also tell us where to plant them so they have the highest chance of success? They have!
It’s called the Oklahoma Proven Program. Oklahoma Proven is an annual plant evaluation and marketing program coordinated by the Department of Horticulture and Landscape Architecture at Oklahoma State University. Designed to help consumers select the best plants for Oklahoma gardens, these plants are tolerant of the varied and difficult environmental conditions found throughout Oklahoma.
Every year, an annual, a perennial, a shrub and a tree are selected. So, the selections for 2018 are:
Annual — Supertunia Vista Bubblegum: a vigorous, self-deadheading petunia that requires little care once established. Their spectacular color can spill over the edge of a container or retaining wall or spread out in a flower bed. Exposure: Full sun to part shade. Soil: Moist, well-drained soil.
Perennial — Versatile Indian Pink: Also called Woodland Pinkroot, it is a native species to the southeastern United States. It grows in shady gardens or sunny locations. It prefers moist soils and is drought-tolerant once established. Use Indian Pink in a woodland garden, perennial border, rain garden or native garden. Exposure: Sun to part shade. Soil: Moist or dry soils. Hardiness: USDA Zone 5-9.
Shrub — Bush Clover: a hardy, semi-woody, deciduous shrub that can reach 4 to 6 feet high and at least as wide with arching stems. Rosy-purple flowers develop on new wood in late summer to early fall. Exposure: Sun to part shade. Soil: tolerates poor, infertile soil, but excellent drainage is essential. Hardiness: USDA Zone 6-10.
Tree — Zelkova Serrata: a deciduous tree with a vase-shaped habit that typically grows 50-80 feet tall and most often occurs in rich, moist woods and hillsides. It is noted for its graceful shape, clean foliage, attractive bark and resistance to Dutch Elm disease. Exposure: Full sun or light shade. Soil: Tolerates wide variety of soils. Hardiness: USDA Zone 5-8.
Note: The Greater Tulsa metropolitan area is in USDA Hardiness Zone 7A, which equates to an average low temperature of 0 to 5 degrees.
The Oklahoma Proven program has been in existence since 1999 and the best part is that you can find every year’s selection back to 1999 online at
Remember that all plants need special attention during the establishment phase or during periods of environmental extremes, which we have been experiencing more of in recent years.
Nothing is guaranteed, but you can improve your odds significantly by choosing Oklahoma Proven varieties.
Garden tips
  • If you had previous damage to the tips of pine tree limbs, especially non-native pines, it may be diplodia tip blight (a fungus) or Nantucket pine tip moth damage. Both are controlled with pesticides starting this month. Call the Master Gardener office at 918-746-3701 for recommendations.
  • Pre-emergent herbicide to control crabgrass and other summer weeds should be applied by the middle of March.
  • Divide, share with friends and replant overcrowded summer- and fall-blooming perennials.
  • One of our most anticipated events is currently underway: The Tulsa Master Gardener Spring Plant Sale. You can choose from 211 plants, including annuals, perennials, grasses, herbs and tomatoes. To shop online or find out more information on any of these programs, visit our website at

Saturday, March 10, 2018 1 comments By: Ask A Master Gardener

Prune Crapemyrtles in Late Winter, But Avoid "Crapemurder"

How not to commit 'crapemurder' on your crapemyrtles this spring

Brian Jervis: Ask a Master Gardener

Saturday, March 10, 2018

Q: How and when should I prune my crapemyrtles?

A: Crapemyrtles, along with all trees and shrubs, should only be pruned for a reason. The best time to prune these and other trees and shrubs is late winter or early spring, before leafing out. An exception to this time are the spring-blooming shrubs, such as azaleas and forsythias, which should be pruned after blooming, if needed. Delaying pruning of spring-blooming plants is only to preserve the flower buds formed the previous year.
There is a common belief by many that crapemyrtles should be pruned back to an ugly set of horizontal nubs in the spring time. Nothing could be further from the truth about good crapemyrtle care. Crapemyrtles should be allowed to let nature have its way and to grow to their full height.
Some people think that blooming will be increased by drastic pruning (many horticulturists call this “crapemurder”), but Dr. Carl Whitcomb, a retired OSU professor and developer of crapemyrtle cultivars, cites evidence that blooming is less, not more, with drastic pruning. Light pruning of endmost 12-18 inches, back to a lower limb, can increase numbers of blossoms. However, these plants were engineered by nature to bloom profusely without this type of pruning. In summer, one can promote a second wave of blossoming by pruning off old blossoms after they fade.
Reasons to prune crapemyrtles are to confine it to the space available or to improve the shrub’s shape and structure. Removal of dead or diseased limbs and elimination of internal crossing branches should be done anytime.
For those plants that are too big for their space, rather than trimming them back each year, consider removal and planting one of the smaller crapemyrtle cultivars. There are many sizes available, ranging from 18 inches to 25 or more feet when mature.
One question that sometimes arises relates to the seed pods left over in fall after blooming is completed. The plant will remove them naturally as they have been doing for thousands of years, and they need no pruning.
Another pruning suggestion one should consider with crapemyrtles concerns those plants with a multitude of trunks. These are best reduced to three to five trunks, which will not only have more curb appeal, but also will allow more energy to be directed toward further growth and blossom formation. To further improve appearance of these shrubs, consider removing the limbs from the lower third or half of the trunks.
Crapemyrtles are notorious for sending up shoots or sprouts from the base of the plants, especially in the spring. These should be removed by pulling off if able, or clipping close to the ground, if needed.
We have an advantage over our northern neighbors in being able to grow these magnificent plants, which are the mainstay of color in Tulsa during the summer. They deserve the best care we can give them, they should not be subjected to “crapemurder.”

Garden tips

  • Now is a good time to cut back your perennial ornamental grasses, such as pampus grass. Cut back to remove the dead grass, but avoid damaging new buds and early green growth at the base.
  • Begin planting blackberries, raspberries, strawberries, grapes, asparagus and other perennial garden crops this month. Contact Tulsa Master Gardeners at 918-746-3701 for specifics about these plants.

Sunday, March 4, 2018 1 comments By: Ask A Master Gardener

Guidelines for Planting Vegetables in Springtime

Spring Vegetable Planting
Tom Ingram: Ask a Master Gardener
Sunday, March 04, 2018
Q: When can I start my vegetable garden? MA
A: Oftentimes, people will suggest certain dates when you can plant your vegetable garden. But dates are only guidelines. To know for sure when you can plant, we must look at the weather and do a little investigation to determine soil temperature.
For example, oftentimes people will say St. Patrick’s Day is when to plant potatoes. There is no potato magic in St. Patrick’s Day, other than in a normal year you are probably OK planting on this day. The truth about when to plant is based on the best soil temperature for planting potatoes.
According to the OSU Extension, soil temps need to be above 50 degrees before we plant potatoes. At the writing of this article, soil temps are hovering around 46 degrees. So, we are getting close, and if the weather continues on as we expect, we will likely have a soil temp above 50 degrees by St. Patrick’s Day. But give us a few warm days and an expectation that spring is on the way and we could plant them sooner.
Peppers are easy to grow in Oklahoma and have the benefit of being a versatile crop. However, peppers are sensitive to temperature. Air temperatures of below 60 degrees or above 90 degrees can prevent fruit set, which can limit the growing window in Oklahoma.
So, how do Oklahoma gardeners get around this? Because cold soils do not encourage germination, it is common for gardeners to start seeds indoors so they will be ready to go when it warms up.
If you have been to any of the garden centers in northeast Oklahoma recently, you will have noticed racks of seeds and seed-starting supplies. Many of us have already gotten our seeds started and can’t wait to get these little ones in the ground.
But the time to plant these transplants still depends on soil temperature and when the danger of a freeze has passed. In northeast Oklahoma, we typically say that date is April 15. Many of us have a hard time waiting that long and tend to plant before that date. However, if you do, you should be ready to cover your plants if a late-season snow arrives.
Now, you may be saying, all this talk about soil temperature, how am I supposed to know that? In Oklahoma, we have a wonderful resource called the Mesonet. The Mesonet is a joint project between OU and OSU with at least one weather-monitoring station in each county.
You can visit for an abundance of weather information, including rainfall and soil temperatures. We also have an abundance of resources on our website to help you grow better vegetables.
Garden tips
  • Our yearly Urban Gardener classes begin March 15. Topics include plant botany, soil, growing fruits and vegetables, flowers, trees and shrubs, and turf.
  • We will also be conducting our educational Lunch & Learn classes at the Tulsa Central Library downtown beginning March 20.
  • One of our most anticipated events is currently underway: The Master Gardener Plant Sale. You can choose from 211 plants including annuals, perennials, grasses, herbs and tomatoes.
  • To sign up or find out more information on any of these programs, visit our website,