Soil Temperatures Are Key to Spring Vegetable Garden Success

Starting a Vegetable Garden in Spring

Tom Ingram: Ask a Master Gardener

Sunday, March 31, 2019

Q: It’s so nice outside, am I safe to start my vegetable garden now? CT

A: Oftentimes, people will suggest certain dates when you can plant your vegetable garden. But dates are only guidelines. To know for sure when we 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 the time 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 potatoes is based on when the soil temperature is appropriate for planting.

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 at a depth of 4 inches are hovering around 51 degrees. So we’re just entering optimal conditions for potato planting.

Cold soils also inhibit seed germination of some of our more popular vegetables, such as tomatoes, squash, cucumber or peppers. To overcome this challenge, it is common for gardeners to start seeds indoors so the plants will be ready to go outside 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 them out in the sun. But if we move them outside too early, we run the risk of a late freeze damaging our fragile new plants. In northeast Oklahoma, we typically say we should be safe after April 15, which is still a couple of weeks away. But it’s not unusual for us to have a late freeze. Last year, we had one night with a low of 28 degrees the first week of April, so if you jump the gun, be ready to spend some time covering your plants.

Sometimes, talking about the need to find out what your soil temperature is at various depths can be a little intimidating. But don’t let that scare you off. 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 mesonet.org for an abundance of weather information, including rainfall and soil temperatures.

For more information on starting and growing vegetables, visit the “hot topics” section on our home page to find a link that will take you to an abundance of information to help you be a more successful vegetable gardener.

Garden tips

• Our annual spring educational Lunch & Learn classes at the Tulsa Central Library downtown have begun.
• One of our most anticipated events is currently underway: The Master Gardener Plant Sale. You can choose from more than 200 plants, including annuals, perennials, grasses, herbs, tomatoes, succulents and stepables.

To find out more information on any of these and other opportunities, visit our website at tulsamastergardeners.org.

Oklahoma Proven Selections for 2019

Oklahoma Proven Selections for 2019

Allen Robinson: Ask a Master Gardener

Sunday, March 17, 2019

Q: Given our erratic weather patterns, is there a good way to know what plants, trees and shrubs grow well in our area? Sam R., Tulsa

Rattlesnake Master
MG Demo Garden

A: This is a good question that many people think about. And it’s a very 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? And also tell us where to plant them so they have the highest chance of success? Well, 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. The selections for 2019 are:

Annual: Star Flower (Graffiti® series) grows to 16 inches high and 12 inches wide, making it a great plant for containers or in a flower bed. They are very heat-tolerant, drought-resistant, make great cut-flowers and attract butterflies and hummingbirds throughout the summer months. Like all Pentas, Graffiti® prefers sun/heat, dry soil with good drainage but not too rich.

Perennial: Rattlesnake Master is a native species to the tallgrass prairies. Leaves are parallel-veined, bristly-edged and sword-shaped, with medium green leaves (up to 3 feet long) resembling those of yucca. Flowers are greenish-white and tightly packed into globular, 1-inch diameter heads resembling thistles. It prefers dry, sandy soils and is best left undisturbed once established. Perfect for a xeriscape garden, perennial border or native garden. Group plants in naturalized areas for the best effect.

Shrub: Flowering Quince (Double Take™ series) are hardy, deciduous shrubs reaching 4 to 5 feet high and as wide. It produces a profusion of early spring double flowers that resemble camellias. A thorn-less shrub with bold 2-inch double flowers, it comes in colors of scarlet, orange, pink and peach. Does not produce fruit. Very drought tolerant. If needed, prune lightly after it blooms in spring.

Tree: Limber Pine (“Vanderwolf’s Pyramid”) is an evergreen tree with a pyramidal habit that typically grows 2 to 30 feet tall and 10 to 15 feet wide. It is noted for its closely spaced, twisted, silvery blue-green needles. Being native to North America, it is an adaptable, low-maintenance tree with few problems, including being resistant to pine wilt disease.

Note: All of these plants do well in the Tulsa metropolitan area whose USDA Hardiness Zone is 7A (average low temperature of 0 to 5 degrees).

The Oklahoma Proven program has been in existence since 1999. The best part is that you can find every year’s selection back to 1999 online at oklahomaproven.org.

Remember that all plants need special attention during the establishment phase or during periods of environmental extremes. So be sure to give them some TLC until they get established. Then, watch them succeed!

While nothing in nature is guaranteed, you can significantly improve your odds by choosing Oklahoma Proven varieties.

Garden tips

• Remove flowers from spring-blooming bulbs after blooming is completed. This will allow the plant to direct its energy into its bulb for next year's blooms, rather than producing seeds. But allow foliage of these bulb plants to die and turn brown naturally before removal. As long as the leaves are green, they are storing energy for the following year. Fertilize them at the time of planting, in the fall or in the spring when their leaves first emerge.

• Cool-season lawns, such as bluegrass, fescue and ryegrass, may be fertilized now with the first application of the season. Usually, four applications of fertilizer are required per year in March, May, October and November. Never fertilize these lawn grasses in summer.

• Start your routine fruit tree spray schedule prior to bud break. Contact the Master Gardener office for a document outlining recommendations for all fruit tree types as they are not all the same.

Master Gardener’s Educational Programs Can Help You Succeed in the Garden

Master Gardener’s Educational Programs Can Help 

Brian Jervis: Ask a Master Gardener

Sunday, March 3, 2019

Q: After a few years of gardening, I am not happy with the results I am getting. How do I “up my game” so to speak? JF

A: That is a good question, and it is one experienced gardeners also deal with. We buy the plant, we do our best, and it still doesn’t thrive. Why?

There are a variety of factors that contribute to your success or failure.

• Did the plant get too much sun?

• Did the plant not get enough sun?

• Did the plant get too much water?

• Did the plant not get enough water?

• Was the soil chemistry appropriate for the plant?

• Did I fertilize properly and with the correct ingredients?

The list goes on and on, and we are not going to be able to cover the variety of variables in a single article.

But what we can do is tell you about all of the opportunities we have this spring for you that can help you become more successful.

First of all, our ever-popular Urban Gardener classes begin March 14. There are six classes on consecutive Thursday evenings where we will cover topics such as plant botany, pollination, composting, soil science, growing vegetables, pollinator gardens, shrubs and trees, and turf. These are fairly in-depth classes for beginners and those wanting to “up their game” as you said. The series costs $40 or you can sign up for individual classes for $10 each. If you are interested, you can sign up on our website.

Next, we have our Lunch & Learn classes at the Tulsa Central Library. For six Tuesdays from 12:10-12:50 p.m. starting March 26 we will have classes covering spring garden tips, tomatoes, fruit trees, pollinator gardens, seed saving and composting. Did you know the Central Library has a seed library where you can check out seeds? Find out about this and a variety of other topics in these free classes. Bring your lunch and learn from the Tulsa County Master Gardeners.

Can’t decide what plants to add to your garden this spring? Each year, we offer a huge selection of Master Gardener-approved flowers in our online plant pre-sale fundraiser. We have more than 200 annuals, perennials, herbs, tomatoes and grasses. Plus, this year we added succulents, steppables and a “sort” for pollinator plants so you can build your own pollinator garden. The shopping is easy (online) and when plant pick up day comes (April 18) you can drop by the Exchange Center at Expo Square, pick up your plants (we’ll even load them in your car for you) and shop a special selection of plants available in our one-day pop-up plant store. We will have a lot of milkweed available so you can do your part to help support the Monarch population this year.

More information is available for all these opportunities on our website: tulsamastergardeners.org.

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 should be applied by the middle of March.
• Divide and share with friends and replant overcrowded summer- and fall-blooming perennials.