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.

Use Preemergent Herbicides Now to Prevent Crabgrass this Summer

Use Preemergent Herbicides to Prevent Crabgrass

Allan Robinson: Ask Master Gardener

Sunday, February 17, 2019

Q: When is the best time to apply preemergent herbicide to help control crabgrass? Johnathan W., Tulsa

A: Preemergent herbicides are definitely helpful in preventing weed establishment. They are used in early spring (mid-February through mid-March) to prevent crabgrass and other summer weeds. They also are useful in the fall (mid-August through mid-September) to prevent winter weeds such as henbit. Many of the herbicides will need a second application in spring 60 days after the first application for complete coverage of crabgrass. The product label will indicate if this is needed.

Many people are reluctant to use herbicides of any sort for weed control. That is a reasonable choice for those who are willing to tolerate some weeds. The best preventative is to maintain a healthy, well-established lawn, as this will help prevent much of the weed invasion. A healthy, thick lawn depends on good soil, proper turf grass for the area, adequate sunlight and supplemental irrigation. Most lawns need some fertilizer, and there are organic and synthetic sources available for nutrients.

The Tulsa Master Gardener website contains several helpful lawn maintenance calendars indicating what to do, what to use and when to use it for Bermuda and fescue lawns. Specifically, see the “Turf” section of the Master Gardener website for complete details.

Master Gardeners are often asked if there are any “organic” preemergent herbicides, as opposed to commercial or “synthetic” ones. Unfortunately, while there are other organic pesticides, there is no effective organic preemergent herbicide.

Corn gluten is an organic sold as crabgrass prevention. Some reports state that if it is applied during a narrow window in spring, there may be some benefit. OSU turf grass specialists cite studies that show little benefit.

For those wishing to use a synthetic pre-emergent herbicide, OSU has some recommendations. While there are several varieties of preemergents available on the market to prevent weeds, especially crabgrass, OSU feels that one of the many commercial brands containing the chemicals dithiopyr, pendimethalin or prodiamine are good choices. These preemergents cost a bit more than other types but last a lot longer and, in many cases, can kill crabgrass and other weeds after they have sprouted.

The labeled directions of all such products must be followed. These herbicides usually come on a dry particle such as fertilizer or other inert material. They may also be found less often as liquids. They must be washed onto the soil with at least ½ inch of water after application. After washed onto the soil, they form a barrier for weed prevention, which may last for months if undisturbed.

One of the benefits of these three products is that they are not soluble in water and, thus, do not leach into groundwater or spread from where they are applied. They are broken down in nature by sunlight and soil microorganisms.

Garden tips

• Now is a good time to cut back your perennial ornamental grasses, such as Pampas 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.

• Most bare-rooted trees and shrubs should be planted in February or March. The roots of these plants are easily damaged and should never be left exposed to air. Plant them at the same depth as in the nursery and make sure good root and soil contact is made by gentle tamping and irrigation after planting.

• Finish pruning shade trees, summer-flowering shrubs and hedges. Spring-blooming shrubs, such as forsythia and azaleas, may be pruned immediately after flowering (not before). Do not top trees or prune just for the sake of pruning.

• Applying preemergent herbicides earlier rather than later may be desirable to prevent crabgrass and other summer weeds.

Soil Tests of Lawn and Garden Beds Are Very Helpful

How Soil Tests are Helpful

Tom Ingram: Ask a Master Gardener

Sunday, February 3, 2019

Q: I wasn’t happy with how my yard looked last year or how my vegetables grew. How much and what kind of fertilizer should I use this year? DJ

A: This is a question we get quite often. The reality is that the question, while well-intentioned, is like me calling you on the phone and asking you how much gas I should put in my car. Your first response would be, “Well how much gas do you have in your tank now and where are you going?” To answer your question, I could look at the fuel gauge and tell you I have half a tank and I just plan on running some errands. In response you could say, “Well you don’t really need gas right now, but you better fill it up at the first of the week.”

It is the same way with soil. When someone asks how much and what kind of fertilizer they should use, we need to ask some questions. Or in this case, we need to take a soil test, which is similar to looking at the gauge to see how much fuel we have.

To perform a soil test, you will need something to collect your samples with and a bucket: a trowel or a bulb planter work well. We recommend you get between 15 to 20 samples of soil from locations scattered throughout your yard. Each individual sample does not need to be large, but you should dig to a depth of about 6 inches.

Once you have your samples in a bucket, mix them up and remove any sticks or debris. From this mixture of soil, bring a representative sample to the OSU Extension office. We will only need about a sandwich bag-sized amount of soil for your test.

When we receive your soil sample, we will send it to the Soil Science Lab at Oklahoma State University for analysis, and within 2 weeks, you should receive the results. Your results will contain the levels of nitrogen, phosphorus and potassium found in your soil, along with the pH level. Included will be a recommendation on the nutrients you need to add and how much, along with recommendations on perhaps the nutrients you need to stop adding. Not only is over-application detrimental to your growing environment, but it is also a waste of money.

The test costs $10, but likely, it will be the best $10 you have ever spent on your lawn or garden. If you want to test a smaller garden or flower bed, this will require a separate test as those environments would be unique from your lawn. The same instructions would apply. So grab a bucket and let’s find out what your soil really needs.

Garden tips

• Early February through March is the recommended time to plant strawberries. It is important to plant them in full sun and in well-drained soil. There are several types to choose from. June-bearing varieties do best in our area. They have a single crop usually early May to mid-June. Ever-bearing strawberry is another variety which fruits May to June, a few during summer and again in the fall. The quality and size of this type of strawberry plant may not be as good as June-bearing varieties. For full information about plant selection and growing tips, visit the “Hot Topics” page of our website.
• Mid-February is a good time to begin pruning and fertilizing trees and small fruits.

Plan Now For a Spring Vegetable Garden

Planning for a Spring Vegetable Garden

Brian Jervis: Ask a Master Gardener

Sunday, January 20, 2019

Q: What suggestions do you have for those of us starting to plan for our spring gardens this year? Also, what resources are available? Lisa P., Tulsa

A: Because it’s so cold and dreary and not much fun to be outside, this is a great time to begin making your spring gardening plans for the new year.

One simple thing you can do is to review your experiences from previous years. What worked? Why did it work? What didn’t work? Why didn’t it work? What do I want to do the same and different this year?

If you are growing vegetable crops, which crops prospered? Which ones struggled? Which pests caused the most trouble? How can I better control them? Did my garden take too much of my time? Should I make some adjustments in how I water and care for my garden?

One of the things we hope will become an even more valuable resource to you than it was in the past is the sort of new Tulsa Master Gardener website (tulsamastergardener.org). It’s celebrating its one-year anniversary. We’ve spent a lot of time updating the interface to be more user-friendly and have uploaded an abundance of gardening resources to help you become a more successful gardener.

In our Lawn & Garden Help section, you will find information on a variety of topics, such as general landscaping, flowers, trees and shrubs, soil, vegetables, fruits, nuts, berries, insects and butterfly gardens. You will also find sections on organic and Earth-kind practices, types of gardens, fertilizers and pesticides, pruning, composting, water conservation, etc.

If your plans for the year include a vegetable garden, we have information and videos on which varieties do well in our area, the best times to plant, garden layouts, how to plant tomatoes, etc. If your plans include flowers, we have recommendations for annuals and perennials that do well in our area.

We are fully aware there is a lot of information available on the internet about gardening, but it is sometimes hard to determine if the advice or suggestion is appropriate for our area. On our site, you will know the information you read or the instructional videos you watch will be university research-based information appropriate for the Tulsa County gardening community. Here are three of the more popular OSU Fact Sheets for your reading pleasure during these cold days. Simply Google them.

• HLA-6005 Oklahoma Garden Planning Guide

• HLA-6408 Landscape Maintenance Schedule

• HLA-6033 Raised Bed Gardening

However, our website is not the only way we can help you prepare for this new year. Our Diagnostic Center is staffed from 9 a.m. to 4 p.m. Monday-Friday with Master Gardeners who would love to share what they know about gardening. You can call us or email your questions via the information below. We hope you have a great garden this year and would love to help.

Garden tips

• Several early season vegetables are grown from seeds and planted as sprouts or transplants. Some examples are cabbage, cauliflower, broccoli, head lettuce, onions, tomatoes, peppers and eggplant. Most of these take 5-7 weeks from planting indoors until ready for transplanting into the garden. Onions take a little longer to grow.
• Of these, cabbage, cauliflower, lettuce and onions sprouts should be set out from mid-February to mid-March. Plant broccoli sprouts in March. Tomatoes, peppers and eggplants need warmth and suggested planting time is mid-April, although many people take a gamble and plant earlier, depending on the weather. Look for seeds at local gardening centers or online now.
• Even though there may be adequate moisture in the ground, it is normal for evergreen broad-leaved shrubs to appear “wilted” during extreme cold. This is rapidly reversible after the temperatures warm. This is a way some plants have in dealing with the cold.
• Try to keep fallen leaves off newly seeded fescue. Fescue is capable of growing roots in winter unless the ground gets extremely cold. A good root system will help fescue to better tolerate the heat next summer. In order to grow roots, the grass needs sunlight.

Options For Christmas Tree Disposal

Christmas Tree Disposal

Allen Robinson: Ask a Master Gardener

Sunday, January 6, 2019

Q: Now that the holidays are winding down, what options do I have for disposing of my live-cut Christmas tree? William L., Tulsa

A: There are several options for disposal of your live-cut tree after the holidays. However, some are more environmentally friendly than others. Most options involve removing all of the ornaments, tinsel and flocking (if possible) before disposal.

The best option is to trim the smaller branches from your tree and place in the garden as mulch. They will decay over time and you will not only reap the benefits of mulch but also the nutrients that it adds back to the soil. These limbs also may be added to your compost pile as a source of green material to help balance the brown material, such as dead leaves. Green materials (for the nitrogen source) and brown materials (for the carbon source) are needed for the microbes that break down the composted material. The larger limbs and stems must be used elsewhere.

For the fisherman, sinking a bundle of evergreen trees creates a “hot-spot” or “magnet” in your favorite fishing hole. Crappies love them. The whole tree may be added, usually with others and tied together, weighted with a concrete block and dropped into your favorite spot, if allowed.

Another option is to use the old tree as a temporary winter bird refuge, sanctuary and feeding station. The fronds of needles make a good temporary shelter from wind and predators. Treats, such as peanut butter, suet and seed mixtures can be added as winter food for the birds.

The last option before placing the tree at curbside collection is to take it to the city of Tulsa’s Mulch Site, 2100 N. 145th East Ave. This site is open seven days a week, 7:30 a.m. to 5 p.m., excluding city holidays. Only green waste is accepted, such as trees, limbs, grass clippings and leaves. All are shredded for mulch. Non-organic material, such as Christmas decorations, lights, tinsel and flocking is not allowed.

The waste site produces huge amounts of mulch, which is available to anyone. There may even be a machine to help load your truck. Wood that can be cut/split for firewood is available in a firewood cutting area, but you must bring your own tools. There is no charge for these services for Tulsa residents. You must have a valid driver’s license or a utility bill showing a Tulsa address; otherwise, there is a small fee. Think about this ... you could take a load of neighborhood trees to the site and perhaps come home with a load of free mulch and/or free firewood.

Lastly, the city of Tulsa curbside pickup service will collect trees. In December and January, residents may put trees at the curb on their primary collection day. All decorations must be removed, and the trees need to be cut into 4-foot sections to fit into the hopper of the refuse trucks. This collection is not for artificial trees, which need to go in the gray trash cart. The live trees are not actually recycled but, instead, are incinerated along with the other green waste collected in Tulsa.

Garden tips

• Any green weed in dormant (brown) Bermuda lawns may now be sprayed with glyphosate, found in Roundup and many other products. This will kill anything green, but will not hurt the Bermuda. Note that glyphosate cannot be used on dormant Zoysia grass or tall fescue lawns at any time.

• Control overwintering insects on deciduous trees or shrubs with horticultural oil sprays in dormant concentrations. Apply when the temperature is above 40°F in late fall and winter. Do not use “dormant” oils on evergreens.

• Ornamental perennial grasses, such as pampas grass, may be cut back to 4-6 inches anytime in winter. However, because of winter attractiveness, most gardeners choose to wait until early spring to cut them back. All the dead tops of these grasses should be removed by early spring, allowing sun to get to new growth.

• Liriope or "monkey grass" — which is not a grass, but in the lily family — stays green year-round. It benefits from trimming to 2-3 inches before new growth begins in spring. Liriope and all ornamental grasses will benefit from nitrogen fertilizer in the spring when pruned.

• Prune fruit trees in January, February and March. OSU has a good fact sheet on pruning fruit trees: "Annual Pruning of Fruit Trees".