Tips For Planting of Warm-Season Crops

Okiedawn OK Zone 7March 19, 2011

By now, for most parts of Oklahoma, the cool-season crops should be in the ground (you still could be succession sowing radishes weekly) or about to go into the ground soon. (Broccoli is an exception. Some of us have found that planting broccoli in latest March or earliest April reduces the likeliness of recurring cold weather causing bolting or buttonheads.) Now it is time to turn our focus to planting the warm season crops.

Warm-season crops fall into two general categories: tender and very tender. In general, tender crops can be planted at or near the last frost date and very tender crops need to go in a bit later when the soil is a bit warmer.

By date, here's the OSU-recommended planting dates for tender and very tender vegetable garden crops:


Sweet Corn, planted from seed or plants, tender

APRIL 10-30:

Snap beans (bush or pole), from seed, tender

Eggplants, from plants, very tender (planting towards the end of the recommended period lessens flea beetle damage most years)

Tomatoes, from plants, tender


Cucumbers, from seed or plants, very tender

Okra, from seed, tender

Peppers, from plants, tender (planting later in recommended period gives better results most years)

Pumpkins, from seed, tender

Summer squash, from seed, very tender

APRIL 15-30:

Lima Beans, from seed, tender

MAY 1-20:

Cantaloupes, seed or plants, tender

Watermelons, seed, very tender

MAY 1-JUNE 10:

Southern Peas, seed, tender

Sweet Potatoes, plants (slips), very tender

MAY 15-JUNE 15

Winter Squash, Seed or Plants, very tender


BEANS: Most beans germinate best if planted after soil temperature at planting depth is staying consistently at or above 60 degrees. Beans planted into colder soil tend to germinate poorly or rot before germination and if they germinate in the colder soil they still are very vulnerable to diseases in cooler soil temps.

For Lima Beans, wait until soil temps are staying at 65 degrees.

Beans produce poorly when air temps are high, so planting on-time or slightly early can pay off in better yields and earlier yields as long as the soil temps are in the right range for seed germination.

CANTALOUPE/MUSKMELON/OTHER MISCELLANEOUS MELONS BUT NOT WATERMELONS: Sow seed or transplant young plants raised in plantable pots only after soil temps are staying consistently above 60 degrees. If your soil is still cold and you are eager to plant, lay down black plastic on a prepared seedbed for about 7-10 days to preheat the soil and raise its temperature a little. Planting into cold soils can give poor germination rates and weak seedlings that remain stunted and slow to grow and produce.

To start your own seedlings indoors, sow seed indoors into plantable pots to reduce transplant shock about 2-4 weeks before your anticipated transplant date. Harden off properly before transplanting into garden.

CUCUMBERS: Sow seeds or transplant your indoor-raised seedlings in plantable pots only after soil at planting depth is remaining at or above 60 degrees. Ideal transplants would be about 3 weeks old and planted in plantable pots or peat pellets to minimize transplant shock. As with beans above, you can lay down black plastic in advance of planting to warm up the soil. If you diret-seed into cold soils, germination rates may be poor and the young seedlings very vulnerable to disease.

EGGPLANTS: Very sensitive to cold weather and frost. While tomato plants can tolerate air temperatures right down to just above freezing, eggplant can be damaged by those cold temps. It generally is recommended that eggplants can go into the ground about 2 weeks after tomato plants. Plant after air and soil temps are stable and soil temps are staying consistently above 65 degrees.

OKRA: Plant seed when soil temperature at planting depth is consistently staying at or above 68 degrees, and only after you've had at least 5 consecutive days with nighttime low temps staying above 50 degrees and unlikely to drop below that level very much again if at all. Okra does best when direct-seeded. If using transplants, use plantable pots. To increase germination rates, you can pre-soak your okra seed in room-temperature water for 24 hours before direct-sowing into the ground, or if desired, heat up water to 110 degrees but no hotter and pre-soak the okra seed for 90 minutes before direct-sowing.

PEPPERS: For best and earliest yields, always use transplants instead of direct seeding. Plants that are direct-seeded tend to not produce well until fall's cooler temps arrive because by the time they're large enough to produce, they're having to fight really high air and soil temperatures although the heat is more of a problem for sweet peppers than hot peppers. (High humidity plays a role in this too.)

Like tomatoes, peppers are very heat-sensitive, and have very specific temperatures at which the best fruitset occurs. In general, and once again this applies more to sweets than hots, peppers set fruit best when nighttime air temps remain above 60 degrees and daytime highs remain below 80 degrees. Luckily for us here in Oklahoma, most peppers set fruit somewhat better at higher temps since we often are exceeding 80 degrees pretty early in the year.

Transplants that are about 8 to 10 weeks old and are 6-8" tall are optimal, but taller and older transplants will work as long as they aren't rootbound.

Peppers are set back by cold temperatures so plant them a couple of weeks after tomatoes.

Pepper plants that are exposed to temperatures in the 40s for only a brief time can remain stunted and produce poorly for their entire life. Some will outgrow the cold-related stunting but still not produce well, and some will outgrow the stunting but not produce well until the fall. Thus, it is advisable to not let your plants be exposed to temps in the 40s if you want an early crop and a big crop.

You can transplant pepper plants into the ground once soil temps have remained above 55 degrees for 3 or more consecutive days. I usually wait until soil temps are 65 degrees or higher and I get better and EARLIER yields from those late plantings that from earlier plantings.

PUMPKINS: Technically these can be planted any time after the last killing frost. However, they'll germinate fastest and produce best if you wait until soil temperatures are staying consistently above 70 degrees.

SOUTHERN PEAS: These are the warm-season peas like blackeyed peas, purple hull pink eye peas, lady, crowder, cream or zipper peas. (The green English peas, shelling peas, or sugar snap peas are cool-season crops that should have been planted in February through mid-March.) Southern peas should be planted only after soil temperature at planting depth is staying consistently above 65 degrees.

SQUASH, SUMMER: These are very cold-sensitive. Plant only after all danger of frost is past and soil temperatures are staying at or above 60 degrees at planting depth and daytime high temps are staying above 65 degrees consistently.

SWEET CORN: Because there are several different types of sweet corn, the planting of sweet corn has become more complicated than it used to be and you need to know what type of corn you're planting in order to know what soil temperatures it needs for best germination and growth.

In each instance, plant only after soil temperatures at planting depth are staying consistently at or above the temperature recommended for that specific type of corn. Corn seed planted into soil temps below 50 degrees tends to rot and germinate poorly if at all.

TRADITIONAL SWEET CORN (SU): This is the traditional sweet corn grown for hundreds of years and there are both open-pollinated and hybrid types. This has traditional corn flavor and is not terribly sweet. The amount of sweetness varies from one variety to another. This is the most cold-tolerant corn. SU corns have sugars that convert rapidly to starch after harvest. Seeds can germinate at soil temperatures as low as 50 degrees but it is better to wait until soil temperatures at planting depth are staying consistently above 55 degrees.

SUGARY ENHANCED (SE, SE+, EH or Enhanced Heritage) corn is bred to have increased tenderness and more sweetness than SU corn types. Its sugars convert to starches more slowly than SU's. No isolation from SU corn is needed. SE corn germinates at or above 60 degrees, and 65-70 is even better.

SHRUNKEN GENE (SH): Commonly referred to as supersweet corn. These are easily recognized because the dry kernels (seed corn, for example) have a shriveled or shrunken appearance. The presence of the SH gene gives the corn much more sweetness and a much slower conversion of starches to sugars after harvest. These SH corn varieties must be isoalted from SU, SE and Synergistic corn varieties to prevent cross-pollination which will give you tough, starchy kernels. In a home garden planting, isolation of 25' is usually recommended or time isolation of 2 weeks between pollination times. Supersweet corns should be planted only after soil temperature is consistently staying at or above 70 degrees.

SYNERGISTIC (AKA TRIPLESWEETS): These ears are 75% SE kernels and 25% SH kernels so they have the tenderness of the SE's and the extreme sweetness of the SH's. These can be grown with other Synergistic varieties, SE's and SU's but cannot be grown with SH's or they will cross-pollinate and all your corn will be starchy and not sweet. Triplesweets can germinate at 65 degrees but 70 degrees is even better.

SWEET POTATOES: Plant from slips after soil temperatures at planting depth are staying consistently at or above 60 degrees.

TOMATOES: Transplant into the ground as soon as possible after the last frost date but only once temperatures have stabilized enough that a return to frost and freezing temperatures is unlikely. Be prepared to cover up the plants to protect them from any possible late frosts or freezes. Planting only after soil temps are at a stable 50-55 degrees at planting depth is recommended.

For the best yields, you want your plants in the ground early enough that they can flower, pollinate and set fruit earlier in the season while temperatures are in the right range. Once it is excessively hot, especially in combination with excessive humidity, pollination and fertilization can be impeded.

You'll get the best bloom and fertilization resulting in good fruit set when the nighttime lows are staying above 55 degrees but below 72-75 degrees. Plants that produce bite-sized tomatoes (grape, cherry, currant, plum or pear-shaped) are not impacted by high temperatures and high humidity to the extent that plants producing larger tomatoes are.

While tomato plants can endure cold soil temps and even cold but above-freezing air temps, they can be damaged or killed by freezing temperatures or frost, so always cover them up if those conditions threaten after plants are in the ground.

Once daytime temperatures are exceeding about 92-95 degrees and night-time temperatures are exceeding 72-75 degrees, fruit-set can be affected as those higher temps can cause blossom drop. That is why we risk planting earlier and covering up plants if late frost or freeze threatens.

WATERMELONS: These need warm weather to germinate and grow. Plant only after soil temperatures have stabilized at or above 70 degrees and all danger of frost has ended.

I hope the above info helps. Although we humans like to use a planting calender, plants don't grow because the calendar says they should. They grow when planted at the right soil and air temperatures, so if your soil/air are at the right level and are staying there consistently, that's the right time to plant no matter what the calendar says. In our state, though, you always have to be prepared for an occasional cold spell even after the last frost date and may need to cover up plants to protect them during an occasional late cold spell.

You may wonder how much later you can plant than the recommended dates or soil temperatures and that is a very complicated topic to discuss because every vegetable is affected negatively by hot temperatures in some way. For example, bean blossoms can drop off the plants at high temperatures, thereby reducing yields. Very hot air temperaturs can impede corn from pollinating/fertilizing properly so that you may get cobs but few corn kernels on sweet corn that pollinates/fertilizes at high temps.

On the crops that have a planting date with the words "or later" added, you can plant later than the recommended dates but your success with later plantings can vary depending on how hot the weather is and how early in the plants' growth it occurs.

Finally, if you are in an area plagued by drought, later plantings may not produce well in extreme heat and extreme drought, so the earlier you can plant the better. In a drought year, I push myself to plant as early as is reasonably possible and I water well and fertilize well (without overfertilizing) to try to push the plants to produce as early as possible before the heat shuts them down.

Also, you should know that in a drought year like much of the state is currently facing, pests tend to arrive early and often, so be prepared to go after them vigorously and to protect your crops from them so that your veggie crops can produce a good yield despite the drought and pests.

You can check the OK Mesonet for your county's soil temps, or use a kitchen thermometer or soil thermometer with a metal probe to check your soil's temperature at planting dept. With beds raised above grade level, you usually will have warmer temps earlier than with grade-level beds.

I've linked the OSU Garden Planning Guide for you as it contains not only planting dates, but also contains in-row spacing, spacing between rows and other helpful info.


Here is a link that might be useful: OSU Garden Planning Guide

Thank you for reporting this comment. Undo

you are AwEsOmE! Thanks, Dawn! I was just wondering this same stuff and wondering where to find out.

    Bookmark   March 20, 2011 at 10:23AM
Thank you for reporting this comment. Undo

Thanks Dawn,

A couple of questions please...

Last year I had great results when I direct sowed my okra seed in mid May, probably 80-90%. I just put it in the freezer for about an hour before planting. This year I plan on planting okra in 'hills', probably 5 seed in each and spaced 18" apart for the Clemson Spineless and 5' apart for the Stewart's Zeebest. My question is have you ever tried pre sprouting okra and if so with what results?

Also last year I remember you experimented with nylon hose (pantie hose) sleeves on Summer squash to help deter SVB. I'm wondering if you could line a starting cup with the hose, with extra pulled down over the cup to use after transplanting to pull up along the vine and tie with twist ties as the plant grows. Would the bottom of the hose need to be cut at transplant time or do you think the roots would be able to grow right through the hose?

Thanks as always, and with a new season upon us expect many more questions from me as we go along...


Though an old man, I am but a young gardener. -- Thomas Jefferson

    Bookmark   March 20, 2011 at 12:46PM
Thank you for reporting this comment. Undo

Thank you Dawn, for the details. This will help me (many) very much. -Chandra

    Bookmark   March 21, 2011 at 2:51PM
Thank you for reporting this comment. Undo
mtilton(7a OK)


The soil temperature (according to the site you've mentioned - Mesonet) is currently 72 degrees F two inches under bare soil and about 70 degrees four inches under bare soil.

Please tell me what would happen if I planted corn now. I know there's a 50% chance of freezing temperatures. Would it come up on its own when the time is right? Thank you.


    Bookmark   March 21, 2011 at 6:12PM
Thank you for reporting this comment. Undo
Okiedawn OK Zone 7


I have pre-sprouted it by soaking it for 24 hours in room-temperature water, wrapping it up in either paper towels or coffee filters (I don't remember which), and putting it in a zip-lock plastic bag. Then, the first year I just placed it on top of the microwave oven so I would see it every day and remember to check it daily for sprouting. It probably germinated in less than a week.

In a different year, I was distracted by constant wildfires and got behind on seed-starting, so was trying to rush the process a bit. I pre-soaked in warm water as described above and then put the seeds in the coffee filter and zip-lock bag, and placed it on top of the heat mat. That seed sprouted in 3 days.

I don't remember which varieties I was planting in those years, but likely most of the time they were either Clemson Spineless 80, Cowhorn, Hill Country Red, Burgundy, Baby Bubba and Little Lucy---some combination of those in any given year, but not all of them in any given year.

Pre-sprouting for faster germination seems to work better with newer seed than older seed.

I like your idea of lining the planting cup but have no clue if the roots would grow through the stocking. I "think" it would, but since we can't know for sure, I'd probably cut off the bottom of the stocking at transplant time as long as roots weren't growing through the stocking (which would prove the point, after all, that they would grow through the stocking).

I did feel like the nylon stocking helped repel SVBs because those plants lasted long after other unprotected ones had been killed by the evil SVBs. I planted both ways to see if the stocking made a difference, and it seemed it did.

You're welcome, and by the way, that's my all-time favorite gardening quote.

Chandra, I hope you find it helpful. I have gardened for so long that I do a lot of things by instinct and just plant when it "feels" right. However, I do know something technical about what the various veggies need in terms of soil temps and air temps and so forth, so figured putting all that down in writing might be helpful.

I also know a lot of the old folk sayings, like "plant your corn seed when the white oak leaves are the size of a squirrel's ear". One day, for fun, I'll try to list the ones I remember and see if anyone else has any old garden folklore to share.

No rules are absolute though. One folklore rule I grew up with was that we are safe from a late freeze or frost after the pecan trees have leafed out, and that always seemed to prove true when I lived in Texas about 80 miles south of the Oklahoma border. However, we have had a late freeze or frost occur at least twice here in the years we've been here, so I'd say that "rule" is correct 80-90% of the time, but not 100%.

Even though it is very warm here, I don't think my pecan tree is doing much of anything, unless it started this weekend and I haven't noticed. The oak trees, though, are pollinating and leafing out so soon it will be safe to plant sweet corn. Technically, by soil temp at my location, it is alright to plant corn now here in our garden, but I'm waiting for those oak leaves to appear.


    Bookmark   March 21, 2011 at 6:22PM
Thank you for reporting this comment. Undo

Very helpful, Dawn. Does it make a big difference, though, if I am planting in containers rather than the ground? Does the soil stay warmer in a container, since it is above ground, than the ground soil temp? The exception being close to freezing and below freezing air temps? How do you work around that?

I mean, if I plant Okra seeds in a 5 gallon container, what would be my concerns if I planted them on April 1st?


    Bookmark   March 22, 2011 at 7:39AM
Thank you for reporting this comment. Undo
Okiedawn OK Zone 7


Containers warm up faster but how much faster they warm up depends on their size, their color (i.e. black warms up faster than white, etc.), their sun exposure, the hours per day of sunlight they receive, etc.

Honestly, in this weather I think you could sow okra seed now and it would sprout. We're going into the 80-85 degree range here now and our soil temps are in the 70s in the ground and higher than that in containers. We have an odd calendar this year....January, February, May......I don't know what happened to March and April. I think we skipped them.

I work with containers by checking the soil temperature in them at planting depth with an ordinary meat thermometer with a metal probe. I keep my garden thermometer (it is just a meat thermometer, but not the same meat thermometer that I use in the kitchen) in the shed, though, instead of in the kitchen so no one in my family accidentally uses it inside after I've been using it in the soil. If air temps and soil temps are in the right range, I plant in containers whenever the temps say I can. I just have a couple of blankets nearby to toss over the containers at night if we're going to have a cold overnight low.


    Bookmark   March 22, 2011 at 7:49AM
Thank you for reporting this comment. Undo

I keep my garden thermometer (it is just a meat thermometer, but not the same meat thermometer that I use in the kitchen) in the shed, though, instead of in the kitchen so no one in my family accidentally uses it inside after I've been using it in the soil.

It's OK, just wipe it off on your pants and it'll be good to go...


    Bookmark   March 22, 2011 at 8:23PM
Thank you for reporting this comment. Undo
Okiedawn OK Zone 7

Margo, The corn will sprout because the soil temps are warm enough, but no, the corn cannot forecast weather and wait to sprout after the danger of frost is gone. So, it will sprout because soil temps are nice and then, if cold enough temperatures return, the corn will freeze. If the growing tips of the plants freeze (even if the leaves do not freeze), the plant will not produce ears of corn. I wouldn't plant corn for another 3 to 5 days at the earliest (unless you're in a warm part of southeastern OK) and only if the forecast through the end of March looks warm enough.

Realistically, if you put seeds in the ground tomorrow, they might not be above ground by next Mon. or Tues., but they might be...and those will be some coolish nights.

Corn can tolerate more cold than most other warm-season plants----that's why OSU has such an early planting date as March 25th listed, but it cannot tolerate freezing temps or frost.

Keith, Your comment reminds me of something my dad would say. If you skinned up your knee or something he'd say "Oh, just rub a a little dirt on it"! (My mom, of course, was not amused by that.)


    Bookmark   March 22, 2011 at 10:51PM
Thank you for reporting this comment. Undo

Thanks for the wonderful information! It always is nice to have a reminder to me to BE PATIENT! Something I have very little of to begin with. (gardening sure is helping with that!) I itch to get things in the ground and this year I fear I have suffered the consequences. :( in that my articokes that was doing very good inside died because I skimped on hardening them off. Live and learn!!

    Bookmark   March 23, 2011 at 6:18AM
Thank you for reporting this comment. Undo

It looks like that cold that Paula was afeared of may happen after all, looking at today's forecast. Of course, we are still a few days out from Monday and Tuesday.

Both of you, Dawn and Keith, are too funny! My mom always just spit on her shirt and wiped the owey, and our dirty faces, and hands.......!


    Bookmark   March 23, 2011 at 8:44AM
Thank you for reporting this comment. Undo
Okiedawn OK Zone 7

Ezzirah, You're welcome. I've found I have a lot better gardening success when I focus on giving each plant what it needs and that's especially true of vegetables. They just won't perform if they are too hot or too cold or too wet or too dry.

Susan, I remember "spit baths" too. lol

The cold doesn't scare me. I have an order of 5,000 square feet of floating row cover scheduled to be delivered tomorrow, so I can do as I please (within reason) and just cover it all up. Now I won't have to decide which plants get covered and which ones don't. I still will have to decide which plants get the premium 8-degree frost blanket (I only have 120 s.f. of it), the midweight 4-degree row cover, or which ones get a more lightweight covering that gives about 2 degrees of protection.

However, at the present time it is a moot point because there's nothing in the ground now that can't survive freezing temperatures although it is always in the back of my mind that the minute I put tender vegetation in the ground, frost will come swooping in unexpectedly to try to kill the plants.

My problem is that I have nine thousand things going on at once and I can't even seem to find the time to get anything planted. Between the fires and company coming to visit, animals needing attention and care, a lawn that needs mowed and weed-eated and watered and a house that needs cleaned, and so on and so forth, I've barely stepped foot in the garden the last 4 or 5 days. Tomorrow, I'm going to get up, go straight outside and get busy planting and I'm not going to let anything distract me.

Next week's cold spell bothers me a little and would bother me more if I were further north. I'm so far south and the soil temps are averaging above 70 at planting depth, so a brief dip at night won't bother my plants because I can cover them.

I sure wouldn't even contemplate putting tender plants into the ground if my soil temps were still low or if I didn't have a way to cover up and protect them.

We need for the cooler weather to return and hopefully it will give some of us some rain.

The humidity here is so low today (right now it is 16%) that my skin feels like it is cracking, and we need moisture in the worst way. Part of my "to do" list today is to water the soil around the foundation of our home and outbuildings. That's usually more of a summer type task.


    Bookmark   March 23, 2011 at 2:39PM
Thank you for reporting this comment. Undo

So when should I plant carrots? I've got my seeds all ready to go, what temps do they germinate best in?

    Bookmark   March 25, 2011 at 10:22AM
Thank you for reporting this comment. Undo

So I did a search and now see that I should have had them in the ground already...shoot!
I guess they will grow just the same. ;D

    Bookmark   March 25, 2011 at 10:27AM
Thank you for reporting this comment. Undo
Okiedawn OK Zone 7


Carrots are planted with cool-season crops, so I've linked the previous thread on cool-season growing tips for you below.

The OSU-recommended planting dates are Feb. 15th through March 10th, so you're a couple of weeks to maybe 6 weeks behind depdning on where you live in the state, which might not be too much of a problem. Why? Since the soil is undoubtedly warmer now than it was 2 to 6 weeks ago, the carrots though planted "late" likely will sprout more quickly.

Newhippie, To a certain extent they'll grow the same. However, their quality decreases when grown in hot soil and hot air temperatures. That's why we plant them early give them a chance to beat the heat.

Since it is just a couple of weeks past their latest recommended planting time (which is for zone 6), I don't think your carrots will suffer terribly unless y'all get really hot really early like we have down here in southern OK.

Y'all be sure and keep the soil moist but not sopping wet. Carrots germinate poorly in dry soil.

Here is a link that might be useful: Tips for Cool Season Crops

    Bookmark   March 25, 2011 at 10:36AM
Thank you for reporting this comment. Undo


    Bookmark   April 6, 2013 at 9:18AM
Sign Up to comment
More Discussions
Lisa, did you see: Work starts to protect monarch butterflies
Their bright orange and black wings are a familiar...
Atwoods Seed Potato Sale $2.99/5lb 3/1/2015
2015 Atwoods Seed Potato Sale $2.99 5lb as of this...
tomatoes are popping
was late starting my first flat. they are starting...
Ark. traveler tomato
Some one sent me a few seeds last yr. and I didn't...
seed swap tulsa
are they having the seed swap in Tulsa today
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™