Ezzirah,

The quick answer is that I would try to go with the recommended planting dates, but you know me....there is now going to be the longer answer that gives all the whys and wherefores.

"It's not the heat, it's the humidity". I say that because that is what our local weather forecasters say every single day, reminding us that we always have these same exact temperatures in July, but usually don't have the high humidity/heat indices we're seeing right now. Every time they say that, it irritates me even though I know that, technically, they are 100% correct.

The problem with going with the later planting date in August in northern Oklahoma is that it is the right date for southern Oklahoma, where the first frost sometimes (though certainly not always) comes later the the first frost in northern Oklahoma. And, that's where you run into trouble with fall planting dates.

The OSU-recommended planting dates are based not on what temperatures are at planting time in summer, but on how many days any given vegetable needs in order to grow, mature and produce a crop before a killing freeze kills the plant, or before temperatures drop so low that a crop failure ensues. If you slide the planting date later into August, you slide your maturity date later into autumn. So, I guess it comes down to how much of a gambler you are.

I have planted broccoli in early August here in southern OK when the daily high temperatures (not the heat index because it is irrelevent here in dry southern OK about 8 years out of 10) have been in the 105-112 degree range and they have survived, grown and produced just fine. After transplanting, I have taken great care to check them morning and evening and give them a little water every time I check them if they need it. Small transplants have small root systems and while they don't need heavy watering daily, they need enough water to keep the root systems moist so they can survive the high temps. I also like to shade the plants for their first 3 or 4 days after they're transplanted just to lessen the likelihood of transplant shock. I usually shade them by placing a lawn chair at the end of each row, and one in the middle of the row, and draping an old sheet over the chairs. It looks goofy out in the garden, but I don't care because it is helping the plants.

The challenge with a fall garden is always going to be that we are trying to get seeds to sprout or young transplants to thrive in high heat, but there's no way around it because proper timing is essential if we are to get a harvest before colder temperatures arrive.

So, my suggestion is to go ahead and plant on time to the extent that you can. (My biggest problem with fall planting is that the spring/summer plants are going strong and I don't have room for fall plants at the proper time unless I sacrifice spring/summer plants while they are still producing well.) Try to pay very close attention to watering and try to shade the young seedlings to help them adjust.

With the specific vegetables you mentioned:

--Broccoli is pretty cold tolerant and you probably could get away with planting it a bit late although it likely would reduce the length of the time frame in which you'd get side shoots after harvesting the main head. You want to complete your broccoli harvest before temperatures at night begin falling to or below about 25 degrees.

--Cauliflower also can tolerate temperatures into the mid-20s, but you want for it to have formed heads before that. Once temps are staying in the mid-40s at night, cauliflower tends to go dormant and just sit there. So, think about your cauliflower variety's DTMs (most cauliflowers need about 10 weeks to produce mature heads) and think about when your nighttime lows are regularly hitting the 40s and plant accordingly.

If you absolutely feel you must delay planting because you feel the young transplants cannot survive the heat, then plant your transplants in a high-quality potting soil (regular Miracle Grow would be fine) in large cups (16 oz. is the minimum and I'd go with larger ones if possible) and keep them in a location where they get at least 6 hours of sun a day....preferably from sunrise until about noon. Water them regularly so their root systems are not just surviving and hanging on, but growing and enlarging. That way, when you put the plants in the ground, they will be pretty large and healthy and have large, healthy root systems. Being nice and large like that, they'll be less affected by a late transplanting date because they've been growing all along...just in paper or plastic cups instead of in the ground. You do have to be careful that you don't hold them so long that they become rootbound.

I always raise my fall transplants outside in full sun so they the plants are used to the heat and sunlight from day one. It seems cruel, but it toughens up the plants and ensures they can handle the conditions in which they'll be growing once they're transplanted.

Finally, there is nothing worse than planting too late in summer and having beautiful plants in Oct. or Nov. that freeze before producing a single bite for you to eat. Even cold-tolerant crops can only handle cold temperatures down to a certain point before their productivity is affected---some of them might not die, but they also might not produce.

If your other cool-season crops are leaf crops like spinach, they can take a lot of heat. Down here in southern OK, they often stay green and productive deep into the winter and, if frozen back by temperatures on a very cold night, they often regrow quickly and continue to produce. So, with something like spinach, you can plant really late into fall. Since you're quite a bit further north than I am, spinach probably will freeze out there before it freezes out here, but I still think it likely you'd get a good harvest even from spinach planted pretty late.

Dawn

Thank you for your thoughtful reply. I have some plants hardening off in the cold frame. It never occurred to me to start them outside in the flats! I have another batch *just* started yesterday under the grow lights that I just may go ahead and stick out side. I love the cup idea. That is a good alternative for the ones in the cold frame (there is no lid on the frame, just black screen for shade). They seem ok out there but my ground cherries are looking kind of rough.

Should I take the ones under the grow light and stick them outside, They were sowed yesterday and not sprouted yet?

The one thing we tend to forget is that now the days also will be getting shorter. I look at the 76 day sweet corn I planted June 10th that is tasslling and think I have plenty of time for another crop. I probably do unless we get a real early frost. But I can assure the next crop of the same variety won't mature as fast as this did. I planted it right before the heat in June and they days were longer. The next will be a lot closer to DTM I'm sure. I've learned that through the years. My okra planted 2 weeks later than the earliest is about the same size. I usually go by dates I've learned through the years or that other growers have shared with me. Being as we are catty cornered from our extension service by almost 500 miles our dates vary some from theirs. And then again like DTM's it is all an educated guess based on an average year. Not sure when we've had that "average year". Jay

Ezzirah,

Yes, I'd move those recently started seeds outside, except....before you do so, check Tom Clothier's database (linked below) that shows the correlation between soil temperature and seed germination. If your seed-starting containers are in full sun in this weather, the soil may be too hot for germination to occur. Often, people think their seeds fail to germinate this time of year because the soil is too dry (and that can be true) but more often it is because unmulched, unshaded soil can easily hit 120 degrees or higher every day. If Tom Clothier's database shows the seed you're tying to start germinates best at, say, 85 degrees or 90 degrees, I'd germinate it in the house and move the containers outside as soon as the first seedlings pop up out of the soil, or I'd germinate in the shade and move them to sun at the time the first ones pop up. Note that for whatever reason broccoli is not on the chart. I'd use the cauliflower or cabbage data for broccoli as they're similar in their needs.

Some seeds germinate very fast at high temps, but that's true only as long as they soil temps aren't too high. As you can see from the charts, some soil temps may be too high for good seed germination outside right now.

I know I give very long answers and go into a lot of detail, but that way everyone can understand where my answer is coming from. I always feel like I should apologize in advance for being so wordy. : )

Jay's point on the decreasing daylength in fall and its effect on maturity of a crop is of huge importance. Professional growers rely on complex degree-day calculations that compute how many hours per day of temperatures or sunlight exposure their plants have. We home gardeners have to rely more on what we know from past experience. So, in any gardener's first year of fall gardening, there isn't that 'past experience' to draw from, but that's why this forum is so helpful.

It also is why OSU's recommended planting dates are a valuable tool---because they have taken into consideration how the decreasing hours of daylight and the decreasing temperatures in fall affect your plants' growth and development. I freely admit I don't always follow OSU's dates, but when I deviate it is based on prior experience over many years of gardening.

Last year I planted a couple of things kind of late and didn't get as high of a yield as I would have if I'd planted on time.

In the same way that late spring frosts can damage a planting and impact our future harvest, very early fall freezes or frosts can ruin our chance to get a good harvest. Usually, a very early fall freeze is unlikely, but in the dozen years we've been here, I've seen the first killing freeze on September 29th and the latest killing freeze in mid-December.

We're always at the mercy of the weather here, and in a year like 2010 when the weather has given us just about every form of extreme weather possible, it wouldn't surprise me if we have a early frost. I expect that if the heat continues unabated in July and August, by mid-August we'll be praying for an early cool-down.

Often, the first freeze of fall is what I call a 'fake freeze' because it occurs abnormally early and likely will be followed by many more weeks of above freezing weather. So, if you can anticipate that first freeze or frost and cover your plants and protect them, you'll then have them alive and producing another month or two.

Jay, I'm still waiting for that 'average' year too. In the years we've lived here, I haven't had it yet, and likely never will. We're known for nothing so much here as our extreme weather. Average weather? lol It ain't gonna happen here, and you know it. : )

Dawn

Here is a link that might be useful: Temperature/Seed Germination Correlation

I bookmarked that site, it is a wonderful site!

Yeah, having no past experience I am a bit confused on what should happen when. I know the dates that are given by the extension is an educated guess a best, I figure, So how to figure out for certain if I should plant is a moot point, really, I figure.

I am going right now to put the ones under the grow light in the cold frame with the screen. In that flat is Brussel sprouts, cauliflower, broccoli. In the frame already is tomatoes and herbs, ground cherries, broccoli, peppers.

I will find some old sheets to have ready.

Geesh this is a lot to learn!!

Thanks everyone!

You're welcome.