James,

I don't know what everyone else will say, but in my experience I wouldn't put them out in that chilly of a temperature. I generally put cosmos, salvia, and the like out once they've been transplanted from the initial seeding flats into pots (6-packs usually) and they're going strong. Then, I'll put them out to harden off, but only after temps are warmer. I'm in zone 7a in central OK, and don't usually put these annuals out until after the last frost date, which here is around April 15. Until then, I keep them under their lights. Even if cool temps don't overtly harm the seedlings, sometimes they can stunt growth, so they won't be as vigorous as if they are babied a little more.

Ada

James,

I don't usually carry out warm-season seedlings of any kind (except tomatoes) until at least March and I am in zone 7B. I will put them on the screened-in porch, but the screens are covered by 6 mm greenhouse plastic in the winter, so the back porch stays 10-20 degrees warmer than the outside temps.

I think the 40s are still kind of cool for warm-season flowers and those temps will slow down growth and delay flowering. If any of your flowers are biennials instead of annuals/perennials, prolonged exposure to temps in the 40s can push them into a false dormancy.

With warm-season veggies, it depends on which veggie it is but, in general, they aren't crazy about temps in the low 40s although they don't really mind air temps in the upper 40s although the 50s are better.

Peppers are an exception. Peppers that are exposed to temps in the 40s often will stay stunted, will flower very little if at all, and will have poor production all season long. I went to Dr. Sam Cotner's book to see what he says about peppers and cold weather and he said: "Exposure to temperatures in the 40s for only a short time can stunt peppers causing them to remain small and nonproductive."

Whereas tomato plants can withstand quite a bit of exposure to cold air temps while they are still in flats or small pots, peppers cannot. So, I will carry tomatoes outside to harden them off when temps are in the upper 40s/lower 50s, but I keep peppers inside until temps are in the 60s during the day. I also don't usually expose melons, squash, cukes, pumpkins or beans to cold temps, although corn can withstand quite a lot of cold.

If, by chance, you are able to set the plants on a concrete slab or up against a south-facing wall where they benefit from heat retention/reflected heat, then I think you could get away with carrying the plants outside on a cool day as long as it is sunny. The weather here is so changeable, though.

A couple of weekends ago I carried my 4 potted tomato plants out and sat them on the concrete slab on the south side of the garage/barn at about 10 a.m. The temps were in the 50s. A couple of hours later, I heard thunder and went outside and could see a storm approaching. I picked up my "precious baby" tomato plants, brought them inside and sat them on the light shelf. By the time I came back downstairs, it was sleeting outside! Of course, the sleet melted because the temps were well above freezing, but I still was glad I got the plants inside before they were pelted with sleet. So, if you are leaving them outside all day while you are away from home, there is a certain element of risk in doing that.

It is hard to say exactly which warm-season crops will tolerate cool weather without having their growth or productivity affected in a negative way, but if I had to rank them....from those with the most cold-tolerance to the least cold-tolerance, I'd list them in this order:

Tomatoes (50 degree soil temp)
Sweet Corn (50 degree soil temp for regular corn, 60 degree soil temp for supersweet varieties)
Peppers (55 degree soil temp)
Bush Beans/Pole Beans (60-65 degree soil temp)
Summer Squash (60 degree soil temp)
Cucumbers (60 degree soil temp)
Cantaloupe/Muskmelon/Other Misc. Melons (60 degree soil temp)
Sweet Potatoes (60 degree soil temp)
Southern Peas (crowder, cream, black-eyed peas) (65 degree soil temp)
Eggplant (65 degree soil temp)
Lima Beans (65-70 degree soil temp)
Okra (68-70 degree soil temp)
Watermelons (70 degree soil temp)
Pumpkins and Winter Squash (70 degree soil temp)

You'll notice that I put a temperature in degrees after each type of veggie. That's the ideal minimum soil temperature at which you should put these plants in the ground, and I don't plant until the soil has been at those temperatures at planting depth for a minimum of 3 consecutive days. Soil temps are more important to me than air temps as long as the air temps are above freezing. Having said that, though, I prefer to keep the plants inside if air temps are lower than 50 degrees for any significant period of time. Look at the soil temp each veggie needs, and then ask yourself how happy they'll be sitting outside in colder air temps every day. You can take your soil temperature using an ordinary meat thermometer is sold in the kitchen utensil section of discount stores. (You could spend 4 to 5 times as much for the same thermometer labeled as a "soil thermometer" in nurseries, but why would you want to?)

Dawn

It looks like I had better go buy a couple more shop lights to place over my seedlings. I certainly don't wnat to risk going through all the trouble to get them going to have them stunted. Thanks for the information.

James

You're welcome.

During our first few years here, I carried plants out too early and also planted too early and the results weren't good. I'll still push tomatoes out a little early, but having a few in pots for early tomatoes has helped break me of that habit--at least a little bit.

Part of my spring planting issues arise from the fact that our property is in a low lying area in a bend of the Red River, so we're way down low in the river valley and will have freezing temps days or even weeks after our neighbors on higher ground just a mile or so away have had their last freezing temps.

I have found it seldom pays to expose plants to cold air or soil temps too early, and there is little benefite to doing so.

I'm the queen of shop lights. I have a 5-shelf plant starting shelf and each shelf is lit up by 2 sets of shop lights suspended by chains from the shelf immediately above it. Each of the fixtures holds 2 bulbs, so that's 4 bulbs per shelf for a total of 20 of the long fluorescent tubes.

For the top shelf, the lights are suspended from plant hooks in the ceiling and that's the shelf where I can put fairly tall plants. Neither the plants nor I could make it through Feb.-Mar. without the shop lights. I have the shop light/plant shelf set-up in a spare room UPSTAIRS and that helps me resist the urge to carry plants outside because I'd have to make an outrageous number of trips up and down the stairs.

I try to avoid carrying the plants (except the 4 early tomatoes) downstairs and outside until the back porch is warm enough at night that I can leave them there 24/7, which for me is sometime in mid- to late-March of most years.

With the 4 potted tomatoes (2 of which are already blooming), I carry them outside every morning and inside every night. I try to keep them inside until the air temp is about 50 degrees, so most days they get direct sunlight while sitting on a concrete slab from about 10 a.m. (or maybe noon on cold days) until about 5 or 6 p.m. From the early tomatoes in pots, I usually start getting ripe tomatoes in April.

Dawn

I've volunteered to start seedlings for my father's garden and he's having me plant them now. They're cool season vegetables: brussels sprouts, cabbage, broccoli and cauliflower. Is this too early to be starting them indoors? I'm still adjusting my "Minnesota" clock from last year to the Oklahoma seasons here. Plus I've never planted those four so I don't know much about them. My father has also said there's no need to invest in lights because by the time the seedlings have true leaves, we'll be able to take them outside nearly all days (though probably bringing them back in at night).

I was also wondering if I should be starting my parlsey that you (Dawn) kindly sent me, since it takes so long to germinate, or if I should still hold off on those?

Gamebird,

I don't think it is too early to start those cool season veggies now. In fact, it probably is the perfect time to do so when you take into account your planting dates, the number of weeks the plants need to grow in order to reach a transplantable size, and the number of days it takes for the seeds to germinate.

As far as whether or not you need lights, that is a personal choice but I'd rather have them than not have them, and here's why:

As long as the weather stays like it is right now, it wouldn't be too bad to carry the flats outside every morning and carry them inside every evening. If you have a somewhat sheltered porch, you could even leave them out on that porch if the overnight lows were going to stay above about 40-45 degrees. However, some years we get a prolonged cold spell in March or April where the days barely get out of the 30s for a few consecutive days and the nights are in the teens or 20s. We had one of those here in Love County in 2007 and I literally had to build a temporary hoophouse over my 2' tall tomato plants that were already in the ground. I left that temporary hoophouse over them for 3 weeks through a miserable prolonged "late" cold spell in which sleet and snow fell in some areas (but only cold rain fell here). In that kind of weather, even the cool-season plants are better off inside where it is slightly warmer but, without lights, they'll get leggy. So, it just depends on how much you trust the weather.

If your dad has gardened there in that area for several years and knows the weather, I'd handle his plants the way he prefers. A long time ago, I learned not to question my dad's garden judgement. : ) So, in daddy's garden, I did things the way he wanted, and in my garden, I did things the way I wanted them done. Different strokes for different folks.

Parsley is slow to germinate and seems to respond to cold stratification. So, I usually soak mine in water for 24 hours, wrap the seeds in a paper towel, put the paper towel in a zip-lock bag and put it in the refrigerator, leaving it there a week or two. THEN, I take it out of the fridge and plant the seeds in a starter flat. I get better results from that method than from any other, including direct sowing.

Dawn