What does "optimum germination temperature" mean to you?

[JerryHaskins]

This is not specific to tomatoes, but when looking into planting seeds, I see guidance regarding the optimum germination temperature.

That is especially true with regard to spinach seeds.

Now, I suppose that means "the constant temperature that the seed would like to be at while it is germinating."

I can kind of control the temperature of seeds in peat pots and trays.

But if I want to plant seeds directly in my garden, the daily high and low temperature ranges this week from 91 degrees in the daytime to a low of 55 degrees at night.

That's a 36 degree swing over 24 hours and is typical for Mississippi (zone 8a) in the fall.

I am not sure what the soil temperature is in my garden---but I would guess that the shallow soil in full sun would exceed the air temperature high in the daytime, but might not get quite down to the low at night.

So what do youall do with regard to "best germination temperature"?

I.e., what temperature do you go by when deciding when to plant?

(I know---I am suppose to find the date of the first or last freeze and back up so many days. But that gets hard to do.)

Thanks.

[Father'sDaughter]

If I'm direct sowing, I put them in a little after the time indicated for my zone and let nature do the rest. When conditions are right, they'll sprout. The only other way is to monitor soil temperature daily and wait until it's within the range you're looking for.

[JLJ_]

Originally Posted by JerryHaskins

This is not specific to tomatoes, but when looking into planting seeds, I see guidance regarding the optimum germination temperature. That is especially true with regard to spinach seeds. . . .

You might find it useful to google (or use other search engine) to search for:

priming spinach seeds

There's a lot of good info on it

Essentials seems to be spinach doesn't like to germinate above 75 degrees F

Don't refrigerate during priming

1) soak seed at room temp for 24 hours

2) place wet seeds on coffee filter, paper towel, or uncoated paper plate and let dry 24 to 48 hrs

3) put seeds in ziplock bag or other airtight container and put in cool dark place (not refrigerator) for another 24 to 48 hrs -- but not more than a week

4) plant

Recommended procedure varies slightly depending on region and outdoor temps but in southern areas people report four good spinach crops annually.

Here's three related posts (from the same thread) by camochef in Pennsylvania, describing his experience with this. Posts are at idigmygarden.com -- tomatoville's 'sister' forum. Camo may have posted about it here at tomatoville, too, but I don't happen to have the link.

http://www.idigmygarden.com/forums/s...8&postcount=24

http://www.idigmygarden.com/forums/s...3&postcount=27

http://www.idigmygarden.com/forums/s...8&postcount=31

Here's a t'ville post from camo on the priming, and a follow up by b54red

http://www.tomatoville.com/showpost....34&postcount=8

http://www.tomatoville.com/showpost....32&postcount=9

[brownrexx]

I used camo's information this spring with wonderful results and much more germination than I had without priming. Spinach seeds are notoriously fussy to get to germinate.

The soil does not change temperature as rapidly as the air does of course but lettuce seeds are not supposed to germinate about 80 degrees and I planted a whole row of seeds in August when we kept having 90 degree days. I got about 6 plants to grow out of a full row of seeds.

Another seed that requires a warm temperature to germinate is peppers. I could never get them to germinate until I started using a heat mat under my pots. Now they germinate well.

Bottom line is that seeds do have an optimum germinating temperature and it you either exceed that temperature or are way below that temperature then you will probably get some germination (like my 6 lettuce plants) but you will not get a high percentage of germination.

[carolyn137]

Go to Johnny's Selected Seeds online and order or request their catalog or just read there to confirm optimum temps for germination there as well b/c for everything they offer they indicate the optimum germination temperature.

I chose Arugala since I didn't want to spend time browsing for spinach.

http://www.johnnyseeds.com/p-6001-arugula.aspx

Almost all early stuff like lettuce and radishes and greens want conditions on the cool side so they mature before they bolt.

Carolyn

[AlittleSalt]

I'm in zone 8A too and learning.

Last week, there were 3 days that the high temperature was 100F. Yet panting guides all said I should be planting Mustard greens. If I had planted them - they would have not had any chance of germinating. It's one of those times when I can say, "Been there, done that, didn't work."

This week is completely different. At 10am, I sitting at the computer beside an open window. It's 60 degrees! I planted mustard greens two days ago - hoping the high temps next week are not 100F again. The 10 day forecast says that it isn't going to happen, but this is zone 8A.

[Cole_Robbie]

The past few years, I have used a plywood box built around a pallet in the greenhouse. I would put an electric heater in at night and crank the thermostat all the way up. It would get to 95-100 degrees easily, maybe hotter. I would open the box and turn off the heat every morning. As long as I didn't leave any seeds in there after they sprouted, which made them leggy, I never had a problem. The only way that heat has ever killed any seeds or plants of mine has been when the heat makes them dry out. But they died from the lack of moisture, not the heat. I don't remember sprouting spinach, but I have done other greens and lettuce that way. What I liked about the hot box was speed: lettuce in two nights, tomatoes in three, and peppers in about four.

[decherdt]

I kinda like these sort of guides http://www.webgrower.com/regional/pd...-ChartPCMS.pdf
This site shows high percentage spinach germination at 50F daytime soil temp over 12 days, and lower percentage at higher temps, over shorter time.
http://tomclothier.hort.net/page11.html

[JerryHaskins]

Originally Posted by decherdt

I kinda like these sort of guides http://www.webgrower.com/regional/pd...-ChartPCMS.pdf
This site shows high percentage spinach germination at 50F daytime soil temp over 12 days, and lower percentage at higher temps, over shorter time.
http://tomclothier.hort.net/page11.html

Super info there, dechert!

I especially like the soil temperature web site. I will keep it for reference.

And this confirms my suspicions: "But it is soil temperature that invites the seeds to germinate, not air temperature. . . the soil temperature is always cooler than the air temperature."

[JerryHaskins]

Thanks for the info, folks.

I tried the "priming spinach seeds" thing this fall. After following the directions carefully, I put 3 seeds in each of 72 little seed starter compartments filled with potting soil, watered them and covered it with the clear plastic cover. Then I put them in the shade outdoors.

Exactly two (2) seeds sprouted.

So I am reverting back to the old technique of sowing lots of spinach seeds every week or two and hoping for the best.

I have grown beautiful spinach in the past, but not lately.

Thanks again. I will click on those links.

[brownrexx]

If your soil temperature is too high to favor germination, then priming will not help.

Priming gets them to germinate faster and it does that for me but you still need to have the right conditions. My primed seeds germinate in less than a week but if I don't prime then it could be more than 2 weeks and it is spotty germination.

If you are planting in pots anyway, why not keep them indoors where it is cooler until they sprout?

[JerryHaskins]

Good point, brownrexx. Thanks.

I measured the air and soil temperature early this morning and just now at noon in my garden (which gets full sun in the middle of the day.)

Early morning around daylight:
Air temperature = 58 degrees F
Soil temperature = 68 degrees F

Noon:
Air temperature = 80 degrees F
Soil temperature = 98 degrees F

So it looks like the sun and warm air are really heating up the shallow soil near the surface.

That means that I get a big variation in shallow soil temperature through a 24-hour period.

And that complicates figuring out when to plant seeds.

I don't think my mama and daddy worried about such things in the 1950s. They just planted seeds and grew wonderful vegetables in the spring and fall. At least that is how I saw it as a child. Maybe they knew more than I gave them credit for.

[brownrexx]

Wow, that's a huge temperature difference. It may help to spread some light straw mulch or grass clippings over the seed beds to keep the direct sun from heating the soil as much. Keep it wet until germination too.

[JerryHaskins]

Originally Posted by brownrexx

Wow, that's a huge temperature difference. It may help to spread some light straw mulch or grass clippings over the seed beds to keep the direct sun from heating the soil as much. Keep it wet until germination too.

Good idea. My soil is pretty dark in color (readily absorbs heat from the sun) from all of the compost I have added over the years.

[aimeehoward]

Speaking of temperature here are a couple of advises:
P { margin-bottom: 0.08in; } One of the most common issues gardeners face when they work is the threat of frosts and freezing weather that could easily damage crops and plants. There are some things you can do to protect the more tender and sensitive plants however, such as the following:

• What exactly is a freeze?

A freeze happens when temperatures drop beneath the freezing point of water (0°C or 32°F). Once the inside of the plant freezes it causes its cells to burst or even shatter the stem or tree trunk when the ice inside expands. Different plants will react in different ways to freezing temperatures:

• Frost tender and tropical plants will not survive freezing temperatures as they only grow in naturally warmer climates for obvious reasons.
• Annual plants will not survive a freeze, but they will instead disperse seeds that help spread and replenish their growth once the weather is warm enough to do so.
• Perennials with strong roots will have their foliage frozen and killed, but the roots will survive and pick right back where they started once spring arrives, making them the easiest to work with from a professional gardening point of view.
• Fully hardy perennials, trees and shrubs will enter a dormant state that will lower the danger they are in during freezing temperatures. They will reduce sap content and preserve water in the process. Spring blooms as well as the earliest foliage will be damaged by sudden flash freezes, but the plants will recover most of the time.

Frost will occur on clear and still nights with low temperatures. As said temperatures plummet, the surface of the plants will also dip below freezing, causing the formation of ice crystals in the same way you can see dew forming on them during warm nights. Because temperatures happen to vary a close to the ground, frost can form even when the temperature on your thermometer shows as above freezing. There are different types of frost:

• Hoarfrost is the most familiar of frost you will see on chilly mornings. It will result whenever you have water in the air deposited in the form of ice crystals.
• Rime frost happens when you have water deposited in liquid form such as fog or dew that then freezes over. It has a glazed appearance.
• Black frost is when frost itself doesn’t form but the plants end up blackened or damaged by freezing temperatures instead.

When it comes down to fragile blossoms, they will be threatened by the freezes in late spring too. When it comes down to it most tender plants will not really suffer under frost or freezing, as long as the temperatures are not too low and the freeze doesn’t last too long.
Most of the time you can protect the plants you have with a good layer of mulch to keep their root system warm during that time. It won’t take too much to deal with it during your gardening efforts. Protecting the plants can be done in a number of ways that go beyond mulch of course.

• Potted plants can be brought back inside to keep them safe from the harsh cold out there. Make sure they still see enough sunlight to thrive, but not touching the windows since the cold can transfer through the glass, damaging them.
• Another good way of ensuring you can keep them safe is to cover them during the night with a tarp or a blanket. It may not do wonders during really cold winters, but you will still have a chance to help them survive, as long as you make sure the covers have been propped up to prevent breaking any stems.
• You can build a greenhouse to protect the more sensitive plants you want to keep alive during the cold winter months. It will take some work, but it will be worth every minute spent on it in the long run. You will however need to ensure your greenhouse sees ventilation to avoid condensation as this can also become a problem.
• You should also choose plants that are well suited to your climate, allowing you to take full advantage of local plant types.