tedln
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Soil Temp?

I've never payed much attention to soil temp when I am planting seed in the ground. I usually simply pay attention to the beginning of a season and plant seed accordingly. We have had an unusually cool or cold winter and I am guessing the soil temp is below the normal average for this time of year. I'm curious if anyone actually keeps a thermometer stuck maybe eight inches in the ground and uses the soil temp as an indicator for the correct time to plant seed. Any ideas what the optimum soil temp is for most vegetables?

Ted
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applestar
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Just received an excellent newsletter link on that subject from Johnny's: https://growingideas.johnnyseeds.com/2010/03/jss-advantage-april-2010.html

I found it interesting to note that broccoli seeds can be planted earlier than cabbage. I thought it was the other way around, though I knew cauliflower needed to be later than broccoli.

This year, I'm trying to be guided by Phenology: https://www.ghorganics.com/Phenology.html
Last edited by applestar on Tue Mar 30, 2010 3:29 pm, edited 1 time in total.

The Helpful Gardener
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I think phenology is a great way to go because it takes soil temps into account by default, along with a slew of other variables...

HG
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tedln
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I like the idea of using Phenology and probably do use it in a limited way by observing when the rye grass blades start to widen, when the dandelions bloom, when the common housefly population is increasing, when the daffodils bloom, and other natural phenomena occur. I've just never grouped those things under a common name.

Since every area of the country is different, what phenomena do you look for applestar?

Ted
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applestar
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I've been trying to apply them directly to what grows in my own garden.

For instance, though the connection is not made on the website I provided, last year, my seed potatoes came with instructions to plant at a certain soil temp. As it turns out, in the link the above, it was specified that "The crabgrass seeds germinate when the soil temperature at a depth of 4" stabilizes at 55°F. This soil temperature can coincide with the time the forsythias are in bloom." Well, hey! THAT'S the temp that came with the seed potato instructions! So I've extrapolated it to mean that seed potatoes should be planted when forsythias are in bloom as well as "when the shadbush flowers." My 3 varieties of shadbush/Amelanchier have not bloomed yet, though they had budbreak a few days ago, so it's not long now.

As you implied, the trick, I think, is to adapt the Phenological signs to your own local micro-climate and varieties of plants. For instance, my own crocuses bloom much earlier than when the neighbors' forsythia are in bloom (I don't have one).

Daffodils have been in bloom. I have green ash, maple, and elm trees to keep an eye on, as well as bearded iris. Maybe I should plant some chokecerries. My only mature oak tree is a Willow oak, so no help there on size of squirrel ears. They say elsewhere to look to mature trees rather than young "whipper snapper" trees because they haven't experienced the seasons for multiple number of years; so, they don't know any better. :lol:

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AndrewH_TX
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My guess was, this was how my grandfather and all those other ol' timers knew when and when not to plant the seeds.

All these "Spring Signs" & "Start Dates" would prompt different plantings.

I've always wanted to learn what the "signs" are, but he passed before I took the chance to ask.

Very good subject, thank you!
Thanks, AndrewH

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rootsy
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Re: Soil Temp?

tedln wrote:I've never payed much attention to soil temp when I am planting seed in the ground. I usually simply pay attention to the beginning of a season and plant seed accordingly. We have had an unusually cool or cold winter and I am guessing the soil temp is below the normal average for this time of year. I'm curious if anyone actually keeps a thermometer stuck maybe eight inches in the ground and uses the soil temp as an indicator for the correct time to plant seed. Any ideas what the optimum soil temp is for most vegetables?

Ted
For sweet corn, yes. Everything else I plant by date... Cold weather products go in April... Everything else Mid May earliest (due to the possibility of frost and wind chill damage)... I push the sweet corn planting as far forward as I can but with an Augmented Sh2 you need a minimum of 60F maintained for adequate germination... 65 is recommended but if I wait for that I won't have corn for market until August...

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