[Gtbaker369]

Hi all,
I’ve dabbled in the past with growing at home and also at a previous allotment with good success. Recently taken on a new plot after a break with young kids and other commitments.
Im just looking for what people would say is the minimum temperature to start sowing most roots and legume seeds on the plot, either air or soil temp.
Previously I basically planted spuds in mid-late March, onions about now, then the rest around mid April.
But as the weather seems to be changing all the time, and temps are different up n down the uk, I was hoping to keep an eye on temps on the plot so can start as soon as the temps are steady.
Cheers all in advance 👍

[New shoot]

It is a cold and wet start to spring, so no point rushing to sow or plant out direct.

My spuds are still in the shed chitting and are staying there for another week or so.  Onions I have started, but they are in modules in the unheated greenhouse, as are a lot of other things.  I’m cheating the weather by starting under cover this year.  My plot has not even really started growing the annual weeds yet, so the soil is not ready for veg seeds.

[AnneB]

It is a cold and wet start to spring, so no point rushing to sow or plant out direct.

My spuds are still in the shed chitting and are staying there for another week or so.  Onions I have started, but they are in modules in the unheated greenhouse, as are a lot of other things.  I’m cheating the weather by starting under cover this year.  My plot has not even really started growing the annual weeds yet, so the soil is not ready for veg seeds.

It's the same here.  I was looking at my records for previous years and round about now I would usually be sowing peas direct but there is no prospect of that at the moment, far too cold.  I have onions in the cold greenhouse after starting them off in heat plus some Syrian black broad beans in modules ready to go out next week. I sowed a lot of brassicas in the cold greenhouse yesterday.  I have peppers indoors and so far that is it.  No sign of it warming up.

[Plot 1 Problems]

Same as New Shoot, I've delayed everything this year as the Spring has started poorly. I have my onions in pots in the greenhouse and I'm sowing my tomatoes and chillies indoors tomorrow under growlights.
I wont be sowing my parsnips or carrots for at least another fortnight.

[coldandwindy]

Hi all,...
Im just looking for what people would say is the minimum temperature to start sowing most roots and legume seeds on the plot, either air or soil temp.

Hello and welcome
THE THEORY
It's soil conditions you want to monitor. Seeds aren't fussy about air temperature as long as it's not so cold that the newly emerging growth is damaged by frost.
What soil temperature the seeds want depends which seeds you're talking about and for each there is a minimum they'll start at all and an optimum where they'll germinate best. For the vast majority, the optimum is so high you'd only reach it in UK with artificial soil warming. Here are the minimum temperatures for some common roots and legumes but bear in mind that the ideal is MUCH higher :-
Broad Beans 1.7C
Beetroot 4.4
French beans 15.6
Parsnip 1.7
Runner Beans 15.6
Turnip 4.4
(Sorry about the strange numbers- I think the work was done in a country that uses Fahrenheit & then it didn't convert to round numbers in Celsius!)
BUT ACTUALLY
 Later sown crops often catch up or overtake earlier sowings. Parsnips especially seem to do better sown much later than books recommend. When all is said & done the best idea is to watch what other gardeners near you are doing and watch what your own weeds are doing. When your soil is warm enough for germination you'll get a big flush of weed seedlings. Don't be in a rush & if you're not sure wait!

[JayG]

Not reminded folk of this link for a few years, but it provides some very useful information on this topic:

https://tomclothier.hort.net/page11.html

In particular, coldandwindy's observation that parsnips germinate much faster in warmer temperatures is backed up by the figures - at a soil temperature of 32F (0C), although parsnip seeds will germinate, you can expect to wait 172 days  (they are likely to have rotted away long before that though.)

At 68F (20C) you should expect to have to wait a much more reasonable 14 days.

[wolveryeti]

Can anyone recommend a good soil thermometer?

[Yorkie]

I remember an old suggestion on here (very much tongue in cheek  ) that when it was warm enough to plonk your bare backside on the soil for a certain length of time, the soil was warm enough.

Not sure I'd recommend this approach though 

[JayG]

I remember an old suggestion on here (very much tongue in cheek  ) that when it was warm enough to plonk your bare backside on the soil for a certain length of time, the soil was warm enough.

Not sure I'd recommend this approach though 

Once upon a time I'd be concerned about being reported for indecent exposure by my neighbours - these days I'd be more concerned about whether I'd be able to stand back up again! 

[missmoneypenny]

That was actually mentioned by Christine Walkden on last weekend’s Gardeners Question Time. I thin a good rule of thumb is have the weeds started growing yet. They haven’t on my plot, apart form the chickweed and a few clutches of couch grass.

[juvenal]

I remember an old suggestion on here (very much tongue in cheek  ) that when it was warm enough to plonk your bare backside on the soil for a certain length of time, the soil was warm enough.

Not sure I'd recommend this approach though 

The last time I tried this method I got a round of applause from the sheltered housing that overlooks my plot...

[coldandwindy]

Can anyone recommend a good soil thermometer?

Don't know how true it is but I've always been told to use my nose! You know that spring smell , when you go outside one day & realize you can smell soil? Apparently soil starts to smell like that when it reaches 10 degrees. Has anyone else heard that?

ETA sorry, that didn't answer your question did it!

[JayG]

Can anyone recommend a good soil thermometer?

I use my 'meat thermometer' for checking the temperature of my aquarium water, but it should also be ideal for checking the soil temperature. It appears to be pretty accurate when checked against my max/min thermometer:

https://www.amazon.co.uk/Thermometer-DOQAUS-Instant-Backlight-Foldable/dp/B07WKKS4HB

[Goosegirl]

Can anyone recommend a good soil thermometer?

I use my 'meat thermometer' for checking the temperature of my aquarium water, but it should also be ideal for checking the soil temperature. It appears to be pretty accurate when checked against my max/min thermometer:


https://www.amazon.co.uk/Thermometer-DOQAUS-Instant-Backlight-Foldable/dp/B07WKKS4HB

Sorry, thought your meat thermometer was a polite way to describe sitting in the nude on bare soil! 

[AnneB]

Not reminded folk of this link for a few years, but it provides some very useful information on this topic:

https://tomclothier.hort.net/page11.html

In particular, coldandwindy's observation that parsnips germinate much faster in warmer temperatures is backed up by the figures - at a soil temperature of 32F (0C), although parsnip seeds will germinate, you can expect to wait 172 days  (they are likely to have rotted away long before that though.)

At 68F (20C) you should expect to have to wait a much more reasonable 14 days.

I don't bother sowing parsnips and carrots until the first week in May now.   Always a better outcome than earlier sowings.