Seed germination temperatures
 

As we're into late February I started sowing things in the greenhouse
and of course we promptly get a cold snap so I've got out the heaters
to keep everything cosy. Now some of the seed packets I have suggest
that temperatures of 18 - 20 degrees are required which seems
reasonable enough for a day time temperature in a greenhouse at this
time of year but what sort of temperatures can seeds survive over
night and still germinate or for that matter what sort of temperatures
can seedlings survive once they have germinated?

(or putting it another way am I going to have to spend a fortune on
paraffin in the next forthnight?)

JB

In article , JB
writes
As we're into late February I started sowing things in the greenhouse
and of course we promptly get a cold snap so I've got out the heaters
to keep everything cosy. Now some of the seed packets I have suggest
that temperatures of 18 - 20 degrees are required which seems
reasonable enough for a day time temperature in a greenhouse at this
time of year but what sort of temperatures can seeds survive over
night and still germinate or for that matter what sort of temperatures
can seedlings survive once they have germinated?

(or putting it another way am I going to have to spend a fortune on
paraffin in the next forthnight?)

18-20 C is about the minimum advisable for seed germination including
overnight. We cover this problem with a propagator set at 20C.
Once germinated, seedlings can survive lower temperatures, but this
present cold snap with February temperatures much lower than January is
causing some difficulties with earlier sown plants. The damage is not
always recognisable at the time, but chilled seedlings can result in
poor plant growth at a later stage.
--
Alan & Joan Gould - North Lincs.

In article ,
Alan Gould wrote:

18-20 C is about the minimum advisable for seed germination including
overnight. We cover this problem with a propagator set at 20C.
Once germinated, seedlings can survive lower temperatures, but this
present cold snap with February temperatures much lower than January is
causing some difficulties with earlier sown plants. The damage is not
always recognisable at the time, but chilled seedlings can result in
poor plant growth at a later stage.

Er, no. That applies to a great many plants, but many alpines and
far northern plants will rot if kept that high, because they can't
make use of it and the fungi and bacteria can. If they are adapted
to germinating when the soil temperature is 5 Celcius, don't push
them too far!

No, I can't tell you which - only that I have failed for that reason.

And, of course, the serious tropicals will rot because they are too
cold at a mere 25 Celcius. Date stones seem to be almost immune
from rotting, but can't be bothered to germinate in such icy conditions.
As you may gather, I am NOT being successful :-(


Regards,
Nick Maclaren.

In article , Nick Maclaren
writes
And, of course, the serious tropicals will rot because they are too
cold at a mere 25 Celcius. Date stones seem to be almost immune
from rotting, but can't be bothered to germinate in such icy conditions.
As you may gather, I am NOT being successful :-(

Try them in your compost heap ;-)
Last autumn I dug out several germinated dates, a couple of avocados and
a mango from my heap. Of course by then it was too cold, but had I
caught them in summer ...
--
Kay
"Do not insult the crocodile until you have crossed the river"

In article , Nick Maclaren
writes

Er, no. That applies to a great many plants, but many alpines and
far northern plants will rot if kept that high, because they can't
make use of it and the fungi and bacteria can. If they are adapted
to germinating when the soil temperature is 5 Celcius, don't push
them too far!

No, I can't tell you which - only that I have failed for that reason.

We must be lucky, virtually all of our sowings are successful at 20C.
--
Alan & Joan Gould - North Lincs.

Here is a site I find very useful for seed germination info etc...one that I
have used for quite some time and have found the info to be quite good..

Tom Clothier's Garden Walk and Talk
http://tomclothier.hort.net/index.html

At least worth taking a peek;

Harold Walker


"Janet Baraclough" wrote in message
...
The message
from JB contains these words:

As we're into late February I started sowing things in the greenhouse
and of course we promptly get a cold snap so I've got out the heaters
to keep everything cosy. Now some of the seed packets I have suggest
that temperatures of 18 - 20 degrees are required which seems
reasonable enough for a day time temperature in a greenhouse at this
time of year but what sort of temperatures can seeds survive over
night and still germinate or for that matter what sort of temperatures
can seedlings survive once they have germinated?

(or putting it another way am I going to have to spend a fortune on
paraffin in the next forthnight?)

How are we supposed to guess, from zero information about what you
sowed and where you are?

Janet.

On Tue, 22 Feb 2005 06:45:03 +0000, Alan Gould
wrote:

In article , JB
writes
As we're into late February I started sowing things in the greenhouse
and of course we promptly get a cold snap so I've got out the heaters
to keep everything cosy. Now some of the seed packets I have suggest
that temperatures of 18 - 20 degrees are required which seems
reasonable enough for a day time temperature in a greenhouse at this
time of year but what sort of temperatures can seeds survive over
night and still germinate or for that matter what sort of temperatures
can seedlings survive once they have germinated?

(or putting it another way am I going to have to spend a fortune on
paraffin in the next forthnight?)

18-20 C is about the minimum advisable for seed germination including
overnight. We cover this problem with a propagator set at 20C.
Once germinated, seedlings can survive lower temperatures, but this
present cold snap with February temperatures much lower than January is
causing some difficulties with earlier sown plants. The damage is not
always recognisable at the time, but chilled seedlings can result in
poor plant growth at a later stage.

Thanks for the useful answer. What happens in the wild then? Does the
soil provide enough insulation to keep daytime and nighttime soil
temperatures much closer than I see in the greenhouse. At present I'm
seeing my greenhouse potting bench swing between 18 degrees in the day
(which seems quite good) and 10 - 12 degrees at night (which seems
quite low and awfully expensive on heating).

I have some seedling trays indoors which are racing away but the ones
in the greenhouse seem to still be dormant. If the seeds are chilled
will that matter as much as if the seedlings are chilled?

JB

In article ,
JB writes:
|
| Thanks for the useful answer. What happens in the wild then? Does the
| soil provide enough insulation to keep daytime and nighttime soil
| temperatures much closer than I see in the greenhouse. At present I'm
| seeing my greenhouse potting bench swing between 18 degrees in the day
| (which seems quite good) and 10 - 12 degrees at night (which seems
| quite low and awfully expensive on heating).

No. As I posted, there is immense variation. The surface of soil
that is exposed to the sun will vary considerably in the UK and
immensely in many other countries. Deeper soil sheltered from the
sun will not. Some plants will shrivel and die if they get too
hot or too much sun; others need high temperatures, but don't mind
cold nights; and yet others require semi-constant temperatures.

| I have some seedling trays indoors which are racing away but the ones
| in the greenhouse seem to still be dormant. If the seeds are chilled
| will that matter as much as if the seedlings are chilled?

It depends what state they are at. If they have germinated but
the cotyledons have not yet emerged, then yes. If they are still
dormant, then no.


Regards,
Nick Maclaren.

In article , JB
writes
Thanks for the useful answer. What happens in the wild then? Does the
soil provide enough insulation to keep daytime and nighttime soil
temperatures much closer than I see in the greenhouse. At present I'm
seeing my greenhouse potting bench swing between 18 degrees in the day
(which seems quite good) and 10 - 12 degrees at night (which seems
quite low and awfully expensive on heating).
In the wild, frost tolerant plants survive much better than less hardy
ones, but it does depend on situation, season, other weather elements
than temperature etc., but there will be many unrecorded losses. Many of
the plants we grow in our gardens originate from wild species, but they
have been adapted for gardening conditions and are inclined to need a
little help.

10-12C overnight should be adequate for average garden seedlings to
survive provided they are kept draught free and the periods at that
temperature not too prolonged.

I have some seedling trays indoors which are racing away but the ones
in the greenhouse seem to still be dormant. If the seeds are chilled
will that matter as much as if the seedlings are chilled?

Ungerminated seeds can tolerate sharp frosts, in fact some require to be
frosted before sowing as part of their life cycle. Once they are
germinated, they become vulnerable.
--
Alan & Joan Gould - North Lincs.

The message
from "Harold Walker" contains these words:

Here is a site I find very useful for seed germination info etc...one
that I
have used for quite some time and have found the info to be quite good..

Tom Clothier's Garden Walk and Talk
http://tomclothier.hort.net/index.html

At least worth taking a peek;

Harold Walker

Another site you might find useful is
http://www.backyardgardener.com/tm.html, but it does not cover veg.

Stuart Wright

The backyard gardener one is the one that T & M used to give out for free
with seeds orders....a great pity they discontinued the publication....mine
that is about 15 years old is getting rather tatty.....but still avery
usefull one...HW



Stuart Wright" wrote in message
...
The message
from "Harold Walker" contains these words:

Here is a site I find very useful for seed germination info etc...one
that I
have used for quite some time and have found the info to be quite good..

Tom Clothier's Garden Walk and Talk
http://tomclothier.hort.net/index.html

At least worth taking a peek;

Harold Walker

Another site you might find useful is
http://www.backyardgardener.com/tm.html, but it does not cover veg.

Stuart Wright