How hot does a greenhouse get???

Loads of different factors come into play when sowing tomato seeds in the UK.
Do you have a greenhouse, if so is it heated, do you have supplementary lighting etc.
The general rule is sow somewhere warm six to eight weeks before last frosts in your zone. You will require to give them as much daylight as possible and keep them at least 10Deg C at night for them to progress, any lower than this will hinder progress and frost is a killer.
To give you an Idea In my case I have a heated greenhouse and a nice warm conservatory plus lighting.
I sowed my first dozen toms on Jan 13th these were kept warm and had lights over them, they are now potted up into 6" pots and are 10" high (this is after burying stems deeper each potting up ) Last year I was eating toms from Jan sowing in May. ( first one 19th)
I will be sowing my next lot this weekend once again in conservatory and expect these to be fruiting by July thus extending my season.
The Jan sown plants will be kept in the conservatory until April by which time they will be in their final pots and around 2ft 6inches high.
Depending upon forecasts the first dozen Jan sown will go into the greenhouse in April which will be heated, the sowing this weekend will be kept in the conservatory until towards the end of may and will go into an unheated greenhouse at this time. just as insurance I will leave a thermostat controlled heater in the greenhouse until June as I live right on the coast in the north east.
Hope this helps Alex.

 

For those of us born after the reign of queen Victoria , 100f = 38°C
I leave the door open on warm sunny days . The window whitewash is easily applied and removed when not required . Not sure where you buy it from . They always used it on glass factory roofs as I remember.

 

Automatic vents are a must for a small greenhouse, mine take the heat off a little when the temperature suddenly increases in the sun this time of year.

I don't sow tomato seed until the end of March, by June they would have caught up with seed sown earlier, as previously mentioned.

 

I started my tomato seeds indoors about a month ago. They are now over a foot tall. As soon as I start heating the greenhouse, they'll be going out there. I have also started asprabroc, hot peppers, kelsae onions, drumstick, marigolds, pansies. Yesterday I started brussels sprouts and thumbergia seeds. Today I will be starting zinnias, osteospermum, gazanias, and some more nicotiana. If I had your climate, I would have my greenhouse in use right now!

 

Hi Lori, I sow my seeds today, 3 types of tomato, 3 types of chilli and 2 different types of cucumber. I'm really proud of myself lol

 

I bought these propergators this morning at my local garden centre. Whilst wandering around I first spotted them on a central display unit priced at £5.49 each so I picked up 3, I carried on walking around the store and I came across another display tucked away at the rear of the store and they were priced at £3.99 each. I checked the labels and they were exactly the same, same brand, size, so I swapped them over and paid the cashier and they did register as £3.99... woo hoo lol

 

I'm struggling to think of anything to add to that, except if sowing plants to bring on in the greenhouse for planting outdoors, sow a few weeks later.

And although bush tomatoes can be a waste of space in a greenhouse, early quick maturing bush varieties, like Red Alert, can be brought on in pots and turfed outside when warm enough.

 

As @Scrungee says, pots work really well until you are ready to plant out in the garden. I do this with my beefsteak and roma tomatoes. I did grow some greenhouse variety last year but in retrospect felt they weren't as productive as the outside ones and therefore taking up expensive real estate.

My greenhouses are transitioning areas for most of what I grow and for the summer usually just have hot peppers in them.

 

That's how I view my greenhouse, just somewhere to bring on loads of plants until they all can be planted out either in polytunnels or open ground as and when conditions permit.

 

I've only sowed onions in mine up to now, but then my greenhouses are mainly for getting tender plants through the winter.
Although I will be sowing more seeds, before the end of the month and into next month for things like outdoor toms.

The only plants that really do well in an unshaded greenhouse in high summer are desert cacti and succulents IMO.

 

Sounds like everyone has been gardening most of the way the the winter too!

I just came across some clear plastic that I had cut in order to make a taller cover for one of my cold frames. I had sewn the first one last summer and will get this one done in the next few weeks.

From indoor to greenhouse - from greenhouse to cold frame - then covers off the cold frames. That is how I get my exercise

Right now it looks pretty sad out there because I didn't have time in the fall to properly store everthing but you can see the cold frame on the right is the original "as bought" and the one on the left is the one that I added height to and made a new cover.