keeping the greenhouse frost free

s4lvatore

Right guys time for advice from experienced growers.

I got a 6x4 blow away type plastic greenhouse. As of the start of March I am going to have to start putting my seedlings in there. Only thing is I need to keep them frost free, so here is my plan.

Initially I am going to line the inside of the g.h with bubblewrap. Inside the g.h I am going to use 4 four shelf blow aways as staging. I will cover these in the fleece covering that you can buy, probably not going to put the plastic covers on them though.

I was also thinking of having two 60 watt tube heaters in there like these, gil-lec.co.uk/products/Heating/Tube+Heaters/1+Foot+Tube+Heater+-+60W+Eterna/1699585480

Keeping the greenhouse door zipped up do you guys think tbat this will be enough, or will it get too sweaty in there?

Your advice is greatly appreciated.

fwor

Depends on what tariff you're on, but running those 2 heaters all the time will cost around £10/month, so it would probably be worthwhile investing either in a frost stat, or a different heater with one built in.

s4lvatore

Yea I have worked the price out and it sounds fine to me.

Just was wondering if you guys reckon it will be fine and if ghose heaters actually will be warm enough

cubegame

It's quite a big area. We have a 2.2 KW gas heater in our 8 x 6.

Davesnave

The main thing about heating seedlings etc, which I don't do any more, is not to have 'adequate' capacity, but to have an excess for when it's needed. This either means spending out on a good thermostat, calibrating one inside a quality heating unit, if you know how, or spending more than you might like on electricity.

If you don't have that emergency capacity, it's a bit like things were years ago when most people had paraffin heaters. If you went out and got a bit drunk in those days, there was no automatic system to light your heater when you came home and crashed......and it only took one cold night of forgetfulness!

So, the short answer is, no, 120 watts isn't total insurance against the lowest temperatures recorded in March. On the other hand, how lucky do you feel, or would a warming mat and cover work for you, rather than heating the whole space? I had a covered sand bed that ran on 40 watts via thermostat all winter and that worked a treat. The sand held on to heat gains made during the day.....we are talking maybe 1/4 tonne here!

alanobrien

I would line the inside with bubble wrap as that will help to insulate it and retain the heat

Mallotum_X

Remember to open the doors on warmer days so the seeds are not sat in stale damp air.

You may want to consider a basic fan in there to keep air moving.

jennifernil

Seedlings like warm feet and cool heads, so bottom heat is always better. You also do need to keep the air circulating or you will get problems with damping off.

I use heating cables on the benches with thermostats, and cover them with fleece overnight. Once I need to heat more than just the bench area I use a fan heater set on frost protection.

Insulating the GH is good, but too many layers of bubble/fleece/etc will cut out a lot of the light and lead to leggy seedlings, especially if you are using shelving units rather than just a single level bench area.

Really it is a compromise between quantity (of seedlings) and quality.

What are you growing, and what quantities?

s4lvatore

I guess the light may be an issue so I may not bother with the bubblewrap although then that would mean the heating has to be spot on. I could open the fleece up during the day.
I am in berks so I an hoping we don't get -6 or so in March.

The damping off is a worry, would having a fan in there work do you think? I could leave the door open every now and again during the daytime.

How would I know if it is getting too damp in there, condensation I would assume.

s4lvatore

I will be growing mostly tomatoes, pepper, chilis, aubergines.

Also onion and leek seedlings. May start some early potatoes in pots too.

jennifernil

I would go with the bubble to insulate the whole house if using it early in the year, but by March it should not be so cold, so the extra light would be better.

If you can put fleece on only when it gets dark and remove the moment it gets light, it will keep the seedlings cosy and still allow the air to circulate a bit, keep it well above the top of the seedlings.

If you get condensation, ventilation and keeping the air moving will help, just watch out for draughts.

Other things to consider are .....

starting a little later, the plants will soon catch up

staggering the planting so you have plants at different stages of fruiting

spacing the seedlings/plants sufficiently so they don't shade each other

if using shelving, as much space between the shelves as possible

raising the seed trays as high as possible for best light

take care with watering, always best from below with seedlings, stand the trays/pots in a tray of shallow water to soak up what they want, then drain well, this encourages the roots to go down to seek the moisture

tomatoes need less heat than peppers, chillies and aubergines.

seeds need different conditions for best germination.....heat....light.....read up on what each needs.

use silver sand instead of compost to cover seeds

if it says not to cover, use a light covering of vermiculite to retain moisture round the seeds

Good luck!