Urgent Greenhouse heating advice needed

[martynsread]

Hi,

I have installed a paraffin heater in the greenhouse today and put a max min thermometer in there. I did have the roof window open for a while but there are a few gaps in the glass which I reckon will provide enough ventilation. I've left some chitting potatoes in there and some unplanted seeds and onion sets (which I hope to plant at the weekend).

It has snowed today so it's a bad weather day anyway but could you please answer me the following couple of questions.

1. Even during the day I've been getting a min temp of 6 degrees so presumably overnight it's going to get even colder. Am I right in thinking that I want to avoid it getting less then 0 degrees - and if so then how warm should I expect the heater to keep the greenhouse overnight?

2. If I wan't to use the greenhouse now with all it's fumes and smell, is it safe for my potatoes and propogating seeds to be in there. It just seems like a very messy (possibly dangerous) and unreliable way to keep things warm.

3. Can I leave this heater on all day and night - the instructions don't tell you about when to use it and when to switch it off.

Any help gratefully received.

Mart.

[martynsread]

Also...

Just also want to ask will having my potatoes growing in pots in the greenhouse (and anything else I'm intending to eat) be at risk of contamination from the fumes?

[NOG]

1. You don't want to let it get below 0. I would bring the pots and seed inside the house or at least in the garage incase the temp goes down too far it it gets to -3 you onions and potatoes are buggered..

How warm it will keep it will depend on the size of the greenhouse the size of the heater and how far up you turn the heater.

2. If you have the heater adjusted corrctly there shouldnt be any fumes or smell. Before you turn on the heater fill it with parafin and leave it for at least an hour for the wick to soak. Light it then trun it down till you get a blue flame across the wick, if it keeps going out turn it up a bit and you will get a yellow flame. If you are getting black smoke you have it turned up too much.

3. Leave it on as long as you want if you can afford the oil. When you burn Parafin it gives off CO2 (not CO) so it is good for the plants.

[rustylady]

Personally don't heat my greenhouse (can't afford it). Have used paraffin heater in the past at old house, but only overnight. I just hope to keep my greenhouse frost free. If you really want to go in for greenhouse heating in a big way then you will need something with a thermostatic control (probably electricity) which will involve wiring the mains to the greenhouse.

[nick the grief]

Hi Martyn

I wouldn’t worry about the smell it won’t hurt anything. As to leaving the heater on during the day, I wouldn’t do that either. Slightest bit of sun and the temperature will rocket. At night you can always cover them over with some fleece.

As to other forms of heating:-

* Electric – needs installing by a qualified electrician or it can be dangerous but is thermostatically controlled. (Heaters cost £40 + although the best are Parwins and they are around £100)

* Bottle Gas – Minimum installation cost, heaters cost about the same (£100 ish) but the fuel is expensive to buy and you really need two bottles and an auto diverter valve as sods law say the bottle will run out in the middle of the coldest night!! Also thermostatic control but not as accurate as the Parwin heaters. ) Needs ventilation as per Paraffin

* Mains Gas (or Oil) – if you can pick up a cheap 2nd hand boiler then get the Gas installed to it ( or run a feed from an oil tank) you can use this with hot water pipes still needs am electric supply though for the pump etc. again Thermostat control

* Solid fuel – as above or you can buy them designed for a greenhouse but can be expensive to run and you can’t go away for the weekend this time of year although the boiler ash is great for the bottom of your cold frame as slugs hate it

* Paraffin – I think you know all about this one !! Needs ventilation as it gives of Water vapour as well as CO2 so you need some airflow in there.


Hope this helps

[martynsread]

Thanks all

Well I've left my chitting potatoes, my various veggie seeds and onion sets (all unplanted as yet) all wrapped up in fleece in the greenhouse with the heater left on (at a safe distance )

I'm not paranoid about the smell and effect on the prospective veggies any more - many thanks all for allaying my fears.

When I last popped in the Min/Max thermometer said 3.2 so who knows how cold it'll get. Hoping the fleece will reduce the risk though.

I tried getting that blue flame but it just started to go out so I've left the 2 flames just under the level of the top of the burner.

Again many thanks everyone for the quick and excellent advice to my urgent need.

All the best

Mart

[Alice]

Hello Martynrsead, Maybe I'm not reading this properly, but I think you said you had chitting potatoes, unplanted seeds and onion sets in the greenhouse. If that's right - why have you got heating on ?
Your unplanted seeds will be fine anywhere, and most can be germinated indoors without additional heat.
Your potatoes will chit any cool, bright place,
And your onion sets could be just about planted.
As for your paraffin heater, some of the more expensive ones can be set to burn with a blue flame which gives more heat and less smell, water vapour etc, while the cheaper ones burn with a yellow flame, give less heat, are very smelly and give off gallons of vapour. I gave it up in favour of electricity although it is more expensive.
I think you need to look at your heating requirements. I try to organise things so that I only need to put a little heating on in April and frosty nights in May. It's not worth putting heating on unless you have enough stuff in there to justify the expense.
A lot of seeds need 15 to 20 degrees to germinate, so it's not worth trying to heat a greenhouse early in the season to do this, Better just to germinate them indoors, then put out into the greenhouse.
A temperature above 5 or 6 degrees is a growing temp for most plants so no need to heat above that.
Many plants and veg are fine as long as the temp is above zero. so no need to heat as long as overnight temp is above freezing.
Many plants are fine at temps around zero if covered with fleece.
Sorry I can't tell you all the answers in one paragraph.
Come back and tell us what you are growing and grapes will tell you what they put heating on for, and what will manage fine without it.

[martynsread]

Hello Martynrsead, Maybe I'm not reading this properly, but I think you said you had chitting potatoes, unplanted seeds and onion sets in the greenhouse. If that's right - why have you got heating on ? ...

Alice thanks for your reply - I think I may be 'over-egging the pudding' with the heater.

I'm going to plant Pentland Javelin potatoes in pots (I want to grow them in pots rather than in the ground) in the greenhouse at the weekend. I also want to start off some onion sets.

I have seeds for cabbage, cauliflower, spinach, rocket which I want germinate then transplant outside.

I also have some tuberous begonias and alpines that I need to keep warm until the frost goes - but I've kept them in the house.

I can germinate the seeds in the house no problems, and I have some fleece. Looking at what I'm trying to do what would your advice be please. Also, when they say cover your plants with fleece, do I lay a sheet over the top of the whole plant or just cover the soil.

Oh boy I feel like such a wet behind the ear, thanks so much for your indulgence and patience.

Mart.

[Alice]

Hello Mart, to use your fleece, just fold it into 2 or 3 thicknesses if you have enough, and put it over your plants like a quilt. It's as light as a feather and won't damage anything. It will protect plants from a few degrees of frost. The weather is billed to get warmer after Thu so there should be less problem.
Do you have a thermometer in your greenhouse ? If not I suggest you buy a max - min one then you can see what is going on in there.
Your potatoes in buckets won't need any heat. Once the shaws are up above the compost they do need to be protected from frost, but flleece thrown over their heads will do this.
Begonia tubers do need to be warm to get started and you're right to keep them in the house. They need to be frost free at all times so can't be planted outdoors until risk of frost is past.
I don't know what kind of alpines you have, but I wouldn't have thought there was any need to keep them warm. They don't like to be too wet so I would have thought an unheated greenhouse would be fine for them, but maybe somebody else can advise.
Your cabbage, cauliflower, spinach and rocket are all quite hardy. Once you have them germinated and pricked out they should be fine in the greenhouse just covered with fleece at night.
Since you have your heater you might want to make some use of it. I use mine in April and cold nights in May. Once I have lots of stuff in the greenhouse, if the day temps are unseasonably cold I put the heater on to keep it up to 10 degrees during the day and 5 degrees at night if poss. to keep the plants growing (plants won't grow below this temp) - but frost free would be fine for most things. Keep an eye on your thermometer and see what goes on in your greenhouse. Off course if you have money to burn you can heat the greenhouse to much higher temps and get things on faster, but I think you get soft, floppy plants which are difficult to acclimatise to outdoor growing. Hope this is of some help Mart. Good luck.

[GardenFan]

HI Mart,

Sound advice from Alice. My GH is rammed to the rafters right now so I am using fleece and heating. My heater is the yellow flame, smelly sort but does the job to lift the temp. I tend to switch it off during the day so I am not wasting fuel (and sow indoors as Alice suggests), you will save money that way. The build up of vapour can be problem, I do open a window if the daytime temps are not cold (which also helps with temps getting high in direct sun). I use bubble wrap attached to the glass, this helps retain night time temps.