Unheated Greenhouse

[Ageing DJ]

Hi
I have just put up my greenhouse, i intend to grow toms, cues and peppers. The greenhouse is not heated but i have today bought an electric propagator. When should i sow the seeds for tomatoes and is it best to have the propagator indoors or in the greenhouse.
The weather is a lot milder here in Cornwall and the night temp in the greenhouse has not been below 8c, daytime temp has been an average of 18c but did rise to 35 today in the sun.
Thank you for any help.

[rustylady]

Hi Dj, whereabouts in Cornwall are you? The weather down ther is certainly a lot milder than here in East Anglia. I was born in Devon and grew up there. However, I would question your reading of 35 degrees today, was it a typo? Any thermometer should be placed out of direct sunlight so that you record the air temperature, not the temp reached by direct sunlight on the thermometer.

Personally, here in E Anglia I am biting my nails waiting to sow toms etc, it's far too early. They will germinate either in a heated propagator or on a windowsill, but you then have the problem of looking after them until they can be planted out.

[Ageing DJ]

Hi rustylady
I am on the lands end peninsular, perhaps the thermometer may have been in the sun because the most it has read before was 18c.
I am an essex boy but i know suffolk quite well as i lived in Sudbury for some time.
So do you think it would be best to wait till the end of the month before i sowed the seeds as i suppose they would have to grow on in the green house as i think it would bo to dark indoors?

[rustylady]

Personally I would hang on for a while before sowing toms, peppers etc. If you sow now they may germinate well, but as you say they need to grow on and they do need a lot of light to keep them sturdy. If you germinate them indoors and try to grow them on there, they will probably grow very talll and leggy due to the warmth and lack of light.

[Ageing DJ]

Ok thank you, i will wait till later in the year

[Alice]

Hello Aging DK, I understand your quandry about when to sow, light and temperature. Some of it is trial and error and how much risk you want to take. I think for tomatoes and cucumbers it is too early. They will be too big to keep indoors before it is safe to put them out. But peppers do want a long growing season and don't get too big too quickly. You could sow some and bring them on , on the windowsill, ready to go out to the greenhouse when the temperatures are safe. I planted mine in December and they are lovely wee plants.
At the end of the day, if it works, you're 3 months ahead. If it fails you've lost a couple of seeds, and not even the compost as you can put it on the compost heap. I'll see if I have time to post pics of my peppers tomorrow. Definately worth a try.

[Ageing DJ]

Thanks Alice
I will give the peppers a go

[Alison]

I've planted up some peppers / chillis and a couple of aubergenes also but I wouldn't bother with toms and cucumbers yet, I've been impatient in previous years and it's a waste of time and effort. Never gone as early as Alice but will be interested to see how she gets on as I may find I could go even earlier.

[nick the grief]

I never bother with my toms till I've finished with the Chrysanth cuttings ( around April) Thats plenty early enough for Warwickshire. You could maybe getaway with 2 or 3 weeks earlier but the problem will be they may run out of steam by the end of the year - you could always so2 or 3 seed then waith a month and so another 2 or 3 but it's a lot of hassle for not much benefit.

[Ageing DJ]

Thank you all for your advise
Regards
Ageing Dj

[Geordie]

Alice raised a good point about early sowings in respect of light and warmth. I feel one of my rambling posts coming on, so you may want to start off with a mug of tea!
I think most people on the Vine look forward to the first or earliest strawberries, tomatoes, new potatoes and so on.
I see the advantages of an early crop as economical; that is the earlier in the season the more expensive a product would be to buy, as quick; early varieties can often crop in time periods where main crop varieties would not, as space; earlier crops free up space sooner for follow on crops, and lastly but perhaps the most important it provides fresh produce and so vitamins earlier in the year after the winter and perhaps spring of eating stored vegetables. ( I make no mention of the competitive spirit that places undue value on beating one’s neighbours and the sense of ambiguous achievement it brings!!)

Of course it gets progressively harder to get crops earlier and earlier. For some of us we will have ripe toms in July, its harder to achieve in June, difficult in May and near impossible in April (without a second mortgage to pay for the heat and grow lamps, unless toms follow marijuana in the pricing structure). So for most of us I guess it may be possible to have any crop as soon as you want the effort and cost do not make sense, but hey don’t let me put you off!

The earlier I try and start the more difficult it is, and although seeds emerge like s**t off a shovel its because they are running on a reserve of stored fuel which soon runs out and they stagnate. The cold combined with the low light levels, the sun is low, dim and absent for longer than it appears. The plants simply can’t grow as strongly as they do not get enough energy and they are then subject to moulds and rots. Even if the top seems to escape the roots may be attacked, resulting in wilting and death. None the less, if I don’t push to hard then each year I can grow most things a bit sooner than I did last.

So, we all know more protection, more heat and more light are all necessary to get the earliest crops. With outdoor crops the best effort is to effectively bring them indoors; be it with plastic bottles, cloches or cold frames. To actually grow indoors enables us to provide heat and even more light artificially. Although these are possible outdoors, as with a hot bed or soil warming cable and outdoor lights, the expense is wasted unless the plants are also given weather protection with glass or plastic. Again outdoors the economics force me back to improving the micro climate and then invariably to putting the crops undercover. An exception could be to use soot to darken the soil or black plastic, but again these would be more worthwhile if combined with a clear plastic cover. I could not plant out a seed potato under a cloche and expect a result but I can grow them year round in pots in a heated greenhouse or polytunnel. I accept that the plants are poor specimens and yield is poor but hey the taste is great.

However this is a major problem for early crops, the more protection you give them against the weather the more you reduce the already dim sunlight. I learnt that it is cheaper to increase the layers of insulation in winter to reduce the expensive heat loss, and to substitute artificial light for the increasing dimness. You will find that a growing light gives off heat anyway.

So the extra light we can use to give the seedlings a boost for a few hours every day, this will make them happier and stronger. Give them more hours and make them happier. But better still is to extend the day length beyond the short winter’s day of 8 hours to a summery 11 or 12. The downside to extra light, whilst comparatively cheap to run is the fairly high start up cost. Just adding heat though can be counter productive, without the extra light the plants get drawn and leggy and it may be best to keep them cooler. Indeed even with extra light it’s probably best to have plants just a little warmer than their barest minimum rather than much warmer.

Extra heat is essential, though, for all the earliest crops being able to maintain this minimum temperature on the coldest nights. These always seem to arrive in February or March when many tender crops will be under way. As for type of heat, heat at the roots seems much more efficient and I think would promote better growth than simply raising the air temperature. If you warm the soil many plants will accept a lower air temperature than when standing in colder soil, so the cost of heating the air can be reduced. This can be extended if the area warmed is given the additional subdivision of its own cloche or cold frame. But once again we are back to low light.

Thinking of light levels, the position of the plant can have an effect upon this. If using a greenhouse, invariably there is more light on top of the staging than down in the border. This difference can be further improved by raising the staging or fitting higher shelves. Raised plants are also in warmer air, it may be many degrees warmer up near the roof, where do you hang the thermometer – toward the top or the bottom of the greenhouse? Raising plants up high has its own downside, that one day that is quite warm may just cook all your seedlings if ventilation is not considered. So I think I will try early strawberries in hanging baskets from the roof of the greenhouse, this certainly will keep the slugs at bay!

If we have managed to supply heat and light to our early plants the question of feed is one that needs consideration to ensure continued development. Two problems seem to arise; too much feed and anything not used by the plant can turn to ammonia and will kill the seedling. Over watering can be as bad as over feeding, I guess most of us base watering on the state of the compost we can see, how good a guide is that? The problem of ammonia appears again if you regularly re-pot your plants, the unused compost will go stale and ammonia can kill the plant. As its early crops we seek, the likes of tomatoes and peppers need to have early flowering induced (effectively bolting) which can only happen if confined to smallish pots at the beginning.

So we have conquered good light and heat, we haven’t over fed or watered but still they don’t grow as well as we want. This could be a lack of carbon dioxide as in a confined space it will be quickly used up. Without carbon dioxide the plants won’t grow and they may get some from the soil they won’t prosper. A tightly shut up greenhouse or cold frame has little decaying compost full of animal life and there is no change of air. I agree this is maybe a little picky and takes no account of opening the door to over water the seedlings! One solution lies in your home brewing techniques….an open bottle of fermenting sugar water and yeast should do the trick.

To the plants themselves, the likes of tomatoes, peppers and melons, stopping and disbudding to direct the growth into the earliest fruits can bring the first to ripen forwards by about a month or more. If you remove the top of a tomato plant one leaf above the first flower truss you may be surprised how quickly the fruits set and swell. And as if by magic a replacement leader will grow from below so the plant can be planted out later as normal anyway.
With tomatoes the disbudded tops and side shoots can be potted up to root as new plants which being biologically mature flower and fruit much sooner than similar sized seedlings would. Cucumbers do not want stopping but melons do, either can be rooted. Peppers can be rooted from cuttings, but in my experience do not go on to perform well. Much better to over winter the plant when the fruits will ripen weeks ahead of those sown afresh.

To ripen quickly many of the greenhouse fruits require more warmth than is available, especially the earlier crops. Luckily we already know how to ripen green tomatoes by using the ethylene gas given of by bananas. Unfortunately there also seems to be a tendency in many plants for a ripening fruit to suppress the setting of other flowers or other fruits swelling. Thus it would be better in terms of production to remove the maturing fruits, and yes that’s the reason behind the folklore of picking produce often to ensure continued cropping.

So after all that I guess I have two choices, the expense, time and effort of striving for early crops which may or may not succeed, or just accept the seasonality of produce and enjoy it when nature delivers it!

Sorry....rambling finished.

[Alison]

Good grief Geordie, have a sit down and rest for a bit!!!!

Seriously though, I agree with most of what you have said. However, from my point of view, the choice is simple and I am not willing to take on the expense (both financially and environmentally) of providing expensive lighting / heating to bring crops in at un-naturally early times. I do have a heater in the greenhouse to use in espeically cold periods (as at present) to keep certain plants going but I limit the amount of time this is going (less than a week of nights during last winter). I try to avoid buying food that is out of season or grown using artificial stimulants as I simply don't see the point, what's wrong with eating what is available and looking forward to the next crop at the right time. I'm not knocking anybody starting things off a bit early and risking tender plants against the last frost, that's all part of the game. Indeed a heated propogator just to get things moving doesn't seem unreasonable. However, if you need to provide additional and heat throughout the major part of a plant's life then surely you're growing the wrong crop for that time of year / geographic location, I'll never understand the need to crop tomatoes in May in the UK.

PS - apologies to anybody who does this, just it's certainly not for me.

[jools]

Oh Gosh, I am bowing down to all this superior knowledge. But I have sowed my Big Boy toms as I thought they needed a longer growing season. The seedlings have popped up but I'll have to leave them in the propogator for the time being. Then, perhaps I'll bring them in. I have been looking at the jumbo propagator. Its huge (47 x 19 ins), almost 20 ins high and with a variable temparature so I might splash out (again!) and get one of those. I figure it must be cheaper using one of these than heating the whole greenhouse. Doesn't resolve the light issue though.
Jools