greenhouse seed starting

[greenfinger]

We are working on building a 6x9 greenhouse kit. Meanwhile, I just gotta know now, when can I start my seeds?
About how far from last frost do ya'll start yours? If we end up heating it, it will only be for the occasional close to freezing nights.
Any tips, please, please?

[garnetmoth]

Where are you?

Lots of folks use thermal mass (ie water barrels, as large as possible), or maybe a wall of stones to absorb heat during the day and radiate out in the night. Using space blanket/mylar on the "backside" of the greenhouse can reflect more light in (north side in the northern hemisphere)

our plant out date is about May 15 here in Cincinnati, Id start mid-March if I had my stuff together ;-)

You can likely grow kale, collards, chard, salad burnet, and other hardy stuff now depending on how cold your area is.

[honeydew]

It will really depend on where you are, and in my opinion, what you really want it to do.

My last frost date is June 2. I usually start my seeds inside under lights, and as this is the first spring I will have a heated greenhouse, I plan to start putting some of the more hardy seedlings out in April, weather depending. Everything will be out there by May. I also built mine so that I could partition off and heat only a small portion of the GH to save on heating.

I plan to use remay cloth and other insulating techniques to protect the seedlings. The idea is the greenhouse is insulating against the cold, why can't you double greenhouse inside the structure? Then I won't have to heat it AS MUCH as soon. Will be closely monitoring temps to make sure this doesn't turn out bad. lol.

Take everything I say with a grain of salt, as I'm flying by the seat of my pants on this one. My only other experience is working in a nursery greenhouse where they heat as necessary starting in March. My boss there always started her seeds indoors, on a schedule, and brought them out when they needed to be transplanted up. They were then cared for in the GH from that point.

Are you just hoping to get an early start on things for the garden? Will you be using it to extend things past your first frost date in the fall or (if you are in a mild area) overwinter things?

Definitely what garnetmoth said could help you...you may find space an issue for the thermal mass.

Marie

[greenfinger]

Garnet
"Where are you?"
1/2 hour from Memphis, TN!! Now you should be able to help a lot.

"You can likely grow kale, collards, chard, salad burnet, and other hardy stuff now depending on how cold"
I haven't proven the chard yet, but the other stuff does just fine under the sky. It doesn't need any help at all.

My plant out date is April 15. I usually start tomato family plants inside in Feb. They just seem so small to me. I was hoping to start in Jan inside and pot up and put in the greenhouse in Feb.

Marie
"The idea is the greenhouse is insulating against the cold, why can't you double greenhouse inside the structure?"
Have you been reading "Four-Season Harvest" by Elliot Coleman? a useful book, though I won't be able to implement much of it. The winter is too mild. A Hoop house could give me a fall harvest of green beans though. Hmmm...
The mylar is a great idea, we will also be stacking bags of leaves outside against the north wall. It is already somewhat sheltered by a shed 10ish feet away.

'My only other experience is working in a nursery greenhouse where they heat as necessary starting in March.'
As necessary=when the temp is expected to be below 35 F?

'...you may find space an issue for the thermal mass'
Uh, yes! 6'x9'! This spring it will NOT be a problem. But next year I hope to overwinter several peppers, tomatoes, ROSEMARY (that I can't seem to keep alive in the house, somehow it freezes outside), and some leafy lettuce to lighten up my dark green salads already containing kale, collards, turnip greens, etc. from the garden.

[honeydew]

Why yes, I have been reading that book, among others..... Could you use more inexpensive season extension techniques outside the GH, such as low tunnels covered with cloth or poly? Maybe plastic mulch for the soil? I really don't know what your 'winters' are like.

Re: my old nursery job. We lived in a zone 3 in Canada, so I think that's a USDA z4(?). She had several GHs and opened them up one at a time. The First House was a 30x100 and she kept it closed off from the next one until there was no more room and so on. She used a cold one for pansies and cold frames outside one GH for strawberries. The First house was heated comfortably - we could work in t-shirts and contained your typical bedding plants that needed an early start. Best job I ever had....would still be there if we didn't move away.

[DarJones]

Greenies. Gotta love em.

The first rule of a greenhouse is to understand that air circulation is critical. You need a fan, not a big one, but something about 12 inches diameter for that size greenhouse.

The second rule is that you MUST have some way to heat a greenhouse if you plan on growing tomatoes and peppers. A small electric heater or a small gas heater on a thermostat will work for you. Caution that tomatoes are VERY sensitive to gas in the air so be sure to have a reliable non-leaking system.

Now think about what you want the greenhouse to do for you. You can grow early starts of peppers and tomatoes at any point you want them. I would suggest starting off with seeding hot peppers about the 1st of January, sweet peppers about the 15th of January, and tomatoes about the 1st of February. Start them inside the house where you can control germination temps to at least 72 degrees F or better yet, get a heat mat to place the seed start trays on.

Your normal frost free date should be about the 10th of April. This means that the tomatoes and peppers should be potted up to at least 6 inch containers though 1 gallon would be a better choice IMO. Whatever container you decide on, make sure you calculate the maximum number you can put in the greenhouse without impacting your ability to get in and care for the plants.

Whatever you think you know about growing plants, get ready to revise it drastically. Growing in a greenhouse is very different from gardening in the summer season.

Why start peppers earlier? because hot peppers can be very slow to emerge and then they grow slowly and sweet peppers are similar but not as finicky.

Why not start earlier? Because the plants will be so large by the time April 10th rolls around that you won't be able to keep them in the greenhouse. A tomato plant at 12 weeks old will either be 3+ feet tall or else it will be severely stunted from growing in too small a container. You DON'T want stunted tomato plants, they rarely fully recover except with expert care.

Figure out what you are going to use for a grow mix. I would suggest getting a couple of 3.8 cubic ft bales of promix BX. That will give you a good baseline to determine where to go in the future. Get familiar with places like this one. You are going to need supplies and will either have to find a local supplier or else order them shipped in. www.mortonproducts.com/

Spiders are your friends. I get asked repeatedly how I control white flies. The answer is simple. As I walk through the house, I keep an eye out for spiders and move them to the plants. It only takes 5 or 6 hungry spiders in a small greenhouse to control virtually all the pesky bugs that want to suck on, eat on, lay eggs on your plants. My greenhouse is 23ft by 32ft so it takes about 50 spiders. I've been known to cultivate fruit flies just so I can turn them loose in the greenhouse to feed the spiders. Note that fruit flies will NOT harm seedlings but don't go there if you are trying to mature fruit!

If you try to overwinter plants, be sure to spray them thoroughly with neem starting about 2 weeks before you move them indoors and repeating every 5 days with a final spray just before you move the plants into the greenhouse. Why? Because the neem will help you avoid moving aphids into the greenhouse. Did I mention that the phrase "population explosion" was invented to describe aphids in a greenhouse?

The temperature you grow tomato seedlings at is important because it determines how productive the plants will be later in the garden. Start out maintaining temps above 60 degrees until the plants are at least 5 weeks old. Then you can drop the temps down as low as 35 degrees for 7 to 10 days. After the cold treatment, raise the temp back up to 60 degrees minimum until you set the plants into the garden. If you dig around on the net you will find a few descriptions of this process that tell how much more the plants produce as a result of the cold treatment. Please note that it is fine to keep the temp above 60 the entire time seedlings are in the greenhouse, you won't really lose anything, but if you choose to cold treat, you will increase the crop the plants produce.

Another trick you will need to know is that cold temps seriously slow down plant growth. Just one night at 35 degrees will inhibit growth for up to a week with temps at 70 degrees. There is a caveat to this. If your greenhouse goes down to 35 degrees in the night, you can completely reverse the growth suppression by letting the greenhouse go up to 100 degrees the next day. This is easy in direct sun, just set the vent to open at a higher temp. The maximum temp you should allow in the greenhouse is 120 degrees for seedlings. It won't hurt them as long as they have plenty of water.

I'm going to wrap this up by saying that the single biggest mistake you can make when growing seedlings is to overwater. Tomatoes and peppers should get to the point where they start to wilt before you give them water. This is another little trick to pull on the plant because it forces the plant into a phase where it puts most of its energy into expanding the root system trying to find more water. Guess what that enhanced root system does when you set the plant out in the garden?

Here are links to review.
www.kdcomm.net/~tomato/Tomato/start.html
www.selectedplants.com/seedlings.htm

DarJones

[greenfinger]

Thanks for all your info!

[DarJones]

Here is something to think about while you are considering your greenhouse.



I picked those in my greenhouse late yesterday and today. Dinner is SERVED!

DarJones

[honeydew]

fusionpower - that's some great info! Thanks for the tidbit about the cold treatment for tomatoes, I had not heard that before!

[ottawagardener]

DarJones: I hadn't heard of cold treating tomatoes but I have started half wintersowing tomatoes (inside at night, outside during the day) and they perform really well. This means that they don't get the initial 5 weeks of warm treatment though.

Actually, my regular technique was to start them off sometime in March (our plant out date is around mid-May but can be as late as June) and then put them outside during the day in a small greenhouse near the house even when it was cool: as long as it was above freezing in the greenhouse. I would bring them in at night. So I suppose this is similar. I don't get stunted growth but I second what you say about tomatoes getting pot damaged if they aren't planted out within a magic window, and I got get great production from them. Also having them outside early, for me, means less supplemental light, more real sunlight, more wind so stouter, stronger stems.

I don't grow plants in a greenhouse during the summer though so I'm not sure about starting from that point of view. Toamtoes end up being started about 6-8 weeks before planting out time.

I start hot peppers up to 12 weeks earlier. I also prestart the seeds on moistened paper towels in plastic bags. I have used bottom heat too though I'm not sure how much it helps. Seems to be okay with just a warm spot under lights.

[Penny]

Nice pics, Fusion.

[ottawagardener]

Hardiness zones:

I had always understood the zone conversion from Canada to US to be that the Can. Z 5 was roughly equivalent to the US. Z. 4 or -1 but if you read the 'official' websites (as I just did), apparently, the variables they use are slightly different so that conversion is not always straight forward.

Canadians variables in zone determination - well whattayaknow:

www.planthardiness.gc.ca/ph_variables.pl?lang=en

From what I can gather on the map found at this site, I'm a US Z. 4a and a Can. Z. 4b (though my microclimate(s) are to be determined).

www.planthardiness.gc.ca/exmint.pl?lang=en

[greenfinger]

"You can likely grow kale, collards, chard, salad burnet, and other hardy stuff now depending on how cold.
I haven't proven the chard yet, but the other stuff does just fine under the sky. It doesn't need any help at all."


Ahem... Well we have had 10 F overnight temps with freezing rain and daytime temps of 24ish F. My turnips have drooped over, not dead, but severe damage to the leaves. I'm hoping that this weeks' daytime temps of 55ish will cause recovery. So perhaps a row cover for such temps would be a good investment.