With a greenhouse, the proposition of when to start which seeds is a bit tricky. I'm curious at what other people do. Obviously everyone's circumstances are a bit different, such as where you live and if your greenhouse is heated and what you are growing. But this forum offers a great way to learn from others.

So here's my list - please add yours!

My greenhouse is in Montana, unheated but pretty well insulated.

mid Feb: Start lettuce, spinach, mesclun, broccoli, green onions, parsley, pansies, alpine strawberries. Broccoli and green onions will be grown inside the greenhouse in ground beds.

mid March: Start tomatoes, peppers. Start basil that will grow in the GH. Plant carrot seeds in the GH ground beds. Transplant lettuces into windowboxes. Harvest first salad!

early April: transplant herbs into windowboxes or larger pots. Harvest lots of lettuce and greens.

mid April: Direct sew cucumbers that will be growing inside the greenhouse. Planted a few seed potatoes in the ground beds as an experiment. (which worked and gave us potatoes in early July). Start flowering sweet peas in 4" pots. Pot up tomatoes and peppers into 4" pots. Plant up various containers of annuals (purchased at nurseries) to get nice big pots before bringing them outside in May. Start more greens.

mid/late April: Major planting of seeds for plants that will be grown outdoors. Start lettuce, broccoli, spinach, green onions, basil, plus cutting flowers zinnias, snaps, rudbeckia.

early May: Harvest first basil for pesto! Plant tomato and pepper starts into ground beds in greenhouse. Pot up remaining tomatoes into gallon pots. Harvest carrots that were planted in GH last fall. (Harvesting the carrots frees up room to plant tomatoes and peppers.)

mid May through late May: Transplant everything outside as needed. Hardy veggies go out in early May with row covers. Tender veggies go out in late May or early June. This year will add row covers for those too. Plant root crops outside.

mid-June: Second round of greenhouse-grown lettuces are done. Switch to outdoor greens. Start heat-tolerant lettuce for outdoor growing.

early July: Harvest GH broccoli; GH tomatoes and peppers growing strong. Outdoor lettuces are at peak, time to start more. (I am terrible at getting lettuce started on time)

mid-July: Harvest first tomatoes from greenhouse! Harvest greenhouse-grown potatoes. Outdoor lettuces/spinach are bolting.

mid-Aug or early Sept: Start new seeds of lettuces, spinach, pansies and greenhouse-grown carrots for fall growing.

Sept - Oct: Spend every free moment harvesting, canning, freezing. Start one last round of lettuces, some of which will overwinter.

Nov: Keep harvesting tomatoes, peppers, cukes from inside the greenhouse, until first deep freeze puts an end to that.

Dec: Plant a few bulbs in the greenhouse ground beds. Harvest lettuces.

Jan - early Feb: Harvest greens occasionally. They grow slowly so we get about one salad every other week.

mid-Feb: Go back to the start of this list and repeat! :)

Phew! I am interested in what timing works for the rest of you. I still find myself lacking in heat-tolerant lettuces to harvest in late July-August. I'm also always seeking the earliest, best-tasting tomato to grow inside the greenhouse.

Second - I've found a good record keeping system is key for learning from my mistakes. I have a notebook where I jot down the status of things every 2 weeks or so. I also keep track of how many plants I start and what varieties. Then I fill in notes like "don't bother with these!" and "start these earlier next time!" and "This type is the best yet!"

I rely heavily on these notes and my own editorial comments. It really helps to have the info written down from year to year because there are too many details to remember and it's those little details that can make a big difference. Plus, there is something therapeutic in writing everything down and reflecting on it.

I did print off Johnny's Seed - Seedling starting calculator - available on their website but will have to adjust the frost date from experience with the GH - may be of help though. Martha Stewart's Seed Starting Worksheet www.marthastewart.com/seed-worksheet may be a form to use a a guide in developing my own history and notes as you suggested.

Getting started the first year in our GH with seedlings it appears we will need a seedling heat matt and not having an inventory - much - of plastic pots, decided to try the Soil Blockers - mini 3/4" and medium 2 1/4". This GH is opening a whole new world of Gardening for us in zone 3-4 (Wyoming). Mixing the soil has us somewhat concerned - thought we could just use potting soil but guess that doesn't work that well for seedlings?

It may be that the weather report (night time temperatures) is a good friend to make sure precautions are taken inside the GH to protect the seedlings? I assume a good thermometer inside the GH is important to gather data comparing - outside temp to GH temp - (our GH is not heated) in determining what precautions to take in the spring/fall when temperatures drop?

Any experience with starting seedlings is helpful to us!

I am certain that you will have fun and do a very thorough job in tracking your seed-starting this spring. For soil, generic "potting soil" is not worth much. After failing with the substitutes, I now only use "pro mix," which is made from peat moss, perlite and vermiculite. This is produced by Sunshine and other companies. There is also "germination mix" which is the same basic thing but with smaller particles.

The Pro Mix comes in compressed bales. They are expensive, but for us junkies there is no doubt it will all get used up in time! It is also sold in normal sized bags if you just want to try it out.

As for predicting temps in the greenhouse, you can start now by setting up a wireless thermometer that has at least two temperature probes. Make sure it records the max and min temp. Put one temperature probe in the GH and one outside. The base station goes in your house so you can monitor the temps while sipping morning coffee.

Every morning, compare the outside low with the GH low. You will quickly get a feel for how the two compare. Armed with that data, you can start to predict what your greenhouse low temp will be.

Once you've gotten seeds started, you can fine tune the temp by using heat mats on cold nights, moving flats to the floor where it's warmer, covering things, or if all else fails, bring the flats inside the house for a night or two.

Today was warm and sunny in the GH. Our cats love to hang out in there and doze in the cozy warmth. The problem is they will not come out! So I let them spend the afternoon in their own private spa. Happy cats.

Jed - if you are only using a greenhouse to start seeds you don't need too much space, so smaller sounds like a good idea. In TN you should be totally fine getting things started in Feb. If you need just a little heat, the heat mats are a good way to go without heating your entire structure.

Then the next step is: if the low temp inside is too low, use water to store heat and release at night. Several calculators out there to determine how much is needed.

Dan

What is your outside temperature? What inside temperature are you trying to achieve? I can't imagine you need much heat to make late-February TN weather work for seed starting.

As I have learned from Dan and others here at the greenhouse forum, plastic coverings offer very little heat retention at night. If it were me, I would invest in a sturdier greenhouse covering and some black water barrels or buckets for heat retention, and then you probably won't need a heater at all.

I don't have any experience with greenhouse heaters, so maybe someone else can add some insight there. Personally, I would be very nervous about putting an oil-filled heater in the middle of a bunch of straw bales, especially with a plywood cover over it. Sounds flammable to me, but like I said, I have no experience there.

There are some great suggestions posted on recent threads. Dan and Jr slick (not sure if that is his handle, but something like that) have outlined various methods for hoop houses and cold frames.

Good luck!

I used to start seeds inside with lamps, but the greenhouse with its strong sunlight produces much stronger plants.

I use Argibon and other types of row covers exactly like you describe: on at night and off during sunny days. In the coldest parts of winter, like now, I leave the covers on for the most part unless its actually sunny. Once mid-Feb hits, the greenhouse starts to get a lot warmer and things start actively growing again, so the covers are definitely off during the day.

I start most seeds in trays but I direct seed cucumbers and carrots in the greenhouse ground beds.

I've also had great luck growing greens in window boxes inside the greenhouse. I direct seed into those, using mesclun type seed mixtures.

Good luck with your soil overhaul. That is almost always a good thing to do!

I have been organic vegetable gardening in small raised beds for 8 years, 1 year at my new home. I grow almost everything on trellises. I just received a 10 x 12 Harbor Freight GH as a gift. The gift giver's wish is to get me, my seeds, pro mix and fish emulsion out of his basement work room, so I am glad to hear that seeds can be started in an unheated greenhouse!

Once the greenhouse is up later this summer, I will start a log of min and max temps. Thank you for the tip! Minimum temps seldom get below zero here, but I am in zone 6A.
I will have electrical service to the greenhouse. I have been reading everything I can find about passive solar heated greenhouses. I plan to insulate the north wall and the foundation with foil backed insulation board. I will have black water-filled barrels on the north wall as heat sinks that will also serve as supports for the north shelf that will hold the seed starting flats.

I am hoping that heat mats under the seed starting flats and plastic covers will supply enough additional heat at night to enable me to seed start. (Are there more than one kind of heat mat? Mine do not have temperature settings.) I do not want compost in the greenhouse, because I do not want to attract vermin.

I copied the calculations for BTU's needed to heat a 10 x 12 ft polycarbonate gh in Ohio. Thank you for this info! I will research minimum temps in March here and hope for the best the first year.

My foremost worry right now is the foundation and drainage, but I haven't found the specific info I am looking for in any of the forums. We are on 30 feet of clay (verified in the well report). I will need to plan carefully for drainage, especially since I plan to grow vegetables in the floor--cold hardy greens in the winter and long season veggies and cucumbers in the summer. Does anyone have suggestions? I thought about digging out the footprint of the gh and laying perforated pipe that would drain down the hill (is this called drainage tile?). Then I would cover the floor with pea gravel. I would build the beds on top of the gravel with untreated wood and fill with good soil, and fill walking areas with more gravel.

Karin, I looked at the pics of your gh, and I love your stone flooring. I see that you have beds in the floor inside. Can you tell me more about these? How did you plan for drainage?

The county building inspector recommended a cement slab and not worrying about the frostline. There are no legal restrictions on how I may build the gh here. No requirement for a rat wall, either, but I am considering one. The property is surrounded by farm fields.

I'm sorry this post is so long, but it is my first. I was delighted to find this topic with recent posts! I hope I can be helpful to you in the future.

Pat

Congratulations on your new greenhouse - that sounds very exciting. Good for you to be doing lots of homework and planning before you build.

We do not have quite the same drainage challenge that you do. Our subsoil is a compacted, alkaline soil that likes to bond tightly together, but it is not as impermeable as clay. I have not taken any special measures for drainage. The beds on either side of the aisle have been dug out about 18 inches down and filled with peat moss, compost and sand. The following year I added gypsum and more compost to try to break up the mineralized clumps that kept forming. So far, so good. It drains with no problems. (But again, we have OK drainage overall.)

The flooring is done with concrete pavers. They are on a bed of sand that is about 3 inches deep. The edge of the flooring is held in place with a strip of composite "trex" wood. The Trex is crzy expensive but it holds up perfectly well in the high-moisture environment of the greenhouse.

If I were you, I'd be hesitant about a concrete floor. Not only will it not drain, but it will be colder in winter than a dirt floor. Insulating the perimeter of the greenhouse is the way to go - if you do a search you will find more info on this topic.

Good luck! Let us know if you have more questions.
Karin

You said in the coldest times of the year (January) you keep the row covers on all of the time except when it is sunny. Two questions for you: First what is the crop that is being grown for this? Second, what kinds of row covers are they?

You have me very excited to try a greenhouse!

My winter crops are carrots, green onions and various greens (lettuce, spinach, pak choi). Also some flowers and this year I am trying burying some pots of bulbs to see if that might get them through the winter for springtime forcing.

My covers are a thick fleecy fabric that I got at JoAnn's fabric store. It happens to be the right width to fit the width of my beds and of course it comes in any length. It's made from recycled bottles and it's white. Cost is about $5/yard last time I bought it.

I also use the heavyweight Remay type fabric, but at least at our local stores it comes in a big square shape which is not as conducive to the shape of our greenhouse. Also it is not as heavy as the fleecy stuff.

This year, with our non-winter, I have been keeping the covers off and actually harvested a salad last week! That is purely ridiculous, but at least the lack of winter has a small benefit.

Do you have a greenhouse? Or are you still in the dreaming phase?

Karin

Sounds like you are making good progress in forming your plan. Lots of research and thinking about it is a great idea, and getting your husband on board is essential, especially when it comes to getting the GH built.

Have fun and keep us posted!
Karin

Oh yes, I start all my seeds in the greenhouse and they love it in there. I use heat mats in March and parts of April for the warm weather plants.

If your plants are leggy they must be not getting enough light. What is your setup like? Are you starting them inside or in the greenhouse? I used to get leggy seedlings when I started them inside under lights. But it the greenhouse they are stocky and strong.

Congrats on your first season with your greenhouse! They are especially nice in this climate. Where in MT are you?

Karin

Thanks for the response! I start them under grow lights inside on a heat mat. I was worried it would be too cold in the greenhouse, mine was getting down to the 20s at night during March and April. I am considering starting them out there and then bringing them in at night next year.

I live in Cardwell, which is in between Butte and Bozeman. I am really excited to use this greenhouse, but I have quite a bit of learning to do. I started peas and cabbage and the like out there in March, but they seem like they got too hot before they matured so I have just moved most of those cool weather plants outside and am hoping they will take the transplant. The cool nights seem like they are going to be a problem because the greenhouse is nearly as cold as the outside temps are. How does your greenhouse fare at night?

Cool, we are nearly neighbors! :)
Our greenhouse stays pretty warm at night. I think it's pretty well frost free by late March/early April. I can usually expect the low temp in the GH to be 5-10 degrees warmer than the low temp outside. Ours is pretty well insulated (8mm twinwall polycarbonate) and we have a nicely insulated foundation. Plus it is chock full of black water buckets.

If you use the heat mats in your greenhouse you'll be fine - that is, if you have electricity in your greenhouse.

Here's a list of a few things I do to keep things warm in the spring:

- put flats on the shelves during the day (warmer there)
- move flats onto the floor at night (warmer there)
- use plastic domes over the flats and then cover the the whole thing with frost blankets. That will almost always be 10 degrees warmer than the outside low temp.
- If it is really cold you can put your flats on the floor near a couple of black water buckets and put the blankets over both the buckets and the flats. Cozy!
- take off the plastic domes during the day, unless it is really cold AND cloudy. I have cooked more plants this way!

- For the heat mats, I put a couple of sheets of styrofoam underneath the heat mat because otherwise much of that heat is lost through the bottom of the shelf.
- When all else fails, bring the flats inside at night. If I do this I try to limit myself to 1-2 flats because that gets old after a while.

Hope that helps!
Karin

Now, having warned you, what is your greenhouse like? Does it have plastic glazing? If so, drill a hole big enough to accommodate the plug end, or cut off a small piece of a corner. After you pass the cord through, you can patch/caulk it to seal the little hole from air leaks. Does that work?

Do you have a wireless thermometer in there so you can see the temperature during different times of the day? That's a key thing to do so you can learn what to expect from your greenhouse during different types of weather. Then you'll be able to look at the weather forecast and know when things inside the GH may be in trouble.

I do have a wireless thermometer and was a little disappointed by the amount the greenhouse cools off at night, nearly to the same as the outside temperature. It does warm up very quickly though once the sun comes back out. I have been reading about the passive solar heat and thinking about putting some black barrels out there. Does it seem to make much of a difference? I am a little hesitant to fill up the space with the barrels because all my beds are ground beds and I would lose space that way.

But kudzu is right, having electricity opens up a lot of options. Such as listening to nice music while starting seeds. :)

I started looking into stand alone power sources (solar, battery with an inverter...) but that is getting quite a bit out of my comfort zone so I think next year I may try some plants inside and some outside with as much physical protection as I can figure out and compare the two results. Have either of you tried the bubble wrap around the walls or anything along those lines? Maybe not, given that you have electricity.

Thanks kudzu for the opinion about the water barrels. I have gone back and forth on that. I'll just continue on without those for now.

I haven't tried bubble wrap but lots of people have. If you search around this forum for that you'll get some more info. Same goes for water buckets/barrels.

I like your idea of trying some seeds both ways. Ultimately we all figure out the best plan for our conditions and I'm sure you will too!

[I should also mention that karin's suggestion about running the cord under the foundation -- while clever -- is not a good solution since you don't want to be burying any part of an extension cord in the dirt or have it some place where it is in a puddle of water as that can pose a shock hazard if there is any failure in cord jacket. My wiring is underground, running from my house to the greenhouse, but I enclosed it in plastic conduit and used the required wires that are rated for this use.]