Mini-Greenhouse and the 36 cell pack

This exercise was all about indoor space - or better yet, the lack of indoor space.  How do you maximize a minimum amount of space?  I was lucky enough to design my own house.  The cornerstone of the design was my kitchen.  It HAD to be in the south-eastern corner.  I sacrificed upper cabinets in order to put in 2 huge windows.  One facing east and the other facing south.  If I would have been really smart, I would have made them greenhouse windows.... sigh, but I digress.  Unfortunately they are only 6" deep but I took advantage of vertical height by improvising a shelving system.  In each window a 6" shelf supported by stacks of paper towel and back taped (white duc tape) to the window casings.  When this picture was taken I was experimenting with some reflective (emergency blanket) lined curtains.  Pfft... they're gone now.  No curtains on the windows.

Next item needed is a 36 cell mini-greenhouse.  I can find them quite easily at Canadian Tire here for $2.99 but I don't know how readily available they are in the US.  I've heard they're almost impossible to find in Texas.  I've found a place where you can order them online through Amazon but watch the pricing.  I had no idea I was getting such a good deal.

The beauty of this product is it's ability to fit onto a window sill almost perfectly.  Hmmm... I just had a 'light-bulb' moment.  I live in an climate where building codes require a 6" exterior wall which makes all of our window depths almost 6".  I suppose if your exterior walls are 4" then window depths may be too shallow for this product.  That might also explain why I can buy these off the shelf locally without any problem yet they're difficult to find in more southern regions.

Due to my window size and the improvised shelves, I have the capacity to run 12 of these containers at the same time... though I wouldn't recommend it to just anyone.  There's a downside to having that many seedlings growing at the same time, which I'll get into later.

In addition to the mini-greenhouse, you'll need those rocks (Walmart fish gravel) and distilled water.

I tend to keep the base and lid but will toss and replace the cell packs themselves.  They are too inexpensive to spend large amounts of time sterilizing them.

This product allows you to do 36 crosses in one container measuring 6" x 21".  It also has the advantage of only adding water to one container as they share the water from the base of the unit.  However, this setup makes it difficult to label the individual crosses.  The key to keeping your crosses properly identified is using stickers on your cell packs and a corresponding map.  More on the map in a bit.

Okay, so once you have your mini-greenhouse all you have to do is add the fish gravel to about 1/2 way up each individual cell.  Then add the distilled water until you can just see it between the rocks but not over top of the rocks.  The water will level across the entire 36 cells so you will have to do some rock adjustments until the rocks level is consistent in each cell using the water as your guide.  Now place a different color sticker on each of the 3x3 groups of cells.  That would be a total of 4 stickers.  Now would be a good time to map those cells according to your sticker colors.


Here's an example of my map done in Excel.  Across the top I have the seedling abbreviation in each of the cells in the color of the sticker.  Also at the top is the date of the setup and the total number of seeds in this mini-greenhouse.  Detailed below is the full cross, the seed seller's name (if purchased seed), the ploidy, and number of seeds placed in the cell.  The last line is to record the number of transplants that you harvest from that cell.  Not all seeds will germinate, of course, and some will be ready for transplant before others so it's a good idea to record the number of seedlings you pull out of the cell.

Depending on your eyesight, you may notice that there were 683 seeds in this particular mini-greenhouse.  Assuming I did the 12 containers that I could fit into my windows, that means I could germinate 8,000+ seeds from my kitchen windows alone.  That is considerably more than I am capable of planting with my current resources of time and space.  If anyone is interested in having a copy of my spreadsheet, I'm happy to give it to you.  Just send an email to canadian.mj at

Now load your seeds into the cells according to your map.  I like to give my seeds a 10% bleach bath before loading them in just to eliminate and/or reduce the possibility of mould.  What you do is entirely up to you.  Then put the cover on and place on the window sill.  Condensation will form during the day and then drain back into the container overnight as the temperatures decline.  In this photo you can see my stickers marking each of the 3x3 groups of cells.

After about 7-10 days your container might look like this.

As the days go by... some seeds germinate faster than others, of course.

Check through the cells at least once a week to remove any scummy looking seeds.  You don't want bad seeds affecting the water that all the cells share.

Depending on how densely you pack your seeds, you could end up with something like this;

The seedlings will actually grow until they lift the lid on the greenhouse.  See the photo below for the 1/2" gap.  Due to a lack of time, I have trimmed the seedlings just to get the lid back on so that I could maintain humidity for those seeds that had not yet germinated.  However, the best approach is to start harvesting you seedlings at this point.  Removing the 4-5" seedlings is easy.  With a gentle tug they will lift right out.  Consult your map for the identity and mark down how many you're transplanting at this stage.

Once the tall ones are out, put the cover back on because you will get continued germination over the summer.  Check your water levels from time to time.  At least once a month (if you are running your containers that long) do a full drain and replenish with the distilled water and a drop or 2 of bleach to combat bacteria or anything else that is undesirable.  This is a lesson I've recently learned the hard way.  :(

Seedlings can be maintained for 90+ days in these containers.  In the summer of 2009, I forgot an almost empty container until September.  The bulk of the seedlings had been harvested intermittently until only the most stubborn of seeds remained.


This system worked well for me in 2009 and 2010.  In the spring of 2011 I decided to push the envelope a little more.  I started one container at the end of April with 449 seeds.  Then I went on vacation for a couple of weeks and loaded up a second container when I returned mid-May with 683 seeds.  These were all purchased seeds from the lily auction.   Here's my warning... with this method it is extremely easy to get a lot of seeds germinating.  However, make sure you have the time 4-6 weeks later to deal with the numbers of seedlings that will need transplant.  Another lesson I learn the hard way.

So, with 1,132 seeds germinating on the window sills, I took a leave of absence from my job in order to spend 6 months working for a client to get their accounting system cleaned up and on track.  As it turned out, I grossly underestimated the work required to turn things around.  At my regular job, we work 33.5 hours per week during the summer months.  This mess I ended up in had me working 55 hours a week.  Ugh!  That all but eliminated my garden time this summer and the constant rains didn't help either.  As a result I did NOT get a single seedling from the 1,132 transplanted.  As I sit here writing this, it is September 25, 2011.  Yup, they are still on my window sill and they are UGLY.   On a positive note, no bugs!

They still looked pretty good into mid-August but the past month they have been deteriorating at a rapid pace.  Some may just be dormant.  Others are dead.  I don't know how I'll tell the difference.  I've decided that the only thing I can do at this point is prepare large 5-gal pots and plant each cross, and any root mass associated with that cell, into the same pot.  The fact that there are still green seedlings makes me wonder a couple of things - (a) are they evergreen? or (b) are these the toughest seedlings of the lot?  There is no match for my ability to abuse a seedling.  Survivors are rare with my neglect and mishandling.   I have a lot of admiration for anything that gets past me to bloom stage.

Okay, time to suck it up and try to salvage some seedlings...


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