Factors that affect romaine growth in a cold frame.

Ah, the joys of gardening. What is supposed to be a relaxing hobby for most can be laborious if you are a compulsive person such as I am.

So, today’s topic will have to do with my previous article on growing romaine in small cold frames. The question is will I have enough time to bring small starts to maturity considering that it is now past the middle of September and time is a wasting.

In order to answer the question, I need to start with some assumptions and some observations. The first is the time it will take for my small starts to mature. That’s an easy one as the published figure is about 65 days. Therefore from the planting in mid September I have until let’s say the end of November to get them grown. That comes to about 75 days, so at least I know what my target is. That is no longer than the end of November.

Next, I want to examine the major factors that will influence plant growth; length of day or sunlight, angle of sunlight or intensity and lastly the ambient temperatures I can expect.

Length of Day

The first thing I wanted to figure out was just how much sun the plants would get. As it gets later in the fall the amount of sunlight decreases as the arc of the sun’s travel dips ever lower in the south. Here’s what I found

As you can see my location here in southwest Missouri only gets a little over twelve hours (12.2) of light at this time of year. By the end of October I’m down to 10.6 hours and then as the end of November arrives my plants will only have 9.7 hours. The times are from official sunrise to sunset, so the actual usable times are much shorter. That is why it is so important to get time your romaine starts begun in such a manner that you hit the window of maturity right before it begin to get really cold which is mid December. (I’ve found that planting indoors anytime prior to the end of August seems to work).  By that time growth pretty much stops and yet the plants don’t seem to age if protected properly. That is as long as you maintain a temperature of at least the low forties in the interior of the frames themselves. I’ve accomplished this over the last couple of winters by using a small forty watt light bulb on a timer and then covering the frames with blankets whenever I knew it was going to get really bad outside. Perhaps surprisingly, whenever it has snowed, I’ve found I don’t need the lights or the blankets as the snow acts as a great insulator and the warmth coming up from the soil does the rest.

Angle of the Sun

The next consideration would the angle of the arc of the sun in your particular locale. The chart here shows how high the sun gets at particular from June through December at my latitude. As you can see, right now in September they’re enjoying pretty decent sunlight angles which can be also described as sun intensity. Too much intensity like I find in mid July will actually burn the plants up, while lesser intensity such as exists this time of year is optimal for growth. That seems to be true until about mid October when the angles begin to get pretty severe. On a side note, I decided for fun to verify that the sun’s angle at noon was a little over fifty degrees by quickly constructing the device you see here. It just a piece of cardboard with a circle drawn on it (I used a dish) and a thin length of metal punched through the middle. The angles I drew were on the rough side, but as you can see fairly accurate. Just make sure to align the board in a true north and south direction (use a compass) and insure the cardboard is level.

Temperatures

OK, so I have the feeling that I will have long enough days at good sun intensity for at least two more months. But what about the temperatures? I would like to keep the frames open as much as possible. Well, according to data taken from last year (2009) that should not be a problem. The graph represents the actual reading taken by a local weather station just a few miles from my home. The blue line represents 32 degrees or freezing. However, that is not really a problem with romaine as it has actually survived temperatures as low as 27F in previous years outdoors. So, assuming this graph of highs and lows is pretty close to what I can expect for 2010, then I should be good to go.

So that’s the plan Jan. I will do some updates as the season progresses. If everything works out, I hope to have a picture of me enjoying some fresh lettuce out of the garden on New Years Day 2011.

Growing romaine lettuce through the winter!

I think I’ve alluded to the growing of lettuce in cold frames in some earlier blogs. Not sure, but that's part of getting old I guess. My mind goes, comes back and then goes again. But, if you're wondering whether it can be done. The answer is yes! Just make sure to check out my seed starting video.

So OK, any earlier blogs not withstanding, I decided to start twenty romaine plants from seed about three weeks prior. (I choose romaine because they can withstand cold temperatures and are generally healthier than leaf lettuce). These have now grown to transplant size (about 2 to 3 inches tall) and have been transplanted into both of my small cold frames (10 in each) that were originally built in 2008. (I produced a You Tube video on these in case you might be interested). Over the last few days, I have refurbished the frames by adding some fresh paint and resealing the glass panes in the window frames that cover the top of each. As you can see, the end result looks pretty good.

During the past two fall and winter seasons, I learned that if I started my plants early enough, I could grow them to close to maturity and then hold them in a kind of suspended animation until I got a chance to harvest them later in the year. The key to doing this was to monitor the inside air temperatures (I used a wireless thermometer to monitor changes from inside my home) and to add heat via a forty watt bulb when needed. I’ve found that by keeping the air temperature in the frames in the forty to fifty degree range, I could keep the plants healthy for a long period of time. I also had to make sure not to let the leaves touch the window panes above the plants on cold days as that would turn their tips brown. That’s one of the reasons I decided to add a little height in one of the frames (designated as CF1). It was only four inches or so, but I think that will help. We’ll see this winter how that works out.

Head-space Increase

By adding a quickly made frame made from 2x4’s onto the top of CF1, I was able to increase the head space appreciably. In CF2 and CF1 the growing surfaces are the same at about 32 inches wide by 21 inches deep (roughly 4.7 square feet each). Head space, however in CF2 is eight inches in the back which tapers to 3 inches in the front compared to CF1 which now has 11 inches in the back versus 6 in the front. The increased area should allow for larger plants. That is one thing I hope to quantify as we go through the fall. By mid November all growth will have basically stopped and I’ll do a follow up blog at that time.

Soil Condition

At the last minute, I decided not to add any amendments to the soil in either frame. A casual inspection revealed to me that the soil is dark with a high crumb structure. It also appeared to be high in humus content, so I will wait to see how well the romaine starts grow before making any changes. If needed, I have blood meal available to increase the nitrogen content. (I may elect to do a full soil test by the end of the month, but for now I want to go with my gut instincts).

So that’s the deal. I’ve cleaned up my cold frames and transplanted the young lettuce starts. All that’s left to do is hope these plants get big before the cold stops them.

It's time for some cold frame lettuce!

It’s almost March now, just a couple of days away. Here in southwest Missouri, you can see how much more bright the days are as the sun now arcs ever higher across the sky. The temperatures are now beginning to respond a little to the increased sunlight. Today, February the 27^th, it we had temps in the mid forties and I can tell you…compared to just a few weeks ago that is warm! With the window sash over the top of the cold frame the air quickly warms into the mid sixties. This is perfect weather for romaine lettuce and radishes.  I just happen to have some seed left over from last season and decided the time was right to put them to good use.

So, with no further ado, I went out this afternoon and prepped the ground in my first cold frame. The space is on the small side, but you’d be amazed at the amount of lettuce I can get from this space. The actual size is just under 24” x 36 inches of growing space or 6 square feet of total growing area. I have two of these frames in the front yard which can provide me with quite a bit of early spring lettuce. The picture at right shows lettuce that was actually planted last fall and even though the plants are small, they are a welcome addition to the dinner table.

My method of planting at this time of year is simple and stupid. I just broadcast some lettuce and radish seed in a random pattern, then wet the surface down, cover everything with newspaper and then water it again. Total time spent was about 15 minutes if that. After covering up the frame, the sun immediately elevated the inside reading to 65F while it was 46F outside. In about four or five days, I’ll take a peek under the newspaper and see what’s germinated. Because it’s still cool outside (and cold at nights) I don’t have to worry much about the top layer of soil drying out. The window sashes also act as a moisture barrier. Kind of a ‘SET IT AND FORGET IT’ deal. My apologies to Ronco.

With a little luck and some supervision, I should have a good harvest sometime in mid to late April or about the time most people are just getting started in their raised beds. Of course, I’ll post an update at that time. Happy gardening!

Cold Frame update - Late December 08

It’s almost the end of December, the 27th actually and I finally got out to check on the health of my romaine, lettuce and radish plants. They reside in two small cold frames in my front yard and would no doubt be complaining about the cold if they were able. The mean temperature for this month has been two degrees lower than normal and that’s a lot!
I noticed some of the larger plants in cold frame #1 show evidence of tip burn. This was caused by their coming in contact with the glass on days that were below freezing. Otherwise, they are in good health. The plants in cold frame #2 are also good to go, just a little smaller due to them get planted after the ones on frame #1.

Two conclusions I’ve come to regarding this effort are; one, that even though plants will grow during the winter, they do so slowly. And two, I need to consider a much larger cold frame if I am to have anything worth harvesting. Eleven square feet (the inside growing area of both frames together) is not enough to produce enough to feed one person. I will need at least sixteen square feet to accomplish this. So, that will be my next project this coming early spring. I am in the planning stage at this time.

Cold Frame Insulation

Over the last couple of days, Mother Nature has dropped an arctic cold wave over much of the county. Here in southwest Missouri, we have taken a pretty good hit also. On Sunday, December 14, 2008, the temperatures went from the high sixties to below freezing in just a couple of hours. Yowsers! Overnight, they then dropped into the teens. This is the first time in my memory that such cold came so early in the season. Hey! It’s not even winter yet! Outside, I have two small cold frames I built out of 2x4’s that house young and tender romaine lettuce plants along with a scattering of radishes and spinach. When I began the experiment in September, I had anticipated December temperatures dipping to the twenties once or twice, but not the teens like we have had for the last two days. That’s just too darn cold!

To their credit, the structures have insulated the plants pretty well so far. The temperatures tonight outside will be very cold again, dropping down to 18F or so. This level of cold has been a trial for the plants. I hope I’ve prepared for them by taking additional steps to insure their survival. On Sunday, I made sure to turn on the small 40 watt light sources I have installed in each frame and then covered them with spare floor mats. As a result, the internal temperatures in both cold frames have stayed in the mid to lower forty degree range.

In reflection, if I made any mistakes, it may be that I have neglected to build up the soil around the back side of each frame. The earth is a great insulator and the other three sides are covered well, just not the backsides. Next week, I plan to attach some additional insulation to see if that will help. Also, I’m hoping the ambient temperatures will moderate a bit during the rest of the month.

Cold Frame construction - Using 2x4's

In response to numerous requests (actually only 2), I wanted to clear the record on what you need when building a cold frame. Actually any materials will do. I’ve seen cold frames made out of plastic, wood, concrete and blocks of soil. Any material that will; act as a thermal barrier, can be tilted to face south and has a lid that admits light will work. I built mine out of 2x4’s as I had a pile of them lying around so the price was right.

I built the frame by working from the top down. That is I started by measuring an old window frame I scored from a friend, measured it and then cut four pieces of lumber to creat a frame. I then too another piece of lumber and four ‘legs’. Two measured 14 inches and two 9 inches. There were nailed to the four corner of the frame to which were added more lengths of wood until I have a box that measured about a foot and a half

deep. There was no bottom to this box. I merely dug a hole in the ground that was also slanted back to front. I then layered in a sheet of weed blocking material, placed the frame over it and then affixed the window sash to the top with the aid of two hinges. During the construction, I used about forty galvanized nails which cost me a few dollars at the local hardware store. Other than that and the labor, the cost to build was nothing. My only other cost was involved in purchasing three cubic feet of potting soil. I used Miracle Gro for CF#1 and Scott's Premium potting mix for the second one. Both are good. You can use whatever soil you choose, just make sure it is weed free.

CF2 on the Way!

It's now mid November 2008 and we are now entering the time of year I like the least. The next fourteen weeks will see some of the coldest weather of the year and most of the trees will be bare. Thank goodness for my cold frame with its spark of spring greenery inside. It will soon have a friend when I install a twin unit next to it. I'm in the process of painting the frame and still need to purchase a soil amendment (vermiculite)to add to the 3 cubic feet of Miracle Gro potting soil bought at a store last week. I now have three trays of plants (lettuce and spinach) that need to be planted out soon, so I need to get to it as they say. The new cold frame will be referred to as CF2 and the original CF1. CF1's plants are going great. I'll try and post a current picture sometime soon. The average temperature in that frame has been about 54F which is near the ideal temperature to grow lettuce and spinach at.

Over the next weeks they are forecasting a series of cold fronts about every other day with lows getting into the twenties. This will be a real test to see how well these guys can surviive.

Cold Frame #2

Yes, I’m at it again with the building of my second cold frame in less than a month. Does one man need two Cold Frames? Apparently, yes they do. Winter is coming and the price of lettuce at the local market is at an all time high. I love my salads (it’s a diet thing) and with lettuce at almost $2 per head, I now have plenty of incentive to grow my own.

The addition of a second 36 inch by 24 inch frame box will give me another 5.8 square feet of growing space. So, the two combined will allow me to grow about 12 to 14 plants at any one time. If I start 4 seeds every two weeks that will assure me a steady harvest of lettuce though out the wintertime and on into spring.

The construction will be documented in a video call Building a Cold Frame Part 2 and will be published on You Tube, I hope.

I had been concerned about the survival of young lettuce plants when it gets really cold outside. Recently we have seen temperatures that have dropped down to the low thirties and I am happy to report that conditions inside the box have remained in the fifty degree range. I have also installed an electric cord with a light bulb on one end to help warm things up in case it gets really cold outside.