On the origins of lettuce

Did you know there are six groups of cultivated lettuce?  I only grew lettuce from one of these groups - romaine - during the past two years.  

To read the rest of my post on the origins and cultivar groups of lettuce visit feedthedatamonster.com.

What did I plant? Telling apart sprouted greens

Does this happen to you?  Do you plant things and forget what they are?  I certainly do! (See vates kale.) It's pretty easy to tell what family salad greens are in based on their cotyledons.  You might not be able to tell what variety is growing, but at least you'll be able to tell the lettuce  and spinach apart.

When lettuce sprouts it's small and cute - the bunny of the salad greens.  The cotyledons spread wide open on the soil surface.  Red varieties of lettuce will change color if it's warm and sunny. 

Spinach cotyledons are long and slender, forming a 'V' shape.  

All brassicas have heart shaped cotyledons.  This includes leafy greens and cole crops (cauliflower, cabbage etc).  The picture above shows tokyo bekana, kale and scarlet frills.  Cotyledon size varies between varieties, and so some brassicas make good microgreens.  Broccoli, although not a salad green, is a good example.

Members of the beta family, including swiss chard and beets, are also good microgreens because their stems are often bright colors.  I've taken a lot of photos of them because of this.  Their cotyledons are oblong with a slightly pointy tip.

Where have I been?

It has been awfully quiet in the wintergreens blog world recently.  First, because I was sick and then because I was busy catching up on everything I put off while being sick.  

Last week I helped with the planting of a school garden.  Over the course of a day a few hundred kids trooping in and out of the garden to plant lettuce, spinach and tatsoi.    In the picture rows or greens are marked with string and the tatsoi beds are hidden under row cover.  I was chuffed that the greens planted followed the same pattern as the greens I primarily study: a lettuce, a spinach and a brassica.  The kids remembered eating lettuce and spinach in previous years, but not tatsoi.  The day was fun, but rather exhausting.  I forgot what it was like to work with kids.  I also forgot to put on sunscreen.

The daffodils are finally blooming in New Hampshire, and the growing season is about to being for most gardeners.  The beginning of the outdoor growing season means the end of the indoor wintergreens season is quickly approaching.  Last week was the last big harvest of greens.  Yesterday I took my last leaf length and harvest weight measurements.  The greenhouses are emptying rapidly.  Soon I will be spending most of my time on the computer crunching numbers.

What is a 'baby' sized green?

There is no standard size to define what is considered a 'baby' sized salad green - at least I haven't seen one yet.  So I made up my own set of parameters based on observation, salad eating and a few reliable sources.  Johnny's Select Seeds suggests harvesting salad greens at 4-5 inches tall  which translates to 10.16- 12.7cm.  I feel like Eliot Coleman of Four Season's Farm wrote that he harvests salad greens at 4 inches, but since I can't find that anywhere in my notes I could be wrong.

For harvesting and data analysis I consider lettuce and brassicas in the 8-12cm range a good size for baby greens.

Currently, I consider 6-10cm perfect size for spinach.  Unlike lettuce and brassicas, spinach has an official size: the size of a soup-spoon (again I can't find my notes on this right now).  I don't have real soup spoons, but hopefully a tablespoon is an ok substitute.

Morning light

We had three sunny days in a row.  

Sunglasses were pulled out, sunscreen was applied and 

greens started growing like crazy.

How I use growing degree units

A few weeks ago I described how to calculated growing degree units.  Remember?  Basically they are a measure of heat accumulation, and pretty useful when you're dealing with changing seasons, night and day, or greenhouses heated to different temperatures.  Here's how I use them.

We'll use lettuce as an example.  I planted lettuce nine time throughout the fall last year.  Using all the growth rate data I collected I figured out how many days it took to reach 8 cm. (8cm is a good baby green size.)  In the graph below you can see that it took more days to reach 8cm as the season changed from fall to winter, especially in the cooler greenhouse.

Still on board?

I did the same thing, but changed growing degree units for days.  So, I calculated how many growing degree units it took for the lettuce to reach 8cm.  The number of growing degree units accumulated by lettuce at 8cm stayed about the same in the warmer greenhouse and slightly decreased in the cooler greenhouse - even though the actual amount of time to reach this size increased.  Make sense?

So, now on to interpretation.  Why does this happen and what does it mean?  I'm not totally sure yet, but here are some ideas:

• It takes about 600 GDU to have a harvestable baby lettuce crop.  How long it takes to accumulate that heat can vary. 
• Why does the number of GDU decrease in the cooler greenhouse?  Maybe because there is so little light late in the fall.  Even if greens were in a warm environment, their growth would be limited due to limited light.  

* As usual, this data pertains only to our greenhouses this fall.  It is not complete and should not be used elsewhere.  If you are looking for complete data pertaining to winter greens growth, and growing degree units you'll just have to wait until I'm done with my thesis! *

Salad mix of the week

This week has got me a bit blue.  Maybe because it's cold and grey outside.  Maybe because all the spinach is dying.  Or maybe because all the tat soi is gone.  Tat soi has such lovely small round leaves.  When paired with frilly fun jen and bright red beets I am cheered right up!

In this mix tokyo bekana could easily be exchanged for fun jen.  With age beet greens get even redder, and taste more beet-y.  If you took out the lettuce, all of these could be quickly wilted in a hot pan.  I'm starting to get hungry.

Salad mix of the week

The hurricane blew away all the remaining fall leaves, and now it looks like winter in New England.  Namely, there are bare, brown trees, empty fields and bleak skies, which, secretly I like as long as I can spend lots of time reading books.  

This salad mix isn't really that summery since it has kale and spinach in it, but the muted colors made me think of late August.  I don't really think of lettuce as very hardy winter green either, more of a fair-weather-only kind of green.

Comparing nutrient density in lettuce (aka Lettuce Smackdown!)

When people think of salad greens usually they think of lettuce.  Even I do, despite the fact that I have a mediocre opinion of it.  But lettuce is what people like and know - so what kind is the most nutritious?  Happily someone else has already thought that question and found the data.  No Baloney, a dietitian and nutrion scientist duo, have compared looseleaf, romaine and mesclun mix.  I know, I know - mesclun is made of more than just lettuce, which may be why they declared it the winner based on nutrient density.

For the full face-off see the article here. 

Lettuce, spinach and mizuna: 4 days till planting!

The school semester started this week which means there are only four more days until I start planting fall greens!  There is going to be an awful lot of lettuce, mizuna and spinach growing in the coming seasons because they are good representatives of many cool weather greens.  You might get tired of hearing about them.  Not to worry - I'll be growing plenty of other greens too and will outline all the projects I'll be working on in a post next week.  Here's a bit about each of the three major varieties:

Seed germination results

I am about half way through the seed germination experiment.  Already trends are appearing in the data.  So far, I've germinated seeds at three temperatures: 75, 65 and 55.  On really hot days I want to crawl into the growth chambers and hang out with a book until it's cooler.  Hopefully there won't be many more hot days this year.   

The maximum number of seeds at each temperature is 50.  So, for defender lettuce at 75 degrees all the seeds germinated by the third day.  As the temperature decreased it took longer for seeds to germinate, and germination was spread over a number of days.  This is useful because it tells a grower or farmer that they don't need to heat their greenhouse all the way to 75 or 65 degrees to have good germination of lettuce seeds.

The pictures on the right don't show what I'm seeing when I count germinated seeds - but they are far prettier.

Tokyo bekana shows a slightly different trend.  Days to germination is similar for seeds sown at 75 and 65 degrees.  At 55 degrees seeds take much longer to germinate, and the percentage of seeds that germinated is much lower.  (You can't tell this from the graph, but it's true.)  So, how is this useful data?  It shows that temperatures lower than 55 degrees will result in poor and lengthy germination compared to warmer temperatures for tokyo bekana.  Eventually I'll add fuel price in as a component to this study, but not until I'm done collecting data.

Graphing the growth rate of greens

I have now measured 14,400 leaves and weighed 8,505 grams of harvested greens, so it's about time to make some graphs out of all that data. (8.5 kg is almost 20 pounds, which is ALOT of greens.  You could make many, many salads.)

I love making graphs.  Partly because they get to be colorful, but mostly because they take a whole bunch of numbers and organize them.  The graphs below took 12,200 numbers to make. Think about that for a while.

(The y-axis is leaf length in cm.  I forgot to label it.)

This graph shows the growth rate of each variety of green that I planted on 3/20.  I didn't start measuring until the plants had harvestable leaves, which was around the 12th/13th of April.  If you remember my overview of this experiment post at the beginning of April I was hoping to see the growth rate level off.  From this graph you can see that did not happen.  The greens just kept growing and growing.  I had to stop measuring leaf length, not because I ran out of greens, but because the greens ran out of nutrients and looked ugly.  (As shown in the stressed out greens post.)  The little black x's mark the best harvests. 

(The y-axis is harvest weight in grams.  I forgot to label it.)

The graph of harvest weights shows a general trend of continued growth for most varieties.  Toyko benkana and Outrageous lettuce have weird, unexplainable dips in harvest weight near the end.  I don't know what happened to cause that, but it does show why I have to do experiments a few times.

These two graphs aren't everything.  Now that I'm done measuring and harvesting four times a week I'll be using this data (all 14,400 numbers) to extrapolate things like: potential harvest weight, optimal harvesting time and how much money it cost to do all this.  Pretty cool stuff eh?

See us grow!

Five varieties, three weeks.

Stressed out greens

I came into the greenhouse on Monday to find I wasn't the only one stressed out this week.  I'm working on finishing lengthy term papers for the end of the semester.  The greens are stressed out because they are running out of nutrients.  In some varieties stress is shown by leaves turning purplish, in others the leaves bleach to bright yellow.  The tokyo bekana, kale, arugula and tat soi above are all brassicas that were first to reach harvestable size (Mizuna was as well, but I didn't take a picture of it looking stressed out).  So, it makes sense that they would use up all their nutrients first.  I am growing the greens in compost, which should provide all the nutrients needed.  If I were growing these to eat, or for sale I would have harvested them last week before they got stressed out.  

Happily, the lettuces still look good.  Most of the year I am not a supporter of lettuce - it is bland, or bitter and doesn't have as many nutrients as other greens.  At this time of year though, it is perfect!  All green and leafy tasting.  Lettuce is in the Aster family, along with dandelions.  I don't think they are close taxonomic relatives, but I do think that lettuce smells a bit like dandelions.

Growth rate of green romaine

Back when I first described the growth rate experiment I'm working on now, I described how I was hoping to see growth rate level off so you could predict how long your greens needed to grow before reaching optimum harvest-ablity.  Only half way through data collection and I am started to see that happening!

Growth rate hasn't slowed down in some species, but it seems to be slowing in the green romaine variety we're using called 'Defender.'  The graph below shows leaf length and harvest weight over a period of about two weeks.  The last time I collected data was April 26th.  Neither the leaf length of harvest weight had increased much since the last time I collected data (three days earlier).  Tomorrow I'll see if this trend continues.

Everything that's growing (except arugula)

Scarlett frills, tokyo bekana, mizuna, red romaine, red russian kale, 

green romaine, tatsoi, spinach, ruby streaks

four weeks of growth - it's time to eat!

All the greens are not 'full size' yet, but the kale, mizuna, tokyo bekana, tatsoi and scarlett frills are!

two weeks of growth!

What a difference just one week can make!

Growth rate of greens (or experiment number two!)

Even though the weather right now is not very winter-like I've started a second experiment.  Describing this one is much simpler:  I am going to see how different varieties of greens grow in the 'cold.'  The same kind of work was done last spring and fall and I'll be doing a lot more of it next winter.  

A few of the greens I'm growing are in this mixed flat.

The goal is to be able to estimate how long it will take green to reach a harvestable size as light and temperature levels change drastically in the fall and spring.  By the end I'd like the be able to say "if you plant lettuce in September you'll be harvesting in late october, but if you plant in october you won't be harvesting until december."

Arugula grown spring 2011

The chart above is a snippet of the data collected last year.  The temperatures are when the greenhouse heaters turn on.  You can see that keeping the greenhouse ten degrees warmer makes a big difference in growth (leaf length).  The length of the arugula grown at 40 degrees seems to be leveling off at around 40 days of growth.  If you knew it was not going to grow anymore you would harvest it at forty days.  Leaving it in the ground won't mean it was going to grow anymore.  The same observation can't be made for the arugula grown at fifty degrees - which is why we need more data!

What's going to happen:

I am growing ten varieties of greens:

1. spinach
2. kale
3. green romaine lettuce
4. red romaine lettuce
5. arugula
6. mizuna
7. tokyo bekana
8. tat soi
9. ruby streaks
10. scarlet frills

I'll make eight harvests at 3 - 10 weeks after planting.

At each harvest I will measure:

• The length of 10 leaves of each species 
• The weight of each species harvested

Pretty simple!  Are there any greens you would like to see on the list?  Leave a comment below and I'll take it into consideration for the next round.