Field day: Germination

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.

Saving seeds

A long time ago, February to be exact, I grew a whole lot 

of mizuna in plug trays.  Maybe you were as sick of hearing 

about mizuna, spinach and lettuce as I was by the end of it.  

Since I had so many plugs (small, baby plants with lots of roots) 

I planted some in bigger trays with the hope they would grow 

and I could eat them.  

Instead I forgot about them and they flowered!  

There are wild mustard flowers like this blooming 

all over the place in New Hampshire right now.  

I think they are pretty, especially along the highway.

I decided to save the seeds from the flowering mizuna.  

I've never successfully seed-saved before - 

I'm good at saving seed, but not finding them again.

So, I waited and waited for the plants to stop flowering.  

The interval between flower and seed was much longer than 

between mature plant and flower. 

Finally last week the seed pods were ready!  

(Actually, they weren't all ready, I was just tired of waiting.)  

If you look closely you can seed dark brown spots in 

the tan seed pods.  Those are the seeds.

I took the stalks home and collected the seeds.  

It was like shelling peas, only I didn't eat any.  

Now I have about a tablespoon of mizuna seeds.  

They are packaged, labeled and stored in a safe place 

that I will probably remember in the fall.  I thought about

planting them right away, but right now I have quite enough greens. 

UNH greenhouse open house

Why be excited about this event - besides that it is about plants which are always worth getting excited about?  Because I am going to have a poster and some plants from the germination trials experiments!  I printed the poster out today and it's all shiny and official looking.  You can see it below.  Many of the pictures should look familier if you've been following me.  To actually be able to read the words you'll just have to come to the open house on Friday and Saturday!

Germination trials: Recap

It's come time to wrap up the Germination Trials so we can move on to the next experiment before the winter season is over.  I won't finish analyzing the data until this summer when I have more time, but  there are a few conclusions that can be made now:

 1.  The different treatments did have an effect on % germination rate and days to germination for all three varieties of seeds.

 2. The three species of greens responded differently to the cool, wintery conditions in terms of germination rate. 

3.  How all the temperature and light data tie into the germination rate will have to wait until I have more time.

As with all experiments, new questions for further experimentation arise.  The questions I'd like to explore in the next experiments are:

• How do the tunnels affect growth rate?  I showed that there seemed to be differences in growth post-germination.  Now it's time to actually measure it.
• What about other species?  We only looked at three species of greens.  What about green leaf lettuce, arugula, kale or tat soi?
• Would combining treatments be advantageous?  Putting heat mats inside clear plastic tunnels seems a good combination to provide root zone heat, above ground heat and a humid environment.
• What questions do you have?

Lettuce and mizuna at 42 days old

Lettuce seedlings at forty-two days of growth.

I am still thinking of different ways to compare the seedlings as they grow.  Here, I pulled the seedlings straight from a cell without being delicate at all.  They are lined up from left to right by treatment: control, clear plastic, white plastic, plastic with holes, row cover, heat mat.  Most of these little lettuces have wimpy little root systems.

Look at that last one on the right!  It is nearly a plug!  I suppose it seems obvious that using heat mats to keep the soil warm will stimulate root growth.  The leafy part of this plug seems to be about the same size as three of the other treatments.

The biggest leaves come from the clear and white plastic treatments.  Because of the non-porous nature of plastic water was retained in these two treatments making them pretty humid.  My data collection notebook was often spattered with condensation falling from the ceiling of these tunnels.  If I had any forethought I would have used my super cool waterproof notebook and a pencil to do all the data collection, but I didn't and have lots of crunchy, dried out pages of data to prove it.

Mizuna seedlings at 42 days old.

In contrast here are mizuna seedlings lined up in the same way: control, clear plastic, white plastic, plastic with holes, row cover, heat mat.  They all have strong root systems and look pretty similar.

Comparing growth post germination

These seeds were all planted on the 13th of January, so the seedlings are now 42 days old.  I tried to pick a good representative tray from each of the treatments  to take a picture of.  A few of the observations that can be made I've written about before, including: lettuce pigmentation and the different germination rates of each species. 

From these pictures it seems like the plastic with holes had the most uniform lettuce growth.  Since I haven't actually been looking at growth rate, I can't demonstratively say that.  But, the plastic with holes lettuces seem to have mostly sprouted and are of similar size compared to the white or clear plastic.  The spinach seedlings seem to be the most consistant species between the six treatments.  The mizuna seems long and leggy in the plastic treatments and shorter in the others.

One week of growth

Although I have finished data collection for the germination trials, I have been observing the sprouted seeds as they grow.

Lettuce from white plastic, plastic with holes and clear plastic low tunnel coverings.

I've commented before on the pigmentation of lettuce grown under the different low tunnel treatments.  Those little seedlings have grown quite a bit in two weeks, but the pigmentation patterns continue.

I planted plugs in trays of soil on the 13th of February (on the left).  A week later the greens look fuller and many of the plugs have more leaves.

These pictures of arugula are also from the 13th and 20th of February, respectively.  In just a week the seedlings have gone from cotyledon stage to the true leaf stage.  

Today I am going to plant a few herbs to see how they grow in the tunnels.  I am thinking about dill, cilantro, parsley and basil.  Any other ideas?  What would you like me to try growing?

Greenhouse temperature

Today is graph day!

This week I have been thinking about temperatures.  If you remember back to when I set up the temperature probes there would be thousands of temperature readings.  All that data in a giant, overwhelming spreadsheet taunting me because I am not so sure how to use it all.  While figuring that out I've been looking at just a few days at a time.  Kind of like snapshots.

The greenhouse temperature itself is a good place to start. 

Soil temperature in control treatments.

I realized after I made the above chart that I had used soil temperature data instead of air temperature.  See what having oodles of numbers in a huge spreadsheet does to me?

Below I graphed soil and air temperatures together.  You can see the treads I highlighted in the soil temperature graph can also be seen in the air.  The major difference is air temperatures are much more volatile.  They seem to jump up or down a few degrees each hour.  This could be due to cloud cover, or air movement from the fans.

Soil and air temperatures in control treatment.

*  This data represents five days in the greenhouse I am working in.  

Other greenhouses or high tunnels may have similar temperature trends but they will not be identical.  *

One month old mizuna

After a month the mizuna grown under clear plastic is a good sized plug.  Look at all those lovely roots!  I've planted a few in bigger pots to see how they will grow.

January light

Lots of light is not a requirement to sprout seeds.  But, light is one of key reasons plants grow and are just so cool.  Taking light and turning it into sugar is pretty amazing.  When I see people outside tanning I know they are just trying really hard to photosynthesize.

Since we had light meters available we set them up to give us a reading of the total moles of PAR light each day.

Moles of light measured in tunnels on a cloudy day (Jan. 27) and a sunny day (Jan. 28).

In January the days are starting to get longer, but they aren't really that long yet.  I graphed the two days above because one was cloudy and one was sunny.  The difference in amount of light that reach the sensors (and thus the plants) is pretty apparent.  There are a couple observations between the different tunnel coverings that deem pointing out:

1. Here it shows that the clear plastic and row cover transmitted about the same amount of light.  Sometimes this is true, and sometimes the clear plastic transmits more moles of light.
2. The white plastic transmits more light than I thought it would and isn't that far behind the other coverings.  The seedlings inside the white plastic treatments are much more etiolated and spindly than all the other seedlings though.

Do you see anything interesting?  If you grow greens in high tunnels, low tunnels or under reemay do you ever worry about light?

* This data is pretty cool, and will be useful for writing my thesis.  

I am not recommending anything besides excitement and interest in plants and photosynthesis. *

Observations on spinach

Total seeds sprouted by species (aka Real Data!)

Total number of seeds sprouted by species over a 20 day period

Would you look at that - a real chart from real data.  Pretty cool right?  (I think so!)  Since there is so much data it's good to start by looking at the big picture.

These are the spinach, lettuce and mizuna seeds planted in all those different low tunnels we built for the germination trials.  I noticed germination trends by species and decided to ignore the fact that the seeds were grown under different conditions to compare the three species.  This chart shows distinctive germination characteristics of each species:

• Mizuna, the fast growing mustard green, was the first species to have any seeds germinate.  The germination rate increased quickly from days 9 to 12 and then started to decreased.  Of the 3360 mizuna seeds planted 60% of them germinated.
• Spinach is known for being a plant that can grown in cool conditions, but like many cold tolerant crops it would prefer to germinate at warmer temperatures.  Here we see that it is slower that mizuna to start germinating but, that 14 days after planting there is a huge spike in germination.  Spinach had a 71% germination rate.
• Lettuce is not a very tough plant.  Only 52% of the seeds germinated and it took nearly 20 days for that to happen.

That's just the beginning of looking at all the data.  Besides germination rates there is also temperature and light data to take into account.

* Because I am a grad student this chart is built with  Real Data, but in no way am I recommending anything other than being excited about plants and eating.  *

Observations on lettuce

I have been looking at germinating seeds for nearly a month and have become quite intimate with these 10000 seedlings.  It takes about two hours everyday to go through all of them.  Such devotion leads to observations.

Lettuce seeds are tiny and their seedlings are tiny too.  So small that I couldn't get a very good picture of a newly emerged seedling.  Their two cotyledons are held together when they first emerge and slowly open like butterfly wings.

Soon after sprouting these seedlings turn dark reddish because they are a red variety of romaine lettuce. It can make them a bit hard to spot when counting.

The seedlings in under the opaque white plastic and the clear plastic don't change color.  They remain a lovely green with a bit of red mottling.  

Germination trials: Correct labeling

As I've started writing it became apparent I needed to work on my terminology.  Perhaps this is not the sexiest topic, but it is important to correctly name the different components of an experiment.  That way if someone wants to replicate what you did they will know how.  Or, if they are reading the paper (you will someday publish) they will have a clue what you did without the aide of a colorful picture. 

Greenhouse:  The setting of all this experimentation.

Block:  Contains one of each treatment.  I have two blocks of six treatments.

Treatment:  You remember all the treatments right? They are the independent variable.

Sub-plot:  With in each treatment there are six sub-plots for each species.  We stuck the three species in one tray because it was convient.

Replicate:  Each individual seed.

Just how many seeds is all this?  If you could make bets with the bill Salmon P. Chase is on you would be in the right ballpark.

Seeds are sprouting!

Last week I did a second planting of lettuce, spinach and mizuna.  I spread the work over three days, so it was far more relaxed than the first planting.

Now, 12 days after being planted, lots of seeds are sprouting.  For each tray-full of seeds I record the day each seed sprouted in a table like this:

Like before the green cells are lettuce seeds, the orange are spinach and the blue are mizuna.  So far the seeds are sprouting in the order we thought they would - first mizuna, then lettuce and finally spinach.

Germination trials: planting

From the comfy, warm brightness at my desk planting the first set of seeds for the germination trials seems like a distant nightmare.  If it had been just cold or just dark or only the left side of my head was hurting I would have been fine.  As it was all three nearly caused me to give and I did not take any pictures.  t picture dark soil in a dark pot at night?

If you remember the three species we are using for the germination trials are spinach, lettuce and mizuna because they are representative slow, middle and fast germinators.  Each treatment (low tunnel or heat mat) had six sets of 48 seeds for each species.  Confused?  I made a diagram: 

Pretend each of these color filled rectangles is a 72 celled flat.  They are pretty standard plug trays for starting seeds.  Each tray is divided into three sections:  green for lettuce, orange for spinach and blue for mizuna.  In theory we put two seeds per cell, so 48 per species per tray.  In actually I doubt that really happened.  If you have ever seed lettuce seeds you will know just how small they are and how they tend to stick together.  Trying to dig them back out of soil after you drop them always is fruitless.  In a week or so we will see how many seeds were really planted.

Germination trials: measuring light

How much light is actually reaching the inside of the greenhouse?
How much light gets through the low tunnel coverings?

To answer these questions we use watch dog weather trackers.  They measure:

    ~ average daily temperature

    ~ daily high and low temperature and the time at which they     

       happened

    ~ amount light in moles/day

Pretty useful little things.  

Germination trials: measuring temperature

The big fancy data logger from onset.com

One of the major components to this first experiment looking at germination rate is measuring the temperature in each of the treatments.  Happily there are data loggers that continually do this for you.  We are using two models from Onset: a big fancy looking one and a plain box one.  The fancy one is more expensive and is water proof so if I spray it with a hose by accident it will be ok.  The smaller one isn't water proof so I installed it way up high where only the hose shouldn't reach.

The small not-so-fancy looking data logger from onset.com

Both data loggers support four temperature sensors.  For the germination trials we need two sensors per treatment for a total of 24 sensors on 6 data loggers.  The data loggers can be programmed to take a temperature reading at any interval you would like.  We are going to set them to measure the temperature every hour on the hour.  In one week there will be over 4,000 temperature readings!  All this data is downloaded into a software program from Hoboware.

The picture above shows how the data is displayed with Hoboware software.  Each line, or dotted line, shows a temperature probe over a five day period.  Hourly temperature readings can be scrolled through or exported to excel.  

Germination trials: low tunnel coverings

Once the PVC pipes were set up on the greenhouse benches it was time to cover them, creating mini-greenhouses.  This led to an introduction into the world of plasticulture.  Tons and tons of plastic is used to grow our food.  So much, that the word plasticulture is used to describe all the greenhouse coverings, drip irrigation, mulches, wind breaks, post harvest handling, marketing, and fertilization tools used to grow food crops.

There are a lot of different kinds, colors and weights of plastic to use when making a greenhouse, high tunnel or low tunnel.  Here are the four kinds of plastic we picked and one non-plastic treatment:

1. Sun Master 70% Opacity overwintering film

From it's name you can tell that not much light gets through this white polyethylene plastic.  It's the kind of plastic that is put over greenhouses or tunnels that house woody plants in the winter to keep temperatures within from fluctuating too much.  So, it should be "warm" inside which will promote seed germination, but it will not be good place for leafy plants to actually grow.

2. Sun Master Greenhouse Film 

This is the clear plastic that you would expect a greenhouse to be made out of.  It is 6mm thick polyethylene and allows a whopping 92% light transmission through.  So, this one should keep it "warm" inside as well as let plants grow because they will have some light.  (I say some light because all the layers of plastic add up.  If there are two layers of plastic on the greenhouse itself and one on the low tunnel only 78% of the available light can be transmitted through.  On a dark winter day that isn't much light.)

3. Agribon+ AG19 Row Cover

This is a agricultural fabric but it made from plastic as well.  Polyester and polypropylene strands are bonded together in a swirly random fashion resulting in the term "spunbonded".  This makes a cloth like covering that allows water through, but doesn't actually absorb water as a true cloth would.  Spunbonded fabric comes in a range of weights.  The one we're using allows an 85% light transmission and weighs 0.55 oz/yd.

4.  Clear plastic with holes in it

I haven't sourced this plastic so I don't know much about it yet.  It is far thinner than the other plastics we chose so presumably more light will be transmitted through.  It is also covered in holes which allows better air flow.

5. KEN-BAR agritape heat mats

These obviously are not a covering, but they are the final treatment in this experiment.  They still alter the plant's environment by keeping the soil and roots warm.  Heat mats come in all sorts of shapes and sizes.  This brand often is used by people who keep terrariums filled with snakes and other cold blooded animals that I wouldn't want to have for a pet.  Right now we have the heat mats set to be 40 degrees Fahrenheit at night.













6. Control

Every experiment needs a control.   I forgot to take a picture, so you'll just have to take my word for it that there is a bench with a bottom layer of plastic and nothing else.