Field day: Germination

The herb garden

 Left over herbs from last fall have sweetened dramatically with the cold weather.  Have you ever had sweet cilantro?  I hadn't until yesterday.  It still tastes like cilantro, but is not sharp.  The dill is fresh tasting, like freshly cut grass or clean laundry.

Remember the low tunnels from last year?  I won't be looking at germination again this year, but I've set one up to jump start germination and growth of greens.  Despite the low temperatures, the greenhouses are warm - as long as the sun is out.  

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.

Experimental design - germination in chambers

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?

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 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.

Germination trials: building tunnels

If you remember step one of Experiment Number One is finish building the low tunnels.  These hoop-shaped structures on top of the greenhouse's benches will hopefully help raise the internal temperature by a few degrees to speed up seed germination (and maybe growth?).  What coverings we are testing will be the topic of a future post, this is all about construction of the low tunnels.

Simplicity and affordability were the constraints in building the tunnels.  We designed them to mimic low tunnel construction used outside: bended hoops covered with a layer of plastic.  Indoor construction on benches involves a few more parts, but they are commonly found things and are cheap. We used only these seven parts:

1/2" PVC pipe

1/2" metal brackets

tech-screws

snap clamps

binder clips

bike hooks

covering

The greenhouse benches are made of aluminum and are 10' x 4'.  So, the first step was screwing the brackets on using the tech-screws.  To ensure the pvc wouldn't wiggle it had to be placed in the bracket as it was being screw on.  

Each bench used three pieces of pvc: one for each end and a middle piece to keep the covering from sagging.  The coverings were attached to the pvc using 1/2" snap clamps from Johnny's.  These are the best and made building the tunnels really easy.  They come in four inch pieces because they are designed for outdoor use.  Since these low tunnels are not outside and blustery winter weather won't be an issue we cut each one into four smaller pieces.  From 40 snap clamps we ended with a big box of 160!

Each low tunnel was covered with three pieces of material.  Each end-piece was attached to the pvc with clamps and to the bench with binder clips.  (Since starting this project I now have binder clips in all of my pockets.)    The largest piece of material is pulled tight over the low tunnel and secured to the bench on only one side.  The other side is attached to a piece of pvc with more snap-clamps.  The weight of the pipe holds this side of the tunnel down and allows it to be easily rolled up.

To get the rolled up side to stay up I duct taped a bike hook to a snap clamp and put it on the central piece of pvc in the tunnel.  So far these have worked really well, although I am careful to unroll the tunnel side and not just let it drop in case the hook could puncture the covering.

Next up: low tunnel coverings!  

Germination trials or an overview of Experiment Number One

The first thing we are going to be looking at are seed germination rates in different low tunnel treatments within the greenhouse.  The goal is to create a low tunnel that will significantly decrease the time it takes for seeds to germinate.  In cold weather seed germination can sometimes be a limiting factor in plant growth.  For example, lettuce will germinate best around 68 degrees Fahrenheit, but will happily grow at much lower temperatures.

Here's an overview of what is going to happen:

The six low tunnel treatments

1. Clear plastic - the thick stuff used to cover greenhouses
2. White plastic 
3. Clear plastic with holes - a light weight plastic with holes that allow for ventilation
4. Floating row cover - often called 'remay' on farms
5. Heat mats - to provide bottom soil heat
6. Control - just plants in the greenhouse

The three varieties of greens

• Spinach - the slow germinator
• Lettuce - the mid-rate germinator
• Mizuna - the fast germinator

Why only these three greens?  To properly conduct a Scientific Experiment there have to be lots of replications.  For instance, if we do six replications of 24 plants per treatment that ends up being almost 2000 seedlings to plant and count for each species of green.  To keep the counting low-ish we picked three greens that represent a range of germination from fast to slow.

An abridged protocol

1. Finish building the low tunnels.  This involves drilling into metal using tech screws.  I am not good at this and have been putting it off.
2. Plant a lot of seeds.  They haven't arrived yet which is why I can put off the drilling.
3. Count the number of seeds that have germinated every day for ten days.  

That's it!  I'll be writing about the process and results as they unfold with plenty of pictures.

building the low tunnels

We have two kinds of benches, wood sided and metal sides.  

The wood ones are way easier to drill into, but either way setting up hoops on them is pretty easy.  

We used:

9' long pieces of 1/2 inch PVC

metal brackets

tech screws or metal to wood screws

The bottom of each bench is covered with a layer of clear plastic since our goal is to build a sealed chamber.  The plastic is a bit brown because it had been used once in the field.  Next we covered each tunnel with a different kind of cloth or plastic to see what effect they would have on internal temperatures.  Each tunnel has a temperature sensor that measures temperature on the hour so all we have to do is sit back and wait.