Category Archives: Population Size

Seed Webinar today

I’m excited to be part of a seed webinar this afternoon at 4PM Eastern.  I’ll be talking about how we approach selecting seed plants on our farm. I’ve got some pictures lined up!


If you’re interested in listening in all the details are below. (Or you can just register here: There is no fee to participate.




“The People’s Choice” Webinar: Seed Questions across Canada!

Hosted by: The Bauta Family Initiative on Canadian Seed Security


Designed according to feedback collected from across Canada, the webinar will start with a presentation on “On-farm Roguing, Selection, and Adaptation” by Dan Brisebois of Tourne-Sol Farm (QC). Part 2 of the webinar will feature a seed panel of experts from across the country who will address YOUR most important questions about seed. The panel will speak to both pre-submitted questions and live questions from webinar participants. Please come prepared to engage!

You can get more info and register here:



What Is Seed Quality?

Seed quality was one of the big topics at USC Canada’s Train the Seed Trainer sessions. All the participants had a lot to say on the topic. And though we had many conflicting opinions on other seed issues, we had consensus making a list of seed quality concerns.

I’ve taken that list and broken it into a few categories and elaborated on each of them:

  • Basic seed concerns
  • Physical handling concerns
  • Genetic concerns
  • Traceability concerns

Basic Seed Concerns

These are some of the first things that folks thing of in terms of good seed:

  • Germination rate: Does the seed germinate well?
  • Seedling vigor: Do the seedlings grow vigorously?
  • Seedborne diseases: Is the seed free of problematic diseases?

Physical Handling Concerns

  • Cleanliness: How much chaff, dirt, or dust is present?
  • Presence of weed seeds
  • Handling mistakes: Was the variety mislabeled? Was there an accidental mixing of another variety of the same species during cleaning or packing?

Genetic Concerns

  • Varietal purity: Has the variety cross-pollinated?
  • Population size: Was seed saved from a large enough population to maintain a wide genetic breadth?

Traceability Concerns

Where is the variety strain from originally? Is it simply another variety that’s been renamed? How were previous generations handled? Does the variety perform/appear different from what it once did?

What Is Seed Quality?

You might notice that I have highlighted all of the above as concerns. In the end we did not put forward a list that defines quality seed as each of these concerns is not all or nothing. They depend greatly on the end use of the seed.

Beets with a 55% germination are fine for a home garden though none of us would want to sell those beets seeds. Slightly crossed up tomato seed is probably good for the vegetable grower who saved it though again none of us would want to sell the seed.

Generally speaking if the seed is for sale, then high standards need to be met, but seed saved for personal garden and farm use needs to meet the standards the seed saver can tolerate.

Do you think we’ve missed anything in this seed quality discussion?

What are your seed quality concerns?

One comment one seed growers made was that he doesn’t often hear back from his clients after they’ve ordered seeds until their next seed order. He  would love to hear their complaints about the seeds (if they have any.) And of course he loves to hear from thrilled clients too!

So, go  and write your seed sources a letter to tell them what you don’t like so much and what you love!

Seed Production Planning Part 2 – Calculating Seed Needs

This is the second part of a series on crop planning for seed production. Seed production planning part 1 covered growing small trials to evaluate whether a variety was worth growing to seed on your farm in your climate.

Once you’ve decided the varieties for  this year’s seed production, you need to determine how much seed you would like to harvest.


Under good storage conditions most seed will last a number of years. You can grow enough in one year to cover your seed needs for multiple years. This has a few benefits:

  • Growing fewer varieties gives you more space for better isolation distances to avoid cross-pollination.
  • Growing a larger number of plants of on variety provides more plants to observe and you can better select the most fit individuals. Large population also maintain a broader genetic pool that ensures more resilient varieties.
  • Cleaning bigger seed lots is easier than cleaning small seed lots.

For most varieties, I aim to grow enough seed for at least a 3-year supply. (This is not possible for all varieties. I.e. parsnip, leeks and onions lose germination quickly after a year in storage.)

(You can read a previous post about isolation distances and population sizes.)


Consider all the ways you sell or use seed, and estimate the needs for each use. This includes

  • Seed you use on-farm. This is calculated from your crop plan – basically the rowfoot you plan to grow multiplied by a seeding rate. (The crop planning for organic vegetable growers handbook covers this.)
  • Seed sold through a seed catalog (in packets or in bulk). This is projected from the previous year’s sales records.
  • Seed sold to other seed companies. This is based on how much seed they need.

Then make a chart to summarize this information. Here are two examples loosely based on our farm.


Tatsoi is a leafy green from the Brassica rapa species.

At Tourne-Sol farm, we seed a lot of Tatsoi to sell bunching or as part of our salad mixes. We also sell Tatsoi seed as packets to gardeners and in bulk quantities to other farmers.  And our seed company clients purchase regular amounts of our Tatsoi seed.

 Purpose 2012 2013 2014 Total
Farm Use 120g 120g 120g

360 g

Packet Sales 100g(50pkts x 2g) 120g(60pkts x 2g) 140g(70pkts x 2g)

360 g

Bulk Sales 1kg 1kg 1kg

3000 g

For Other Seed Companies 1kg 1kg 1kg

3000 g


6720 g

We’ll need to harvest about 7 kg of Tatsoi seed to meet our projections for the next 3 years.


We need significantly less tomato seeds than Tatsoi seeds. Since we transplant tomatoes, our on-farm needs are low and we only sell packets through our seed catalog. Our seed company clients purchase a significant volume but they usually buy enough seed for multiple years at once.

 Purpose 2012 2013 2014 Total
Farm Use 1g 1g 1g

3 g

Packet Sales 5g(50pkts x 0.1g) 6g(60pkts x 0.1g) 7g(70pkts x 0.1g)

18 g

Bulk Sales

0 g

For Other Seed Companies 300g

300 g


321 g

We’ll need to harvest 321 g of Jaune Flammée tomato seed to meet our projections.


In our next seed production planning installment we’ll figure out how many plants to grow to meet these seed needs.

Visiting Even’star Organic Farm

When Emily and I get away in the winter, we usually fit a few farm visits into our travel plans. Recently, when we went to visit some friends in Virginia we also visited two nearby farms. The first farm we visited was Even’star Organic Farm in Lexington, Maryland run by Brett Grohsgal and Dr. Christine Bergman.

On today’s menu:

  • Introducing Even’star Organic Farm
  • Growing winter crops in open fields
  • Growing winter crops in tunnels
  • Breeding plants for cold hardiness
  • Thinking about climatic differences between Maryland and Quebec


Even’star produces certified organic vegetables that are distributed year-round through a CSA and to wholesale clients. Even’star also goes to a farmers market during the summer and fall.

A significant amount of the seed that Even’star uses is bred and produced in their own fields.

I’ve been reading Brett’s articles in Growing for Market for years. His  articles Saving seed makes sense (The Best of 2002, Growing For Market) and Time to get ready for winter! (Growing for Market Vol. 13 #8-9) were critical in refining my ideas of on-farm seed breeding and season extension.  I was excited  to see his operation.


Even’star grows about 25 acres of winter crops. This is more than double their summer vegetable acreage. They mainly grow this amount of winter crops to offset slower growing conditions and leaf damage from inclement weather.

A field of Ice-Bred Arugula.

Though the outer leaves of the arugula plants are yellowing and nipped by frost,  the central leaves are in prime condition.

Similarly for these kales.

Chinese Thick-Stem Mustard is one of Brett’s hardiest and most vigorous varieties.

In addition to a lot of leafy brassicas,  there were also quite a lot of turnips in the fields such as this Colletto Viola turnip.


Even’star also had a couple of tunnels seeded to brassica greens and lettuces.

Pampered in a sheltered area, these greens had a higher percentage of marketable leaves. These structures also ensured harvest possibilities during snowy periods outdoors.

Despite some of the advantages to growing in tunnels, they require a financial investment to build and maintain. Brett also mentioned that it wasn’t unusual to lose the greenhouse plastic during hurricane season.


Brett Grohsgal focuses on breeding plants for cold hardiness, taste, and disease resistance.

Most of Brett’s winter production wouldn’t be possible without the cold-hardy  gene lines he has developed.

Brett’s plant breeding usually starts by crossing different varieties of a species, or different strains of the same variety. This generates greater genetic diversity from which to select better adapted plants. This also adds some variability in growing habit and leaf shape to the gene lines. Brett generally doesn’t mind this variability.

However, when Brett wants to maintain a plants traits and simply introduce cold hardiness (such as with this Mizuna), he will grow tens of thousands of plants of a variety, save seeds from the hardiest plants, and repeat this cycle until he attains the cold hardiness levels he wants.


From the pictures above you can see that Even’star in USDA zone 7 is noticeably warmer than our farm  in Canada hardiness zone 5A. Though the temperatures never reach the -35C we can experience, Even’star still has to contend with periods of heavy snows, hard frosts, and ice.

Visiting farms such as Even’star and seeing the results that breeders like Brett Grohsgal can achieve inspires me to see what we can do in the early spring and late fall when our weather conditions are similar to winter Maryland.

Emily and I had a lot to dream and talk about as we left the farm, grabbed some sandwiches at a local deli, and went for a picnic on nearby Chesapeake bay


In other news, in the winter 2011 issue of the Small Farmer’s Journal Eric Nordell mentioned Fred and my book Crop Planning for Organic Vegetable Growers in the introduction to a Horsedrawn Circle Letter. He called it the “The best book we have come across written specifically for new growers with a couple of years of apprenticeship experience and ready to start market gardening on their own”. Needless to say, I was ecstatic to get such a great endorsement. also recently reviewed the book and will be updating their review as their crop plan unfolds through the growing season. I’m hoping their plans work well!

Now that I’m back from vacation, I’ll try to write more about seed packing and another farm visit summary.

See you later.

Growing Out Crossed-Up Lettuce Seed

When folks start saving seeds, their biggest fear is usually cross-pollination between different varieties. But unless you are selling the seed or trying to preserve it  as a named variety, a little crossing won’t kill you. In fact, growing out crossed out plants can be a learning and aesthetic experience.

With some crops, growing two varieties within 100 feet of each other will  easily result in 10-20% of the seed being crossed. Other crops barely cross even planted right beside each other. Lettuce is one of these stubborn crops.


In 2006, I attended a plant breeding workshop partially led by Frank Morton at the annual MOFGA farmer to farmer conference. Frank explained that to get lettuce varieties to cross he grew them side by side. When the lettuces bolted, he bent the flower stalks from each plant together and tied them up. This encouraged insects to travel between the flowers of both varieties increasing the chance of a pollen exchange.

In 2007, I followed his advice.

I grew out a small green oak leaf and a red lollo rossa side-by-side. When they bolted, I tied the flowers together to encourage cross-pollination. (I don’t have a picture of this.) I saved the seed from each variety in separate well-labelled envelopes.


In 2008, I grew out some of the lettuce seed. I thickly sowed the seed in open flats in the greenhouse. When the seed from the green oak leaf plants germinated, out of hundreds of green seedlings, a few had red leaves. These different coloured seedlings were the crossed individuals. I grew these plants out.

They all looked similar to this picture. You can see some blending of the parents’s characteristics – oak leaves with a reddish blush. However these plants were much bigger than either parent.

This first generation after crossing is called the F1 (first filial) generation. It is usually quite uniform and often very vigourous.

I saved the seed from each F1 plant separately.


In 2009, I grew out 30-40 plants from each F1 plant.

Whereas the F1 plants had all been similar, the F2 generation expressed all types combinations of the original plant’s genetic traits. I had expected this but was still caught unprepared. I didn’t know what to do with these plants. Each individual lettuce was a new potential line. If I saved seed from each plant to grow out in seperate batches the following year, I would never have the space. I was paralysed.

In the end, I saved seed from all the plants and just mixed it up to use in salad mixes.

I also made a plan for the next year (which is this year).


In 2010, I grew out some more seed from the 2008 F1 plants.

I started the seed in the greenhouse ( see this post to read more about that).

Late April to early May, I planted the lettuces out by colour – the reddest plants to the greenest plants. I also planted the seedlings on 6″ spacing (I usually plant lettuce for seed 12″ apart) to get more plants in the same area.

Near the end of the May, I started cutting the inner leaves of the medium-sized plants for mesclun salad mixes. This let me devellop a relationship with each plant. I marked any plants that stood out and pulled those I didn’t like. I harvested this way once a week for three weeks.

I marked the plants with phragmite stems. (This selection process was also inspired by Frank Morton whose early seed selection days coincided with growing speciality salad mixes.)

When the plants were bigger and somewhat bitter, I culled  more agressively to leave at least 12″ spacing between plants.

At this point, I walked the beds regularly dividing the plants into 2 categories

  • those lettuces I would save seed from individual plants
  • lettuces that had similar characteristic that I would bulk the seeds to develop new populations

The plants then bolted.

And kept bolting.

In the next day or two I will be bring these plants into the barn to dry.

Now, I have to make a plan for next year’s growout!

Balancing Crop Profitability and Plant Populations

Today’s post wrap up this series on seed economics (that began here.) The topic of plant population sizes came up during the last ECOSGN meeting as we compared the profitability of selling seeds by packet vs. bulk.

The Challenge: Profit vs. Population Size

Andrea Berry (of Hope seeds) noted that seed companies that mainly distribute small seed packets don’t need to grow many plants to meet their seed needs. Andrea highlighted that to maintain good genetic diversity in cross-pollinating (crosser) varieties, it is better to grow a large number of plants. This means at least 60-80 but preferably around 200 plants (read this post for more on population size). That many plants produces way more seed than most seed companies can sell solely in packets. Andrea concluded that the potential profit of selling seeds in packets is a disincentive to maintaining large plant populations.

Seed growers need to take the possibility of eroding plant genetics seriously. Growing seed out with inadequate populations for 1-2 generations might not have drastic consequences. But, if we grow a crosser variety out for 4-5 generations with small populations, we may see decreases in yields, disease tolerance, and some of the varieties’s desired traits.

Some solutions for small seed companies to maintain good crosser genetics

  • Grow seed in one year for multiple years,
  • Offer bulk seed for sale to gardeners and farmers, or other seed companies,
  • Buy new seed every 2-3 generations to replace or reinvigorate your stock seed,
  • Buy seed from growers who maintain large populations.

An important exception: Cucurbits

Cucurbit species (squash, zukes, cukes, melons, and the like) are crossers. However, they have evolved to resist most inbreeding depression – you only need to save seed from 12-16 plants to maintain  a minimum genetic breadth for a variety  (though more is always better.)

Wrapping Up Seed Economics 101

This is my last post on seed profitability for now. We’ve looked at two quick tools to compare seed crops: profit in space and profit in time. Of course seed crops are only profitable if you can sell them. (This is speaking economically. There are a slew of ecological and agricultural reasons to grow your own seed.) I will tackle the seed selling part of the equation later this spring – specifically selling bulk seed to seed companies on contract.

Over the next weeks, I will switch to more pictures and less math. At Tourne-Sol farm, we are currently building a catterpillar tunnel. When we’re finished, I will share how we did that. See you later!

Seed Yields

Today, we are going to look at how to calculate seed yields. This information will help you set your prices and will be useful in crop planning. We will look at

  1. Using your harvest data to calculate yield
  2. Consulting (and interpreting) reference material for yield data

This post is one in a series on seed economics that begins here. Quick Review of previous posts:

  • Seed profitability can be evaluated as $/bedft.
  • Small scale growers should average $2.50/bedft to $5.00/bedft
  • Profit in space is calculated by :                                                                                                        Seed yield (g/bedft) x seed price ($/g) = $/bedft

A warning – I mix and match metric weights and evil imperial distances with reckless abandon. Take heed …

Calculate yield from harvest data

This is done after you have harvested a seed crop. Weigh your total seed harvest and divide that amount by the area in which it was grown.

  • Let’s say I grew 100bedft of Tatsoi  and harvested 2.5kg.
  • My yield would be: 2500g / 100bedft = 25g/bedft

Good simple recording keeping makes this easy. Here is a PDF Seed yield worksheet. If you would like this as an excel sheet, e-mail me. (WordPress doesn’t accept excel attachments)

  • Columns F, G and H are the relevant columns to calculate yield.
  • I keep track of rows/bed and inrow spacing to compare what happens when these variables change.  (I posted on plant spacing and yield here.)
  • The number of plants is important when considering whether your plant population size is adequate.

As you grow a variety to seed multiple times, you will discover the yield range you can expect. Here are some yield ranges we have measured on our farm:

Crop grams/bedft










*Tomatoes sometimes grown 2 rows/bed to augment number of plants in population.

**These lettuce yields are much lower than what growers in better climates can get.

Consult Reference Materials for Yield Data

These two books have yield information for most seed crops and some varieties:

You’ll quickly notice that these yields are not presented as g/bedft. You’ll have to convert the yields before you can use them with the equations I have provided. This isn’t always easy:

1. If the yield is in weight/acre then convert to g/bedft similar to what was done with $/acre here)

  • Tatsoi in Brian Connolly’s book: Brassica Rapas are 1200-2400 lbs/acre
  • 1200lbs/acre x 454g/lb ÷ 28 beds/acre ÷ 300 bedft/bed = 65 g/bedft

2. If the  yield is in rowft (or rft) then you have to assume how many rows/bed the grower planted:

  • Weight (g) x Rows/Bed ÷ Rowft  = g/bedft
  • Tatsoi in Patrick Steiner’s book: 25 lbs for 1500 rowft
  • Assuming 3 rows/bed: 25 lbs x 454g/lb x 3 rows/bed ÷ 1500 = 23 g/bedft

3. If the yield is in # of plants, you will need to assume rows/bed and inrow spacing

  • Weight (g) x rows/bed ÷ inrow spacing (rowft/plant) ÷ plants = g/bedft
  • Mustard in Patrick Steiner’s book: 1lb for 40 plants
  • Assume 3 rows/bed and 1ft per plant: 1 lb x 454g/lb x 3 rows/bed ÷ 1 rowft/plant ÷ 40 plants = 34 g/bedft

4. If the yield is in the number of fruit (melons, squash, … ) … well this one I will let you work out yourself.

Using Yield Data

  • Remember  data from reference materials is not  from your farm.
  • Yield varies from crop to crop, variety to variety, farm to farm, and season to season.
  • When there is a range of yield data, use the lower values. If you harvest more than this, you can revise your prices and future planning yields .
  • Until you are familiar with a crop and what you can expect it to yield, don’t overcommit yourself. Grow small amounts at first and increase gradually.

Next, we’ll look at setting prices.