This is a great time of year to think about growing a seed crop. The demand for organic and heirloom seeds is growing, and seeds can bring a good financial return for the time and land invested. There are both practical and political reasons to grow seed crops. And there are perhaps new skills to learn on the way. Growing seed allows you to improve on a variety if you want that, or simply maintain the variety for bulk sale.

Starting small
You could start small, by growing one or two seed crops for yourself. Growing seed for use on your own farm is a valuable project, as you can select plants that grow especially well under the conditions on your farm, as well as save on seed costs. Read up on seed-growing, and the isolation distances required for your particular crop. Cucurbits need as much as ¼ mile distance from other flowering plants of the same type, whereas tomatoes only need 180 feet at the most. Be sure to have a large enough population of plants to ensure a diverse genetic pool. With self-pollinators (in-breeders) such as beans, 20 plants may be enough, but for out-breeders (cross-pollinators), 100 are needed, in order to avoid in-breeding depression.
USDA Certified Organic seed is in demand, but uncertified sustainably/ecologically grown seed also has a market, especially for heirloom or heritage varieties.
It’s possible to sell your seeds directly by joining Local Harvest and selling on their website, www.localharvest.org, where there are more than 1,000 entries on seed for sale. Even eBay now has heirloom seeds! Most seed growers continue to grow a mix of crops – a seed crop, like any other crop, could fail. But if seed-growing really suits you, you could move more towards growing seeds and away from other crops. According to Ira Wallace of Southern Exposure Seed Exchange, it is possible for one person to grow seeds for several different companies and earn $25,000 a year, on 2 acres.

What crop to grow?
Choose an open-pollinated variety of the crop you want to grow. Hybrids, which are produced by deliberately crossing two separate varieties, do not “run true;” that is, seed saved from hybrids produces very mixed progeny.
Self-pollinators have flowers which all contain both the female and male parts (botanically these are called “perfect flowers”). Some self-pollinating flowers are self-fertilizing, while others are self-incompatible, and so are usually pollinated by insects transferring pollen from one flower to another. Cross-pollinators have separate male and female flowers, either on the same plant (as corn does), or as completely separate plants. (It was quite a revelation to me when I found out that spinach has male plants and female plants.) Cross-pollinating plants are mostly wind-pollinated.
Self-pollinated crops often have good open-pollinated varieties, so they are a good place to start. Hybrids of cross-pollinators such as corn exhibit  “hybrid vigor” (meaning hybrids undeniably have an edge as far as productivity goes), but hybrids of self-pollinators don’t show this trait as much. While experienced seed growers can develop stable strains from a hybrid, over several years of work, this is not the place to start.
Choose a crop you can easily grow to maturity in your climate, something you only grow one variety of, or can easily grow far enough from others. Choose something that interests you. Maybe you’d love to see a host of orange cosmos flowers brighten your vegetable field!
We have been growing Roma paste tomato seeds because we suffer with Septoria Leaf Spot. The reward for developing a strain of Roma that is resistant to Septoria is of great value to us. Likewise, we started growing Crimson Sweet watermelon seed because we wanted larger, earlier melons. I’m hoping that never introducing other watermelons into our gardens means we can avoid the Watermelon Fruit Blotch disease. Here are details of how we grow these two crops:

Roma paste tomatoes
We have been growing Roma paste tomato seeds because we make a lot of sauce, juice and salsa, and our yields were for several years, much reduced by Septoria Leaf Spot. There didn’t seem to be any commercially available Septoria resistant variety when we looked, so I decided to develop our own resistant strain. Here’s how we do it: We put out our 250 transplants as usual in late April or early May. We make sure when we plan our plot layouts that we don’t put any tomato plants of any other varieties within 180′ of any of our Romas. We use the Florida string weave system, with a metal T-post after every two plants (the plants are two feet apart), and a new round of twine each week.
As soon as the tomatoes start to ripen, we start monitoring the plants, selecting those with healthy foliage, and those apparently yielding very well. We use flagging tape (plastic or crepe paper marking tape). We use green flagging tape to indicate healthy foliage with reasonable yield, and red flagging tape to indicate abundant fruit with reasonable foliage. (So the best plants get both a green and a red ribbon!) We tie the tape on the T-post next to the chosen plant, with the bow or knot on the side of the post  facing the plant. We do this once a week, on the day before the crew comes through to do a harvest (it’s no good looking for high yields when they’ve already been picked!)
After one or two weeks of just looking and flagging, we start picking for seed, on those same just-before-bulk-harvest days. We assess the flagged plants, and take one or two tomatoes from each plant that has both green and red flags, or has one flag and is not worse than average on the other factor. If the plant no longer looks so great, we remove its ribbon. If a plant without a ribbon starts to excel in the healthy foliage department as the season wears on, we add a ribbon. (We don’t add many red ribbons after the start of the harvest, because we want to keep selecting for early fruit, and plants that yield well later are not really what we want.) Our method combines well with crew harvesting most of the fruit as produce. If you are growing the variety only or mainly as a seed crop, you would save all the seed from the chosen plants, or from the whole row after pulling out any unpromising plants (“roguing”).
We usually pick about 5 gallons for seed each week. We then store those buckets of tomatoes in a secret location, where noone will eat them, for 5 days, which lets the fruit get dead ripe. Then we cut the fruits in half, rejecting any diseased ones. Next, we scoop out the seeds with a tablespoon. This lets us use the “shells” for tomato sauce for our own use. The seeds ferment in the bucket in a shed for 2 or 3 days, nominally at 70°F (hmmm, it’s higher than that!). If we remember, we stir two or three times a day. When fermentation is over (no more bubbling), we take several clean buckets and a sieve, and wash the seed clean. This art gets easier and quicker with practice. The good seed sinks to the bottom, so the process is a matter of pouring off the top half of the bucket (mostly no good), then adding water to both buckets, stirring, letting things settle, and then pouring off the junk from both. Consolidate the better stuff in one bucket, the worse stuff in another, and pour away the seedless water. Once the seed looks fairly clean, strain it through the sieve, and put it in clean water. When the seed is really clean, strain it and spread it to dry indoors with a fan, on a window screen or paper towels. After  12 hours, scrape the clumps of seed off the surface with a putty knife, turn them over and crumble the clumps by hand. Once the seed is thoroughly dry, gather it into a paper bag, with some desiccant. I hold back on storing in an airtight container until I’m absolutely sure the seed is dry. We usually do 4 or 5 batches of seed, all in August. It’s not good to save seed from plants in decline, so get started as soon as you can, and quit while the going is good. Last year I sold some of this seed for the first time, to Southern Exposure Seed Exchange.
Tomatoes are self-pollinating, so planting 200 or more, pulling out any off-types, and making a selection of 80-100 of those plants gives enough genetic diversity

‘Crimson Sweet’ watermelon
We started growing Crimson Sweet watermelon seed because we wanted to select for large early melons. For the past two years we have used the bio-degradable black mulch (Bio-telos mater-Bi and Eco-One – we’re not USDA certified, so the fact that they are not OMRI listed doesn’t matter). This change alone gives us melons almost 4 weeks earlier than when we used hay mulch. At the very end of July, as the melons reach ripeness, I walk through the plot with a grease pencil (china marker) and number my selected melons. I’ve tried other ways to mark the selected melons: flags, magic markers, but the grease pencil works nicely. Having a big number right there on the skin of the melon works to stop any crew about to harvest it.  We have already done some selection for healthy plants when we transplant. Now as I walk through, I look for big melons with vigorous healthy vines. I aim to number 30-35 melons. The crew are told not to ever pick any melons with numbers on. (Confession; one year when I suspected our cantaloupes were being “browsed”, I put numbers on them too. It looked so official and scientific! It worked a charm!)
Once a week, I harvest for seed, taking the melons once they are about a week over-ripe, and discarding any that don’t look healthy. I like to deal with 6-8 melons each time. I keep notes of which numbers I harvest each week, and assess them for size, ripeness, and once I open them, taste. I take a big knife and several clean buckets, and big spoon (and a damp cloth – it’s messy!). I cut the melon across the middle and taste a chunk from the heart. If I don’t like the taste, I don’t save seed from that one. If the taste is good I scoop out the heart, which is seedless, into a very clean bucket, for eating later. Then there is a layer that is thick with seeds. I scoop this into the seed bucket. Lastly I scoop the outer flesh, also relatively seed-free, into the food bucket also. One time, I was sitting on the edge of a garden cart, with my horde of melons, and my big knife and spoon, when a 10-year old came by. His eyes popped out on stalks, at the sight of me eating a melon, with giant silverware, enjoying my private feast!
These seeds get fermented for about 4 days, then washed, similarly to the tomato seed washing, and dried. They take longer to dry, being considerably bigger. The scooped out watermelon flesh makes great smoothies and sorbets.
It can get hard to find all the numbered melons (that’s where the notebook comes in handy, so I don’t waste time looking for one that I already harvested.) I abandon any numbered melons that don’t ripen early, and I sometimes add in any huge melons that pop up after the initial numbering. Earliness is important to us, though, so I only harvest 4 or 5 times and then stop. Again, for us that’s an August task.

Hoophouses for seed growing
I mentioned hoophouse seed crops in my June 2008 article in Growing for Market. There is not much material available yet about growing seed crops in hoophouses, but I feel sure this is a very promising opportunity. Where it is humid or rainy, it is hard to grow “dry” seed crops such as legumes, lettuce, spinach, beets (as opposed to “wet” seed crops inside fruits, like tomatoes, melons) outdoors, but using covered space opens new possibilities.
Obviously it’s important with hoophouse summer crops that you don’t forget to keep your fall planting dates and crop rotations in mind, especially if the winter greens and salads are the main purpose of the hoophouse. Essentially we have 3 crop seasons in our hoophouse: winter crops planted in the fall, early warm weather crops planted in March and April, and summer crops planted in July. Summer crops have from mid July at the earliest to early November at the latest, to be in the ground, to fit in with our all-important winter and spring crops. Obviously we can only grow crops that mature quickly, unless we either give up some space from our spring/early summer crops, or our fall/early winter crops, or get very creative!

Isolation distances
The isolation distance required for a particular species depends on how the plants get pollinated. Bees fly a long way, so cucurbits have long isolation distances of 1500′, or even as much as ½ mile (2640′) if you have no physical barriers in place. Tomatoes, especially heirloom varieties, mostly self-pollinate, and only require an isolation distance of 75-180′. Choose something your next door neighbors don’t have growing on the other side of your fence-line!
Once you know the required isolation distance for the crop you plan to grow, make sure your planting map gives you this space. Early each year, we write a “Seed Saving Letter” to others who grow plants here at Twin Oaks, to tell them where we plan to grow our seed crops, and asking them not to plant anything that could cross-pollinate with that crop within the isolation distance. In return, we offer our surplus transplants, and we also ask them if they have any seed saving plans we need to know about. I found out which dill to grow in our insectaries in order not to mess up the Herb Garden dill seed, and how far away to keep our flashy calendula so it didn’t meet the medicinal ones.
Barriers such as buildings, including hoophouses, and tall crops such as corn or sunflowers, can help a borderline isolation be more certain. Collecting seed only from the middle of a planting block rather than at the edges, can also help.. There are more advanced tricks to help isolation, involving bagging, caging and hand-pollinating, for those determined to find a way to get the crop they want.
The need to pay attention to isolation distances can restrict what you can grow for food, but if your growing season is long enough, you may be able to have a zucchini crop for early market, then sow pumpkins for seed, and ruthlessly pull up the zucchini before the pumpkins flower. This is known as isolating by time: plant an early crop for food, and then a later crop for seed – or if your season is long enough and the crop maturity quick, plant two seed crops. The various squash varieties can cross within the same family, and if you want pie pumpkin seeds, you need to keep the zucchini away. Suzanne Ashworth’s Seed To Seed gives everything you need to know on this aspect

How much to grow? How much space? How long will it take?
Never save seed from just one plant, (unless it’s the second to last on the planet). Grow a big enough population of plants to keep enough genetic diversity for future adaptability, and prevent a genetic “bottleneck”. In practice this means a minimum of 20 in-breeders (self-pollinators), 100 out-breeders (cross-pollinators). Self-pollinators (for example, beans) are naturally already inbred, and contain little diversity. For these, a small population is enough. In-breeding depression occurs when seed is saved from too small a planting. It leads, over time, to lower quality, less vigorous plants. To avoid this, cross-pollinators need a bigger population. (Cucurbits, although cross-pollinators, show relatively little inbreeding depression, and a population of 8-24 plants will be enough).
There is, as yet, no published table of time from sowing to seed crop maturity. Lettuce can take up to two months beyond the eating stage to get to the mature seed stage. (I found this information in Fedco’s charming Seed Growing School Curriculum.) Crops where we eat the ripe fruit take very little extra time to mature seeds – just make sure the fruit is really ripe. Cucumbers are eaten as under-ripe fruits, and the seed is mature when the cucumber reaches the yellow blimp stage. Biennials (onions, carrots, most other root crops) need a second growing season to mature seed.

Selecting “mother plants”
If you are selling seed, you will need more plants than if you are just keeping seed to re-supply yourself. You have a certain responsibility to maintain that variety and all the genetic diversity it contains. Grow enough to allow for roguing out any atypical plants, if you are maintaining a variety for a seed company, and more to allow for selection if you are improving a variety. Roguing involves removing off-type plants, and also existing fruits from the immediate neighbor plants. Also rogue out diseased plants and any early bolting plants of crops where bolting is very undesirable.

Seed cleaning
There are two types of seed processing: wet and dry. Wet seeds are embedded in the fruit – tomatoes, cucumbers, melons, eggplant. Dry seeds are found in pods, husks or ears, and dry down on the plant – beans, okra, corn, radish. Wet processing has several steps: scooping out the seed or mashing the fruit; fermenting the seed pulp for a few days; washing the seed and removing the pulp; drying the washed seed. Wet-processed seed is naturally cleaned during the fermentation and washing. The challenge is to ferment the seed long enough to release the clean seed, without waiting so long that the seed starts to sprout.
Dry seed processing involves harvesting the pods or the entire plants, completing the drying indoors if needed, then cracking or breaking the pods to release the seeds. Surprisingly, hoophouses with shade and good ventilation can be good places to quickly dry seeds. “If it’s not too hot in there to grow a crop, it’s likely not to hot to dry seeds for a short time,” says Ira Wallace. After drying, the seeds and chaff are then sieved through at least two different gauge mesh screens: the larger one keeps back the big pieces of chaff and lets the seed pass through. The smaller one keeps back the seed and lets the small chaff pass through. After screening, the seed is winnowed, perhaps using a box fan and a sheet of cloth or plastic to catch the seed.
There are good details on seed cleaning methods in the Seed Processing and Storage Guide from Saving Our Seed (see Resources). While small quantities of seed can be cleaned with little equipment, if you move into growing larger quantities, you will want to buy some of the specialized equipment available, or make your own.

Seed storage
Make sure your storage places are mouseproof. Initial storage can begin when seeds are down to 8% moisture. At this level, seeds break or shatter when you try to fold them, or hit them with a hammer. They don’t bend or mash. Put them in a jar with an equal weight of dessicant for 7 days. Then remove the dessicant, put in a labeled bag inside a labeled glass or metal container with an airtight lid. Seeds need to be stored dry and cool and airtight once dry, with some dessicant. For long term storage, put this jar or can in the freezer. When removing seeds from the freezer, allow the unopened container to warm up to room temperature for a day before opening. This prevents moisture from condensing on the seeds. For USDA Certified Organic, check the OMRI list before using dessicant, to ensure you only use allowed materials.
Biennial plants such as carrots need to be replanted in spring (or left over winter in the field). In the second year, the flower heads and seeds will form. Leaving the roots in the ground over the winter is easier, but if your climate gets very cold, or fluctuates a lot (ours does) , or if you have lots of voles (we do), then digging the roots and storing in a cool, damp root cellar is wiser. It also gives you the chance to select well shaped roots as your seed stock.

Germination testing
To find out how well your seeds will do, test their germination. Take a thick paper towel, fold it lengthwise, unfold it and spread 50 or 100 seeds along the inside of the fold. Close the fold, dampen the towel with water, and roll it up loosely. Put it inside a loosely closed plastic bag, and set the bag somewhere at a suitable temperature. See Bubel for ideal temperatures for different crops.  Often on top of the fridge is suitable. Beware the top of water heaters which use natural gas: this inhibits tomato seeds and other nightshades. A lightbulb can be a suitable heater. 75F is good for most vegetables, 80F is better for tomatoes and peppers, 85F for melons. Check twice a day (the air change will help the seeds even if you know it’s too early to see sprouts.)  Count the number of sprouted seeds after 7 days, and remove the sprouted ones. Repeat after another 7 days and add this count to the first one, to calculate your percent germination.

Double benefits
In some cases, your crop could produce both food and seed, as we do with our tomatoes and watermelon. I’ve heard of a grower who sells prepared winter squash to restaurants, after he has removed the seeds. But getting two crops from one plant does take more time, compared to simply mashing the whole tomatoes, for instance.
There are other ways to have your crop and eat it too. Harvesting a few leaves from greens grown for seed will not detract from seed production. Eat the produce from the edges of a block planting and save seed from plants in the center – this helps preserves the purity of the seed, without “wasting” the edge plants. Eat the earliest fruit and save seed later, or save seed first and eat the later fruit. Seed should not be saved from plants past their prime, however, and you would not want to risk your seed crop by reducing the time it has to mature by too much. Rat tail radish can be grown for seed and some of the pods can be eaten first.
You may be able to grow seed for flowers which attract beneficial insects or pest-eating birds to your crops. Ira Wallace suggests that biennials such as carrots or onions for seed can be interplanted in a hoophouse with overwintered greens. As the biennial plants start to grow bigger, remove the early spring greens, and let the seed plants grow. Keep records of  your dates, as the timing might get critical, and some crops will work better than others.

Pam Dawling is the garden manager at Twin Oaks Community in Louisa, Virginia. She can be emailed at pam@twinoaks.org.