Open pollinated varieties are those crops pollinated through natural functions like wind, pollinators like bees, and water. They produce seeds that will grow into plants that are similar to the parent plant. This method of seed saving likely pre-dates modern agriculture and is the oldest seed saving method. We currently offer over 700 hundred varieties of open pollinated seed. 

So how do our seed growers and seed savers maintain all these varieties without cross pollination (the mixing of pollen between separate varieties)? There are several simple methods to isolate open pollinated crops. 

All crops listed as heirlooms are also open pollinated. The heirloom designation means that an open pollinated variety dates to 1940 or earlier. 

Isolation by Distance

One of the most common ways to isolate open pollinated varieties is by distance. We include isolation distances for all our crops in our growing guides, so you can use this method to save seed. You’ll notice that we list a distance for home use and for pure seed, which is important for professional seed growers. 

A great example is our tomato growing guide:

Isolate varieties of the common tomato (L. lycopersicum) by a minimum of 35’ for home use and 75’ to 150’ for pure seed. Isolate varieties of the currant tomato (L. pimpinellifolium) species from all other tomato species by a minimum of 150’. 

Reaching isolation distances can be tough, especially for growers looking for pure seed. That’s why even many seed growers will stick to just a couple varieties of one crop.

However, if you’re looking to save seed for home use, this isn’t as critical. A little cross pollination can increase genetic diversity and isn’t the end of the world!

You can also get creative with some other isolation methods.

Isolation Through Time

Another great way to isolation open pollinated varieties is through time. When crops don’t bloom at the same time, there’s no way for them to cross pollinate. 

Some crops naturally bloom at different times. If you find two varieties with vastly different days to maturity and limited bloom periods, you can often get away with planting them at the same time. 

For example, planted on the same day, Aunt Mary’s Sweet Corn, which is ready to harvest in just 69 days, won’t typically cross pollinate with Jellicorse Twin Dent Corn, which takes 120 days to mature. Just keep in mind that environmental conditions can affect the blooming period. 

You can also isolate crops through time by using succession planting, particularly in much of the Southeast where we have long, hot growing seasons. For example, you can sneak in a crop of Gold Rush Yellow Wax Bush Snap Bean (ready to harvest in 52 days) in spring or early summer. Then grow a different bean like Contender (Buff Valentine) Bush Snap Bean (ready to harvest in 49 days) in late summer and fall. 

Hand Pollination and Mechanical Isolation

Occasionally, growers want more control over pollination. This is when more mechanical isolation techniques and hand pollination often come into play. These techniques can be especially helpful for growers trying to breed new open pollinated varieties from a few existing ones. 

Hoop Houses, High Tunnels, Row Cover

Growers often use hoop houses, high tunnels, and row cover to isolate varieties. When kept closed, they can exclude insect pollinators, preventing cross pollination. However, this means that humans will need to hand pollinate plants themselves. 

In the Southeast, it may also be necessary to cover structures like high tunnels with shade cloth to prevent burning the plants. 

Pollination Bags

Alternatively, growers may place pollination bags over the blossoms of each plant. Also called isolation bags or exclusion bags, these bags, usually made of fine mesh, exclude insects and pollen. They prevent natural pollination and allow growers to hand pollinate as desired.

Hand Pollination 

Hand pollination is when humans manually transfer pollen from the stamen or male pollen bearing structure on a plant to the pistil or female structure which produces the fruit and seed. While growers will often hand pollinate to control pollination, they may also do it when other, natural pollination fails. Sadly, pollinator decline has made this strategy more common. 

Usually, growers will use a small paintbrush or Q-Tip to move the pollen, but not always. When hand pollinating corn, you can simply break off a tassel and brush it on the silks of the desired plants. Make sure you use a clean tool for each variety.

If using pollination bags, you must remove the bag, pollinate the flower, and them replace the bag to ensure a bee or other pollinator doesn’t follow in your wake.

The Pueblo County Extension has more helpful hand pollination tips. 

Storing Seed 

Another way we can easily isolate varieties is by growing them out in different years. If you’ve been gardening awhile, you probably know that most seed doesn’t expire doesn’t expire after one year.

At SESE, we’re privileged to have a climate controlled seed storage space. We can store many varieties for several years without worrying. Our team checks germination rates periodically and we can work with our network of growers to make sure seed is replenished with fresh stock as needed. 

Our seed storage system allows us and our growers to maintain a wide range of varieties. 

 

Preserving open pollinated varieties is of critical importance. It allows communities, gardeners, and farmers to save seed year after year. This helps preserve genetic diversity, adapt varieties to climate change, and encourages food sovereignty. Which method will you try this season?

If you have been perusing the website or catalog, you may have noticed that we carry both open pollinated and hybrid sweet corn. The hybrid sweet corn is actually the only hybrid that we carry. So why do we carry both? What are the differences and how do you choose the right one for your garden? In today’s blog, we’ll discuss the fundamental differences and pros and cons of hybrid and open pollinated corn.

What is Open Pollinated Sweet Corn?

The basic fundamental between hybrid and open-pollinated is how they’re bred. Open pollinated means that the plant is fertilized naturally, like by wind, insects, or birds.

Seed growers save seed from open-pollinated varieties over generations to create varieties that are relatively stable, but still genetically diverse. If you save seed from open pollinated corn, you will get the same corn next season, so long as you don’t have another variety nearby that cross-pollinated it. 

To isolate different varieties, growers usually use distance or time. Crops that flower at different times won’t cross-pollinate.

Heirlooms are open-pollinated varieties dating to before 1940.

Corn is wind pollinated. Home gardeners should separate varieties by 600 ft. for home use, or 1/2 to 1 mile for absolute purity. Save at least 500 seeds from at least 10% of the plants to maintain vigor and genetic diversity of the variety.

What is Hybrid Sweet Corn?

Hybrid crops are the first generation crosses of two varieties. In breeding hybrid sweet corn, seed growers select two genetically pure lines of corn to cross.

Breeding hybrid corn is tricky! Typically, growers will alternate rows of the two types of corn. Though corn has both male and female parts, growers think about them as male and female parents. 

Growers leave the male parent stalks intact. These will provide the pollen for the pollination. Growers remove the tassels from the female parent rows as they form, ensuring that they don’t produce pollen. The pollen from the male parent rows will fertilize the silks of the female parent rows. The growers then harvest the seeds from the female parent rows.

This technique ensures growers get the desired mix of genetics. 

During the season, growers also go through and remove and volunteer or “off-type” corn in a technique called rogueing.

Pros and Cons Open Pollinated Sweet Corn

While we love open pollinated crops, we know they come with a unique set of benefits and challenges. 

The Pros

• Farmers and gardeners can easily save seed from open-pollinated sweet corn.
• Foodies often find that open-pollinated varieties have more “real corn flavor” rather than just sweetness.
• Growers can save open-pollinated varieties can over years to adapt to a specific local climate.
• Home gardeners may enjoy that they tend to have an extended harvest period. 
• Open-pollinated varieties typically have higher protein content than hybrid varieties. 
• When pigs, chickens, horses, and cows have a choice between open-pollinated and hybrid corn, the animals invariably prefer the old open-pollinated varieties (possibly because of the protein content).

The Cons

• They typically aren’t as sugary sweet as hybrid sweet corn varieties.
• They don’t store well and are best used or preserved quickly after harvest.
• Open pollinated corn isn’t uniform in size, which can be an issue for commercial growers.
• It also doesn’t mature all at the same time, another feature which can be a struggle for commercial growers.

Pros and Cons of Hybrid Sweet Corn

While hybrid may be a typical choice for market growers, it too has its pros and cons.

The Pros

• Hybrid corn tends to mature all at once, which is ideal for market growers. 
• The ears are uniform in size.
• They are sugary sweet and hold their sweetness well in storage. 
• Hybrids often have better disease resistance. 

The uniformity of hybrid sweet size and maturity are the two main reasons we offer hybrid for our commercial growers.

The Cons

• Hybrid seeds tend to rot in cool soil. 
• They may have weak seedling vigor. 
• The ears are more susceptible to insect damage than open pollinated corn. 
• You cannot reliably save seed from hybrid corn.

Which Should You Grow?

What you should grow depends on your needs and personal preferences. As mentioned above, hybrid sweet corn’s uniformity is a key feature for many of our market gardeners, but if you’re looking to enjoy sweet corn over an extended period, open pollinated may be the right choice.

Open pollinated is also a good choice if you’re hoping to save seed. Saving seed from your corn can help preserve genetic diversity, connect you with your land, and adapt a variety to your garden’s specific conditions as you work to save seed from the best plants over the years. 

If open-pollinated corn is new to you, we suggest planting less than 1/4 lb. until you are familiar with its characteristics. It grows a bit differently and has a distinct flavor. Don’t forget, you’ll need to use it more quickly, too. Open pollinated corn doesn’t store quite as well as hybrid corn. 

For good pollination and ear development, plant open-pollinated corn in blocks at least 5-6 rows wide, and hybrid corn in blocks at least 4 rows wide.

Want to save seed from your open pollinated sweet corn? Check out the 8 Steps to Saving Corn Seed.

Each winter gardeners dream of spring, tucking seeds into the soil indoors where they’re safe from winter’s chill. Most of garden seeds like tomatoes, zinnias, cabbage, and basil all benefit from relatively warm soil conditions. But, there are some seeds that actually require cold temperatures to germinate. This is when gardeners must use a method called cold stratification.

What is Cold Stratification?

Cold stratification is a seed starting technique where the gardener exposes the seeds to cold, moist conditions to mimic natural conditions. For some species, these conditions are necessary for the seed to break dormancy. 

Seeds that require cold stratification typically have a hard seed coating. In a natural setting, the frosts, snow, low temperatures, and rain of winter break down the coating.

What Seeds Require Cold Stratification

While you can simply plunk many annual vegetable, flower, and herb seeds straight into warm soil in the spring, some varieties, especially native perennials, need or benefit from cold stratification.

Some species like Butterfly Weed will germinate without cold stratification. However, they may have a lower germination rate and germinate more slowly. Others, like the Yellow Coneflower, require cold stratification. I have marked those species that require cold stratification to break dormancy with a “*.”

• Butterfly Weed
• Milkweed*
• Narrow-Leaved Coneflower (Echinacea Angustifolia)*
• Pale Purple Coneflower (Echinacea Pallida)*
• Yellow Coneflower (Echinacea Paradoxa)*
• Purple Coneflower (Echinacea Purpurea)
• Lupine
• St. John’s Wort
• Asparagus
• Rudbeckia
• Catnip
• Soapwort
• Perennial Sunflowers
• Larkspur
• Violas
• Coreopsis
• Anise-Hyssop

This list includes many of the common plants that benefit from cold stratification but isn’t comprehensive. Always check on your specific variety’s needs. 

How to Cold Stratify Seeds

There are several techniques for cold stratifying seeds, but we like to keep it as simple as possible at SESE. However, these seeds will still need to be started far in advance of your typical crops. While a few species will germinate after just 3 weeks of cold stratification, most need 2 to 4 months before they break dormancy.

To stratify seeds indoors, sow them as directed in pots or flats, and then place them in the refrigerator for 2 to 4 months. Keep the soil moist during this period. If you have access to a cold frame or hoop house, you can also set your pots or flats into it for the winter.

Some native perennials may still have relatively low germination rates, even after cold stratification. 

That’s what makes them sow tricky to grow. Thankfully, once established, they will often self sow or you can divide them after a couple of years. 

Cold Stratification Alternative: Direct Sow Fall Planting

If cold stratification doesn’t sound like a fun project for you, there is an easy alternative, direct sowing in fall. As long as you live in a region where the winters naturally provide moist, cold conditions, the stratification process will happen over the winter.

In a previous post, Spring Flowers: Fall Sowing, we discuss how to use this technique and what flowers grow well using this method. Some flowers, like Dara, will grow well when fall sown even if they don’t require cold stratification.

Generally, we recommend fall sowing any of your seeds about 4 to 6 weeks before your first expected frost date.