Pollination & Isolation

If saving seeds is your goal, then the process of plant pollination must not be overlooked.   Plants produce their fruits once their blooms have been fertilized by pollen.  While this is a desired result of seed-saving, if the plant has been pollinated by a different plant, their seed will be a cross between the two.

You may not notice the alterations in that first year harvest.  The initial fruit should be fine.  However, if you save that seed and plant it next year, it will contain genes from both parent plants.  That's why pollination control is essential to saving pure seed.

The way to control pollination is by isolation.  Protect the blooms and you protect the seeds.

First get acquainted with the vegetables within each botanical family, as we mentioned in our previous post 5 Rules to Saving Seeds.  Remember, only plants within the same family will cross with each other.  The rest are fine and will not affect seed results.

There are 3 main methods of plant isolation:

1.  Time Isolation involves planting conflicting varieties at alternate times.  Either plant your second variety once your first has already begun to flower or separate their planting dates far enough apart to be safe.  It is important that the first sets its seed before the second variety flowers or there will be reason to be concerned that cross-pollination has occurred.

If you want to grow two types of sweet corn and save seed from both, for example, plant varieties approximately 3 weeks apart.  Once the first is done tasseling and is ready to pick, the second variety should be starting to pollinate.  Maturity dates may vary with each variety, so the required time isolation may differ some.

Lettuce, corn, and sunflowers are just a few of many crops that favor this method.

2.  Bagging is your second option for isolation.  This process requires you to cover the flower heads to keep unwanted pollen out.  Whatever you use for protection, it must allow air in and keep insects out.  Nylon mesh bags, lightweight fabric, or bridal tulle secured around the entire plant or individual blossoms will work well.  Once the variety has finished flowering, mark the fruit with a string and uncover barrier.

(If you don't bag the entire plant, make sure to protect multiple blooms in case something happens to one of the fruits later.  You wouldn't want to put all your seed saving hopes on one tomato, let's say.  If that tomato ended up getting chewed on by bugs later in the season, you will have lost your only chance.)

This method does take some extra work and attention to detail, but it also gives you a little more freedom with what you can grow where.  Tomatoes, which are mostly self-pollinating, are often saved this way. However, others like spinach, beets, and corn are pollinated by wind and should not be isolated through bagging.

Image courtesy of freedigitalphotos.net

3. The other main choice you have is Distance Isolation, which is exactly what it sounds like.  Plant space in between family members to prevent pollination.  If you have ideal growing space, this may be your solution.  Follow our chart below for recommended and required distances for proper seed saving.  (And don't forget about any nearby neighbors who might be growing conflicting varieties adjacent to yours.)

Smaller gardens may have a problem providing enough distance, however.  If so, they should try one of the methods already mentioned.  Everyone can save seed.  They just have to figure out what works best for them.

Plant Isolation Distances
every Seed-Saving Gardener needs to know:

Plant Isolation Distance
Bean--------------------- 25 – 100 feet
Beet--------------------- 1/2 mile
Broccoli------------------ 1/2 mile
Cabbage----------------- 1 mile
Carrot------------------- 1500 feet
Corn--------------------- 1/2 mile
Cucumber--------------- 1/2 mile
Lettuce------------------ 25 – 50 feet
Melon-------------------- 1500 feet
Okra--------------------- 1/2 mile
Onion------------------- 1500 feet
Pea---------------------- 50 feet
Pepper------------------- 500 feet
Radish------------------- 1500 feet
Squash------------------ 1/2 mile
Tomato------------------ 25 – 100 feet
Watermelon------------ 1/2 mile

Do you save your own seed?
If so, what method do you use to control pollination in your garden?

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