Seed Saving Nerd Out Part 1: Plant Reproduction

Posted by Anne Fletcher on

Seed saving basket

This is part 1 of a series (click here for the whole series) that goes deeper than usual into the botany behind seeds to help you become a better seed saver.

Mechanically speaking, it’s not at all hard to save seeds.  In most cases, you simply pick them, dry them and store them.  BUT (and this is a big but) in order to get plants with the characteristics you expect from your saved seeds, you have to do some research and planning before you get to the stage of picking, drying and storing.

The first step is to understand plant reproduction.  While animals can really only reproduce one way (genetic material from one male and one female of the species combine to form an embryo), plants have 2 main methods, plus several variations within each method.

Plant Reproduction Method 1: Vegetative reproduction produces clones

One of the coolest things about plants is that you can grow new, identical plants from pieces of a parent plant.  It’s as if you could clone yourself by cutting off your finger and letting it grow into a new you.  Weird, right?

apple trees are propagated vegetatively

Most fruit is grown vegetatively.  All Granny Smith apple trees are genetically identical to each other, and to the original tree that Maria Ann Smith discovered and propagated in Australia in 1868.  Twigs are cut from mature trees, grafted (fused) onto roots from a different variety chosen for the health of the roots, and grown into mature trees which then, in turn, have twigs cut from them to be turned into new trees.  The only way to get a Granny Smith apple tree is to use a twig from the line that continues unbroken from the original.

If you save and plant seeds from a Granny Smith apple (or any other named fruit variety from apples to pears to avocados to lemons) you will get a tree, but the fruit will not be the same as the parent.  It might be good, but it probably won’t be.  Fruit tree breeders grow hundreds of new crosses to find just one that meets their standards.

If you want good fruit in your garden, don't start it from seed.

It’s a fun project to root an avocado pit or start seeds from a supermarket apple, but if you want good fruit in your garden, you shouldn't start seeds.  Buy a tree instead.  (See here for my post on ordering bare root trees.)

Plant Reproduction Method 2: Sexual reproduction in plants produces seeds

Just like with animals, for plants to create a new generation that is genetically similar, but not identical to parents, they reproduce sexually. (Sex in plants just means the combination of male + female genetic material.)  Pollen (the male genetic material) combines with an ovule (the female genetic material) to produce an embryo that is encased in a seed.

Every seed is like you: sharing traits from, but not exactly the same as, your parents.

But plants can do way more with sexual reproduction than animals.  They can create seeds with other members of their own species (like animals); they can self-pollinate, where pollen fertilizes the ovule of the same flower, often before it opens; and they are far more likely than animals to cross with other related species.

All this flexibility in reproduction creates lots of genetic diversity, which is great for plants adapting to new environments, or for those growing alone without another member of the species nearby, but can be vexing for the gardener saving seeds. 

The main issue gardeners find when saving seed is that the child plant doesn’t produce what you were expecting it would. 

This happens for two reasons, both due to hybridizing.


Reason 1: F1 Hybrids

Don't save seed from unstable F1 hybrids!

F1 hybrids are commercially available seeds created by intentionally crossing two different varieties to create offspring with desirable characteristics, particularly for commercial growers.  Lots of familiar varieties are F1 hybrids: Sun Gold, Early Girl, Sweet 100, to name just a few common F1 tomatoes.

Growing F1’s at home can give great results because the varieties are predictable and vigorous.  Though because they're most often bred for commercial viability, they're primarily selected for traits that home gardeners don't need -- things like ripening well in a truck on the way to the supermarket, or having all the fruit ripen at once for bulk harvesting.

The biggest problem for home gardeners, however, comes with seed saving. In F1 hybrids, the combined genetic material from the parent plants goes haywire in the second generation.  That’s why we call F1 hybrids unstable, because after the first generation, the offspring are really unpredictable.

The solution to this problem is to know what your varieties are.  Do not save seed from hybrids.

Open-pollinated varieties are the alternative to F1’s. They have been stabilized by plant breeders over many generations so that the seed you save from them will produce offspring that are very similar to their parents.  That’s what plant people mean when they say that a variety “breeds true.”

If you know the name of a variety you’d like to save seed from, it’s easy to look up whether or not it’s open-pollinated.  If you don’t know the name, it’s probably best not to save seed because it could be a hybrid. 

(I should mention that hybrids are completely different than GMO’s.  Hybrids are created with traditional breeding methods and are not at all controversial, except perhaps because they can be expensive to buy year after year.  GMO’s are created in a lab with genetic engineering and are the source of lots of controversy.  Hybrids can be grown organically. GMO’s cannot.)

Reason 2: Accidental cross-breeding / hybridizing

If a species is self-pollinating, accidental cross-breeding is rare, and not something home growers need to worry about. 

tomato flowers are self-pollinatingTomato flowers have usually pollinated themselves before opening.

Some common self-pollinating veggies:

  • Tomatoes
  • Beans
  • Peas
  • Peppers
  • Lettuce
  • Eggplant

As long as the variety is open-pollinated you can confidently save seeds from self-pollinating plants without worrying about accidental cross-fertilization. 

For everything else, read on . . .

If a flower doesn't pollinate itself, it relies on wind or insects to carry pollen from the male part of the flower to the female part, or in some cases from male flowers to female flowers. As the insects fly and the wind blows around, pollen can get mixed up and spread around a pretty large area.

If two varieties of the same species, like zucchini and crookneck squash, are planted near one another, insects will carry pollen between the two, and this results in cross-breeding, a.k.a. a hybrid.  The problem, however, is that each seed you save from a zucchini that’s been pollinated from a crookneck will have a random collection of genes from each, like a bunch of siblings from the same parents.  You might get crookneck-shaped zucchini, or half-yellow, half-green squashes, etc.  And because plant genomes are way bigger than animal ones, cross-bred plants can give you lots of really weird combos, some of them great, but most of them not so tasty.

Cross-bred plants can give you lots of really weird combos, some of them great, but most of them not so tasty.

The first solution to this problem is to plant different varieties of the same species at their specified isolation distances (once you know what to look for, there are lots of charts online – it’s different for every species).  For those of us in urban or suburban areas, this isn’t practical because you really never know what your neighbors are growing just over the fence.

The second solution is to pollinate the flowers by hand, and then block insects from entering them until fruit starts to form.  I'll go into lots more detail about that in the next post! 

Click here to see part 2 for a handy graphic to help you decide which plants to save seed from!



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