The Birds and the Bees, Plant-Style August 12, 2013 22:52

In my last blog post and gardening workshop I talked a lot about corn, squash, and beans--the Three Sisters, so called because they form a classic companion planting trio.  Plants have a mind of their own, however.  Or rather, sometimes their biological needs trump our best laid plans. The squash in my own garden has decided to climb the fence rather than be a ground cover beneath my corn.

 This Kuri squash didn't want to be ground cover.
This Kuri squash didn't want to be ground cover.

At least it's using vertical space, as well as providing me an excellent view of the maturing Kuri squash from my living room window!  In just a couple of weeks, I've watched this little guy grow from a flower to a fruit the size of a softball.  That's right: I said 'fruit.'  We tend to think of squash as a vegetable because it isn't sweet like a peach or a berry and is usually prepared more like a potato.  But, in fact, a squash--like a tomato or a cucumber--is a fruit because it contains the seeds of the next generation.  As in mammalian baby-making, fruit won't form without fertilization.  In plant sex terms, we call this pollination.  

 A miniature squash fruit can be seen at the base of the female flower.
A miniature squash fruit can be seen at the base of the female flower.  After pollination, the flower will fall off and the fruit will begin to grow.  If it doesn't get pollinated, the whole thing will shrivel up and fall off.
Male flowers are identified by the absence of a fruit at their base.
Male flowers are identified by the absence of a fruit at their base and are typically more numerous than female flowers.  The flowers open in the morning when bees are out foraging.

Plant sex takes many forms.  In some species (like asparagus or kiwi vines), the male and female flowers grow on separate plants, so you would need to have both for fruit production.  In others, the male and female parts are found in the same flower so that the plants are self-fertile. In squash, it happens that there are separate male and female flowers on the same plant and they require pollination by insects, usually bees, to move pollen from the male to the female flowers.  Members of the squash family can, therefore, cross-pollinate very easily, which is how we get interesting and delicious new varieties... and many not so great ones.  If you can separate different varieties of squash or hand-pollinate them to control their crossing, it isn't hard to save their seeds so that you can plant them the following year.  With winter squash, which mature completely on the vine to where the outer skin is hard and dry, it only requires scooping the seeds out of a fruit you are about to eat and then cleaning and drying them.  To save seeds from a summer squash (or a cucumber since they're related), you would have to let the fruit mature way past the point at which you would normally want to eat it.

Corn is another plant that we think of as a vegetable, but is in fact a fruit.  Well, actually, its a whole bunch of little fruits (kernels) lined up in rows on what we call a cob.  Interesting fact: a corn cob always has an even number of rows!

 The female parts of the corn plant.  Each silk is attached to a single kernel.
The female parts of the corn plant. Each silk is attached to a single kernel.  When pollen from the tassels above falls on the silks, the kernels begin to grow, resulting in an ear of corn.
The male reproductive part of the corn plant forms at the top of the stalk and is called a tassel.
The male reproductive part of the corn plant forms at the top of the stalk and is called a tassel.  When pollen is mature, it is carried on the wind a distance of up to 20 feet.
Because corn is wind-pollinated, meaning it requires wind rather than insects to move its pollen from its male parts to its female parts, optimum fertilization is had by planting corn in a block or a circle instead of just one long row.  Also, although a single corn plant has male and female parts, they usually receive pollen from neighboring plants rather than themselves, so planting a single corn plant won't yield edible ears of corn.
 This corn was not completely fertilized.  Most of the kernels never developed.
Poor pollination results in very funny looking corn.

 When planting a small stand of corn in an urban garden, it may help to gently shake your corn's tassels to encourage pollen to waft down to the silks, rather than rely solely on the wind.  This may ensure good enough fertilization to produce edible corn, but the number of plants the typical backyard gardener is able to grow isn't enough to protect genetic diversity if you're wanting to save seed corn for next year.  To protect genetic variety, it's recommended that corn growers save seed from at least 100 different plants, which isn't very practical for urban growers.  In the end, that's what all this plant sex talk is about--the why's and how's of plant reproduction (i.e. seed production) for the purpose of being able to save viable seed from year to year rather than buying it over and over.

 

There are, however, lots of other plants that are more practical for the backyard gardener to save seed from.  At the next workshop, coming up this Thursday, we'll talk about some of the easiest garden plants to start saving seeds from.   It's also about time we started some fall and winter plantings--lucky for us, Vancouver's temperate climate allows us to garden for most of the year!  We'll also check in on earlier plantings and see what's ready to harvest.  Participants in the workshops get a share of the harvest and the opportunity to have their personal gardening questions answered.  Can't wait to see you there!