Have you ever seen a broccoflower? It looks like a pale green cauliflower and appears, every now and then, in the produce section of your supermarket.
The broccoflower is an excellent illustration of the hybridizing potential found between any two varieties of the same species. Broccoli and cauliflower are nothing more than two varieties of a remarkable plant species known simply as wild cabbage (Brassica oleracea). This means that they can pollinate one another just as easily as two varieties of plum or apple or avocado can pollinate one another.
Creating a broccoflower is a challenge that any dedicated gardener could conceivably meet. This fall, if you plant broccoli and cauliflower side by side, allow some of the plants to bloom and then, with a small paintbrush, take pollen from the flowers of one plant and dust it over the flowers of the other. By this act, you will have taken the first step in producing your own hybrid variety. Allow the plants to set seed, which you will collect and sow in early spring or save until next fall. When you plant out these seeds, created from your cross-pollination, you may get some plants that look like broccoli, some that look like cauliflower and some that have characteristics of each.
Let’s say you get one plant that yields cauliflowers with the slightest hint of green. You would then allow those greenish cauliflowers (a cauliflower is just a huge flower bud) to bloom and set seed, plant those seeds and allow plants with slightly greener cauliflowers to flower and set seed. Continue this process again and again, selecting what will ideally be progressively greener cauliflowers, until you get the broccoflower that you desire.
Broccoli and cauliflower are not the only familiar garden plants that are hybrids of that same wild cabbage known as Brassica oleracea. Brussels sprouts, kale, collards, kohlrabi and cabbage are all varieties of this same species, with the potential to pollinate one another and create exotic new additions to the vegetable kingdom.
The pear essentials
Speaking of pollination and what it will produce, a number of readers questioned my assertion that single Asian pear trees, in isolation from other pear varieties, could not bear fruit. Single Asian pear trees may indeed produce fruit on their own, but their crops will be significantly increased by the presence of a nearby pollinator variety.
If you only have room for a single pear tree, you can increase your harvest by taking flowering branches from another pear variety and hanging those branches in your tree when it is in bloom.
The tendency toward self-sterility – when a plant requires a related but different variety to ensure fruit and seed production – is actually beneficial to the long-term future of a species. When a fruit tree is self-fruitful, it means it is self-pollinating and that the seeds it produces will grow into trees very much like itself.
This is a perfectly acceptable situation until there is a sudden change in the environment, such as that brought on by excessive droughts, flooding or cold. If the environment should suddenly change, but all the seedlings of a tree are accustomed to a more moderate former environment, those seedlings may all die and the species will become extinct.
However, if the offspring of that tree are the product of cross-pollination with another tree. there is a greater chance that the hybrid will have offspring with some “wild” traits taken from the other variety. Such traits may include tolerance of more severe climatic conditions.