Sex, drugs, and plant propagation

Which is better, sexual or asexual reproduction? It depends who’s doing the reproducing. This spring I’m making new plants both ways. Seeds are produced through sexual reproduction. Each seed has two parents with different genetic make-ups. That means each seed, and the plant it grows into, is a unique individual, like us. I’m growing a lot of my new plants from seed, including vegetables, herbs, and annual flowers.

Each borage and basil seedling is a genetically unique

    Asexual reproduction accounts for a lot of the perennials, trees and shrubs we buy. If you’re a breeder who wants to make sure your dogwood or azalea is exactly like its parent, you clone it. Unlike human tissues (so far), plant tissues have the ability to reproduce whole plants from parts of the parent plant.

A desirable rhododendron can be cloned infinitely

     Right now I’m growing cuttings from last year’s rosemary, bearberry (Arctostaphylos uva-ursi), and coleus. I’m hoping to do the same with tarragon and oregano I bought at the garden center. If these cuttings take root and grow, the plants they grow into will be genetically identical to the parent plant.

Cuttings from bearberry and coleus are clones

I’ve read that some named shrub varieties consist entirely of clones from one desirable plant. Many plants, but identical genes.

    People concerned about biodiversity have a problem with this system. In addition to encouraging us to grow native plants, they want us to foster genetic diversity among plant species. The reason is that a broader gene pool allows a species to adapt to changing environmental conditions. Some individuals in the population will develop greater resistance to heat, drought, flooding, and other challenges. As climate change speeds up changes plants face, they need to be ready to evolve in response.

    There’s an inherent tension between promoting biodiversity and maintaining desirable varieties. If you’re trying to grow a particular tomato, say ‘Brandywine,’ which is open pollinated (not a hybrid), you don’t want your ‘Brandywine’ plants fertilized by pollen from other tomato varieties. 

Tomato growers want to keep varieties distinct

     But if you’re just growing a patch of perennials, say native purple coneflowers (Echinacea purpurea), there’s no reason not to let them mix with nearby members of their species and create a genetically mixed population. In fact, your stand of coneflowers will be more likely to survive if it includes members with different genes that can tolerate varying conditions.

A genetically diverse coneflower population is adaptable

    Except for letting willing self-seeders do their thing, I haven’t propagated perennials from seed. When I want more, I may divide the plants or, as with rosemary, bearberry, and ivy, grow more from cuttings. If a snippet from the growing end of a plant is willing to send down roots, why not make more that way? Divisions and cuttings make clones, just as tissue cultures made by breeders from a few cells grow into clones of a newly-developed perennial. In future I want to learn to grow native perennials from seed so I can help maintain their genetic diversity.

Felix, a new garden helper visiting from New York

I’m off on a trip to the Southeast, hoping to experience spring flowers there and again at home when I return. See you in two weeks.