Dear Garden Problem Lady

360

A friend gave me a Clethra bush called Ruby Spice that blooms in late summer. After three years it still struggles. It’s in a sunny spot under a cedar tree – but I’ve read that Clethra likes to be planted by a stream – which we don’t have. Can I still save Ruby Spice?

Some years ago, I learned that anything near the thirsty roots of a cedar tree is not going to get much water. Also, your sweet-smelling and very beautiful Clethra bush needs moist soil and a shady spot, not a sunny one. Please try to find another spot – with let’s say half a day of shade – where you can concentrate on amending the soil (even adding sphagnum moss to a rich mix of compost and manure) and keeping the bush well-watered.

In 2021 I bought hybrid zinnia plants with unforgettable magenta-purple flowers. I saved the seeds, and planted them last year, 2022. They turned out to be a kind of “Barbie-Doll Pink” – and worse – “Pepto-Bismol Pink.” It must have to do with hybrid plants, but exactly what?

A plant seed is composed of two sets of genes – from an egg in one plant, and from pollen in another plant. Seeds will “come true,” that is produce plants identical to its source plant, only if both the pollen and the egg come from the same plant. This egg is called “in-bred.”

Many plants cannot “in-breed” – they require pollen from a different plant or their seeds will not germinate. They must be “cross-bred.” Their seeds must come from two different genetic sources, pollen from one plant, and an egg from another. Seeds from cross-bred plants germinate, but do not “come true” to either of their two sources. They are like human families, where different children resemble one parent or another, or both, or neither.

To further complicate the story of plant breeding, hybrid plants are themselves the product of a very complicated cross-breeding process, where cherished characteristics of one plant (height, or strength) are crossed with (preferred color or scent) of another plant. The cross-breeding is performed not by just any old bee or fly, but under precision in a greenhouse by specialist botanists. No wonder hybrids cost more.

Your hybrid zinnia seeds were never going to “come true” because they came from a secret, costly, years-long hybridizing process from two dissimilar genetic strains. That awful pink came from one of the parents!

Bottom line: do not save seeds from hybrid plants if you want to be certain the new plants’ flowers will be like the hybrid from which the seeds came.

The Capitol Hill Garden Club is on summer break; programs will resume on the second Tuesday in September. For program information visit the club website: capitolhillgardenclub.org.

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