Everyone knows that plants grow from seed. Some are more easily grown from seed than others. Fountain grass and Mexican evening primrose grow so easily from seed that they can become invasive. These two examples have not been bred or otherwise improved from the species as they are found in the wild. Seedlings are consequently not much different genetically from the parents and can be perpetuated indefinitely. With irrigation, or in moist areas, nasturtiums may also become invasive, but eventually revert to a more feral state, because they have been bred to produce varieties that are more appropriate for gardening but lack the genetic stability.

Rhododendrons are not only difficult to grow from seed, but take many years to mature and are usually very different from the parents, which was likely derived from extensive hybridization or mutation. Only those obtained directly from the wild will produce similar seedlings. Rhododendrons are propagated from cuttings because they root so reliably, because cuttings mature more rapidly than seedlings and so that the offspring will be genetically identically to the parent. ‘Cultivars’ are variations of species that require such ‘vegetative’ propagation, technically known as ‘cloning’, to preserve genetic continuity.

‘Varieties’, such as the variations of nasturtium, differ from cultivars in that they may be propagated ‘sexually’, by seed to obtain reasonably predictable results. (I don’t make up this terminology.) Varieties that are produced as hybrids of very specific parents, such as some tomatoes, revert to a more feral state in fewer generations than those that occur naturally in the wild. For example, yellow violets that grow wild in the Willamette Valley of Oregon will naturally continue to produce yellow blooming offspring and might be considered to be a variety of the common violet that otherwise blooms white or ‘violet’.

Simply speaking, cultivars are genetically identically to their single parent, but varieties are essentially genetically indistinguishable from their pair of parents, which may also be indistinguishable, but are technically not genetically identical. I hope that this was not too confusing. So, as I said earlier, “Everyone knows that plants grow from seed.” but for one reason or another, some are propagated vegetatively.

As for vegetables and other plants, seeds can be purchased from mail order seed companies or your local nurseries. Most other vegetables should be planted as seed directly in the soil for just the opposite reasons. For example, some vegetable seeds may include individual beets, carrots and corn stalks only produce a minimal amount of vegetable or fruit product.