How to Propagate Plants

Help your native garden grow

Cultivating your outdoor spaces with plants that make sense in Southern California’s climate, soil types and wildlife could be as easy (and economical) as propagating one plant into many.

Some plants propagate best by seed, others by cuttings of leaves, stems or roots. Either way, vegetative propagation is a time-honored gardening process for aggregating your plant supply. Take a snip (or sow a seed), do a few nips and tucks, plant it, water it and let it grow.

Jim Wadman is a propagation wizard. He’s the committee chair for the San Diego chapter of the California Native Plant Society (CNPS), a statewide nonprofit that works to conserve and restore native plants in their natural habitat. The San Diego propagation committee members donate their time to make new plants for city-owned habitats around San Diego, and for the society’s native plant sales each spring and fall in Balboa Park.

“There’s a huge palette of what’s available,” Jim says. “Hundreds of native plants grow well in San Diego.”

He encourages homeowners to take native garden tours (most happen in the spring—San Diego’s CNPS annual tour takes place in April, cnpssd.org—but there’s one that’s year-round at the San Diego Botanic Garden, sdbgarden.org/tours.htm) and seek guidance from local landscape specialists.

Seeds vs. cuttings
The CNPS prefers to propagate plants from seed rather than from cuttings for reasons of diversity, Jim says. Cuttings essentially produce clones, while seeds produce plants that are genetically different from the source plant.

“If you plant a bunch of plants with the same genetic makeup, if a pathogen or insect comes along, all the plants are susceptible. The survival rate plummets,” Jim says. “If there’s some diversity, some of the plants will die and some won’t. Susceptibility is genetically predetermined.”

That said, if a large canyon bottom needs to be restored with a lot of plants quickly, CNPS volunteers propagate from cuttings, using species such as the California sycamore (Platanus racemosa).

Green thumbs hoping to populate their yards with new plants likewise might not be willing to wait for seeds to grow into seedlings.

“Theoretically, if you put seed on the ground it does work,” Jim says. “However, for the home consumer, that’s not necessarily fast or satisfying.”

San Diego is fortunate to have a number of commercial nurseries that sell native plants for instant results and can be easily propagated, he says. (Check cnpssd.org for a list of nurseries as well as annual plant sales through various garden clubs.)

Plant selection
The Beginners should try milkweed or purple sage. Both natives require very little water, propagate well and, as an added bonus, attract butterflies. (Monarch butterflies actually depend on milkweed for survival.)

Milkweed counts 15 species native to California, so you’ve got options. Both narrow-leaf (Asclepias fascicularis) and showy (Asclepias speciosa) are readily available in San Diego and produce pretty flowers.

Purple sage (Salvia leucophylla) has gained popularity in San Diego xeriscape gardens, Jim says, because it’s an evergreen that’s aromatic, prefers full sun and gravelly soil, and grows in large clumps, ideal for dividing.

TIP: CNPS advises against propagating non-native, invasive plants like brightly-flowered nasturtium (Tropaeolum) with seeds that spread far and wide and strangle native plants. Other invasive species to avoid? Mustard plants (Brassica) and stinging nettle (Urtica dioica), according to Jim.

milkweedHow to propagate milkweed
The Milkweed plants are perennials that can be propagated from seeds or cuttings in moist, well-drained soil.

From seeds Clean mature milkweed seeds of their feathery pappi by either rubbing the seeds against a screen, or shaking the seeds in a plastic bag with a rubber ball. Milkweed pappi can be messy and a skin irritant, so experts recommend cleaning seeds outdoors while wearing rubber gloves.

From cuttings Pick a stem without flowers or buds, says Tiger Palafox, one of the hosts of the Saturday morning radio program “Garden America” (gardenamerica.com). Clip the stem below the third node (where the leaf sprouts from), then gently pull off the leaves from the lower two nodes. Leave the leaves at the top. Plant cuttings 18 inches apart, burying the bottom two nodes—where the roots will grow from—beneath the soil.

TIP: Propagate only during a plant’s growing season.

purple sageHow to propagate purple sage
The Purple sage, with its pale purple flowers and grayish green leaves, is a coastal shrub that tolerates drought conditions and sloped sites.

From seeds Be forewarned: Propagating sage from seeds can be a slow process—those sown directly into soil can take a year to reach a mature height.

From cuttings Follow the same steps for propagating purple sage that you do for milkweed, or young, growing tips of sage can be rooted in a vase with water, perlite or moist sand. Rooting hormone, found at most commercial nurseries, can be used to stimulate growth.

TIP: Tiger says that both milkweed and purple sage propagate without rooting hormone but that using it betters the success rate since the hormone also acts as an antifungal, protecting tender cuttings from pathogens. 

By division Purple sage naturally clumps so it can—and should—be divided to produce new plants. Dig up the root ball and separate it into sections with at least two to three shoots and several roots on each. Replant with a mix of soil and compost to improve drainage.

TIP: Before you buy, visit CNPS’s online database (www.cnpssd.org/plant-profiles) to find specific information and photos for more than 500 California natives (listed alphabetically by their scientific names), including gardening tips and geographic range.
Categories: Garden Planner, Gardening, Tricks of the trade

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