When gardeners visit a garden center, attend a plant sale, or browse a plant catalog, they might impulsively select one or several plants for the garden. These could be good choices, or the gardener might eventually learn to appreciate the addition of the plant(s) to the garden.

Admittedly, I have selected and bought plants casually. Most recently, I picked up three plants during an unplanned visit to Norrie’s Garden Shop at the UCSC Arboretum. Here are my impulsive picks.

• Scarlet Monkey Flower (Diplacus aurantiacus ‘Dorothy’). Bright red flowers complement the pale yellow blossoms of the familiar Monkey Flower, already in my garden. It will fit into my bed of California native plants or the butterfly garden I’m developing with California native plants that are local to my area. A successful selection.

• Downy Zieria, Dwarf Zieria (Zieria littoralis). According to Australian Plants Online, it’s a “dense-growing Australian native shrub critically endangered in the wild, where it grows on exposed rocky coastal headlands (littoralis means seashore.) Neat small grey-green velvety foliage; small starry white flowers in winter-spring.” It grows to 3 feet tall and will provide an unusual gray-green look in my bed of Australian plants, which has open space.

• Wax Flower (Crowea ‘Poorinda Ecstasy’). An attractive shrub native to Australia grows about 3 feet high and wide and produces comparatively large solitary pink flowers from early summer to autumn and occasionally at other times. My Australian garden bed has this plant, but the Arboretum’s garden shop offered a “multi-colored” cultivar, likely with blossoms with a range of blossom hues, ranging from full pink to white. It will fill a place in this bed with a fresh look.

Today’s photo gallery includes images of these plants.

While these selections will add to my garden, a more systematic approach to choosing plants could contribute to the long-term development of the garden with specific goals in mind.

The goal of my systematic plant selection project is to identify locally native shrubs and perennials for the butterfly garden I have been developing.

This involves comparing two plant lists.

The first is a list generated by the California Native Plant Society’s Calscape database (calscape.org). Using this resource, I searched for shrubs and perennials that (a) are native to Santa Cruz County, (b) up to 6 feet tall, and (c) attract butterflies. This search yielded 102 plants.

Calscape provides an option to download the list in Microsoft Excel format. My efforts to download this list were not successful. Calscape downloaded a dozen plants from my list, nicely organized in columns of information from the database. This was potentially helpful, but it did not include the 102 plants that my search listed.

An alternative was to download the search results into a Microsoft Word file, delete the images, and edit the text to produce a table with columns for common names and botanical names.

This was a time-consuming task, but it did yield a list of targeted plants for reference.

The second plant list was the Fall Sale Plant List posted online by the Santa Cruz Chapter of the California Native Plant Society (cruzcnps.org). This sale, described in a recent column, will be held at the Cabrillo College Horticulture Center from 9 a.m. to 1 p.m. Saturday.The list includes 131 plants.

A skilled programmer could compare botanical names on the digital Calscape and California Native Plant Society lists and produce a third list of names that occur on both lists. My approach was to use a pen to mark the plants on the California Native Plant Society list that also occurred on the Calscape list.

In some cases, the California Native Plant Society list included plant genera and species that were also on the Calscape list but did not include cultivars not on the Calscape list. Varieties often represent blossom hues and might be new introductions not yet added to the Calscape database. With that in mind, I focused on genus and species matches and ignored cultivars.

This task identified the “short list” of 55 plants on both lists.

The easy next step is to review Calscape’s pages for these 55 plants to confirm heights of no more than 6 feet (verifying the search filter), review the photos for appeal, and read the notes to ensure that the plants are suitable for partial-to-full exposure to sunlight. A few of these plants might be deleted from the list.

I should also mark each listed plant as small, medium or large within the 6-foot range. My butterfly bed should have a mix of sizes to follow the basic landscaping rule: small plants in front and tall plants in back.

I might also study the list to note blossom colors and bloom periods. A thorough design would result in a good color mix and a long bloom period for the bed. This could require more time.

Then, at the sale, locate the targeted plants that are still available for purchase (gardeners move quickly through the California Native Plant Society sale) and buy enough to complete my 270-square-foot butterfly garden. I would want to include at least three of each selected cultivar to provide an organized design rather than a “one of each” approach.

At the time of this writing, there’s not much time to study this plant list before the plant sale.

I might just choose plants on the spot to cover the available space in my butterfly garden!

Advance your gardening knowledge

The California Native Plant Society has posted several video recordings on youtube.com on various topics. These are not slick commercial presentations but typically informal talks by California gardeners. To broaden your information on gardening with plants of this category, browse youtube.com and search for “California Native Plant Society.”

Enjoy your garden.

Tom Karwin is a past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and Lifetime Member of the Monterey Bay Area Cactus & Succulent Society, and a Lifetime UC Master Gardener (Certified 1999-2009). He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society. To view photos from his garden, https://www.facebook.com/ongardeningcom-566511 763375123/ . For garden coaching info and an archive of On Gardening columns, visit ongardening.com for earlier columns or visit www.santacruzsentinel.com/ and search for “Karwin” for more recent columns. Email comments or questions to gardening@karwin.com.