The Native Plant Garden in Late Spring

Our garden escape on the slough—third in a series on growing a native garden in the California Central Valley.

By: Patricia Carpenter Pat Dressendorfer

Patricia Carpenter is a California Native Plant Society Garden Ambassador who has enjoyed inspiring gardeners of all ages and skill…

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Pat Dressendorfer is an avid naturalist and educator who enjoys being outdoors in places where native plants still thrive….

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The floor of the Sacramento Valley is mostly flat agricultural land veined with a network of creeks, sloughs, levees, and dams, all constructed to collect and direct winter rainfall. Along such a slough is our one-acre private native garden begun more than 15 years ago by Patricia, and now enjoyed and managed in a wonderful partnership with Pat.  

Late Spring geophytes blooming along the slough, red Ida-maia and purple Corrina Ithuriel’s spear with large white Philadelphus shrub. Patricia Carpenter photo

Geophytes 

As the early spring (February and March) flowers start to fizzle with the warming weather, the late spring brings an escalation of color with changes daily. This is when we start to see most of our geophytes blooming. In our opinion, they are among the easiest of the native plants to grow, but often the most difficult to source.

These natives start to grow when there is enough moisture in the winter and early spring, bloom in the late spring, and then go dormant. Underground storage organs like bulbs, corms, rhizomes, tubers, and taproots allow geophytes to survive our hot, dry summers and they grow and multiply with ease. We have had little pest damage; a rabbit might munch on the new leaves and the turkeys sometimes dig up the bulbs or corms, but that doesn’t seem to matter. Actually, this is the one time we don’t mind the turkeys because these plants increase in number with fire and soil disturbances.

Valley Grassland 

Our valley grassland started with 400 geophytes about 12 years ago—100 one-leaf onion bulbs (Allium unifolium) and 300 corms of Ithuriel’s spear (Triteleia laxa ‘Queen Fabiola’). Now we have many thousands of them! The onions bloom first and thrive in clay soil. By May the early spring wildflowers are starting to wither, the grasses are browning, and the Ithuriel’s spear flowers are the stars. Over the years we have also added golden stars (Bloomeria crocea), yellow mariposa lily (Calochortus luteus), Hartweg’s odontostomum (Odontostomum hartwegii), and white Ithuriel’s spear (Triteleia laxa ‘Silver Queen‘) in this open and hot, dry area. We have not yet been brave enough to burn our grassland, but it would be an interesting experiment and we like experimenting with different techniques.

As spring temperatures warm June grass (Koeleria macrantha) starts to fade and Triteleia ‘Queen Fabiola’ and ‘Silver Queen’ take center stage in the valley grassland. Beth Savidge

Recently we have seen some clumps of geophytes with reduced bloom, a sign of overcrowding and/or compaction. To encourage new plants, we disturb the soil as California indigenous cultures do when they harvest the largest for food, replant the bulblets or cormlets and also disperse seeds. Many geophytes multiply both by reseeding and producing offsets from the base of the bulbs or corms. We use our digging fork instead of a traditional digging stick to decrease compaction and sometimes collect and spread the geophytes to new areas. Now that we have so many Tritileia and Allium, this might be the year to try harvesting, roasting, and eating some of the biggest ones, while reducing crowding and increasing the supply for future years.  

 

Foothill Slope—South-Facing and Hot 

Although it is considered edible, I am not sure about eating the bulb of the amole or soap plant (Chlorogalum pomeridianum), used by indigenous people for washing, making glue, and stupefying fish. The saponins in the bulb supply the soap and the outer fibrous coating makes a useful scrub brush. These bulbs are roasted in earth ovens for many hours to remove toxins and reported to be quite tasty. This is the very first bulb Patricia planted when the garden was new. Two bulbs dug from her childhood home in the foothills west of Redding were planted on the south-facing slope of the slough. These have grown very large and multiplied to fill a 100-square-foot area. We have shared numerous seeds and bulbs as they germinate and transplant easily. An annual family ritual with my children in the early evening hours in April or May was to watch the flower buds suddenly burst open, trying to guess which bud would be the next. They became very proficient at spotting a bud about to burst.

Young soap plant (Chlorogalum pomeridianum) bulbs showing their bristly covers have naturalized and spread by seedlings. Patricia Carpenter

We have many other geophytes on our foothill slope. California brodiaea (Brodiaea californica) has returned for 15 years. Near a Ceanothus is a large patch of Corrina Ithuriel’s spear (Triteleia laxa ‘Corrina’) and narrow-leaved onion (Allium amplectens ‘Graceful’) that are mixed with annual foothill wildflowers. Farnsworth’s jewel flower (Streptanthus farnsworthianus) is one of the four annual jewel flowers we grow—and always an eye-catcher. Kellogg’s yampah (Perideridia kelloggii) is found nearby and is most often mixed with grasses, which makes the plants difficult to find until they bloom. We can’t wait for the thickened roots to grow bigger to taste their sweet, nutty flavor. Near a large, old, bush anemone (Carpenteria californica) is another favorite annual, large-flowered collomia (Collomia grandiflora), with unusual blue pollen. This super annual can be direct seeded, seems pest proof, transplants easily, and even takes some flooding.

Farnsworth’s jewelflower (Streptanthus farnsworthianus) draws the visitor’s attention due to its unusual flowers. Beth Savidge

Loving the sunny, low-water slope, many Dichelostemma species are flourishing.   Dichelostemma ida-maia and D. ‘Pink Diamond’ return each year and prefer a bit of afternoon shade. Blue dicks (formerly Dichelostemma capitatum, now Dipterostemon capitatus), however, have been our biggest geophyte challenge. It has been difficult to find bulbs but the seeds are easily available. For us, the planted seeds are very slow growing and take years to reach flowering maturity—we are on year four! Luckily, we did find a few expensive bulbs last year and had our first bloom. Fork-toothed ookow (Dichelostemma congestum) looks similar to blue dicks—it may even be showier—but is a much easier bulb to source and we recently added about 100 more corms to this slope. Now, numerous bulb companies include quite a few California native geophytes at reasonable prices. Native plant sales are also a great source.

An annual, large flowered collomia (Collomia grandiflora) can be direct seeded in the ground. Patricia Carpenter

 

Coastal Slope—North-Facing and Cooler 

On a north-facing slope of the slough, we planted most of our coastal plants to take advantage of the cooler microclimate. The air here is a bit more humid due to the irrigation of the redwood trees nearby. Geophytes found here include many robust Pacific Coast hybrid iris that provide wonderful pockets of color. There are also twining lilies (Dichelostemma volubile); they are slow to establish but we hope they will vine happily up some of the coastal shrubs.

At the edge of our little Shly Creek the California tiger lilies (Lilium pardalinum) have flourished, mixed with yellow monkey flower (Erythranthe guttata). Nearby is a patch of shiny green leaves topped with delicate, pale-yellow fawn lily blooms (Erythronium ‘Pagoda’). Unlike the geophytes in the valley grassland and foothill areas, these two species prefer some moisture during the summer months when they go dormant.

Two of our favorite perennials found on the slope are the amazing cobweb thistles (Cirsium occidentale var. occidentale) and the pale-yellow curly wallflower (Erysimum concinnum). The wallflower in nature grows on well-drained rocky or sandy soil but grows just fine on our clay, low-water slope. The annual San Benito jewel flower (Streptanthus insignis) is combined with the geophytes and grasses.

The beautiful flowers of bush anemone (Carpenteria californica) have an attractive puff of anthers in the center. Beth Savidge

Although we are very busy monitoring plants in bloom and all the changes of the late spring season, there is one task we try to start during this time—pruning the spring-flowering shrubs. Ceanothus, Ribes, Arctostaphylos, Fremontodendron, and Carpenteria are some of the plants that benefit from light pruning or pinching back after bloom, mimicking deer browse (which we don’t have). We keep Ceanothus pruned up off the ground by cutting only pencil size shoots because pruning larger-diameter stems seems to cause stem dieback.

 

Redwood Grove  

By late spring the redwood understory has come to life, with many winter-dormant plants now lush and green. We need significant rain to penetrate the dense canopy and replenish the soil. If we have little rain, like this year, we irrigate to keep the soil moist.

Our redwood grove was inherited as part of the neighbor’s acre that we took over. Fifteen years ago, the redwoods were very small and lots of light fell between the trees. But now they have matured into a proper grove, challenging us to find appropriate understory plants that will do well in the shade with Central Valley heat.  Pat has lived many years near the coast and has gardened in shaded forests so contributes ideas of additional plants to try.

Bulbs and corms of native geophytes like ookow, (Dichelostemma congestum) are harvested for food by indigenous cultures. Beth Savidge

Coastal redwoods are not the best choice in the Central Valley as they need coastal fog to thrive. This area requires more water than the rest of the native garden; we irrigate it every week or two in the summer. Our redwood area has dense shade and plenty of water, but the tree roots compete with other plants for resources and limit planting areas. Our clay soil and alkaline well water are also problems. Naturally-occurring redwood understory plants are adapted to more acidic and well-drained loam soils. In order to manage this situation, this is the only area where we add compost to loosen our compacted soil, lower the pH, and improve drainage. We are already noticing a bit of humus from the decomposing redwood needles that we hope will help to acidify the soil as well.

Of the dozen or so ferns we grow under the redwoods, those thriving tolerate more alkaline soil conditions. Giant chain fern (Woodwardia fimbriata) is big and impressive while southern maidenhair fern (Adiantum capillus-veneris) looks fragile but has proven to be tough and reliable. California polypody fern (Polypodium californicum ‘Sara Lyman’) has been spreading for ten years and adapts to our hot summers by going dormant. These ferns are mixed with some of our most successful understory perennials: vanilla grass (Anoxanthum nitens), water parsley (Oenanthe sarmentosa), Pacific May lily (Maianthemum dilatatum), red fescue (Festuca rubra), and wild strawberry (Fragaria vesca).

Maidenhair fern (Adiantum capillus-veneris) is a tough and dependable fern for shade despite its delicate appearance. Ellen Zagory

The sunnier redwood margins provide a unique microclimate and allow different plants to grow. These more open but moist areas have additional geophytes. Blue and white camas (Camassia quamash, C. leichtlinii ‘Blue Danube’, and C. ‘Alba’) return each year and numerous seeds are sprouting. Large-flowered star tulip (Calochortus uniiflorus ‘Cupido’) with delicate pink flowers persists here as well.

The showy perennial owl’s claws (Hymenoxys hoopesii) always attract visitors’ comments and is easily increased by both divisions and seeds. In the early years, coastal hedgenettle (Stachys chamissonis) grew well among the trees but slowly died out as the redwoods matured. Now it is expanding on the redwood margins. The coastal plantain (Plantago subnuda), with its eye-catching leaves and edible seeds, was one of the first plants added to the margin.

Coastal plantain (Plantago subnuda) has attractive foliage and produces edible seeds. Beth Savidge

Soon summer will begin in our native garden on the slough—our time to slow down a bit and embrace the season. Most of our many geophyte species are edible and some are becoming quite plentiful, so some soil disturbance and harvesting is planned!

  

Beth Savidge photos of Patricia’s native and main gardens  

2020  https://photos.app.goo.gl/A6zKmRdKPqr5AQb5A 

2021  https://photos.app.goo.gl/xPchJsRNomLPzTdH6 

 

California Native Plant Society Garden Ambassador profile of the Native garden   

https://www.cnps.org/gardening/patricia-carpenters-davis-garden-2-1272 

 

View the Winter article 

The Native Plant Garden in Winter

 

View the Early Spring article (garden map included) 

The Native Plant Garden in Early Spring