Understanding the Growing Requirements of Native Plants
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Incorporating native plants into your landscape and landscape designs can be a very gratifying experience. The key to success with native plants is learning where the plants are from and what the climate and growing conditions of their native habitats tell us about their cultural needs in the garden.
Many of the non-native perennials that dominate our landscapes have been widely cultivated for many years in Europe and the United States and have very wide tolerances as to the type of climates they enjoy and their cultural needs in the garden. This is in large part because over the years plants that were difficult to grow and propagate using traditional methods disappeared from the trade. Many native plant introductions are very new to the gardening public and their cultural needs less understood. However, we are already finding that many natives are also easy to grow and propagate and have also become common in gardens across the country. Rudbeckia fulgida 'Goldsturm' (although selected by German breeders) is one of this country's most popular native perennials. To increase the gardening public's use of other native plants, our general knowledge about a native plant's soil preferences, sun exposure, moisture needs and tolerances must be understood and accompany the plant as it moves from the grower's greenhouse to the homeowner's yard.
The compatibility of a given native plant to your local area is highly dependent on that plant's need for moisture. The amount of precipitation that plants receive in their habitats is a very important piece of cultural information. Looking at a precipitation map of the United States the pattern shows us that, in general, as we move west from the eastern seaboard toward California the terrain becomes drier and drier. Thus plants native to the various desert regions of the western United States will not be well suited to average garden conditions in moist Ohio. However, in my experience, a native plant from Ohio may do fine in Santa Fe's high desert climate if given enriched soil, sufficient irrigation and afternoon shade to avoid heat stroke.
Soil drainage is a critical but often overlooked factor in growing native plants.
Soil chemistry and drainage are two other critical factors that must be taken into account. My experience has been that native plants from the East and Midwest make the transition to western growing conditions more easily than western natives transition the other direction. It would seem that many western plants are more specialized and closely matched to the harsh, dry conditions of their habitats and are less adaptable to richer soils and more moisture. But like all generalizations there are notable (and often surprising) exceptions.
Western soils tend to be very mineral (low in organic materials) and alkaline. Many Midwestern soils are humus rich and their pH ranges from neutral to acidic. Eastern soils can be much more variable but in general are acidic. Westerners don't use lime and wood ashes in our soils, as these soil amendments are for making soils more alkaline. Gardeners with acidic soil conditions must raise the soil pH using these additives to provide the alkaline conditions required by many western natives. Many western natives also need higher trace mineral levels and benefit greatly by using trace mineral fertilizers like Planters II (rock dust in organic gardening circles). Moving eastern plants west can be accomplished using lots of greensand and soil sulfur to bring down the soil alkalinity. However, acid loving plants are very difficult to grow long term without constant acidification efforts and use of rainwater to irrigate. (Many western regions have very hard, alkaline well water.)
Soil drainage is a critical but often overlooked factor in growing native plants. Many western natives require fast draining soil when grown in wetter climates. So when gardening in wetter conditions sandy and sandy/loam soils provide drier conditions than clay. Natives that like moister, high humus soils can be accommodated out west by incorporating generous amounts of compost and Broadleaf P4 water retaining crystals into the soil and irrigating more frequently. Clay loving plants are common in all areas of the United States.
It is more challenging when we move dry clay lovers from west to east than vice versa. Clay soils that stay wet from plentiful rain and snow will be deadly for dry clay lovers from the west. A sand/gravel/clay soil mixture used in a raised bed or berm is often the best solution to this dilemma.
I'm not as familiar with native plants from the Midwest and eastern United States, as I don't often have the opportunity to see and study these plants in their native habitats. However I look to the many native plant experts in these regions and trial their introductions in Santa Fe. Interestingly, these regions offer many summer and fall blooming species that are invaluable for coloring the garden when the many late spring and early summer bloomers natives have past. Solidago rugosa 'Fireworks' and S. sphacelata 'Golden Fleece' are two standouts valued for their late summer yellow flowers. The novae-belgie and novae-angliae Asters from back east are parents to a huge number of hybrids and selections. A favorite selection originally found in the wild is Aster n.-a. 'Purple Dome'.
The compatibility of a given native plant to your local area is highly dependent on that plant's need for moisture.
An aster relative that has proven itself as a valued source of long lasting cut flowers is the white daisy flowered Boltonia asteriodes "Snowbank". Eupatorium can be a difficult genus in the high, dry desert of northern NM, but Eupatorium maculatum "Gateway" is a wonderful exception. It still needs regular irrigation and rich, moisture-retentive soils but will grow well in non-bog conditions. The same is true for several of the Monarda cultivars like Monarda x 'Violet Queen'. This hybrid has outstanding mildew tolerance and thrives in drier conditions. Liatris ligulistylus is a superb Gayfeather with long showy purple flower spikes. Of course the Coneflowers (Echinacea) reign supreme in the summer garden. Echinacea purpurea and its various cultivars ('Magnus' and 'White Swan') are well known. Less familiar but equally deserving a place in the garden are the rare yellow flowered E. paradoxa from the Ozarks of Missouri and Arkansas and the graceful E. angustifolia, native to the prairies of the Midwest and eastern Great Plains. Almost all of the above natives are highly valued nectar sources for adult butterflies.
The Great Plains provide a treasure trove of tough but beautiful native plants. These plants are adapted to surviving extremes of temperatures and moisture as well as grazing animals. They favor well-drained, not-too-rich soils with a neutral to alkaline pH. Their natural climatic precipitation arrives during the winter, spring and sporadically during the heat of the summer months. My favorites include the duet of Scutellaria resinosa, a mounding blue-flowered beauty and Hymenoxys scaposa, a gray, thread-leaved little gem with yellow daisies. I like to plant these species with plains cacti like the magenta flowered Coryphantha (Escobaria) vivipara and the yellow-green flowered Echinocereus viridiflorus. Our native cacti are some of our most spectacular but overlooked wildflowers. I encourage their inclusion when planting other xeric (drought resistant) perennial native flowers.
Another outstanding succulent from the plains is the everblooming, magenta-flowered Talinum calycinum. This quirky little native's odd behavior is an excellent example of why some folks avoid native plants, thinking they are too hard to grow—but it's actually a showy, easy-to-grow plant once you understand its needs. I recommend it to everybody. Talinum likes dry, sandy or sandy/loam soils. It is very slow to wake from its winter slumber, waiting until the late spring frosts have past. It also withers (goes dormant) before frost, using short days as its dormancy trigger. If you didn't know better you would think the plant either died suddenly in the fall or didn't make it through the winter. However it easily survives the cold winters as a shallow rooted succulent crown (stem at the junction of the roots and above ground stem) that looks like a fat twig. Be patient in the spring because it returns to get bigger and showier every year.
Other indispensable flowering perennials from the Great Plains include Berlandiera, Calylophus serrulatus, Callirhoe involucrata, Liatris punctata and various grasses like Schizachyrium scoparum "The Blues" (Little Blue Stem) and Panicum virgatum 'Prairie Sky'.
The Great Plants for the Great Plains program sponsored by the Nebraska Statewide Arboretum and supported by NE nurseries that grow and propagate new finds is an excellent program devoted to bringing natives for the plains into cultivation.