Amsonia tabernaemontana

Amsonia tabernaemontana is quite a garden trooper. My respect for this plant, commonly called Blue Star Flower, has gained ground this year given its outstanding, and unexpected, performance during this year's drought. Dr. Allan Armitage has been extoling the virtues of this garden plant for years (Thanks Allan!) but did I listen? Not until about five years ago. And I must admit – I’m a little slow but I did, finally, get it. 

Amsonia tabernaemontana is a lovely U.S. native plant with a range that stretches from the lower east coast to the Great Plains, growing in sites from moist shade to dry, full sun locations steeped in limestone. Although right now this is touted as adaptability within this specific species, I think we'll see some separations and/or species re-classifications in the future. 

Early in the spring, Blue Star Flower pokes through the soil surface, the tips resembling large, purplish-green asparagus spears. The 2’ – 3’ stems sport 2” wide, dark green leaves are lovely as they open and develop in spring. But even though I love shades of green - oh - the leaves cannot compare to the icy glow of the pretty, star-shaped blue flowers that sit atop the stems in May.

Amsonia tabernaemontana flowers will fade to a pale, icy blue as they age.

Conditions for good growth and root development are not difficult to provide – these plants are quite adaptable. Again - I have to say, the drought tolerance was quite surprising. If placed in rich soil, the plant will grow very well, quickly developing stem height. And while for many plants that would be a desirable result, for Amsonia tabernaemontana, it will result in a floppy structure - especially given that the plant is tall with a natural tendency to a vase-like shape, plentiful leaves and flowers make the stem weighty at the top. The plants will love you if just placed into a decent site. 

Nice shape!

Full sun is suggested for the best growth but I’ve seen some fantastic plantings in shade as well. If the plants do flop over, whether it’s from too much shade, fast growth, or rich soil, feel free to give them a trim after flowering. Although I, personally, have not felt the need – you can cut them back to within a foot of the ground after flowering to get nice dense, leafy growth. Or if you’re one of those gardeners that just want your plants to present a neat and tidy appearance, and have no need for the seed heads, trimming them back just little may make your life complete. Go for it.

Want more? Division is an easy way to multiply your population of Amsonia tabernaemontana. You won’t need to divide very often (every 8 – 10 years) but when you do, early spring or fall are great times to get your shovel in the ground and split a healthy crown apart. Be sure to include at least one growth point in each division. Propagation via seed is purported to be easy and successful although it does take a few years to develop plentiful flowering. Terminal cuttings (use rooting hormone), taken early in the season, are also an effective method of propagation. 

Amsonia tabernaemontana problems are difficult to locate. Makes them a treat to grow. I can see the potential for root rot in consistently wet soils but that problem is our fault for poor site choice, not a plant health liability. Try as I might to locate any critter/insect feeding or damage on the plantings – I have not. Again – a treat.

it's been tough

Wow. It has been a tough summer all over - too much rain, too little rain, too much heat, too much heat, and too much heat. If, like me, you live in an area that is suffering from a severe rain deficit - and like me, you could not even begin to match plant needs with hose action – you will be seeing some incredible variances in plant response.

Amsonia tabernaemontana and Amsonia hubrichtii have shown remarkable drought tolerance - especially given my yard's exposure to Round Up over-spray this spring (thank the neighbor). When surrounding perennials went toes up, the Amsonia species were calmly holding their own.

Amsonia hubrichtii with a bit of early Round Up damage showing - otherwise looks great for a drought stricken July.

The behavior of my beloved Phlox paniculata ‘Peacock Series’ ('White' and 'Neon Rose') caused me to rethink that affection as they did not perform well (at all) throughout the months of intensely dry, high temperature conditions. Even those planted in partial shade just couldn’t even pretend to thrive. I watched as the leaves discolored, the plants continually refused to show any response to the water (yes, it was meager) provided. Eventually goodbyes were uttered, as it appeared to be a permanent decline. But to my surprise, and delight, new leaves eventually emerged and, now, continue to develop. Although they still look rather wicked from an overall perspective, growth is happening. I love it when plants surprise me.

Phlox paniculata 'Peacock Series' - Round Up damage from neighboring farm over-spray, followed by drought. Look at it tough it out!

Whether the effects are obvious or a bit more insidious, lots of plants are certainly suffering. Normal treatments need to be modified, depending on plant reactions to the conditions. What changes need to be made? Stick with advised water needs for your area and soil type. Generally for established plants, that means the equivalent to 1” of rainfall per week. For new plants that moisture need rises to the equivalent of about 2” of rainfall per week. During periods of drought, do the best you can while staying within area water guidelines and/or bans.

In the case of fertilizer, as summer blends into fall, the general recommendation is to hold off fertilizing until after normal leaf fall – or in the northern regions, until we’re hit with at least a couple of good, hard frosts. This year, the extended drought has created a period of dormancy extensive enough for the plants to re-leaf, re-bloom (August Magnolia blooms in my Wisconsin yard?!), and/or re-grow (new asparagus spears in August as well) – all, of course at non-usual times. Well…that places severe demand on plant system reserves. As those reserves are depleted, provision of additional nutrients will assist those plants in restoring reserve levels, ultimately reducing plant system stress during the upcoming spring. 

Appropriate timing of fertilizer applications is crucial at this time of the year. For those plants that are sporting a second (or third) set of leaves, get a light application of a balanced fertilizer down and watered in NOW. For those trees and plants that are holding on to this year’s first set of leaves, wait until the generally recommended time - after leaf fall. The worst thing you could do is to encourage any more new growth that will not harden off before winter arrives. Creating additional stress on the plant system is not what we need this, or any, year. 

Disanthus cercidifolius - rallying in August.

  As always, an overall, a planned fertility program is preferred to the shotgun approach (throw everything at anything or anything at everything). Thinking wholistically and planning ahead are invaluable for maintaining your plants. Start with a panel of quality soil tests from various planting areas of your yard - e.g. grasses, ornamentals, trees, vegetables – as all need differing levels of care and potentially different product formulations. Start with the tests, then plan, and execute a fertility program that will get the most out of your plants, and your pocket book.