Fertilizer Nutrient Elements

A bag of fertilizer has three numbers prominently featured on the label...something like...5-2-0. It's important to know what those numbers mean because the wrong combination can do more harm than good. The numbers indicates the amount of three major plant nutrients: nitrogen, phosphorus, and potassium, abbreviated NPK.

One way to remember what those things do, and keep them straight is the phrase "up, down, and all around." Nitrogen is needed for green, leafy growth...the up. Phosphorus helps produce healthy roots...the down. Potassium is important for overall plant health and resistance to water or insect stresses, so it's...the all around.

Plants need anywhere from 14 to 18 plant nutrients for best health and production. Magnesium and sulfur comprise the macronutrients along with NPK. The micronutrients include: iron, manganese, boron, zinc, copper, molybdenum, and maybe chlorine. Testing your soil is the way to determine what is needed.

Success With Heathers

The singular species, Calluna vulgaris, inhabits large portions of Europe and northern Africa, from Siberia to Morocco, in vast tracts of open land and hillsides. The predominant flower color is purple...but it sports out in pink, red, and white. For well over 100 years, avid plants men have made over 500 selections of form, bloom, and foliage variations, and some of them are real eye-poppers!

Now, if you are one of those people that think that they always look so ratty, I am about to show you the error of your ways. Site selection is probably the most important factor. These are ericaceous plants...in the same family as rhododendrons...and like them, we should take our lessons from Mother Nature. Full sun is an absolute must and some slope to the ground is very beneficial. Soil should drain well, but retain some moisture, especially in summer during bloom time, anywhere from July to November depending on cultivars. An acid, humus-rich soil with no manures or strong fertilizers is necessary...a lean media keeps the growth compact. If you cannot engineer even a bit of a slope, then be sure that the soil is deep and loose. And then...prepare to PRUNE!

Ok, ok, and ok! I know no busy band of elves prunes on the moors, but truth be told, if you took aside only one or two of those million of plants, they probably would be ratty...but there's safety in numbers and distance. We do not have that advantage in our gardens...so get out the hedge clippers. March is a good time to do this...trim just to the bottom of last year's flower spikes to make a somewhat mounded shape. Now, was that so hard? Once a year is all it takes, and a spring pruning still lets you enjoy all that wonderful winter foliage on the colored forms.

Choosing varieties for your garden will be by personal preference. With that many to pick from, it is like roses or rhodos...grow the ones you like to look at. I can only give guidelines of the forms that are available. The flowers can be single or double on long or short spikes. I have taken full open spikes of 'Peter Sparkes' and 'H.E. Beale' and hung them to dry, and they make wonderful bouquets...unfortunately, not too durable...but so easy you can do new ones every year. Colors range from white and pale pink to bright pink, crimson, and purple. There are varieties like 'Marleen' that seem to bloom forever since the blossoms don't ever actually open, just show outer color.

The foliage on some is so spectacular that even if they didn't bloom, no one would notice. Red-gold ones like 'Firefly', 'Blazeaway', 'Boskoop', and 'Sir John Charrington' are bright all year round. Silver ones like 'Jan Dekker', 'Silver Knight', and 'Grey Carpet' will gleam against dark backgrounds. Some like 'Spring Torch' and 'Spring Cream', have colored foliage on new growth only...almost like an early bloom...and then the proper flowers come later. Very dwarf ones can be used in troughs or rockeries, as 'Foxii Nana', 'Dainty Bess', 'Humpty Dumpty' and 'J. H. Hamilton'.

The list is endless...but this should give you an idea of the lovely ones there are to choose from. Visit gardens and plant centers in summer when they are in bloom. I only wish I had more room in my garden to have an entire bank devoted to them...in drifts of all year color.

Happy planting!

Rhododendron williamsianum

Rhododendron williamsianum, introduced to horticulturists of the western world in 1908 by Ernest "Chinese" Wilson is at once one of the most recognizable and one of the most enchanting rhododendrons. Its unique combination of almost orbicular, mid-green leaves, spreading and somewhat rounded or dome-shaped habit, and disproportionately large, candy-pink, campanulate flowers make it easy to recognize and well-adapted to gardens both large and small. Its densely mounded shape often has a somewhat brooding appearance, a bit like having a very large toadstool in the garden...but its solid presence makes a good anchor to a plant grouping, and can provide an effective screen, if needed.

Although never thought of as a large rhododendron, it can in time become quite massive, spreading up and out in large billowy curves that are certainly beyond the reach of vertically-challenged gardeners.

R. williamsianum flower
Photo by Chris Klapwijk

It was a species that has so captured the imagination of rhododendron fanciers that a veritable frenzy of hybridizing ensured. After all, there were so many positive characteristics to try to attach to other rhododendrons: small, tidy, glabrous leaves, with lovely bronze new growth, well-shaped, pretty pink blossoms that were large in relation to the leaf size, and a spreading compact habit that keep the blossom down where people could easily admire them.

Looking through Salley and Greer's book Rhododendron Hybrids, I gave up counting at the end of the C's, having reached something over 55 hybrids. Each decade seemed to bring on a new wave of williamsianum crosses:

  • Rothschild in the early 30s, including the iconic hybrid 'Bow Bells'.
  • Lord Aberconway in the late 30s and early 40s, with a whole series of hybrids beginning with "A" ('Adrastia', 'Adrean', 'Amata') as if he were trying to get in first in the Yellow Pages, but also developing the wonderful 'Cowslip', a williamsianum x wardii cross.
  • Hobbie in the mid 40s, with his 'Gartendirektor(s) 'Glocker' and 'Reiger'
  • all the way up to Weldon Delp and Hans Hachman's more recent hybrids.
  • Even J. C . Williams of Caerhays Castle used this namesake rhodo in his inspired 'Hummingbird' cross with R. haematodes.

R. williamsianum is truly endemic to Sichuan, China, being found only there, and even within that province its distribution is very limited. However, it is now in constant and widespread production and cultivation all over the world.

Lepidote Rhododendrons

Rhododendron enthusiasts are often asked what they mean when they refer to a rhododendron as a "lepidote". The confusion is compounded when one sees quite a bit of space devoted to lepidotes in flower shows.

A nurseryman may tell you casually that it refers to the small-leaved evergreen rhododendron. This can be used as a generality...but not as a hard and fast rule...as there is a fair amount of overlap between lepidotes and the "large-leaved" elepidotes.

Real traits that make it a useful distinction is lepidote rhododendrons have scales on the underside of the leaf which protect the plant's stomata (leaf pores) through which oxygen, carbon dioxide, and water vapor pass. The scales evolved originally to regulate moisture, to help keep water in the cells in dry times, and help shed it in times of surfeit . This allowed plants evolving in the tropics to live in the quick-drying forest duff on the very thin soils of the tropics, or even epiphytically on rocks or tree trunks. Turn a leaf of the lepidote over and look for the tiny scales; some are big enough to see with the naked eye, but a hand lens will reveal a world of otherwise hidden detail. Elepidotes, on the other hand, are without scales to cover their stomata.

But winter brings many of the same demands as the tropics on a plant...encasing it in wet snow or desiccating it with cold dry winds, and the scales evolved to become adept at dealing with harsh winters as well. As a result, lepidote rhododendrons have adopted and spread to nearly all environments, from tropical jungles and Siberian woodlands to mountain meadows and alpine tundra. Because of this wide tolerance of soils, temperatures and exposures, they are especially useful to gardeners in the Northeast United States. Other adaptations, such as fast regrowth after predation from grazing animals, and early bloom to deal with short growing seasons in cold climates, give us a plant that is easily pruned to shape and early to give the gardener a boost after a long winter.

Most lepidotes have axillary buds...extra flower buds under the terminal flower bud or along the branch...and in bloom often smother the foliage until all you can see are the flowers. Lepidote species range from tiny creeping alpines suitable for the rock garden to tall forest and meadow plants for woodland wildflower gardens and formal borders.

Best of all, the hybrids developed by plant breeders bring hybrid vigor to the party, giving us a huge range of plants, among them some of the easiest and the hardiest rhododendrons to grow in cold climates. A commonly grown lepidote cultivar is "Rhododendron 'PJM', which was hybridized by the Mezitts, and is now grown and admired all around the gardening world.

The large-leaved fancy varieties of rhododendrons may get all the big press...but for vigor, hardiness, adaptability, easy of culture, and sheer traffic-stopping, eye-popping show of flowers in the spring...my money is on the lepidotes!

 From the Massachusetts Chapter Newsletter, September 2006.

Growing Rhododendrons From Seed

Rhododendrons and azaleas are easily grown from seed. Unless the parent plants are species from isolated areas, the resulting seedlings will exhibit much variability. Unless you are interested in hybridizing and selecting new cultivars, use of seeds as a means of propagation should thus be limited to species plants. Even then some physical differences will be evident.

Procedure:

  1. Obtain clean seeds.
  2. Prepare a sterile container at least three inches deep, with bottom drainage; size depending on how many seeds you wish to plant.
  3. Fill the container to within ½ inch of the top with a mixture of 40% perlite and 60% fine sphagnum peat moss. This mixture should be moist...but not wet.
  4. Level and firm the surface of the mix.
  5. To control fungal disease, spray the soil surface with fungicide Captan. Read and follow product instructions.
  6. Sprinkle seeds thinly on the surface...do not water again.
  7. Put plastic or glass over the container to make it moisture tight.
  8. Place in a warm dimly lit area until seeds germinate.
  9. Put under fluorescent light for 18 hours a day at 70-75°F.
  10. Anytime after true leaves have formed, harden the seedlings off by gradually opening the cover over the period of at least one week. Water carefully as needed to keep moist. Watering through drainage holes in the bottom is safest.
  11. Transplant when ½ to 1 inch tall to flats using 50% sphagnum peat and 50% perlite. Lift under the roots and handle by a leaf. Plant at same depth. Water to settle in.
  12. Water to keep moist, but not wet. Fertilize with azalea food or other acid fertilizer once a month using ½ half strength. Always water at least once between fertilizer applications. To slow growth and harden off, stop fertilizing and water less frequently.
  13. Transplant when seedlings become crowded.

Keep the growing area clean to prevent damping off, water properly, and...success is almost assured!

A Black-flowered Rhododendron

Looking for a rhododendron with black-looking flowers? Rhododendron 'Black Widow' is causing quite a stir among collectors as its very dark maroon flowers appear to be almost black. Also, to add even more interest, this interesting hybrid has white stamens which stand out against the black, wavy-edged petals. Up to 21 flowers are held in ball-shaped flower trusses. Bloom-time is typically May in North America.


Photo by Harold Greer

This unique cultivar was created by Roy Thompson of Waldport, Oregon by first crossing the dark purple, flowered rhododendron 'Frank Galsworthy' with 'Leo', which has a rich, dark-red flower. He called this hybrid 'Gal-Leo'. He then crossed this plant with the maroon-flowered rhododendron 'Warlock'. In order to increase his chances of finding a black flower, he planted out several hundred seedlings of this cross. The best one of the lot Roy named 'Black Widow'

The plant's bright green foliage is 6.5" long, elliptic in shape, ribbed and shiny on top. It has an upright and spreading growth habit, and it grows to a typical height of 3 feet in 10 years. The plant is cold hardy to at least -5°F (-21°C).

Consider having this wonderful rhododendron cultivar in your garden.

 
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