- Clematis - Hints for Successful Culture
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Clematis - Hints for Successful Culture

Clematis have a reputation for being finicky growers.  With proper planting, proper care and judicious selection of varieties, this need not be the case.

Clematis Wilt
The biggest problem with clematis is that they are subject to a fungus called clematis wilt, that attacks the stem right where it emerges from the soil.  This usually occurs just before or right after full bloom—the period at which the clematis requires maximum water and nutrient uptake.  When a clematis is attacked by the fungus, the entire plant just wilts and dies from the tip to the ground in a manner of days.  Usually the root is not dead and the clematis regrows; but the disease often recurs the same way each year.  Drenching the soil around the clematis with fungicide will often alleviate this problem.  Sometimes several applications are needed.  However, this is, at best, only a partial solution.  The most satisfactory way to have a clematis perform reliably in soil that has been infected with clematis wilt is to change the plant to one of the Clematis viticella varieties, such as Clematis Viticella Betty Corning, as all C. viticella varieties are resistant to clematis wilt.

Planting
We have found that a properly planted clematis is much less likely to be subject to clematis wilt.  A ½ bag of Chesapeake Blue Crab Compost should be mixed into the soil for each clematis you are about to plant.  Adding the crushed shells of a dozen eggs also helps.  A clematis should be planted about 1” deeper than it grew in the pot at the nursery.  Mulch should never touch the stems of the clematis.  One way to keep the mulch away from the clematis is to cut the bottom out of a 1-2 gallon plastic nursery pot and bury it 1/3 deep as a collar around the clematis.

Pruning
Much is written about the pruning requirements of clematis in three categories (click here to learn more about clematis categories).  This is fine if you know what variety of clematis you have.  Even the group # 3 clematis that are supposed to require pruning every year will bloom (although mostly at the top) if left unpruned.  Conversely, many group #1 clematis, that require no pruning, eventually become such a tangled mass that they must be pruned severely.  These clematis tend to be the ones that bloom the earliest and are properly pruned right after blooming.  However, I have found that many varieties of Group #1 clematis will bloom, although somewhat later than usual, if pruned to the ground in early spring before the leaves come on.

In short, to make life easy whenever any clematis has turned into an ugly, tangled mass, I cut it to the ground in early spring before the leaves come on.  Otherwise I just leave the clematis alone.

Feeding
Fertilizing clematis is particularly easy.  A couple of handfuls of Bulb-Tone^® and a handful of Kelp Meal^® in early spring before the leaves come on and followed up by a similar feeding in the late fall is all that is needed.

Varietal Selection
I have found some clematis to be much more satisfactory in the garden than others.  I admit to having a prejudice.  I prefer a clematis with round-tipped overlapping petals, rather than those with starry pointed petals and gaps between them.  Through the years, I have deleted from our list those that are not strong growers in Zones 6 and 7.  Of the regular large flower clematis, I think Elsa Spath is the best.  It is a beautiful shade of lavender blue. 

The most shade tolerant clematis is the sweet-autumn clematis, Clematis Paniculata, which is covered with multitudes of tiny sweet smelling blooms in August/September.  But, unlike other clematis, it can attract multitudes of bees and therefore requires careful placement.  Incidentally, clematis Silver Moon is the most misunderstood clematis of all.  It is often described as a clematis for shady sites.  In actuality, there are many other clematis that are equally tolerant of light or dappled shade.  The reason why the word shade becomes associated with Silver Moon is, if it is not planted in the shade it fades horribly and turns ugly, not that it performs any better in the shade than any of a dozen other clematis. 

As stated earlier, the clematis Viticella varieties are the easiest to grow.  Two other small flowered clematis that I have found to be particularly easy to grow are texensis Duchess of Albany, with its beautiful pink bells, and Clematis Tangutica, with its lantern-shaped yellow flowers.  When considering clematis, I feel it’s particularly important to remember there are some shrubby clematis that do not climb.  These are perfect for the perennial garden or mixed in with shrubs.  Clematis integrifolia (non-climbing Clematis such as i. Caerulea) are particularly satisfactory and long lived.  Its hybrid, Clematis Durandii, has been proven to be an exceedingly reliable performer.

Next week we are back to roses, specifically climbing and ground cover roses.

Happy Gardening,
Alan Summers

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Question of the Week

Up against the back wall of my house, I have a large overgrown hydrangea that needs a lot of help. It’s too big. When should I cut it back and how far? Also, it’s never really loaded with blooms like all the other hydrangeas I see in other people’s yards. In most years, mine has a few lavender blooms at the bottom and up against the wall of the house, and in some years it has a few blooms on the top and in the front. But mostly it’s just leaves and even those aren’t a nice dark green, more like a yellowish-green. Finally, I really want my hydrangea to be dark blue and I have heard there is something you can sprinkle on the soil to change the color.  HELP!!!

Answer:
Don’t feel like the “Lone Ranger”, these are common problems.  Whether your hydrangea is blue or pink (or something in-between), a mop head (ball type flower) or a lace cap (flat flower), the care is exactly the same.  In most cases, white hydrangeas require different care and these instructions do not apply.

Just about all pink and blue hydrangeas produce their buds for next year’s flowers just as this year’s flowers start to fade.  These buds are produced at the branch tips, right under the old flowers.  This usually occurs at the end of August or early September.  Thus, in order for the hydrangea to bloom well, these flower buds must not be removed by late fall or early spring pruning and they must survive the winter.  You stand the greatest opportunity for good bloom next year if you prune the hydrangea before these new buds form.  If you are going to remove more than just the old flowers, you need to cut it back as soon as the hydrangea flowers start to turn brown.

Many hydrangeas are leaf and stem hardy, but not bud hardy.  These are usually Easter or Mother’s Day forced, florist hydrangeas that people plant outside after they are through with them inside the house.  Because these potted plants are sold without labels, there is no way to know if any particular hydrangea is truly winter hardy.  Some are; some are not.  I suspect you have one of these non-hardy hydrangeas, because it is only blooming in the most protected places at the bottom where it was snow covered and up against the warm wall of the house.  Without going into a great deal of effort to protect this hydrangea from the winter winds (for example; putting a burlap screen around it), this hydrangea is never going to perform satisfactorily in your garden.  It is genetically not bud hardy; that is, it forms its buds and the winter kills them.  I suggest you tear it out and start over. 

I recommend you try the new variety “Endless Summer” which forms its buds both in the late summer, as well as in the spring and early summer.  This hydrangea is easier to manage because you can cut it back in the winter or early spring and still have blooms the following summer.  In fact, it should give several cycles of repeated bloom. 

To be sure that Endless Summer blooms a dark blue rather than pink or lavender, mix 2 or 3 handfuls of aluminum sulfate into the soil at planting.  If you decide you would prefer pink, use the same amount of lime instead of aluminum sulfate.  To correct the soil so that your new hydrangea has dark green leaves rather than yellowish green, also mix in 1 or 2 handfuls of iron sulfate.

Click for more info:   Endless Summer

New for 2003 at Carroll Gardens!

Hemerocallis 'Big Time Happy'

Big Time Happy is the daughter of 'Happy Returns,' and is almost identical in color to Happy, but sports a flower with a larger surface area.  These 4” blooms are very fragrant, lemon yellow in color and feature some slight ruffling.  Despite its large blooms, Big Time Happy maintains a short habit at 18", with wider, greener foliage and more substance.  It is easy to grow, undemanding, and very high-performing.  This dormant diploid is a repeat bloomer that starts very early and continues until frost.

Carroll Gardens is pleased to introduce 'Big Time Happy' to our 2003 online catalog.  Click here to learn more about 'Big Time Happy' or to place an order.