Growing Concerns 611: Clematis Care, Honeysuckle Vine Mildew

1) Pruning Clematis Jackmanii and 'Polish Spirit'

2) Deciding to grow honeysuckle vine... or not

(Jump to #2)

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I planted five 'Polish spirit' clematis along my fence last summer and I would like to know how to take care of them so they will grow well. They are in full sun with their roots shaded by Stella d'Oro daylilies. When, if ever, do I prune them and what is the best kind of fertilizer to give them? 

I also have two Jackmanii clematis so could I have the same information on them? They're also in full sun and their roots are shaded by roses bushes. - T. -

Dear T.,

Clematis 'Polish Spirit' is a hybrid variety of C. viticella, one of the clematis that blooms later than most of the large-flowered hybrids. If it's a hybrid and purple, a Clematis probably has some C. viticella in its lineage. For instance, C. viticella is one of the parents of the Jackmanii hybrids.

C. viticella can be pruned right to the ground every spring before bud break. Cut the previous year's main canes to leave just a few inches of each above ground. It will grow back vigorously and bloom that year without diminishment.

As for other care, C. viticella doesn't need anything except sun and water, and soil enriched with annual doses of organic mulch and slow release fertilizer. (Fertilize in April and October; for more see articles such as Overthrow Snow, Growing Concerns 559 or What's Coming Up 8). You don't even have to prune it, but it does bloom better
and more evenly along the whole length of the vine if it's pruned
to have mostly new wood. It's resistant to clematis wilt,
the bane of the large flowered hybrids.

Jackmanii is a C. viticella hybrid that acts a bit more like its other parents. So you can cut a Jackmanii to the ground in spring but in doing that you will probably forfeit its first flush of bloom, the one it puts on as a result of its other parents' genes. So gardeners usually cut Jackmanii like the common large flowered hybrids. Just shorten the vines that have already bloomed and remove one or more of the oldest canes right to the base. This keeps the proportion of young to old wood high and keeps the plant blooming well, even low down. You can cut after the first bloom of the year, in mid-to late June, or now while it's dormant. We opt to do it now, before leaves are out when it's simpler to see what we're doing

Photos at right and above: If Clematis pruning directions and exceptions make your head spin, just ignore them and cut only for neatness and to stimulate new wood. (Take a look at the detailed Clematis pruning photos in Growing Concerns 511 .)
Any loss of bloom is temporary and a healthy vine will grow back vigorously from most any treatment.
For instance t
his Clematis viticella can be cut to the ground each year and still bloom wonderfully. Last year we did just that -- cut all its canes to the ground. This year a thunderstorm rolled in just as we got to it so we quickly clipped off the top third and high tailed it out of the garden. If we don't get back to it, at least it won't begin growing mostly from its spindliest tips, leaving the bottom bare.

Honeysuckle decisions

My three year old honeysuckle vine is beautiful the first couple of months of spring. As summer comes it gets a white powdery mildew and leaves die, blooming gets less and less. How can I prevent this? - P. -

 

Dear P.,

Grow something besides honeysuckle -- it's just a dog for being mildew-prone.

Or:

Move it to a place where the air moves more freely. Keep in mind that sometimes means moving it into someone else's yard. Our yard, for instance, our whole property has poor air movement because it's at the bottom of a hill, on the east side of that hill. The prevailing wind goes over us. Jack, six houses uphill, can grow things we can't, mildew-free.

Or:

Apply a fungicide regularly, beginning when the leaves are about half developed and nights start reaching 65 degrees.

There are prepared fungicides and there are recipes you can mix yourself. Cornell University's published their work regarding baking soda and soap (2T baking soda and 1t dish soap per gallon of water; reapply after every rain; perhaps 80% as effective as prepared fungicides) and the Rodale Institute reports success with vegetable oils (including garlic oil, citrus-based products and Neem oil) when these are used as preventives. Other options include Wilt-pruf, compost tea, seaweed sprays and mixtures made from crushed and steeped horsetail/scouring rush (Equisetum arvense) -- each has shown some effectiveness in controlling mildew.

The two real tricks are 1) to begin early since these things (store bought or homemade) are all preventives, not remedies, and 2) to recognize your formula's ability to stick and last so you can re-apply at appropriate intervals.

 Originally published April 16, 2005

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