All About Clematis

The majority of written information about clematis is from books that are written in Great Britain.  Although they are filled with valuable information, you need to be aware that their growing zones and conditions are considerably different than in the United States.  There is, however, a huge amount of information available on the internet regarding clematis grown in the United States, and you’ll find lots of information in the ever-expanding All Things Plants database. 

Keep in mind that if you look at five pictures of the same plant on five different websites, the colors could be different on every one.  Type of camera, lighting conditions when the picture was taken, your monitor, etc. will all impact the color you see.  Also, what I consider lavender, someone else might describe as blue.  This also holds true for catalogs.  So if you fall in love with the color of a clematis flower, do your homework to verify the true color. 

Another consideration should be your zone. All clematis are not hardy in all zones, but chances are you can find a good selection of clematis for any given zone.  The same clematis planted in different zones may also have differing plant and flower size, color and bloom times. 

Clematis can be selected based on any combination of criteria that fits your needs:

*Zone

*Height – Clematis are available from 1 ft. to 30+ ft.

*Plant Habit – Vine or bush

*Flower color – Many colors available including white, pink, purple, red, blue, yellow, bi-color

*Flower shape – Single, double, bell, nodding, etc.

*Bloom period – Spring, summer, summer through fall, repeat bloomer, etc.

*Site requirements – Ground, container, partial shade, sun, moist, dry, west wall, etc.

*Companion plants – Grown through roses or shrubs, used as groundcover, etc.

*Available supports – Fence, trellis, mailbox, downspout, gazebo, arch, etc.

Clematis will do best if planted in the spring so they have time to become established before winter sets in.  The time you spend in planting preparation will be well worth the effort when you experience the difference it makes.  Clematis need a large planting hole, 18” x 18” should be the minimum size; 24” x 24” would be better, and they require good drainage, so amend your soil as needed.  Mix about two fork-fulls of rotted manure or compost with the amended soil before returning it into the bottom half of the hole.  Then mix about 2 good sized handfuls of bone meal into the rest of the soil that will fill the top portion of the hole.  The amended soil should be at a level so you can plant your clematis 3-5” below ground level.  If your clematis receives any surface damage from animals, lawnmowers, etc., or suffers from “clematis wilt”, this deep planting will give it the chance to grow new stems from the leaf axis buds underground. 

Before removing your clematis from the pot, soak in a bucket of water for 15-20 minutes.  Then remove from pot, disturbing the root ball as little as possible.  If it appears root bound, loosen the outermost roots to encourage growth.  Try not to kink any stems when handling the plant as it could cause the entire stem to die.  Set plants at a 45 degree angle when planting to encourage new shoots.  If the clematis is attached to a support in the container do not remove the support.  If the support is short you can add another longer one close to the rootball before planting and attach the existing support to the longer one.  As new growth occurs, train onto the support until it reaches the permanent support (trellis, fence, shrub, etc.)  Leave in place for the first year to give the main stem support. 

All clematis should receive an inch of water a week during the growing season, either through rain or hand watering.  This is especially important for newly planted clematis.  A good rule of thumb is to water each one with a minimum of a gallon of water.  In dry conditions and/or when clematis are actively growing, they can benefit from as much as 4 gallons of water each.

Early each spring I sprinkle a large handful of bone meal around the base of the plants and lightly scratch it into the top layer of soil, making sure I don’t damage the feeder roots.  Then I mulch each plant with composted manure, being careful not to let any touch the stems or foliage.  If no rain is forecast for the next week or so, water this in well.  Generally any fertilizer that is used for roses can be used for clematis in place of manure.

If you live in an extremely cold area, consider mulching your plants in the fall with straw or other materials.  Container grown plants should be moved into a garage or protected area.

There are a few pests and diseases that plague clematis.  Snails and earwigs are two of the most annoying.  Powderly mildew occasionally strikes but can be minimized by planting in an area with good air circulation and proper light.  Kinked stems can prevent water from travelling through the plants and may cause some stems to die.

The most devastating problem to attack clematis is “wilt” or stem rot.  One day your plant looks great, and then BAM, you’ll start to see the top shoots go limp, as if it needs water.  New foliage starts to turn brown and all of a sudden a stem, or sometimes the entire plant, collapses and dies.  This happens very quickly.  It’s not certain what causes this - possibly a fungal infection.  If wilt strikes your plant, carefully clip off any affected stems all the way down to the ground and put them in a sealed plastic bag to dispose of them, preventing the spread of this disease.  Be sure to disinfect your clippers after each cut.  If you’ve planted your clematis 3-5” below ground level your plant will nearly always survive.  However, if the entire plant collapsed, it may not return until the following year.

Clematis also have a little trick up their sleeve!  Sometimes a plant will appear dead.  It could happen the year you plant it or maybe several seasons later.  It simply doesn’t grow for one or two seasons.  Do not dig it up!  I would give it at least three seasons to recover.  All of a sudden it will start to grow and be bushier and more beautiful than ever.   I’ve had this happen to me several times but from my experience it only happens once to any particular plant.  Again, there is no known reason for this.  But do be patient – I think Mother Nature is just trying to show us that she’s in charge!

Clematis are divided into three main groups for pruning purposes.   It sounds confusing but isn’t as hard as you think.  This can get more technical, but I’ll provide the basic information for each group.  Most plants that are sold by reputable dealers will list the pruning group on the label or on their website.

Note that in the spring of the first year any clematis, regardless of pruning group, should have all stems cut back to a strong pair of buds to a height of approximately 12”.  It’s a difficult thing to talk yourself into doing because you want to see the early flowers, but this will encourage more stems to grow producing a bushier plant. 

Group 1:  These are the evergreen and early flowering clematis, alpina and macropetala types, and montanas.  This group flowers mainly in the spring and produces their flowers on old (last year’s) stems, so pruning isn’t done until all flowering has been completed.  Remove all dead and weak stems as soon as flowering is done, and do any thinning if plants have outgrown their space.  When pruning is done, new growth begins and these are the stems that will produce flowers next spring.  This is sometimes referred to as light pruning.

Group 2:  Early large flowering, double and semi-double flowering, and mid-season large flowers.  Flowers will be produced on old stems any time from late spring to autumn, depending on the specific plant.  More flowers are produced again later on current year’s stems.  The second year, immediately after last flowering, cut entire plant back to a strong pair of buds to a height of about 3 feet.  After the second year, cut about half the stems back to a strong pair of buds and remove all dead and weak stems, and tidy up the plants.  The following year cut back the other half.  Alternate this method in following years.  This is sometimes referred to as optional pruning.

Group 3:  Late large flowering, viticella and late flowering species.  Flowers are produced on current year’s growth.  Most, if not all, of the previous year’s stems will die back to the ground in winter (especially in colder areas), so late winter/early spring is when this group should be pruned.  This method is sometimes referred to as hard pruning.

But really, if you make a mistake and prune too much from your plant, it won’t hurt it.  You may not get double flowers for a year but other than that, it will come back just fine.

Large flowered clematis and the viticellas make beautiful cut flowers that often last up to two weeks.  As with any flowers cut for bouquets, cut them either early in the morning or in the evening.  Cut stems at a 45 degree angle, dip the ends into boiling water for 10 seconds, and place in warm water overnight before using in arrangements.  Or just cut off one flower and float in a bowl of water.

And don’t forget about the gorgeous seed heads clematis have.  They’re beautiful left on the plant or included in arrangements.

If you’ve been admiring these beautiful plants but have been hesitant to try them, this is the year to do it!  You’ll be pleasantly surprised how easy it is.  You'll soon find endless ways to use them in your landscape and wonder how you ever got along without them.