Clematis Is Easier To Grow Than You Think

It’s been over a decade since I’ve written about Clematis, and while you may think this plant is a difficult vine to grow, it isn’t.

First, it isn’t always a sprawling vine. In fact, there’s one variety, Clematis Sapphire Indigo, that forms a mound 3 feet high and just as wide when it matures. No staking or pruning on this one. There are also short varieties only growing a foot or more, but the more traditional types that we’re familiar with are 4-to-8-foot-long flowering vines.

There’s also some confusion about a variety that likes to grow along stone walls and has sweet, scented flowers in the fall. Aptly called the “sweet Clematis” (C. terniflora, or Japanese virgin’s bower) it is invasive and should be avoided if not eradicated. However, it can be replaced with a native, C. virginiana, that has a similar habit and is noninvasive.

Young Clematis vines may need protection from rabbits and deer until they are a foot or so tall. Many will need trellising or staking so they can climb, as many will not flower if their supporting and attaching tendrils are not allowed to hang on to something. And lastly, most Clematis fall into one of three pruning groups. Always know the name of your Clematis (no, not Jane or Dave, but its scientific name) and keep the plant tagged. If pruned incorrectly or at the wrong time they will not flower.

Ah, but there is much joy to be found in this plant. Not only can they be grown tall, thus flowering above other garden plants or elements, their flowers can be magnificent from only an inch in diameter to 8 inches across. Colors range from white to red and pinks with some near blues and several varieties are available as doubles. If their beauty isn’t enough for you, many are also great for attracting pollinators and hummingbirds. Many of the plants provide seeds that birds will eat, and the seedheads are an attractive element as well.

The viny types that tend to get tall will need to be staked, caged or given other means of climbing and holding on. I’ve grown them on 1-inch-square wooden stakes as well as triangles of wooden stakes where the stakes are driven into the ground for stability then joined at the top, 6 to 8 feet above the ground, making a tall and narrow triangle with the stakes a foot or more apart at the base.

There are also premade supports, and I’ve seen Clematis grown along wire garden fences. But my collection of these plants grow on steel — rebar steel to be exact. These are steel rods that are used in reinforced concrete. They can be purchased at stone yards and lumber yards in 8-to-10-foot lengths. I bought three 10-footers and drove the end of each one into the ground at a slight angle. The bars are joined 8 feet above the ground at the top with stainless steel wire. While not technically permanent, this setup will last for a decade. The Clematis vines are trained to grow up each bar (with one plant planted at the inside base of each leg). As the Clematis vines emerge, I use natural-colored garden twine to add a bit of lattice work, and I use this twine to softly coax the vines and to stabilize them from wind damage.

Sometimes the vines need help in the initial attachments (the tendrils always attach counter-clockwise) but be very gentle when coaxing them because most broken vines won’t flower. In addition, I tie a few strands of twine across from bar to bar for additional attachment opportunities, and I always leave a couple of strands hanging from the top of the bars for vertical growth. These strings and lines only get added as the vines explore upward, and in that way the strings are only seen for a few days as they’re covered with the vines and the strings disappear.

My rebar tower is a great way to add height to the center of my long perennial bed, and it’s the summer focal point of the long double-sided bed at the north end. A tower this tall would cost hundreds of dollars to buy. The cost of making your own rebar tower? About $30.

When buying Clematis plants, you’ll have a few choices. Many vendors sell them online or in catalogs. These will run $20 to $40 each. This is usually how gardeners get their plants, but you can also find them in garden centers bagged in plastic filled with peat or wood chips. It’s critical to buy dormant plants, not plants that have already begun to “shoot,” keeping in mind that a broken shoot or stem is one that won’t flower.

Later in the spring, many garden centers will sell potted Clematis plants with vines that are already reaching onto small ladders (stakes) in the pots. There’s some challenge in transplanting these without damaging the vines, but with care and attention it can be done. These preplanted Clematis may flower a few weeks earlier than those you plant on your own.

Where do they grow best? Most varieties will tolerate everything but full shade or bright, hot sun in the middle of the day. Their true nemesis though is wind as it will tend to break and snap the vines. They won’t do well on the oceanside of homes near the water, but they will grow in sheltered spots on the opposite side of your house. Inland, simply keep them out of wind-swept locations and keep the vines well supported, and they’ll be fine. Most of the varieties (there are several hundred) will be very hardy, but if buying by mail or online make sure it’s hardy in zones 4 to as high as 7, but with some risk.

There are a few disease and pest issues with Clematis, but if you buy healthy stock from a reputable retailer or grower the disease issues will be minimal. Having a well-drained but not sandy soil will help here, as well as keeping the foliage dry. Regular irrigation from lawn sprinklers isn’t great for them. They do get spider mites, and watch for aphids on the buds and blooms as aphids can be disease vectors. As mentioned earlier, protect the emerging vines from deer and rabbit browse by encircling with temporary chicken wire until the vines are taller. But don’t let vines attach to the chicken wire — keep the caging about a foot from the vines.

If your vines arrive too early to plant outdoors or directly in the garden they can be planted into large peat pots (8 to 10 inches wide and deep) in a potting soil and grown indoors or on a sun porch until outdoor planting. You must stake the vines in the pot and don’t prune them. When placing an online or mail order try to get delivery scheduled for late April as our frost-free and safe planting date on the East End is around April 25.

Newbies should limit their initial varietal choices to the standards like Nubia Boulevard (red), Duchess of Albany (two tone pink), Nelly Moser (two-tone light pink) and The President (purple) among others.

Next week we delve into the various types and varieties of Clematis, some challenging and some not, as well as seasonal care, a bit on pruning and more. Everyone should have at least three of these beauties. Keep growing

Garden Notes

It’s that time of the year to apply or have your contractor apply dormant oils, which are also called horticultural oils. These can be natural vegetable oils or petroleum-based hort oils. They are generally applied to fruit trees as well as other trees, shrubs and roses to control scale, insect eggs and some disease pathogens. This can often be the most important spray you can do in your landscape all year as it reduces or eliminates many issues going into the growing season. Spraying can be done on a small scale with your compression sprayer (hand operated) as long as you get good coverage on the trunk, stems and twigs. Spray when the daytime temperature is 50 degrees or higher, when rain is not expected within 24 hours, and when the night temperature will be above freezing.