Gardening with Gary




Gardening Advice from an Expert

Clematis

Q. I bought a clematis last year. I don't know the type of plant I have. It is growing like gangbusters but I have no blossoms. I have 3 questions: What can I do to get the plant to blossom? Can I prune it this autumn if it doesn't bloom? It has grown so vigorously and extensively that I can't keep it at this size - it's in the way! If I can prune it, how do I do it?

A. First, the blooming season for clematis is over for the most part. The ones in Ohio peaked in May and are straggly in July. Here is what I recommend:

Vines need to become well-established before they will bloom. Do not worry. The fact that it is growing well bodes well for the future flowering. Continue to water the vines well and feed them with a general garden fertilizer for foliage as a 30-10-10 or 20-20-20, once every three weeks at one tablespoon per gallon water. This will build up the plants and strengthen the root systems.

Clematis like their roots cool and shady, with their foliage in full sun. They prefer rich, well drained soil and make good companions for roses. They will grow near water as long as they are planted well above the waterline, and can get their roots down to the water if they want it. When planting it is best to prepare the hole, sit the plant in position and cut away as much of the plastic as possible. This will leave the bottom of the bag in place, but avoids unnecessary root disturbance. Stake the plant, then back fill the hole and firm it in gently.

One of the most important aspects of Clematis culture is the pruning method. Remove dead wood and prune to shape after flowering to 3-5'. A general cleanup of weak growth after flowering is also beneficial. All summer, trim any poor or dead growth to provide more light and nutrients for the healthy stems.

As a general consideration, 3 - 5 year old growth buds on old wood will die completely, so every few years a good cleanup directly after flowering is required. This will make sure you can see the best growth buds to cut back to, and maintain a relatively young, healthy framework. Give a good feed of compost and bonemeal at pruning time, as well as fresh mulch to prevent soil splash.

Watch for clematis wilt, caused by soil splashing onto the stem, easily prevented with a mulch of bark, compost, gravel, or anything that prevents soil splashing around the stems. Deep planting allows the susceptible forms to develop a crown of growth buds below ground level, and since the wilt disease affects the stem at ground level or just above, healthy new shoots from below ground can restore the plant very quickly if attacked by the wilt disease. When watering in summer it is best not to wet the foliage, but trickle the water around the base of the plant and give a good deep soak twice a week.

Assistance from Van Plant Co., a good source of clematis vines, is acknowledged.

Q. Should I trim back my climbing clematis now or do I wait until summer?

A. I do not know where you live, but no pruning should be done until spring has started and the danger of frosts in your area are over. Otherwise, you would be encouraging new growth which could be killed by the cold temperatures.

Clematis likes some early spring attention, and pruning your plants at that time will encourage more vigorous plant growth this summer. For those large summer-flowering clematis types, prune the plant's new shoots to about 12" from the soil line. For older clematis plants, cut all stems back to just above the previous season's growth, within 3' tall.

Q. What is the best companion plant to plant with my Clematis to protect the roots? Any other growing tips would be appreciated.

A. I like to grow these shallow-rooted plants around the base of clematis:

lobelia
pachysandra
myrtle
sweet alyssum
ivy
pansy
viola
Johnny jump ups

The rule of thumb is that Clematis perform best with a cool root area and their tops in the sun. Most Clematis enjoy being exposed to at least 5-6 hours sunlight daily. In hotter inland and canyon areas, planting pastel pink varieties in bright shade helps to minimize fading.

In heavy soil, dig a big hole about 24" x 24". In lighter or sandy soil, a hole 18" x 18" will work. For heavier soils, thoroughly mix the native topsoil with 2 bags of Uni-GroTM Premium Organic SuccessTM Planting Soil. For lighter soils use 1 1/2 bags.

Always cut the container before planting your Clematis. This minimizes the risk of damaging your plant when removing it from the container. Gently remove the rootball from the container and plant it in the hole so that the base of the plant is sunk 3"-5" below soil level. Leave the original stake on the Clematis for the first year to act as a support as well as a protection against accidental breakage.

Mulching is essential because it keeps the plant's feet cool while improving the soil. Place a 3"-4" layer of Uni-GroTM Premium Organic SuccessTM Roger's Planting Mix or Master Nurserymans Azalea Gardenia Planting Mix over the root zone. Keep the mulch 8" away from the stem to avoid stem rot.

Clematis is a heavy feeder. In spring, once the Clematis buds are about 2" long, start feeding them with Roger's Soil Activator. Use approximately 2 Ts per plant. Continue this feeding until the end of September.

Clematis need regular watering. Always water thoroughly and deeply during the hot summer months. Remember, if the soil under your Clematis is shaded it will not dry out as quickly as a sunny area. Don't keep them too wet, especially in the winter when they're dormant.

Clematis need support to grow. Try growing them on an arbor or on a trellis, onto other shrubs, on a fence, or an obelisk.

Just as in growing Clematis in the ground, the following steps for planting in a container are crucial. Select a container that is at least 18" x 18". Using straight Uni-GroTM Premium Organic SuccessTM Planting Soil, fill your container with potting mix leaving an adequate amount of space for a good watering basin. Always cut the container to remove the plant. Gently lift the Clematis rootball from the nursery container and plant it so that it is sunk 3"-5" below soil level. Feed and water as if it were planted in the ground.

Assistance from:
http://www.clematis.org
http://www.rogersgardens.com

Note:
Clematis are susceptible to many fungi that can cause them to wilt or turn black. These fungi enter the plant via the stem and work their way up. Although this is a very disappointing malady, it is usually not fatal if you planted correctly. Carefully cut off all of the diseased parts of the vine and then disinfect your clippers with Physan 20. Dispose of all diseased parts in a sealed plastic bag into a garbage can. Never add to your compost pile!

Dajevuy writes~
I have a clematis I planted this spring. It will be fall here soon and the weather gets very cold in the winter. Do I need to cut back my clematis for winter? If so, how far back?

A. The main purpose in pruning is to help plants produce the maximum number of flowers. Annual pruning is recommended. Sometimes older, neglected plants can be cut back into older wood and new buds may break. Growth from old wood will likely be weak and slow; however. If no pruning were done at all, plants would still grow and flower profusely, though not where you may want them to. Some flowering would occur high in the plant and out of sight. Not all clematis can be pruned in the same way. There are three methods that can be applied to major groups depending on the time of year the plant flowers. No new growth must occur to enable the earliest flowering clematis to bloom, but the later flowering types must make new growth in order for flower buds to form. A few plants are not strictly bound to the following groups but may cross lines. Because vines will likely be entangled, make cuts carefully among the intertwining vines and spread and train them in various directions in order to cover the maximum possible area. This enables the plant to display its blooms rather than be bunched up.

Clematis are divided into 3 distinctive groups. Knowing what group your clematis falls under, will guide you on when and how to prune.

Group A
This group is the early flowering species that produce bloom on previous year's growth. Prune within a month after flowering. This allows the vine to make new growth that produces next year's flowers. Prune out damaged or dead wood or cut back overgrown s hoots to keep it in bounds of the space allotted for it.  Do not cut into woody trunks. Plants in this group include:

C. alpina, C. macropetala, C. armandii, C. montana and C. chrysocoma

Group B
This group includes the early, large-flowered cultivars. These are all large single, semidouble or double blossoms. Flowers bloom on both previous year's growth and new growth. Two flower sessions from one vine! Prune before new growth begins around mid-F ebruary or first part of March. Pruning in the fall is another option. Prune out damaged or dead wood and lightly prune the portions of the vine that bloomed to keep it in shape and to keep it from getting bare legs. Plants in this group include:

'Nelly Moser,' 'Miss Bateman,' 'Lasurstern,' 'Duchess of Edinburgh,' 'Mrs. Cholmondeley.'

Group C
This group is the late blooming species and cultivars. Bloom times are summer and fall and all bloom on current season's growth. Prune severely down to within one foot of soil level before new growth begins (mid-February or first part of March). You may also prune in the fall. I prefer to cut it back in the fall when leaves are brown to about three feet. I followup in spring with pruning the vine to one foot high. Admittedly I sometimes leave the vine on the arbor over winter, if my fall cleanup chores ge t behind. Plants in this group include:

C. viticella, C. flammula, C. tangutica, C. x jackmanii, C. maximowicziana, 'Perle d'Azur,' 'Royal Velours,' 'Duchess of Albany.'

There are several excellent articles which you can click on at this site below. Scroll down to the bottom:

http://www.rainyside.com/ornamentals/clematis_care.html
Assistance also from: ohioline.osu.edu

Q. Have you ever grown Clematis? I am unsure as to where they do best in the garden.

A. Clematis vines do best in semishaded locations with good light for blooms and healthy growth and cool roots during the hot summer. They are light feeders, but love a good general fertilizer once every 2-4 weeks during the growing season. Cut back as the days shorten and the temperatures drop, in order to harden the vines for the winter.

They take 2–3 years to become fully established. Grow in full sun to produce heavier blooms for a shorter time period. Those grown in partial shade show lighter blooms, but last longer. Clematis benefit from shade over their roots. Plant annuals, shallow-rooted perennial or short ground covers as myrtle around their base.

In early spring, cut back to just above the lowest set of healthy buds. In summer, avoid heavy bark or leaf mulches which can promote Clematis wilt. Some of the newer varieties available are rather resistant to wilt. They are not too prone to insects but be on the lookout for aphids and white flies. Keep the moisture level of your vines as even as you can, that is, never too dry or too wet.

Phyllis writes~
I enjoyed reading your comments about clematis. You have some really good tips! How do you get rid of white flies on the clematis?



A. There are basically two methods: safe and organic or chemical insecticides.

Organic:
Try Safer's Insecticidal Soap or Nature's Answers, available widely at garden centers. Follow the directions carefully. Tap the leaves and as a cloud of flies up, suck them up with a vacuum cleaner. White flies are also attracted to yellow paper, so hang strips of sticky yellow card which the flies fly at and stick to. Works good on thrips and fungus gnats, too.

Chemical:
There are lots of sprays you can use. As the whitefly moves so rapidly, a systemic spray is a good idea. Seek one at your local garden supply company. A systemic spray enters the plants sap killing the insect when it feeds. (A contact insecticide only kills when it comes into contact/touches the insect). Repeat weekly for four weeks, applying again after any rainfall. The eggs must hatch and then the adults are killed by the chemical.

Carol writes~ How do I prevent/or cure black leaves on my clematis?

A. The most devastating problem of clematis is a stem rot and black leaf spot caused by the fungus Ascochyta clematidina and commonly called "wilt." This is a disease on large-flowered hybrids. Small-flowered hybrids and the species and their cultivars are less susceptible to wilt. Symptoms include a sudden stem collapse typically as the flower buds are about to open, and within a few days, the stem and leaves turn black. Only one or perhaps several stems in a plant may wilt. The stem discolors and may exhibit lesions below the first pair of wilted leaves. Any part of the plant can be attacked down to and just below the soil level. The usual treatment is to remove the diseased stem below the wilted section, even below soil line. Plants usually recover from buds lower on the stem. It should be treated with a fungicide when first noticed as the fungus can disfigure leaves and flower buds, causing them not to open. Check your local nursery or garden center as black leaf fungicides are readily available.

Assistance from Ohio State University