Container clematis

I have seen clematis used as container plants in magazines. Which clematis are best for this purpose? Do they need to be wintered indoors? How do I feed them? P.G. Tinley Park

Clematis can be used as a container subject, provided the container is large enough. Clematis roots like lots of cool soil to spread out in and probably wouldn’t be happy for long in a small, cramped pot. Choose a pot that will hold around 5 to 10 gallons of soil, then choose a good organic potting mix. Amend the soil mix before planting with some compost or composted cow manure. Be sure to have adequate drainage.

You may use a twisty branch from a contorted filbert, a small decorative trellis, or some other support for the vine. We have seen pot clematis allowed to simply cascade and hang from the container, but vines that are intended to climb produce better when they do, in fact, climb. For best effect you will want to use a clematis that is daintier in stature than say, ‘Jackmanii.’ For early spring bloom, try one of the C. alpinas that bear dangling blue blooms. For summer bloom you can’t go wrong with C. viticella ‘Betty Corning.’ It has the unique habit of spreading its top growth out horizontally from its support in a sort of umbrella fashion. The flowers are light blue, shaped like flaring bells, and fragrant. C. texensis ‘Duchess of Albany’ has dangling lipstick pink blooms and ‘Venosa violacea’ has perky purple flowers with a white eye. C. tangutica bears small yellow flowers in late summer.

You may want to underplant the vine with other perennials like bergenia, heuchera, sedges, hosta or liriope. Clematis like for their roots to be kept somewhat shaded and their heads to be in the sun. You will need to feed containerized clematis because frequent watering will leach nutrients out of the soil. Overwinter your pot in an unheated garage or shed, watering once a month. Cut the vine back each spring to make it fuller and more floriferous.

Disappointing performance

Last year I bought a brugmansia (Angel’s Trumpet) from a good garden center. The one that was on display there bloomed all summer with beautiful peach-colored blooms that dangled from every stem. Mine just sat there. It never bloomed until September when it put out two measly flowers. I fed it with Osmocote when I planted it and I kept it in full sun. I watered it daily but it still wilted a lot. What happened? P.P., Bourbonnais

Tropical daturas, or brugmansias have large, fibrous root systems, are very heavy feeders, and require lots of water. My guess is that the plant was fairly root bound (they often are) and water was running along the sides of the pot without soaking into the soil and the roots. You can correct this by repotting the plant into a slightly larger container and gently prying the roots apart to allow more soil to cling to them. Then place a saucer under the pot and fill it as many times as necessary to fully imbibe the plant with water. Keep filling the saucer when you water, and only empty it if water stands for more than a day.
Because you will be watering so frequently, time release fertilizers like Osmocote will break down rapidly and flush through the soil, leaving the plant depleted. Instead, use a weak solution (half the recommended rate) of liquid fertilizer in every other watering. It is always best to use a watering can anyway, since watering containers with a hose will compact soil and damage roots. Brugmansias grow in protected areas, so try to situate yours where it gets some protection from wind and from the hottest afternoon sun as well.

No-pinch policy

Are there any mums that don’t need to be pinched back? I never remember to do it and mine are done blooming by the end of August. B.F., Tinley Park

There is a fantastic group of mums that bloom late without pinching. Properly Dendranthema, not Chrysanthemum, these garden mums are rather tall and tend to flop a bit, but they look right at home in the midst of burnished ornamental grasses and fallen leaves. They are D. ‘Mary Stoker,’ which is a pale yellow straw color, D. ‘Single Late Korean Pink’ or D. ‘Single Late Korean Apricot,’ sometimes sold as ‘Sheffield Pink’ or ‘Sheffield Apricot.’ Plant mums in the spring; they will grow rapidly to form large clumps by fall. Mums need good drainage and will rot over winter if planted in wet, heavy clay.

A case of mistaken identity

I received an advertisement for pink Pampas grass that looks beautiful. Is the pink form as hardy as the silver flowered form that I have now? Also, the description says it will attain 8 feet in height. Will mine eventually become that large? R.H. Manhattan

We’re almost certain that you do not currently grow pampas grass. True pampas grass (Cortaderia selloana) is not hardy in Zone 5 and needs warmer temperatures year round to flower. Some game gardeners have attempted to grow it here and found that it may resprout after a particularly mild winter, but remains puny and doesn’t flower. It doesn’t even do as well in the South as the pictures in ads would have you think. The leaves of this grass are coarse textured and unattractive. And only the female plants flower with the large plumes seen in photos. (The photo of the pink form that is used heavily in trades was taken in South Africa.)

Certain varieties of maiden grass (Miscanthus species) are mistakenly called Pampas grass here in the Midwest. Miscanthus sinensis cultivars have silvery plumes and even some fairly pink and coppery red plumes in late summer and fall. Try these instead. If you want a really tall grass, try Miscanthus floridulus or gigantia.

Burned boxwood

My boxwood hedge developed a small brown patch on one side, which I trimmed out last spring. Within weeks, the area where I trimmed also turned brown. I am afraid to cut out any more. What is happening? B. S. Kankakee

The spot you first noticed might have been winter burn or it may have been caused by a fungal infection. Boxwood blight, caused by various fungal diseases, is not an uncommon problem. It is also not uncommon for boxwood to develop brown twigs around an area that has been trimmed. If you want to check for fungal problems, you can try placing the stem in a baggie with a wet paper towel and leaving it in a warm place for a couple of days. If fungal spores grow, the plant is infected. Saving an infected plant is not easy and requires the timed use of fungicides. Ask your local garden center or extension office for help in choosing the right one.

If the hedge is formal and the developing hole spoils the hedge, you have some choices. You may buy another plant that is slightly larger than the one you are replacing and trim it to ‘match’ as well as possible. If the plant is very large, a less costly remedy may be to remove the offending plant and replace it with a rose, small flowering shrub or some other evergreen plant. You could also fill the space with garden statuary, a gate or other structure.

Rudbeckia vs. echinacea

I love the new brightly colored coneflowers, but I see they are all labeled for full sun. My other yellow coneflowers are in afternoon shade and do very well. Do the new ones really need full sun? D.P. Kankakee

We think your older ‘yellow coneflowers’ may in fact be rudbeckia, or black-eyed Susans. The new coneflowers are echinacea, or ‘purple coneflowers’—well, sort of. They are orange, yellow and red coneflowers obtained by crossing the standard purple coneflower with a western species that has yellow flowers. They do need full sun and they are also a little fussier about soils than their familiar purple counterparts. One of their parents, E. paradoxa, grows in very dry conditions year round. This makes the children a bit more intolerant of wet soils, particularly in cold weather and humidity.

Your older yellow flowers, rudbeckia cultivars, do bloom reasonably well in shade and we thank you for reminding us of that.