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I want to plant cannas in containers this year. What type of soil should I use? Do cannas need to be constantly moist and, if so, should I plug up the drainage hole in the container?

Although cannas are water-loving plants and actually do very well in a pond or water garden setting, they adapt very well to containers.

Use a soilless mix of sphagnum peat and perlite. Select a container large enough to support your canna. Most cannas will grow between 36 and 48 inches tall. A 14 inch or larger pot should work well. Also think about planting other shorter or trailing annuals in with your canna to help balance the overall look of your container garden.

Water only when the soil is dry but realize with growth your canna will dry out quicker and probably require a daily watering. Do not plug the drainage hole. All it takes is a few rainy days in a row to fill the pot with water and ruin your plants.

I would like to grow herbs, but I have partial shade conditions. Are there any herbs that will grow in partial shade?

Most herbs can be grown in 4 hours of sunlight (part shade), but realize the plants will stretch for the sunlight and could become “leggy” looking. A constant pruning will help keep the herbs full and healthy, so the more you use your herbs for cooking, the better off they will be.

I have had trouble growing tomatoes near a walnut tree. The tomatoes do get 4 or 5 hours of sun daily. I have heard that it can be difficult to grow things near a walnut tree – is that true? Could that be the problem?

It is definitely true that it is difficult to grow certain plants under black walnut trees. All parts of a black walnut tree contain a substance called juglone which affects plants growing beneath and around the tree. Different plants have varying levels of tolerance to being planted by black walnuts. Unfortunately, tomatoes are probably one of the worst plants to plant around this particular tree. Some fruits and vegetables that have more tolerance to black walnut trees include: lima beans, snap beans, beets, sweet corn, onions, parsnips and black raspberries. One option would be to try growing your tomatoes in a large-size container in order to keep them out of the same soil as the roots of the tree. Be sure to get a bush type tomato which will not be as aggressive and overtake the container.

We have had a Wisteria sinensis (Chinese wisteria) for about 4 years. I have been shaping it into a umbrella-shaped tree and it has been growing well, but has failed to bloom for us. I read that I should cut the roots, so we have done that and still no blooms. It is located where it receives morning shade and then sun from noon on. Can you give me some ideas to try to make it bloom? Also what time of the year should it bloom?

Wisteria sinensis (Chinese wisteria), along with any other wisteria, may often prove difficult to flower. The tree and vine forms both require a site with full sun as well as a well-drained soil. Wisteria also need to be planted in a protected area as winter winds may kill off any flower buds. Little, if any, nitrogen fertilizers should be used since they promote leafy growth and inhibit flowering. Instead, use a fertilizer high in phosphorus. Heavy pruning should be done only in June, after normal flowering should have occurred. Very rarely does Chinese wisteria bloom on new growth, meaning a fall or winter pruning would remove potential buds for the next flowering season.

“Root pruning” is a technique used to stress the plant into producing a bloom. This technique is best done in May or June, after the flowering occurs. Use a sharply pointed shovel to make the slits, which should form a circle around the tree at a diameter of two feet for every inch of stem diameter. Be patient, as it sometimes takes two to three seasons for root pruning to be effective.

Another tip is to always purchase named cultivars, rather than seed-grown stock. The cultivars tend to produce better and more reliable blooms.

We have 2 hanging baskets on our patio—one a fuchsia and the other geraniums and ivy. Birds go from one to the other to make a nest. How can we stop them? It is spoiling the plants.

Most gardeners invite and welcome birds into their gardens. Every once in a while, however, one of the little chirpers refuses to obey the local zoning ordinances and chooses to build her nest where she is not welcome. Her persistence is most amazing once her mind is made up. She will rebuild her nest nearly as fast as you can take it down. If she gets ahead of you and lays eggs, few gardeners would have the heart to disturb the soon-to-be-family.

The trick is to prevent her from getting to that point. Repellents used against rodents seldom work for birds as they do not experience taste in the same way as mammals. Physically keeping her out may be the best answer. Use a bit of tree netting over your basket (the same that is used for keeping birds off of fruit trees and berry patches). It will only have to be left in place for a couple of weeks until she builds her nest elsewhere.

When do I prune my hydrangeas?

When to prune depends on the type of hydrangeas you have. Pink and blue hydrangeas (Hydrangea macrophylla) and oakleaf hydrangea (Hydrangea quercifolia) bloom on last year’s wood. They should only be pruned just after flowering. Pruning them in late summer, fall or in spring before they bloom will remove the flower buds for next year’s blooms. PeeGee, Annabelle, and tardiva hydrangeas (Hydrangea paniculata and H. arborescens) bloom on the current season’s growth and can be pruned in fall, winter or early spring.

Five years ago I planted a large trumpet vine (‘Madame Galen’). It has grown into a beautiful shrub, but has never flowered. It gets full sun, is protected by and planted on the south side of our shed. I have tried different fertilizers, raised the pH, lowered the pH, pruned it, and not pruned it. A few neighbors have trumpet vines; they put little effort into them, yet they flower.

Getting a trumpet vine to flower is simiar to getting a wisteria to flower; it sometimes takes patience. First, make sure the location you choose has lots of sun. Plants in shade rarely flower. Second, avoid high nitrogen fertilizers. If you have a lawn service, don’t let them fertilize near the trumpet vine. Nitrogen fertilizers promote vigorous stem and leaf growth which will take away the plant’s energy from producing flowers. Third, prune the plant back each spring to only a few buds per stem. This way the plant is expending less energy on vegetative growth (stems and leaves).

If these methods fail to produce flowers, you can try fertilizing with a high phosphate fertilizer such as superphosphate or try root pruning. Root pruning is cutting a circular slit in the ground that is centered around the stem of the plant. The circle should be 2 feet in diameter for every 1 inch of trunk stem diameter. Use a sharp, pointed shovel to make the slit by digging into the ground as deep as possible and rocking the handle back and forth to create a V-shaped cut. You can apply the superphosphate directly to this cut if you like. Root pruning often produces flowers the following year. Once the plant begins to flower, removing the seed pods will encourage more flowers.

Can you recommend some annuals for partial sun that have nice flowers and a spreading habit that covers a relatively large area? Rather than plant a traditional groundcover, I would like to try annuals, since they have season-long blooms and I can change them each year.

There’s a good reason that impatiens are the number one variety of annuals grown today. Not only do they bloom all summer long, but they spread together which reduces the need to weed. Impatiens are very low maintenance and will grow in sun, part sun or shade. Wax begonias will also bloom all summer and grow in part sun but won’t spread quite as much as impatiens. The colorful leaves and spreading habit of coleus would add an interesting look to a flower bed. Coleus will also grow well in part sun or shade.