How to revive trees, identify Japanese wisteria and more in Sonoma County gardening

Pops writes: My dwarf tangerine is having a difficult time.

It is in a small-sized wine barrel and it sits directly on top of the soil. The exposure is a south facing and the house protects it.

I water it once a week. Now the limbs are leaning and looking very bad. But, there is a lot of fruit on the tree. Help!

The tree appears too large for its current container. Raise the wine barrel up off of the ground so it has better drainage and air can get to its roots. Placing some bricks under the wine barrel should do the trick. Carefully tie up the branches with some stakes and ties. Use strips of old pantyhose or special rubber ties designed for this purpose. Keep in mind not to use metal ties that will cut into the bark. Fertilize lightly with a citrus fertilizer or 0-10-10 according to package directions for the size of the plant. The fertilizer should be gently scraped into the soil. Always water first and then again after fertilizing.

In the spring, you might consider planting the tangerine in the ground or repotting the plant in a larger container using fresh soil. At that time prune any damaged roots and those roots that are girdling around the main root ball. The container should be 2 inches larger than the root ball and the soil should be one inch lower than the edge of the container.

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Ashley Peters writes: My husband repotted an azalea in a larger container, but filled the potting soil to the rim. Now the water runs over the rim.

How much space should be left below the rim of the container when transplanting? I plan on potting up some bare root roses as soon as they are available and I don’t want to make the same mistake.

Leaving 1 inch below the rim of the container should be sufficient. It is not too late to remove some excess soil around the base of your azalea.

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Kristin Strout asks: My Owari Satsuma mandarin appears to be failing. The leaves are yellowing and steadily falling. On closer inspection I found the lower trunk severely girdled and damaged. A friend suggestion I try bridge grafting in an effort to save the tree. How is bridge grafting different from other types of grafting.

This type of grafting is used to repair trunks of trees that have been girdled by voles. Its purpose is to maintain connection between the fruit tree canopy and the roots, therefore, nutrients can flow uninterrupted. The procedure includes trimming and cleaning up the ragged bark where the vole has done its damage.

Long longitudinal slits are then made above and below the wound thus loosening the bark.

Scions are collected from the healthy part of your mandarin tree and the scions should be three inches longer than the wound and from one-year-old wood. The scion stems should be flexible.

Next, bevel each end of the scion with cuts ½ to 1 inch on each end.

It's these beveled ends that will slip under the bark and the scions will appear bowed. Anchor the beveled ends with small brads. The insertion of the points are then covered with grafting wax. The scions are numerous and are inserted every 2 inches around the trunk. Having said that, the bad news is it may be too late to try bridge grafting to save your tree.

Protect the tree as much as possible from freezing conditions during the upcoming months.

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Deanna asks: Can I graft an English walnut onto a black walnut?

Yes! They are compatible and grafting is usually confined to related plants to form a successful union.

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Mary Ann asks: A wisteria was planted by a previous owner near our front porch. We understand that the Japanese wisteria is the most fragrant. How does one identify whether a wisteria is a Japanese or a Chinese variety?

Japanese wisteria twine from RIGHT TO LEFT. And when the flower clusters begin to bloom they open from the base first and then to the tip. The Chinese wisteria twine up a support from LEFT TO RIGHT.

You mentioned that the wisteria is planted near the front door. This is a very aggressive vine that is capable of damaging gutters and lifting shingles. It requires diligent pruning to make sure that this does not happen. This gorgeous vine requires massive and sturdy support to handle the size of its mature growth.

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Lana asks: Would you settle an argument and give me the correct pronunciation of the Kalanchoe succulent that is sold in all the stores during the holidays?

Sure. You didn’t give us a hint on who was hoping to win this argument! Unfortunately, there are at least two phonetic pronunciations that gardening folk swear by: kal-en-KOH-ee or KAHL-an-koh-ay. I prefer the first pronunciation because it rolls off the lips easier!

As an added bit of fun, try teaching young children the pronunciation of this plant. It has a bit of rhythm and mystery to its name.

Dana Lozano and Gwen Kilchherr are garden consultants. Send your gardening questions to The Garden Doctors, at pdgardendoctor@gmail.com. The Garden Doctors can answer questions only through their column, which appears twice a month in the newspaper and online at pressdemocrat.com.