Q:I live in Novato and two years ago planted a rhododendron, north facing, in the shade, under the eaves of my house. I get lots of buds, but they never open. I’ve tried feeding it plant food for azaleas and rhodies, but no luck. Any thoughts?

A: Almost certainly the buds you see on your plant are only leaf buds, not flower buds. These form at the ends of branches, separately from the flower buds. If there are no flower buds, there are no flowers. (Look at some rhododendrons that are blooming this spring to see what I mean.)

There are two strong possibilities to explain a lack of flower buds. One is that the plant is still becoming established.

But if you’ve had the plant in for more than two years, unless it is a very young or small plant, I suspect that you have placed it in too much shade. While we think of them as shade plants, rhododendrons want open or bright shade, or morning sun and afternoon shade.

Sun reaches the north side of a house or other barrier only briefly in early morning and late afternoon in midsummer, not at all the rest of the year. An overhang will further reduce light reaching the plant. Morning sun strikes the east side of your house. I suggest you move your plant to a place where it will get more light. In the Bay Area, the best time to do that is in fall. (Water deeply three days before the move, transplant in the evening. See books on rhododendron growing for more details.)

Be careful not to overfeed your rhododendron. In deep shade, it will be growing slowly, so it won’t be able to use much fertilizer. A rule of thumb is to fertilize in response to a plant’s growth, not to try to stimulate it to grow.

If your rhodie ever does bloom, break the spent flowers off after the petals fall, being careful not to injure any leaf buds, since those will open into this year’s leafy growth. This deadheading will encourage more bloom the next year.
Q: I need a solution for ever-invading bamboo. I am referring to the very tall, thick stalk bamboo. The property is in east Contra Costa County. While I have been able to cut it back, dig it up and seemingly remove it from my property (along the back fence), it returns without fail. Of course, part of the problem is that it has grown without interference in my neighbors’ yards for years. (Both property owners have ignored complaints.)

What can I do, if anything, to eradicate it from my side? I’m concerned that someday it may topple my fence, and most probably will envelop the toolshed that was built near that fence.

Q: Do you have any suggestion how to protect ourselves from a neighbor’s bamboo? It’s growing into our gardening area and breaking up our driveway. I have heard that it can break up home foundations. Is that true?

A: There are two kinds of bamboo, running and clumping. Gardeners sometimes install a barrier to contain even the much slower-spreading clumping types that are close to structures. The one your neighbors have planted sounds like the running kind. Running bamboo spreads through underground rhizomes that are usually only a few inches deep, but occasionally turn deeper. If your neighbors had installed a proper barrier at planting time, the bamboo would have been stopped. (Take heed, gardeners contemplating planting bamboo: Choose a clumper if you can, or contain your planting as described below!)

You may be able to install a barrier on your side of the bamboo. You would need to dig a trench (call a tool rental company to discuss your options) and install a 30- to 36-inch barrier made of 40- to 60-mil thick polypropylene. Angle the top of the barrier farther from the bamboo than the bottom, and leave an aboveground lip of 2 to 4 inches. Use a continuous piece or follow the supplier’s instructions for joining pieces tightly. Pack the soil on the bamboo side back in firmly. Check at least once a year for rhizomes trying to leap over this barrier.

If this is not doable, dig a trench 8 to 10 inches deep and a foot wide at the edge of your property. Fill it with loose mulch and search through it at least twice a year to remove any rhizomes growing into it.

You may be able to sever bamboo rhizomes with a spade or a saw, but older ones may require a mattock or a digging bar. What is important is to separate your neighbor’s plant from the part that is on your side, since as long as they are connected, the stems in your yard can get energy from theirs, and if you applied an herbicide to your part, you could kill their part. (I know, that sounds good, but it could lead to a lawsuit.)

Once you have your part of what was one big plant separated, you can concentrate on killing the plant in your yard. If you cut it down or mow it repeatedly, make sure it has no leaves at all; it will eventually run out of energy and die.

There is a formulation of glyphosate herbicide registered for bamboo. I recommend cutting as your primary method, but the herbicide could be useful for plants growing in crevices or concrete cracks.

Pam Peirce is the author of “Golden Gate Gardening” and “Wildly Successful Plants: Northern California.” She teaches gardening at City College of San Francisco. Read her blog at goldengategarden.typepad.com or e-mail questions and comments to her at home@sfchronicle.com. We cannot guarantee a response to all questions submitted.

source : sfgate.com