Gardening with Gary

Gardening Advice from an Expert

Rhododendrons

Q. Several Rhodie plants I put in last year...2 are rather small, one is about 3-4 feet tall and nicely bushed out. First, I live in the state of Washington at about 1800 ft. elevation, the trees are planted under fir trees, in a park like setting, nicely spaced apart (the trees) to let in adequate light, but are protected from heavy snows.

When I planted them last summer they were already in bloom. We have pretty good soil, fairly loamy and rich, and I don't believe I fertilized them but once or twice. The trouble is, that in looking at them this spring I realized that not one single plant had put out a single new flower bud. My two older plants on the other side of the house, in a flower bed against the house, have both set blooms....they get the same care and are actually in poorer soil. Is there anything I can do at this point? Plus, what about getting buds to set for next year?

A. You know, this happens from time to time. First off the bat, the bushes are new to their locale and must adjust to a different condition to what they had wherever they were before. The soil, light, temp, and moisture are all different. It takes time for most flowering perennials to adjust.

Many times they send up a couple flowers just to tell you that they are alive. Remember that the flowers you see this spring were initiated in the tips last late summer and fall. By winter, the amount of flowers is already determined by the plant. Therefore, it is obvious that you can do absolutely nothing right now to get flowers, but you have to think about the care of the bushes and getting flower set this year!

I would like you to start feeding them monthly with MirAcid fertilizer [good for lowering the pH of the soil, making it more acidic]. Follow the directions on the label. I am pleased with the description of where you have them growing, including the fir needles which will keep the pH of the soil acidic, which is what they need.

Please water them this year, too. I know they are protected and cool, but slow, deep drenches are so valuable for perennials.

Q. This summer, the leaves on some of my rhododendrons in Indiana are curling. Why?

A. Rhododendron leaves begin to cup and curl at the edges when temperatures rise but the water source is lacking. The leaves will be curled very tight and begin to droop. This problem is not caused by insects or disease but is a way the plant reduces water loss from its leaves during dry, windy weather. Carefully watch their watering as you can prevent this with additional waterings when the climate is hot and dry. A two inch mulch would keep the top feeder roots cool and moist, so consider this.

Gardeners who don't believe our climate is changing haven't been paying very close attention. Either that or they aren't growing rhododendrons and azaleas! Whether we're simply going through a warming cycle, dominated by higher temperatures and less precipitation, or whether the globe is really heating up, rhododendrons and azaleas aren't happy about the shift in the status quo. Former stalwarts of our gardens, these popular plants are now hurting and their distress has gardeners wondering about their future in our yards.

Leaf curl is directly attributable to drought or lack of water during dry spells. It can be prevented and the damage stopped by watering well and deeply often.

Given strong preferences for cool, moist growing conditions, it's not surprising that rhodies are sulking. Extensive but shallow root systems adapt them to the rich, well-drained soils common along riverbanks. Overhead shade and plenty of moisture in their favored environments keep them cool, content and healthy.
Shade helps some, but higher ambient air temperatures in summer are simply beyond our control. Lack of rainfall and snow cover is a real problem for them. As a result, new landscape plantings of rhododendrons and azaleas often fail to thrive and many gardeners have lost large old established plants to the elements. Even the "ironclads" like 'Roseum Elegans' and 'English Roseum' are in decline.

Keep a watchful eye on these cool-loving plants since their spring flowers are set in the latter months of summer. Keep them well-fed with an acid fertilizer, too.

Assistance from Lindsay Bond Totten

Debra writes~ I have just moved to Vermont from SC and know absolutely nothing about plants. However I am learning, and have recently purchased a rather large amount of different colored rhododendron plants. They look like azaleas, however are more hardy. I am trying to make a new yard that was covered with what the natives here call slash or trash trees look better. I have had a landscaper come in to clear out the trash, and clean up the area, but he doesn't know much about plants, just yard guy. These plants supposedly get 5'x 5' and I want to plant them like a wall against my house, and also a privacy wall between our neighbor's and our yard. Do you think this will look right, or should I just use these bushes as wall-like bushes for making the property line obvious? Thanks for your input.

A. That is your call. Rhodies should do very well for you. Check my website for a page of cultural advice as I will not repeat it here. They can be grown beautifully up against a wall, in a garden bed or used to make a privacy wall, though they will not reach a height which will totally block your neighbors. The shiny thick foliage looks good all year-round and the blooms are a tremendous added bonus. Choose hardy hybrids of various colors which appeal to you. Local nurseries should have a fair collection and you can order them from catalogs or online companies. Work the soil to a good depth and adjust the pH below 7.0 with additives and fertilizers prior to planting.