Better Blooms on Lilacs, Dogwoods and Rhododendron
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Q. Mike: Our three lilacs are six years old and had a total of three flowering "bunches" this year,which is typical of just about every year. They are almost six feet tall and healthy (very green and lots of new growth), and get atleast six hours of sun per day (more in the middle of summer). Can you please help—before I rip them out of the ground and feed them to the compost pile?! Thank You!!
- ---Jamie in Rosman, N.C.
A. Lack of sun is the most common reason for badly blooming lilacs. "Six hours" may seem like a lot, but it's pretty close to the minimum necessary to get those huge sprays of flowers you're hoping for. And how can your plants get MORE sun in the summer?! Generally,that's when leafed-out trees turn full sun into deep shade, not the other way around. Anyway, with lilacs, the more sun the more blooms;maybe you can prune back a few other plants to let even more rays through.
Lilacs are notorious for sulking for years after planting—so don't expect blooms right away, new lilac owners! But six years is plenty long to get over it, and you say you do get pitiful little displays every year, so it could be overfeeding—which produces big plants with lots of growth but few flowers. If you're using chemical fertilizers,stop and sin no more; an inch of compost a year will provide the naturally rich soil they crave.
Prune off those few flowers right after they fade; then don't prune the plants again till next year. Pruning from June on risks cutting off buds, which of course, reduces flowering. Keep the plants well-watered during droughts; lack of summer water can cause the flower buds that are forming to dry out. And finally, lilacs bloom best in cold climates; your mild NC winters may simply be limiting your display (but making the rest of your life a LOT easier!).
Q. My rhododendron has large buds that never open. The plant gets full southern sun and the soil is rather clayish, but we try to augment with fertilizer. My spouse also likes to add topsoil to the base of the plant for some reason. The plant has been in this location for seven years. Why doesn't it bloom?
---Heidi from Green Brook, NJ
Q. I have a compact Rhododendron on the south facing side of my house. In the spring, its blossoms start out a rich, light pink, but after several days they turn white. Why? And only a small percentage of the buds produce flowers. I have examined the non-blooming buds and they look brown inside with no sign of insects. The soil is fortified with peat moss and liquid fertilizer throughout the season. The surrounding mature trees provide shade all summer long, with about two hours of sun maximum once their leaves are out. Do you have any suggestions that will enhance the appearance of this plant?
---Dr. Fred in Elkton MD
A. "Full Southern sun?" Yow! You New Joisey-ites are lucky your darn plant is still ALIVE, much less blooming. Rhodies are "under story" plants in the wild; as Dr. Fred seems to know, they thrive in the summertime shade of deciduous trees.I'm surprised the Red Cross hasn't come by to charge you with Plant Crimes for baking the poor thing—it needs shade! It also needs your husband to stop with the fertilizer and "topsoil" and to mulch with peat moss and compost to provide the NATURALLY-rich (not chemically enhanced) soil rhododendrons crave. It also needs some shade so those buds don't bake dead in the summertime; did I mention that?
Dr. Fred: Your flowers start out pink and open to white because that's what color they are. Rhododendron flowers come in virtually every color of the rainbow; and several varieties behave exactly the way you describe, including "King George"and "White Pearl". If it's really compact, I'll bet it's "Loder's White".
You also need to replace those chemical feedings with compost. And I'm a little concerned that your South-facing buds may also be cooking a bit after those protective leaves drop, but it's more likely that you just need to have a heavier hand with the water during dry times.Rhododendrons are THIRSTY plants that should be first in line for the hose when we go a week without rain; otherwise the flower buds dry out.
Q. I am baffled by two questions, and am hoping you know the answers. (1) When do I fertilize my dogwood trees? And (2) Why did some bloom and others not, even though I planted them at the same time? (They all bloomed last year.)Thanks a million,
- ---Geri in Stafford, Va.
If you're talking about chemical fertilizers, how about 'never'? Is 'never' good for you? Chemical fertilizers are one of the biggest reasons for lack of bloom on dogwoods. So wake up and smell the compost, Ger! And then give some to your trees—some peat moss too;because like many Spring blooming beauties, dogwoods thrive in a naturally rich, acidic soil. (It also takes dogwoods a REALLY long time to flower—so again, be patient new owners; it will be at least five years before you can expect a new tree to bloom.)
After that it gets tricky. Dogwoods bloom best in full sun, but the tree itself prefers afternoon shade in warmer climes, for which your Virginia certainly qualifies. Dogwoods that grow in full sun in your zone MUST be watered during dry times to prevent stress to the tree.
My best guess for your "Bizarro Boom" is that some of your trees got more sun and/or water than others last summer. Or, if they're not all the same variety, some might be the type of dogwood that only blooms every OTHER year. Or….