Hi all, I'm hoping you can help me preempt a gardening problem I've had for 3 years running. I have a front hedge of alternating Pieris Japonica (I think its 'lily of the valley') and Spirea 'Gold Flame'. The east and west sides of the hedge are separated by a cement walkway. At the end of the west side there are 3-4 large cedar trees that have been there forever. Since the second year after they were planted, the Pieris plants on the west side keep dying (see picture of how it starts). The foliage barely settles in before they they start getting crispy and die altogether. The Pieris plants on the east side are just fine. The associated Spirea plants are fine, although you could say the ones among the dying Pieris plants are slightly stunted compared to the counterparts in the east. Last year I got fed up and ripped out all of the Pieris plants (I took no chances) and replaced them with new ones. By the end of the summer, same thing...the ones on the west started dying. Last 2 years running I have sprayed various insect killers/soaps, antifungals, miracle grow, you name it. I've watered conservatively to prevent root rot. I'm at a loss on how to deal with this. Help?!? Worse comes to worse, what can I replace the Pieris plants with to still have something perennial + hardy + contrasting + similar height to the Spirea? * it seems i'm having the same problem as Coast.....though no solution yet...... http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=61274
From your photo it looks as if there is an oddity about the soil -- is it in a black rich garden soil from a packaged soil mixture, surrounded by gravel? Or just darkened from moisture from an irrigation nozzle. I think I see an irrigation nozzle but I'm not sure. If the soil isn't an acid mix, with some well and pre-moistened bark/peat in it, I don't think the Pieris would do too well. They tend to like a loose mulchy soil mixed in with pre-soaked and moist peat and bark pieces from mulch, and topped by mulch. The Forsythia would be ok either way. I have been cautioned before in this Forum to get soil tested in a lab, and I intend to do so, but it is not cheap and it has to be done judiciously to serve a number of plantings, so I have not got round to that yet -- but in this case I certainly would promptly. Searching "soil testing labs Greater Vancouver" should bring up some, or a good nursery would help you find one. You may have put in a limed packaged mix, or mix meant for potted perennials, and the lime would not be good for Pieris, contributing towards a neutral or even slightly alkaline soil. You want a lower pH for acid soil. Make sure there is no weed-killer or weed-'n-feed type compound being used nearby. Also, I wouldn't spray the plant with spray liquid fertilizers meant for bedding plants in a neutral soil. If you change the soil, just mix some azalea and rhododenron fertilizer in pellets in with it -- and water well. Someone here may also suggest other soil acidifiers but I think you should get the soil tested quickly. Let us know what happens.
Never plant in small amended holes surrounded by different material. Plant with the same soil throughout the entire rooting area. Use fertilizers and other chemicals carefully on heath family plants, including Pieris sp. Most occur in nature on soils heavily affected by precipitation, low in nitrogen and calcium. On Yaku Jima, home of now the now much favored garden shrub Rhododendron metternichii yakushimanum mountain streams are lined with P. japonica - in an area where the summer precipitation is already very high. Going easy on the water is not what P. japonica likes in our region at all, same as with many other commonly planted heaths such as rhododendrons and azaleas. Such plants are correctly placed in a highly aerated, porous substrate and then watered liberally during summer drought. Root rot from water molds is avoided by providing excellent aeration and drainage, and in the case of this group keeping the roots cool as well. Hot + wet = rot. Not integral to this discussion but note also that lily-of-the-valley shrub is a common name for this plant and therefore not presented in single quotes. Those are used instead to indicate cultivar names.
Another potential problem is the presence of the large Cedar trees at the west end where you're having problems. I assume that you are referring to Western Red Cedar, which has roots that damage the growth of many types of plants. Aside from drying out the soil, the roots are actually toxic to many species. I planted a Box hedge along the front of my property when I first moved in, and there was a Cedar growing near one end. The affect of the Cedar was obvious from the height of the hedge after a year. The plants closest to the Cedar hardly grew at all. After I removed the Cedar, the hedge eventually evened out.
I wondered about that. I have a large old Camellia near some cedars [also near my foundation slab] which stand tall fairly close by the Camellia and the townhouse -- [this suburb of Saanich has strict native tree non-removal guidelines for large native trees unless they definitely threaten the structures]. This Camellia buds but does not bloom -- the buds just don't fully open. I have fertilized and watered this one this past Fall and early Spring, but the buds may not open -- some look close to opening, but not sure they will. However, don't rhododendrons do ok near cedars? It is the first time I've heard they may be toxic to other plants.
Sorry for the confusion. What you're seeing is actually really good soil with composted bark mulch on top. The discoloration is just water from the soaker hose! I fear having to re-replace that hedge if it is indeed the cedar. If they are so toxic, what else would work there? I really like the color contrast with the perennial spirea and evergreen pieris that lasts through the winter to at least give a partial hedge.
I think you should get the soil tested. It will cost maybe $35-$50, but you need to know if it's contaminated or out of whack somehow. There should be a lab in your area that would do it -- ask at the most professional nursery you know near you... or Google "soil testing labs Greater Vancouver" or "soil testing labs British Columbia" and make some phone calls, if one isn't near you they may know of one which is... Are you sure no weed-killer was used in the vicinity? No one dumped a chemical waste, paint-thinner, or oil or gasoline in the soil there?
I've been pretty careful to water only as needed to prevent any mold from overly wet soil. Besides, both sides of the hedge get watered evenly so it would not make sense if only one side had mold. flameonglass, i have no idea what type of composted bark mulch it is. like looking outside right now, the spirea plants on the affected side are less dense than the ones on the non-cedar side. the pieris plants are just starting to bloom whereas they have been blooming for a while on the non-cedar side. at the end of the day, i can't do anything about the cedars (they're like 50 year old beautiful trees) but I need a solution for the hedge -- and of course a cost-effective one. I love love love the spirea plants so those ain't going anywhere!
So all the pieris plants between the spireas aren't growing so well...seems to be the cedars making them unhappy. I would really like to have a proper hedge this year so I'm ready to toss them and replace them with another plant. Suggestions for an evergreen shrub to go between spirea plants? Would a Choisya type plant work (cultivar?)?
