|Though I tilled manure, peat moss, and top soil into a newly established bed (over red clay) about 6-12 inches, it displays poor drainage. It does slope down. Nevertheless, it stays wet. Some plants are doing very well despite the wet soil--little Richard, nandina, other shrubs, day lilies, etc. I'm concerned mostly about my standardized Knock-out rose. The foliage is yellowing. It has flowered profusely but is now resting. I recently fertilized. I chose to plant it because of its disease/insect resistance. So far I'm not impressed. Is the wet soil the culprit? What other things could be affecting its health? The heat? The Japanese beetles? Verbena and penta are planted in the same area and likewise are suffering. How can I amend the soil to make it drain better (if that is the problem)? Can you suggest flowering plants that are not affected by poorly drained soil? It's strange because other parts of the same bed drain better. Thanks for your attention to this matter.|
|Lack of sunshine, poorly draining soils, lack of fertility, are all causes for yellowing foliage on roses. Since you've recently fertilized, this may correct the problem.
Outside of putting in a curtain drain to redirect the excess moisture, there's no easy way to improve poor drainage. If you're not quite up to having everything regraded or installing a curtain drain, you might concentrate on plants that will tolerate the conditions. As a matter of fact, there are really quite a few shrubs that will tolerate clay soils. Here's a list: Deciduous shrubs Berberis thunbergii, Japanese Barberry Chaenomeles japonica, Flowering Quince Cornus sericea, Red or Yellow Twig Dogwood Corylus avellana, Harry Lauders Walking Stick Cotinus coggygria, Smokebush Euonymus alatus, Burning Bush Forsythia intermedia, Forsythia Hydrangea macrophylla, Hydranga Spiraea bumalda, Spirea Viburnum sp., Viburnums Weigela florida, Flowering Weigela. Evergreen shrubs: Buxus microphylla, Korean Boxwood Chamaecyparis pisifera, Plume Cypress, Cotoneaster, Ilex glabra, Inkberry Mahonia aquifolium, Oregon Grape Holly Picea abies varieties, Dwarf Norway Spruce Hope one (or more) fit the bill!