I have a rose, 'Poulsen's Pearl' Poulsen 1949, growing in a container 14 x 14 x 16" deep. It blooms ok, but the leaves are yellow between the veins. Both new and old leaves are this way, but the new leaves especially so. I was told there was not good enough drainage, so I moved the pot up so it drains easily and that helped for a while. But now the leaves have turned yellow again. The soil is from the garden with much clay mixed in with organic matter. The rose behaved very well in the garden with this same soil. It's been fertilized with Rosetone in spring and Peters 20-20-20 diluted 1:2 in July with no improvement. A cutting from this plant, rooted, and planted in the garden soil is doing very well. What[s wrong with the container grown plant? How can I fix it?
Soil is often too dense and heavy for container use. Since you are saying yours has a noticeable clay content it will certainly be unsuitable. Replace with a soilless potting medium.
Interesting. I gave it a shot of Miracid and it's greening up nicely. Also put on some more new flower buds. I guess it was just hungry.
Your container grown rose is underfed. Rosetone is advertised as a "slow release" fertilizer. But still, a single application will not last much more than a month. In fact, the package instructions suggest monthly aplication. In a container, once the nutrients are leached out by rain and irrigation water, there isn't much else for the rose to rely on. And most roses are heavy feeders. Your single application of a soluble fertilser won't salvage the situation either. It's usually not a good idea to use garden soil, especially if clayey, in containers. You have far better control over the drainage properties and aeration if you use a soil-less mix. Something like Scots' Sunshine #4, for example. And drainage itself is depending on the nature of potting media, not how high off the ground the container is. In addition, the excessive weight associated with garden soil is a real disadvantage. Your only option is to repot the plant. However, this may not be a good time to do it. Giving it a new lease of life may encourage the production of tender young shoots which will be winter killed unless you intend to bring the pot into a frost free area (the garage, for example). You could give it a weekly application of a soluble fertiliser like Miracle Gro, half strength until first frost, let it go dormant, then repot in the spring. Make sure that you knock off the "old" potting soil, and use a fresh soil less media. My formula for spring repotting of containder grown roses is Sunshine #4 mix, bone meal, Osmocote (or any other granulated slow release fertiliser would do), alfalfa meal and, some water absorbant polymer crystals. By the end of June, after the first flush of flowers, I start a regular application once every week of a soluble feed, usually Miracle Gro. When potting up a rose, I place a 1/2 inch layer of lava rock (lighter than pebbles) in the bottom of container, then line this with a layer of landscape fabric. It presumably helps to prevent waterlogging of the potting medium. More importantly, I find it easier to extricate the root ball from the container when it comes time for repotting.
