The Beginner's Guide to Planting Roses
Copyright © 2014 by McGroarty Enterprises Inc.
Written by: Kris Kremser
Several years ago I began experimenting and changing the way roses are planted and grown in my gardens. The old garden adage ‘don’t plant at $20 rose plant in a $1 hole’ was tossed into the compost heap of myths that die hard.
In the process, I have virtually eliminated the use of costly fertilizers and have saved tons of time and money, neither in plentiful supply here. The results have been not only impressive but much more sustainable as well.
Most of the websites and books about planting roses all say pretty much the same thing. The following instructions come from Ortho’s All About Roses…Dig a hole 2 feet wide by two feet deep. Replace one-third of the soil back in the hole and mix in another third with good commercial potting soil.
Fill the remainder of the hole with two parts organic compost and one part peat moss. Sure, it seems logical that peat moss, cow manure, compost, etc. would improve poor soils. After all, don’t soil amendments increase aeration, nutritional value, and water-holding capacity? Absolutely!
But only IN THE IMMEDIATE VICINITY OF THE PLANTING HOLE! Amending the soil in planting holes is eventually going to have a negative impact on the health of the plant. To understand this, let’s look at plant physiology and the reaction of water in different soil types.
As we know, an ideal soil contains 5% organic matter by volume. When planting a rose (or any landscape shrub) it is recommended to incorporate the typical 25-50 percent organic matter into the backfill.
When I first began growing roses, I took heed of this advice. The initial results were very positive. The plants grew vigorously. After all, the roots were in an ideal environment as long as they were kept well watered. But eventually, an overall decline in the growth and health of the plants was noticed.
Here’s what was happening. The roots began to encounter the interface between the soil in the planting hole and the surrounding native soil. The native soil has much less nutrients than the amended soil.
It is also much less aerated and more finely textured. Instead of leaving the hospitable environment of the soil in the planting hole and establishing into the less nutritious native soil, the roots just began to circle the interface of the amended soil much like a plant in a container.
This resulted in growth rates that were much reduced from the initial time they were planted. Admittedly, rose plants and other shrubs of mine eventually succumbed because of planting them in this way.
Watering plants that are installed in this manner soon becomes a problem. The newly created amended soil has much different properties than the native soil surrounding it. It is much more porous and better aerated than the native soil. Water flows freely through it and wicks away to the more finely textured native soil.
This becomes a concern during the hot summer months. The native soil is going to tightly hold on to the available moisture, while the moisture in the planting hole will be depleted and not replaced.
The plant then undergoes enormous water stress, a problem solved only by keeping the planting hole constantly irrigated- a practice both time consuming and impractical. Another situation also arises during periods of heavy rainfall.
The water in the amended soil will move quickly while being held back by the less porous native soil. This creates a ‘bathtub’ effect where water collects in the planting hole drowning the roots and finally killing the plant.
Another problem with planting plants in this manner is the fact that all organic material decomposes over time. If you’ve incorporated the recommended one-half or one-third organic matter by volume into the backfill, it will only be a few years until you have a sunken garden. This will only make the flooding problem worse during periods of heavy rainfall.
With the exception of plants growing in containers, there is absolutely no scientific data that indicates any benefits of adding organic amendments to the backfill of planting holes in permanent landscape installations.
Better root establishment and much more vigorous growth are both consistent in plants that are allowed to grow into the native soil. Additionally, when you consider the time involved and cost of amendments and materials needed, it is hard to justify planting in this way.
One of the best ways to incorporate organics into your rose soil is the use of mulches. While there are many different types of mulches available, I have found the use of arborist wood chips to be an easy, inexpensive, and sustainable way to keep a constant supply of nutrients in your soil.
Of all the organic mulches including grass clippings, leaves, compost, pine straw and bark mulch, wood chips are the best performers as far as weed control, moisture retention, temperature control, and sustainability. And in many areas…they are free!
Wood chips are slow decomposers. Their tissues are rich in lignin, suberin, tannins and other natural compounds. They supply nutrients slowly to your soil system and unlike bark mulch they are also capable of absorbing large amounts of water that is released slowly into the soil. Wood chips are the ultimate slow release fertilizer!
At this point you’re probably wondering why I use and recommend the use of wood mulch. After all, it ties up soil nitrogen during the breakdown process causing deficiencies in plants, right?
The reality is that wood chips do not bind up the necessary nitrogen needed by landscape plants and there is positively no scientific data to support that assumption. But, here’s where the confusion may lie.
Scientific research shows that the microbial action which helps to decompose the wood chips takes place only where the mulch meets the soil. It is only within this interface that nitrogen deficiencies occur.
This means that from the top of the soil surface to approximately one millimeter or so below the surface nitrogen levels may be too low for most plants to survive. For this reason it may not be advisable to use wood chip mulch for seedlings, in vegetable gardens, or with flowers or annuals having shallow roots.
The roots of roses and landscape shrubs are well below this interface where tests show normal nitrogen levels exist. It is important, therefore, when installing wood chip mulch to simply lay it on top without cultivating it into the soil.
To effectively keep down weeds, mulches must be applied at the proper depth. Mulches that are applied too sparingly will promote weed growth. A depth of at least four to six inches for roses and ornamental plants is recommended.
When applying wood chips in your rose beds avoid piling it against the rose canes. Doing so creates the right conditions for fungal pathogens to enter the plant. Instead, taper the mulch layer down to nearly nothing as it approaches the canes of the plant
If nitrogen deficiencies are still a concern when using wood chip mulch, you can also apply a layer of nutrient rich compost underneath your wood chips, thus creating a ‘mulch sandwich’.
This will serve to speed up the natural process. I have done this in the past using mushroom compost as a top dressing. It really isn’t necessary though, because as the wood chips break down over time they will develop the same structure.
Here are some key points to remember when planting roses and shrubs in permanent landscape installations:
About Kris Kremser: He has been involved in gardening for most of his 55 years. He's been growing roses for about 20 years. Kris enjoys exhibiting roses for competition. As an American Rose Society consulting rosarian, he writes and teaches about rose culture in the Columbia, SC area. Kris is also a member of the Greater Columbia Rose Society, the South Carolina Rose Society and the American Horticulture Society.