When tending roses and other plants that prefer somewhat acidic soils, it's important to understand the type of soil you're planting in.
Soils, particularly in the West and Southwest, but also in other parts of North America, and elsewhere in the world, tend to have high pH balances, and are high in alkaline.
So is your soil alkaline or acidic? Probably the best way to find out is to have your soil tested. You can do this by purchasing a soil testing kit, or, for a similar amount of money, you can have it tested by your cooperative extension service (in the U.S.) or by your area agricultural college or university. You can find your Cooperative Extension Service in your phone book under "county" entries, or you can go to this USDA site for a list of county extension offices.
If you already have roses planted and suspect you have an excess of alkali salts in your soil, look for browning of tips and margins of older leaves. This is a symptom of salt burn. In many cases, the browning may grow to encompass the whole leaf. Generally speaking, salt burn is more common in clay soils than in sandy soils.
How do you get rid of the alkali salts? Heavy irrigation leaching is the first step. This will wash out soluble particles of sodium and chlorine. Adding sulfur to your soil (one lb. to every 40 square feet) will help make the alkali salts more soluble. You will also need to insure that you have good drainage. Without good drainage, alkali salts can accumulate again.
You also need to be aware of the origins and treatment of the water used in irrigation. There may be an excessive amount of chlorine (used as an antibacterial agent) in your water supply. You may also be using a salt-amplified water softener in your home. Either of these elements may create havoc, not only with your roses, but with other plants as well.
A way to handle excess chlorine is to have a holding tank for irrigation purposes, which will allow the chlorine to dissipate. For water softeners, you may want to bypass your softener apparatus for your plant watering supply.
Another problem with roses (and other plants as well) is that alkaline soils and limestone deposits tend to interfere with the plant's ability to intake iron. This can lead to iron chlorosis. You can identify iron chlorosis by looking at the leaves. If the leaves are turning yellow, but the veins of the leaves are still green, changes are you have iron chlorosis.
There may be iron present in the soil, but the plant roots cannot absorb it. Addition of an iron chelate (from the Greek chelas = claw), a form of iron which will bind to water molecules and can be taken in by the roots, should resolve the problem.
Many desert soils are low in, or almost entirely devoid of, organic materials. Adding organic material to the soil, particularly tight clay soils like caliche or adobe, will make the clay become loose and crumbly, adding to its water-holding capacity, and allowing more room for roots to grow.
Barnyard manure has been highly touted as being good for roses, and I'm not here to deny that. However, peat, compost, leaf mold and decomposed sawdust work as well. The thing about barnyard manure is that it's usually more available and less expensive than other organic material.
A word of caution here: never apply manure around your rose roots as you are planting them unless it has been composted for at least a year. Composting will kill harmful bacteria and weed seeds and further break down nutrients. Manure from feed lots also contains an excess of sodium, so be careful where your barnyard manure comes from.
Next article: Fertilizing Roses
See also:
- Plant Roses in A Desert Garden
- Watering Desert Garden Roses
- Fertilize Desert Garden Roses
- Rose Pests and Diseases
