Creosote more harmful to plants than people

Q: I purchased a home last year that has 35-year-old used railroad ties that have been painted white on some sides and used for raised planter beds. I have heard that treated wood could leach toxins into the soil, which would not be good for a vegetable garden. Would these ties be old enough that its toxins would have already all leached out?

A: There are several methods for treating wood so that it does not decay. Your lumber is treated with creosote, which is what I think you are talking about. Discussions about railroad ties, how toxic they are to plants, whether people should use them or should not use them, are all over the board.

Some people don't think there's a problem if you keep plants six or more inches away from treated lumber. Other people think that treated lumber has a limited time when toxins come from them and are safe after a dozen years or so. Others would never use treated lumber, ever.

Now, I think you are asking for my opinion on how I view lumber treated with creosote. Creosote never has been demonstrated to be a problem with regards to plants absorbing it, then the creosote, or byproducts from it, being available to humans. It has been a problem however, if plants are growing too close to it.

Creosote, or byproducts from creosote breakdown, are generally not taken up by plants. They can damage the outside of plants but are not taken inside the plants and passed on to humans or other animals. Plants growing too close can get damaged so it is recommended to keep them a few inches from the wood.

In your particular case of creosote-treated railroad ties, I believe all you have to do is keep the plants 6 inches away from treated lumber and that's really for the plants' sake, not yours. I would point out that this is not necessarily the case with some other wood preservatives.

Q: Do you recommend using my automatic fertilizer injection system that emits a little fertilizer every time I water or using a good plant/tree fertilizer just once?

A: The biggest advantage to using a fertilizer injector, a device that meters liquid fertilizer through an irrigation system, is the savings in time and labor.

Most landscape plants can be fertilized just once during the growing season and do just fine. The exceptions would be annuals such as bedding plants, lawns and perennials like roses that bloom multiple times during the season or constantly have to put on new growth.

It makes quite a bit of sense if you have a large yard and you are paying a maintenance company a significant amount of money to do these things. It does not make much sense if your landscape is a small one and your landscape doesn't require much maintenance.

When fertilizing with an injector, the accuracy in the application of the fertilizer depends on how good your irrigation system is. If your irrigation system has a lot of wasted water or it does not deliver water accurately, then the fertilizer will not be delivered accurately either and is wasted. If you have a wide variation of plants and their needs for fertilizer also are varied, then it may not make much sense.

An injector does a much better job if you have multiple valves watering different types of plants with a varied need for fertilizer. If I could afford it and had a large landscape, I probably would use one.

Q: Do you have a good recipe for organic rose food?

A: I am taking this "organic" request literally. If it is to be an organic source, then it must be approved by Organic Materials Review Institute. If you care to search its website for approved products, you can go to https://www.omri.org/

I also am trying to recommend things that I have seen available locally. For a nitrogen source, I would use one of the organic nitrogen fertilizers such as blood meal, fish emulsion or guano. For phosphorus, you can use bone meal. For potassium, you can use greensand, which is available locally from nurseries.

To this I also would add an iron source. Now this is more complicated. Approved iron sources that work in our alkaline soils are hard to find. You cannot use any iron that contains nitrates or chlorides. According to OMRI, you must document that your plants require an iron application to apply it.

I usually use an iron chelate, iron EDDHA, at about one teaspoon per plant and water it in. Chelates are not OMRI approved but I know this particular chelate will work in any of our desert soils. Apply 2-4 inches of wood mulch to the soil surface to keep the soil biologically active. Keep the mulch a foot away from newly planted shrubs.

Q: What am I to prune off my pomegranate trees? There are many small limbs that I suspect are last year's growth, or new growth, and probably will be the fruit-bearing ones. If that is correct, should they be thinned out? My trees are still small only a couple of years old.

A: Pomegranates grow like a fountain. Suckers and water sprouts from them grow straight up. Suckers come up from the ground; water sprouts grow from other limbs.

Depending on the variety of pomegranate, these suckers and water sprouts will get flowers in one to three years and produce fruit. The weight of these fruits bend the suckers and water sprouts toward the ground. New water sprouts grow from the upper surfaces of these bent limbs and grow straight up.

This creates a plant that gets taller and taller and resembles a fountain in its growth pattern. The fountain pattern results from upright growth and subsequent bending of suckers and water sprouts.

I usually suggest keeping the number of stems coming from the ground to either one, as a single-trunked tree, or no more than about five trunks. This means that you remove at, or slightly below ground level, all but the largest of these suckers. After about three years of religiously removing suckers, this kind of growth will eventually subside.

Then, in the canopy look for water sprouts rising from trunks that are going straight up and growing rapidly. Remove these from their source, leaving no stubs. That pretty much does it.

Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at xtremehorticulture.blogspot.com.