Apply iron now for growth next spring

You should have any of your stone fruit trees such as peaches, nectarines and apricots pruned and fertilized by Feb. 1. I would put roses in that category as well. You could delay pruning and fertilizing other fruit trees such as apples and pears and most ornamental plants until later in the month.

Don't forget your early iron fertilizer applications, which are applied to the soil and watered in. Iron needs to be available to plants as soon as growth begins in the spring.

Iron products that are sprayed on plants need to be applied when they are actively growing and should be applied multiple times to get good results. Just because your plant did not green up after a single application of iron liquid does not mean you should give up. Some plants do not green up as easily as others. Always use a liquid spreader when applying iron liquids to foliage.

I would not dethatch a lawn this time of year. Although it can be done successfully now, thatching a lawn will open it up to spring-germinating weeds such as crabgrass and spurge. Dethatching is really best done during the fall .

However, now is a really great time to aerate lawns. Aeration will help push grass roots deeper provided you are stretching your irrigations longer between applications. This helps to develop heat tolerance in fescue lawns.

Q: I use Superthrive on my indoor plants. Since I only have a few, the bottle is little used and is about 5 years old. Is it still effective? How long do fertilizers keep their potency in the desert?

A: As long as fertilizers remain dry, they can be kept indefinitely. Nitrogen, in particular, can be released as a gas from the fertilizer once it is moistened and there are warm temperatures. Moisture also may cause fertilizer ingredients to interact with one another once they are wet.

Superthrive is different. The manufacturer of this product tells people point-blank on its expanded label that it is not a fertilizer. It also is recommended that this product be combined with any normal fertilizer program. Because Superthrive claims to contain vitamins and hormones, the shelf life of a product like this will, most likely, be limited. If I had this product, I would keep it refrigerated, but I found no references regarding its storage anywhere.

Discussions of trademarked products in my column are not endorsements.

Q: I have many plants and trees on my property that thrive from the care I have given them for the past 11 years. What is your opinion for planting gardenias in our area?

A: As far as gardenias are concerned, they are not plants that I would recommend for a gardener who does not get involved with his landscape very often. Gardenias are fun plants for those willing to spend the time, energy and money they will need for them to be successful here.

Planting a few of them in an appropriate location, amending the soil thoroughly and giving them regular attention would be a tremendous learning experience. Expect that you may not be successful the first few times that you try them, but you will learn a lot about growing plants that are borderline in our desert environment. This knowledge will help you understand how to grow other plants that are difficult to grow here.

Q: In my neighborhood is a house with three large saguaro cacti. They are at least 30 feet tall and very big around. One of the huge ones is splitting. What should be done?

A: Splitting of saguaro cactus is most likely due to frequent overwatering. These cacti have ridges and furrows running vertically along with their trunks and stems so that they can expand and contract like an accordion.

When water is available, saguaro cactus stems expand with stored water. When water is no longer available from the roots, stored water in the trunk and limbs is used for survival, ultimately causing the trunks and stems to contract.

Applying water frequently never gives the trunk and stems a chance to contract. As it grows, the already-expanded trunk splits.

Water these plants less often. They are shallow rooted, so water them deeply and apply it quite a distance away from the trunk. This will help keep the trunk sturdy and prevent it from possibly falling over. Watering this large cactus close to the trunk could be dangerous.

Another possibility is bacterial necrosis, but the split would be foul smelling with ooze coming from it and flies attracted to it.

There is nothing you can do about a split saguaro. It should heal on its own if you follow good irrigation practices.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at extremehort@aol.com.