Question: I use Jobe spikes to fertilize my fruit and nut trees. Last year I fertilized in mid-February and when I went to fertilize again at the end of May, I noticed the February spikes were not used up. I use drip irrigation and put the spikes near the emitters. How long do I need to wait between refertilizing with the spikes?

Answer: It depends. Fertilizers in a solid spike or granular form are going to dissolve as a result of exposure to water and warm temperatures. The manufacturer typically recommends applying them at the drip line of your trees so that rain falling off the tree or drip irrigation properly installed there will help dissolve the fertilizer. If we have a cooler spring or not much winter rain, it’s possible the spikes will last longer than advertised. Also, you probably don’t need to fertilize throughout the year. Mature trees don’t need much fertilizer and they are able to get many nutrients from the soil. A late winter application will likely suffice for the year.

Question: We are contemplating purchasing a home in Green Valley. There is a beautiful white oak in the front yard about 15 feet away from the home. There is a root lifting the brick pavers. How or what should I do to make sure the roots aren’t going under the foundation. Also, could I dig up that root and cut it so it doesn’t do any more damage, without hurting the tree?

Answer: The Arizona white oak (Quercus arizonica) is a beautiful tree, but unfortunately someone planted it too close to the house. The mature size of that species can be as wide as 50 feet. The problem you described could get worse as the tree matures. You should probably hire a certified arborist to take a look at the tree and determine the gravity of the situation. Some companies have an air spade to temporarily blow away the surface soil to get a better sense of where the roots are and which ones are expendable, if any. Some roots are critical to the stability of the tree so you wouldn’t want to cut away one that is preventing the tree from falling over.

Question: I have a problem with deer entering our yard and eating the flowers in our patio container pots. I have tried a spray-on repellent, but it hasn’t worked. A fence is not possible. Any suggestions?

Answer: Fencing is the gold standard for protecting plants from deer. Otherwise, it is a bit more of a challenge. Some people use repellents with limited success because the deer either get used to the smell or the repellent wears off. If you want to try other repellents, some people hang small cloth bags with fragrant soap in them from outside branches. Others use various types of predator urine. You could also get a big dog that will bark at the deer as needed. Another tactic is to alter your landscape so the plants are difficult to access. This might be accomplished by putting the containers behind something else that blocks the deer. If there is enough other food nearby, they may see it’s too much trouble and change their route.

Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com