When growing bird of paradise as a shrub, only prune frost-damaged limbs.

Inger Sandal / Arizona Daily Star

In my plot I have fava beans growing and flowering nicely but seemingly finding it impossible to convert the flower to a bean pod?

A: Fava beans or broad beans are a cool-season crop that grows best in temperatures as low as 40 degrees and as warm as 75 degrees. They can be planted in early spring or late summer in our area. If we have a cold winter they might need protection from frost. Too much fertilizer or too high temperatures can cause the problem you describe. Fertilizer is not required at planting if you plant into a fertile, composted soil. Legumes such as fava beans are able to fix nitrogen from the soil. It would be good to give them a light dose of fertilizer after the first harvest to improve the quality of the second harvest. Once harvested, I hear they go well with liver and a nice Chianti.

What is the proper way to prune bird of paradise? I neglected to cut back my red bird of paradise last winter and I’d appreciate advice on promoting the most blooms. Should I now cut back to the newest bright green growth?

A: When grown as a shrub, pruning is necessary only to remove frost-damaged limbs. More pruning will be needed if the Mexican bird of paradise is to be developed and maintained as a small tree. Once blooming is finished, the flower stalks on all three species may be removed to prevent seedpods from forming and to reduce the likelihood of volunteer seedlings. Because the red bird of paradise generally dies back to ground during Tucson’s winter months, mulching the base of the plant in colder areas of the city may be done to protect the plant’s crown until spring.

I have a mature Arizona sweet orange tree (a Marrs semi-dwarf) in my backyard. It’s never done great, usually produces small size oranges, but it’s done OK and the fruit in good years is very tasty — like it was this winter. But it often seems to lose leaves and get sparse after flowering and fruiting, and this year is no exception. Is this a problem?

A: The Marrs variety is known for its small and early maturing oranges. The cause of defoliation could be a few things, the most common being underwatering, overwatering, and underfertilization. Watering should be in the zone of the absorbing roots of the tree. This is the area near the edge of the crown of the tree and beyond. The watering schedule should be every seven to 10 days in summer, every 10 to 14 days in spring and fall, and every 14 to 21 days in winter. The depth of the water should reach 36 inches in all cases for mature citrus trees. To measure this we recommend a soil probe of some sort. We use a piece of rebar and push it down near where the crown of the tree extends until we feel resistance and that is generally how far your water is reaching. The fertilization schedule we recommend is three times per year, around January/February, April/May, and August/September. The amount of fertilizer recommended for a mature orange tree is 1ƒ pounds of nitrogen for the entire year, so split this in thirds and apply half a pound of nitrogen each time.

Peter Warren is the urban horticulture agent for the Pima County Cooperative Extension at the University of Arizona. He works with landscape professionals, urban farmers and homeowners to promote integrated pest management and best management practices for desert horticulture in southern Arizona. Questions can be sent to plwarren@cals.arizona.edu