Q: If I put mulch around the trees, how do I apply fertilizer around the drip irrigation line? Isn't the cover in the way?

A: When we talk about watering and fertilizing at or around the drip irrigation line of the tree, we are referring to the edge of the area under the canopy. As the tree grows and spreads, the drip tube keeps away from the trunk. Watering and fertilizing on the drip line will encourage the roots to spread out, expand the root system and make it stronger.

Ideally, you should avoid planting anything (especially grass) in this area, because tree roots cannot compete with other roots. For citrus and other shallow-rooted trees, you may find that it is almost impossible to dig holes in the root zone due to root density. If you want to plant some shade-loving plants under the tree, plant them in a container that drains fast, and then place them under the tree. When you fertilize container plants, the excess fertilizer will drain from the pots and nourish the roots.

The finished compost or bark mulch should not interfere with the fertilization of the trees. Liquid fertilizer can easily penetrate into the soil, while granular fertilizer penetrates into the soil and dissolves.

If you use organic materials that are still actively decomposing, watch for signs of nitrogen deficiency, such as yellowing of the leaves and slow growth. Bacteria that decompose organic matter need nitrogen in this process, so nitrogen may need to be supplemented.

Q: Should you remove the moldy sawdust last year?

Answer: Sawdust, like any other organic mulch, will eventually decompose and become part of the soil. Fungi (and molds) are part of this process. If mold grows in your mulch, you may need to replenish the mulch as the old thing breaks down. Nature will dispose of the old mulch, so you don't have to discard it.

If you like fishing and need night walkers, you can find some very large ones under the old mulch!

Question: My nectarine tree is five years old. It never bears fruit. This year it bloomed pink and white flowers, but they fell and still no results. Is it worth keeping this tree? 

Answer: If you haven't harvested any fruit at all, your tree may not have enough winter cold. Peach and nectarine trees are usually self-pollinated (but produce more fruit through pollination), so even if your tree is lonely, it should give you at least some fruit.

I recommend removing this tree and replacing it with a low-cold variety. For information on low temperature fruit trees, please visit

https://www.davewilson.com/home-garden/fruit-variety-recommendations/toms-picks-winners-low-chill-southwest/

Is there a problem? Email gardening@scng.com.

Looking for more gardening tips? Here is how to contact the Master Gardener Program in your area.

mglosangeleshelpline@ucdavis.edu; 626-586-1988; http://celosangeles.ucanr.edu/UC_Master_Gardener_Program/

ucceocmghotline@ucanr.edu; 949-809-9760; http://mgorange.ucanr.edu/

anrmgriverside@ucanr.edu; 951-683-6491 extension 231; https://ucanr.edu/sites/RiversideMG/

mgsanbern@ucanr.edu; 909-387-2182; http://mgsb.ucanr.edu/

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