Garden columnist Dan Gill answers readers' questions each week. To send a question, email Gill at gnogardening@agcenter.lsu.edu.

I need to add mulch to my landscaping. I have used crushed pine straw in the past but find it pricey. I like the look, but budgetwise, I need a cheaper mulch. Also, is it necessary to remove the old mulch before adding the new? Ive been told that is the proper way to do it. Ruth Finley

Feel free to use a less expensive option. It is more important that you apply the mulch 2 to 3 inches thick than what type you use.

Do not remove the old mulch before spreading the new mulch. Spread the fresh mulch right over the old decaying mulch so that together the old mulch and new mulch form a layer 2 to 3 inches thick.

The layer of decomposing mulch is beneficial to the soil and the plants growing in the bed. Also, it saves you money because you don't have to add as much new mulch.

I was out of town for a week and returned to see a lot of brown stems where flowers had been on my cannas. I see no evidence that more flowers will open on the stalks with brown flowers. Should I cut the stalk off, and if so, how much? Wilma Stark

In gardening, we remove unattractive, faded flowers from our blooming plants, a process called deadheading. Yes, you may deadhead the cannas. It will make the planting look much neater and attractive.

You may do this two ways. Cut off the old flower stalk with faded flowers and seed pods back just to the first leaf.

But know that every shoot that a canna grows up from the ground blooms only once. New shoots that grow up over the summer will continue the floral display, but shoots that have already bloomed will not bloom again.

So, you also have the option of cutting a shoot that has already bloomed back all the way to the ground, removing it completely. This can be done to shoots that begin to look tired and unattractive or to thin out the growth to make room for new shoots.

Recently, I fertilized my outdoor potted plants with Miracle-Gro brand fertilizer. Several hours later, it rained hard but briefly. I was wondering if the rain likely washed the nutrients out of the soil. Judi

Im sure the rain did leach out some of the fertilizer. But the last time you watered the plants did, too. Minerals provided by soluble fertilizers are leached out of the soil and lost every time you water your container plants (or they get rained on). This is unavoidable.

Soluble fertilizers provide mineral nutrients in solution, and that makes them immediately available to be absorbed by the roots of plants. Thats a good thing. But because they are water soluble, it also means that they leach easily from the soil. That is why you need to reapply a soluble fertilizer every two weeks.

To avoid the need to fertilize containers so often, you can choose to use a slow release or controlled release fertilizer such as Osmocote or other brands. These fertilizers slowly release mineral nutrients over a long period of time. You need to apply them to containers only once at the beginning of the growing season.

Our large live oak was struck by lightning. Both sides of the trunk had bark damage. I don't know if there is anything I need to do for the tree. Phil and Sandra Van

Im so sorry to hear your old oak was struck by lightning. There is not much that can be done to help a tree that has been struck. Sometimes a struck tree will die in the months after the strike, but often they survive.

Remove (cut away) any loose bark, being careful not to pull off any bark still attached. If it survives the strike, fertilize the tree or have it professionally fertilized in February.

Ajuga makes a delightful ground cover, but it may be attacked by Southern blight.

AJUGA BLIGHT:Southern blight will attack plantings of ajuga this time of year, especially if the weather is rainy. Individual plants or whole areas of a planting will suddenly wilt and die. This disease is fairly common, and that makes the extensive use of this otherwise delightful ground cover questionable here.

HEAT STRESS: Some bedding plants may look a little stressed now. Blame the heat, both day and night. Many bedding plants (especially the tender perennials we grow as annuals) can be cut back in August. They will revive as the weather cools and provide color until November or longer.

PROTECT THE DECK: Container plants should not be placed directly onto wooden decks. The moisture underneath can damage the wood (saucers do the same thing). Boost pots off the surface an inch or two with pieces of brick or special pot supports (sometimes called pot feet) available at some nurseries and garden centers and online.

WATCH THE AZALEAS: Keep an eye out for azalea caterpillars, which are showing up on the north shore. These black and white caterpillars with red heads can virtually strip azalea bushes.

North shore gardeners should monitor their azaleas for damage and the presence of azalea caterpillars regularly. Treat with BT (Dipel, Thuricide) or spinosad these two insecticides are the least toxic choices or one of the pyrethroids, such as permethrin or bifenthrin, for quicker knock down.

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Using enough mulch is more important than what type you use: Dan Gill explains - NOLA.com