Lydia J. asks, what are the very tall, spiky-looking plants with purplish flowers that grow in mass near the coast? I have also seen some with the same tall shape but with rose-colored blossoms. Can I grow them in Santa Rosa?

These stately and beautiful plants are called Pride of Madeira (purplish-blue) and Tower of Jewels (pinkish). Yes, they do thrive in the tough conditions near the seashore with its sandy soil, wind and salt spray, but they will also thrive in the warm inland areas of Sonoma County.

The shrub, Pride of Madeira, botanically known as Echium candicans, is easy to grow and readily reseeds, so cut off the flowering spikes when they fade and collect the seeds, or let the seeds fall and be surprised with new starts in unexpected places. The hairy, grey-green mounding foliage remains and each spring new flower spikes grow. It needs room to grow as it can reach a height of 5 to 6 feet and equally as wide. Bees are attracted to Pride of Madeira.

Echium wildpretii, Tower of Jewels, is a biennial. When its flowers die, the entire plant dies. New seeds that have dropped to the ground will germinate, form grey narrow leaves and bloom the second season in mid to late spring. This plant is very tall, 6 to 10 feet, but only 1 to 2 feet wide.

Both plants should receive weekly water during the hotter months; otherwise, little care is required.

Cathi Shudde writes: What effect do products for controlling aphids, spider mites, etc., like neem oil have on the bees and other beneficial insects? What about the environmentally friendly products for slugs and snails on salamanders?

I'm very good at raising aphids, spider mites, earwigs, slugs and snails. I don't use anything that is not organic and pet friendly, but still worry about how to use these products to control the insects without adversely affecting the garden-friendly residents like salamanders, bees, etc.

My first advice to you is visit a garden center, nursery or business that carries organic products, and read the label on the various organic product containers — such as neem oil. It will also have on the front label a word such as CAUTION (a label received from the federal Environmental Protection Agency), which means the least toxic. The labels will give you a long list of precautions, correct applications and timing of controls; this applies to organic products as well.

The following information is from the National Pesticide Information Center:

Neem oil is practically non-toxic to birds, mammals, bees and plants. Neem oil is slightly toxic to fish and other aquatic organisms. Azadirachtin, a component of neem oil, is moderately toxic to fish and other aquatic animals. It is important to remember that insects must eat the treated plant to be killed. Therefore, bees and other pollinators are not likely to be harmed.

About beneficial insects: Beneficial insects don't eat your plants so they are not ingesting the product. But you can still kill beneficial insects if you smother them with neem oil spray. Beware that neem can also repel bees and butterflies. Beneficials are most active during the day, so sprays should only be used early in the morning or evening so they can dry before the good insects become active.

Sluggo, an iron phosphate product, should not harm salamanders since they are carnivorous. They are not ingesting treated plant material, but after reading label warnings, what is the effect of neem on aquatic animals other than fish? Another question to ponder.

Following are two references that are helpful for controlling pests:

1) Pests of Landscape Trees and Shrubs, An Integrated Pest Management Guide, Second Edition written by Steve H. Dreistadt. This is University of California publication #3359.

2) The Organic Gardener's Handbook of Natural Pest and Disease Control, A Complete Guide to Maintaining a Healthy Garden and Yard the Earth-Friendly Way by Fern Marshall Bradley, Barbara W. Ellis and Deborah L. Martin.

Send your gardening questions to The Garden Doctors at pdgardendoctor@gmail.com. The Garden Doctors can answer questions only through their column, which appears twice a month in the newspaper and online at pressdemocrat.com.