Garden Docs: All types of rosemary plants are great for cooking, edible?

Nadine asks: “I have a tall ‘Tuscan Blue' rosemary plant; can I use it for cooking?”

Yes. All of the rosemary herbs can be used for cooking. The leaves on this variety are wide and very aromatic and especially nice to use on the barbecue.

Joseph M. writes: “Would topping or heading back poplar trees stop the roots from running rampant through my lawn and garden and possibly into my septic tank?”

All the poplars are known for their rapid growth and invasive root systems and are not recommended for city streets, lawns or small gardens. They definitely shouldn't be planted near water features, swimming pools, sewer lines, septic tanks or leach lines.

If a crack develops, (no matter how small) in irrigation lines, sewer pipes or water mains, the roots from the poplar tree will find the fissure, damage the pipes by enlarging the crack and completely plug and fill it up with roots.

“Topping” or “heading back” is the most popular way to reduce the tree's size, but will do nothing to control the roots.

Topping means cutting back to a stub, a lateral bud or a small lateral branch. Re-growth is vigorous and upright from the stubs.

The new branches form a compact head or canopy, cast dense shade and are weakly attached to the older ones; sadly the tree loses its natural form.

Jim L. asks: “What is the best milkweed plant (Asclepias) for attracting butterflies?”

Narrowleaf milkweed is the preferred larval food for Monarch butterflies. Showy milkweed has showier flowers, as the name suggest. It is a California native.

Why plant milkweed? The plant attracts egg laying Monarch females. Planting a variety of milkweed - the more the better for optimum success. Cal Flora nursery and Emerisa are excellent sources for milkweed plants, particularly since their plants are free of treated insecticides and Bacillus thuringiensis (known as Bt - a non-toxic, naturally occurring biological larvacide). The effects of Bt can last up to 2 weeks. Always ask your local nurseries if their plants have been treated with insecticides.

Birds avoid eating Monarch caterpillars and adults because the Monarchs have fed on the toxic and poisonous milky sap from the milkweed; they are a distasteful snack.

In humans, handling the milky sap when planting can cause a contact dermatitis.

Milkweed is also poisonous to dogs, cat, horses, cattle and other grazing animals.

Julie West, our local butterfly “guru” offers additional non-native and native nectar plant selections for the garden. She grows all of these successfully and they have attracted Monarch butterflies and other varieties of butterflies. Her picks include: Red valerian, abelia, lantana, heliotrope, marigold, zinnias, scabiosa and mints. Among the native plants: asters, goldenrod, brodiaea, coffeeberry, bacharris, wild sweet fennel and monardella.

A butterfly garden is a stop and go site for critters passing through, so plant to attract butterflies, eliminate toxic sprays and enjoy their beauty while they are there.

Daniel A. asks: “I purchased a gorgeous staghorn fern at a local plant sale. I now have it hung on a fence in a shady area. Can you give me any additional advice on its care. It is too important to lose! The fern is mounted on a flat piece of wood with chicken wire wrapped around the wood with a wire hanger making it easy to hang.”

Your staghorn fern, Platycerium bifurcatum, is an Epiphyte. Epiphytes thrive and grow on other plants in their native environment. They absorb water and nutrients through their fronds (fern leaves) that develop from spores on the lower part of the frond in the form of brown fuzz! They are not parasitic plants meaning they do not use nutrients from the other plants that support them.

Staghorn ferns have round plate-like leaves that surround the base of the plant. Their function is to protect the roots, take up water and nutrients. Dried brown plates are part of its growth cycle; don't be tidy and remove the “plates”.

Platycerium bifurcatum requires bright, indirect or diffused light and no direct sun. One usually sees these unusual ferns shaped like stag horns hung in protected entryways that have an eastern exposure.

Water can be applied through misting, focusing on the undersides of the fronds. Or, using a watering can, water from the top until the fern root-ball is saturated and feels heavier. So allow the fern to drain before rehanging the shady location.

In cooler months, plan om watering every 2 to 3 weeks.

Tucking a piece of banana behind the fronds and the round plate-like leaves has some nutrient benefits. This was a tip given to me by Mary Brown who grows staghorn ferns successfully.

For more information try the website pistilnursery.com.

Dana Lozano and Gwen Kilchherr are garden consultants. 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.