Purple coneflowers grow wild in many parts of North America.

Purple coneflowers were used extensively by Native Americans to treat a variety of maladies. Its botanical name Echinacea purpurea comes from the Greek echinos, (their word for hedgehog) which refers to the spiny-like center of the flower, and the Latin purpurea which refers to its purple-red color.

Echinacea purpurea are perennials that grow to a height of 2 to 3 feet. They are often propagated by root division, but are just as easily started from seed. Plants started from seed will bloom in October the first year and in July thereafter.

Plant echinacea in full sun to part shade in fertile loamy soil, although they will grow in clay or sandy soil. They are relatively drought resistant, but will show signs of wilting if the soil becomes excessively dry.

Divide the plants by digging up and dividing the roots every 4 to 5 years.

Purple coneflowers attract a variety of different bees and butterflies. Goldfinches eat the mature seeds in early fall. Their pointy seed heads add a unique component to dried flower arrangements.

They were used by Native Americans to treat everything from toothaches to colds to minor cuts, wounds and burns. Rather than using the plant’s parts to make a healing tea, the roots were chewed or the foliage was mashed up and made into a salve.

European settlers adopted the use of the plant for medicinal purposes until it fell out of use in the 1930’s. It has been re-discovered in recent years primarily as a cold and flu preventative, although its medicinal uses are far more extensive than that.

The juice of the roots was mixed with water and sprinkled on hot coals in traditional Native American “sweat lodges” for purification purposes. It is regarded today as an antibiotic and blood purifier which builds up the immune system. Some claim it provides immunity to a host of non-specific diseases.

Scientific research has not yet determined the exact compounds in purple coneflower that give it medicinal properties, but a long history of use in traditional folk medicine suggests that it is, in fact, effective as a medicinal herb.

Perennial baby's breath spilling over a hillside onto the sidewalk below.

Perennial baby’s breath adds a light, airy presence to your urban garden. The tiny flowers and delicate stems of Gypsophila paniculata seem to hover in the air like little fairies.

In the language of flowers, baby’s breath stands for everlasting love, pureness and innocence. It is often found as a filler in bouquets of flowers, particularly red roses.

Baby’s breath is native to Eurasia but has escaped cultivation and become naturalized in much of North America. In the Great Plains it is considered an invasive plant because it can take over fields, vacant lots and roadside ditches.

The baby’s breath in the picture above is a single plant growing on a small hillside in a front yard. It has outgrown its allotted space and landed on the public sidewalk below.

Perennial baby’s breath is usually grown from seed or division. Double forms are grafted onto seedling rootstock because the seeds do not reliably come true to their parents.

Plant these delicate looking wildflowers in full sun with moist, moderately fertile and well-drained soil. Add limestone if your soil is at all acid. Let them dry out between waterings, but don’t let them get overly dry.

They will grow slowly the first year and begin to produce showy blooms like in the accompanying photo after the second year. Unlike most other flowering perennials, they only need to be divided every 5 or 6 years.

Cut them back after they finish blooming in late June or early July. Keep them watered and give them a side dressing of compost and they will most likely bloom for you again later in the summer.

You can make your hydrangeas turn pink or blue, depending on how you amend the soil.

Hydrangeas are those large, bush-type perennials with the giant flower heads in either white, pink, or blue. They’re also called “mophead” or “lacecap.”

Fossil records show that hydrangeas grew in North America between 40 and 70 million years ago, and about 25 million years ago in Asia.

They bloom in mid to late summer and keep their flowers long after their leaves drop off in fall. The flowers look spectacular on the plants for winter interest in the garden, or cut and dried for indoor flower arrangements.

Plant hydrangeas in full sun to partial shade in moist, rich, loamy soil that is well drained. Add generous amounts of compost when transplanting and top dress with compost every spring.

The name “hydrangea” comes from the Greek words hydro (water) and angeion (vase) or “water vase.” The name doesn’t refer to the flowers; it refers to the shape of the seed capsule.

Hydrangeas are unusual in that you can change the color of their flowers by changing the pH of the soil in which they grow.

To make hydrangeas flowers pink like the ones in the photo above, raise the pH of their soil. Do this by adding dolomitic lime to the soil several times a year (available at garden supply stores). Follow the manufacturer’s instructions for correct quantities and add that amount to the soil around each plant in spring, summer and fall.

Another thing to do to keep your hydrangeas blooming pink is to use a fertilizer that is high is phosphorus (the second number on the fertilizer label—for example 10-15-10).

If blue hydrangeas are what you are after, add aluminum sulfate (a soil additive available at garden supply stores) to the soil in which they are growing. Mix 1 tablespoon aluminum sulfate with one gallon of water and apply a half gallon of this mixture to the soil around each plant. Caution: water your hydrangeas well the day before you do this so the roots can more easily take up the aluminum sulfate without getting burnt. Apply the aluminum sulfate mixture to the soil in spring, summer and fall.

To help keep your hydrangeas blooming blue, use a fertilizer that is low in phosphorus (the second number on the fertilizer label) and high in potassium (the third number on the fertilizer label). For example, use a fertilizer labeled 25-5-30.  Avoid using superphosphates or bone meal if trying for blue hydrangeas.

If your best efforts to turn hydrangeas either pink or blue result in them turning the opposite color, the culprit is most likely your water. Water that has a high pH will tend to produce pink hydrangeas; conversely, water with a lower pH will tend to produce blue hydrangeas—both in spite of soil amendments to the contrary.

Finally, hydrangeas planted near a concrete foundation or walk will tend to bloom pink because of the considerable amount of lime leaching out of the concrete, which raises the pH of the soil.

One last note on changing the color of hydrangeas: white hydrangeas will always be white and cannot be changed to pink or blue.

Cold-hardy cactus growing in Minneapolis.

It’s amazing what you find on a leisurely stroll through an urban neighborhood. Imagine my surprise when I found the cactus in the photo at right spilling over the retaining wall of a neighbor’s front yard.

So enchanted was I that I didn’t even see her dogs until they startled me. They turned out to be friendly, but their barking brought the owner of the cactus out of the house.

She told me that she had brought it from Phoenix last spring. She had simply dug it up out of her yard there. When she got here she plopped it into a perennial bed, which is where I found it.

There are many cold-hardy varieties of cactus native to the mountains and high deserts of the southwestern United States and Mexico. Many are hardy to 25 degrees below zero.

I know that our winter temperatures were not colder than that this past year. We also had a consistent snow cover, which no doubt helped to protect the cactus from extreme temperatures.

If you want to try to grow hardy cactus in your urban garden, you’ll find several sites online that offer small plants.

Cactus need good drainage. They prefer to grow in poor, unimproved soil where the water drains away quickly after it rains. If your soil is a heavy clay resign yourself to the fact that it will be difficult, if not impossible, to successfully grow cactus.

Plant them in full sun. They do best in raised beds or at the edge of a retaining wall that faces southwest. That’s exactly where this cactus is growing.

Gently shake off any soil that is clinging to the roots. Plant cactus like you do iris, in a shallow hole just barely below the surface of the surrounding soil. Spread the roots out evenly and backfill so that the crown is just above the surface of the soil. Gently jiggle the plant back and forth to settle the dirt around the roots. Do not firm the soil with your hands.

Wait a day or two after transplanting before watering. This gives it a chance to callus over.

In early fall stop watering, although natural rainfall is OK. Cactus need a dry period before winter to toughen up. This helps them more easily survive winter’s freezing temperatures.

Don’t write them off too early when spring comes around. This cactus didn’t break into bud until late May. My neighbor had given it up for dead. She said it looked shriveled. Then suddenly it sprouted new growth.

I think the buds look like the tips of asparagus.