A Southwest Harbor gardener has several rosemary plants, one of which bloomed for the first time in January, covering itself in heavenly blue florets. He wonders: Was it something he did or perhaps something he said, that made the herb burst into flower, and why didn’t the others follow suit?

Rosmarinus officinalis is an Old World plant that gets its generic name from the fact that it grows in thickets along the Mediterranean shore (rose plus marine). Sailors of old are said to have known when they were near land because they could smell the rosemary wafting across the water. Indeed, the plant is extra generous in its production of a resinous essence to the point that the leaves are quite sticky to the touch.

So if rosemary is a Mediterranean plant, it must prefer a Mediterranean climate. California is said to have such a climate, but Maine clearly does not. I think the essential difference is that summers are hot and dry and winters are cool (not cold) and wet in the Mediterranean, but it could be just the other way around. In any case, Southwest Harbor’s climate is clearly superior, and rosemary is just going to have to adapt. Cool foggy summers and hot, dry, centrally heated indoor winters are the new order of the day!

Seriously now, our rosemary plants are most apt to bloom in winter, which is their normal time to do so, in response to the shorter day length presumably. But with being shuffled around from greenhouse to greenhouse in the cooler months and put out for summer, the plants do become confused and may put on a second bloom in summer or almost any time of year. I suspect that the Southwest Harborian’s other plants will bloom when they grow a little older.

There are dozens of named varieties of rosemary, and if the flowers become the chief attraction, one ought to seek out the white- and pink-flowered forms. Tuscan Blue is supposed to have the deepest blue flowers and Sawyer’s Selection grows very vigorously up to 8 feet with mauve-blue blossoms.

Incidentally, there is a Spanish legend that a rosemary bush sheltered Mary on her flight to Egypt, and when she spread her cloak over the herb, its white flowers turned blue. Nowadays, natives of the region sometimes spread their linen over rosemary bushes to imbue the cloth with fragrance, which acts as a natural moth repellent.

Rosemary is easily grown from seed, if one is patient. Germination rates of only 10 percent are considered satisfactory by this herbalist, so it’s best to be generous at sowing time. And don’t forget to cut the growing medium with one-quarter to one-third sand. If you grow a few dozen seedlings, you will undoubtedly be impressed with the variability among plants. Some grow straight up like Lombardy poplars, others branch thickly like Scotch pines. Occasionally one will grow more or less horizontally, making an excellent subject for a hanging basket.

Arp, Texas, gave its name to the hardiest of rosemary selections, hardy to zero, at least. Has anyone out there tried to overwinter Arp in the ground in Maine? A styrofoam rose cone and a sheltered spot might make it possible.

We recently suffered a catastrophic outbreak of powdery mildew in our rosemary collection, and since the greenhouse is more than ideal for the spread of the disease, it was necessary to discard all the plants. Fungicides are not especially effective against rosemary powdery mildew, and we don’t like the idea of using them as an herb anyhow. The plants were sent to PERC rather than composted because the fungus is quite able to overwinter outdoors and reinfect from a considerable distance.

A nifty culinary use of rosemary is to pick a sprig and use it to paint barbecue sauce on chicken, ribs or whatever. Then toss the sprig on the fire to release the last of its flavor in the form of aromatic smoke.

Michael Zuck is a horticulturist and the NEWS garden columnist. Send inquiries to him at 2106 Essex St., Bangor 04401.