Green Patch: Rosemary, Sage and Basil Growing Problems Solved

Your growing problems—solved!

| February/March 2011

  • Are your basil leaves turning yellow? Is your garden sage having trouble staying alive? Have your rosemary leaves fallen off? Keep your herbs thriving with our expert advice.

• Sidebar: 5 Common Herb Diseases 
• Learn the Visual Symptoms of Basil Downy Mildew
• Report Your Observation: Make Report  

Q. My rosemary limbs have lost leaves from the bottom sections. Knobby growths, which look like root sprouts, are growing out from the stems. What is happening with my rosemary?

A. These rosemary disease symptoms are called “stem knot” and are caused by a systemic bacterial infection. According to Arthur Tucker and Thomas DeBaggio, in The Encyclopedia of Herbs, there is no cure; in fact, the cause is unknown, although it resembles bacterial infections caused by Pseudomonas, Agrobacterium and Xanthomonas species. These systemic types of infection are difficult to control because they grow from the inside out. However, infected plants can live for many years if good practices are followed. Prune the diseased stems back to healthy growth during the early spring. Be sure to disinfect pruning tools by dipping them in a 10 percent chlorine bleach solution or rubbing alcohol between each cut. Do not use organic material around the base of the plants. Choose coarse sand, crushed oyster shell, lava rock or white marble chunks for mulch instead. Remove all fallen tree leaves and do not allow weeds and other plants to block air circulation around the rosemary. Keep enjoying your rosemary by whipping up the rosemary mayonnaise recipe on Page 80.

Q. I am not able to keep garden sage in the ground for longer than one season in my humid Arkansas garden. The leaves and stems turn black overnight and the plants die. Is there anything I can do to grow sage and similar culinary perennials?

A.  It is possible for herb gardeners in the Eastern United States to develop a successful garden spot for sage and other gray/green Mediterranean
natives. First of all, get to know the enemy. As a group, the fungal diseases that cause this fatal symptom are aptly called “sudden wilt.” They live in the soil, on seed and on almost any surface. The diseases are spread by spores and are passed on to plants by fingers, pruning tools, air currents and in water droplets.

Never replant sage or any other perennial Mediterranean herb in the same place where sudden wilt has taken a victim. Begin a new herb bed in a well-drained, full-sun location. Incorporate aggregates such as sharp sand and gravel to improve drainage. Use mineral-based mulch (rather than materials that come from plants, such as tree bark or straw) around sage. Organic mulch holds moisture longer than rocks.

3/2/2014 2:33:32 PM

I read somewhere not to plant sage and basil together. Is this right, and if so, why? Thanks

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