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MASTER GARDENERS: Try some herbs indoors this winter

Days are shorter, nights are cooler, and it’s time to think about bringing plants in for the winter or providing winter protection. Herb gardens, like flower gardens, often have both perennial and annual plants in them.

Before the first frost, take the opportunity to trim back the plants and enjoy a last harvest from these herbs. As with other perennials a 2- to 5-inch layer of organic mulch such as loose compost, straw or decomposing leaves helps protect the roots and maintains moisture in the soil. Leaving a 4- to 6-inch, mulch-free circle at the plant base discourages pests. Place mulch once the ground has frozen. If the herbs are left standing all winter, the plants help hold the snow mulch in place.

Herbs hardy to Zone 3 include caraway, catnip, chamomile, chives, garlic (which is planted in the fall), hops, hyssop, horseradish, various mints, parsley, and sorrel. There are Zone 4 herbs that are hardy in our area as well including lemon balm, bee balm (monarda), sweet cicely, anise hyssop, lovage, winter savory, French tarragon and thyme. Sometimes lavender succeeds over winter as well. Parsley is considered to be a biennial, blooms the second season if it survives the winter.

There are annual herbs that reseed themselves and are often thought of as perennial such borage, coriander, dill, calendula and feverfew. They need little help until spring when they come up all over the garden and need thinning.

Tender perennial herbs such as rosemary, lavender, scented geraniums and bay laurel should be grown in pots outside in summer and may be brought indoors to winter. Before bringing these plants indoors, inspect them for insect infestation and take care of any problems. Prune any broken or injured branches. If you’ve grown parsley, sage or thyme in a pot, they can be brought into the house as well.

Bay laurel likes a sunny window and has few problems with insects although it sometimes suffers from scale. Scented geraniums are happy in a cool room and will tolerate somewhat less light. Trim them back in the fall and again in the spring if they get leggy. Water them sparingly and, as with all other plants, check for insects.

Rosemary can be difficult indoors. If the center of the plant is thinned to allow light and good air circulation, rosemary will do better over the winter. It likes as much light as it can get.

The plants will likely drop leaves after being brought indoors and most will not thrive during the darker days of winter. Don’t fertilize them and water only as necessary when the soil feels dry. Try not to use too much of the foliage during winter to keep the plant strong.

Most herbs prefer a sunny location in winter, a west or south window. A “grow lamp” or small fluorescent lamp may be needed to supplement light. If the herbs are in smaller pots, grouping the plants on a tray of moist pebbles will help provide the humidity needed in our drier winter homes.

Information on growing herbs, and many other horticultural topics can be found in the Yard and Garden section of the University of Minnesota website  <