Growing Herbs at High Altitude
Susan Fernalld, Mountain Master Gardener
Gardeners like to grow herbs for their beauty, fragrance, and seasoning in cooking. How does one grow herbs at high altitude (over 7500 feet) where the growing season is shortened, temperatures are cooler, and water is scarcer?
Moisture and soil factors
Mountain soils naturally provide good drainage, a plus for growing herbs. As plants go, herbs have “low to average” water needs, but in our arid environment this may mean herbs need supplemental water to survive. Tips on growing these without using well water include: direct downspout drainage to disperse via soaker hoses through your garden. Add organic material such as manure or compost to rocky soil to retain moisture longer. Mulch around plants to slow evaporation.
Short season strategies
To compensate for the shorter growing season in the high country, start perennials from young plants in early summer. Some perennial herbs that aren’t hardy in our high altitude USDA hardiness zones (3-4) are grown as annuals, or we grow them in containers and bring them inside to over-winter. Start annuals from seed in early summer. Alternatively, sow them in a cold frame in the fall to take advantage of the greater natural precipitation during fall and winter. Seedlings will emerge the following spring ready to be thinned and eventually transplanted into the warm garden. Most herbs need six hours of sun after 10 o’clock daily. Some, such as basil, rosemary, and dill, need protection from drying winds. Find sheltered spots for them in the garden, or grow them in containers that can be moved around according to the conditions.
To keep non-native herbs corralled, prevent self-seeding by trimming back annuals when flowers are beginning to fade. Border perennials with deep edging, or keep their roots from spreading too far afield by planting them in five-gallon nursery containers (bottoms cut off) sunk into the ground.
Harvesting and preserving.
Harvest herbs in the morning after the dew is off the plant and essential oils are at their highest concentrations. Hang herb bundles in a cool, dry place. Remove the completely dry foliage or seed and store in labeled, airtight and dark containers. Dried herbs store well up to a year.
(Adapted from Fact sheet 9.335 by P. Kendall)
|Basil (Ocimum basilicum)
|Tender annual. Grown in several varieties for leaves with different flavors. Attractive to bees and butterflies.
|Plant seeds in well-drained, medium-rich soil. Likes sunny, sheltered spot. Space mature plants 12 inches apart. Plant in rich soil and clip to first pair of leaves from base. May be grown in containers inside and out.
|Chervil (Anthriscus cerefolium)
|Annual. Resembles a fine-leaved parsley and fennel combined. Leaves have a light licorice, peppery flavor.
|Plant seeds in shade or part shade. Avoid transplanting. Thin plants to 9 inches apart. May be grown in containers indoors or out.
|Chives (Allium schoenoprasum)
|Native perennial (USDA Zone 3). Flowers in early summer. Similar to green onion, but milder and finer leaves. Don’t grow Garlic Chives (Allium tuberosum) which can be invasive.
|Plant bulbs or starter clumps in light, medium-rich soil in sunny place. Cut flower stalks to the ground after blooming. Thin clumps every third spring. Space mature plants 5 inches apart. Transfer some clumps to grow in containers indoors or out.
|Dill (Anethum graveolens)
|Annual. Feathery foliage, flower umbels. Grows 2-3 feet tall. Grown for both foliage and seed, although it may not have time to form seed at high altitude. Attractive to bees and butterflies.
|Plant seeds in medium-rich, sandy, well-drained soil in sun. Needs wind protection. Avoid transplanting. Thin seedlings to 12 inches apart. Stake when 18 inches tall. Do not plant near fennel or they may cross-pollinate. May self-seed.
|Fennel (Foeniculum vulgare)
|Annual. At high altitude grow it for the leaves with their slightly anise taste. Flowers appear toward fall. Attractive to bees and butterflies.
|Plant seed in well-drained soil in sunny spot. Thin seedlings to 2 feet apart. Makes a good container plant indoors or out when kept trimmed to 12 inches.
|Marjoram, sweet (Origanum majorana)
|Perennial (USDA Zone 7) treated as an annual since it is not hardy in our Zones 3-4. Small bush with white flowers. Gray-green leaves with slightly bitter undertone. Attractive to bees, butterflies, and birds.
|Plant in medium-rich soil. Requires shade until well started, then full sun. Space mature plants 8-10 inches apart. May be grown in containers and brought indoors to overwinter.
|Mint (Mentha piperita ‘Chocolate,’ ‘Peppermint,’ and ‘Lavender’
and native Monarda fistulosa
|Perennial. (Varieties listed here are hardy to USDA Zone 3.) Grown for leaves. Refreshing odor and flavor. Attractive to bees and butterflies. Deer avoid it. Nepeta cataria (catmint) is hardy here as well.
|Plant seedlings in rich, moist soil. To prevent invasiveness, do not allow it to go to seed. (Cut back plant severely as flowers begin to fade). Can be grown in containers indoors as well.
|Oregano (Oreganum vulgare)
|Perennial (USDA Zone 5) treated as an annual since it is not hardy in our Zones 3-4. Grown for leaves. Flavor similar to sweet marjoram, but stronger and more sage-like.
|Plant in light, well-drained soil in full sun. Shelter from cold winds. Space mature plants 12 inches apart. Can be grown in containers indoors or out if roots given enough room.
|Parsley (Petroselinum crispum)
|Annual. Grown for finely curled, aromatic leaves. Attractive to bees and butterflies.
|Plant in medium-rich soil in sun or part shade. Seeds best started in cold frame or window box. Space mature plants 6-8 inches. Good in pots indoors or out if roots given enough room. Keep leaves producing by never allowing plant to flower.
|Rosemary (Rosmarinus officinalis)
|Perennial (USDA Zone 7) treated as an annual since it is not hardy in our Zones 3-4. Pine-like bush in mint family. Pale blue flowers. Leaves have a spicy odor and warm, piney flavor. Attractive to bees and butterflies.
|Plant seedlings one each in containers using well-drained soil. Place in a sunny, sheltered spot. Bring inside in the winter and place in a bright sunny window.
|Sage (Salvia officinalis)
|Perennial (USDA Zone 5). Grown for leaves. Don’t use Western U.S. varieties (Artemisia spp), as these taste like turpentine. Attractive to bees and butterflies.
|Plant small plants in well-drained soil in full sun. Can be grown in containers indoors or out in full sun. Can be brought inside as a houseplant in a sunny window to overwinter.
|Summer savory (Satureja hortensis)
|Annual. Bushy plant with long, narrow leaves and weak, woody stems. Use only young leaves. Attractive to bees.
|Plant in medium-rich soil in sun. Thin seedlings to 6 inches apart. Can be grown in containers indoors or out.
|Tarragon (Artemisia dracunculus)
|Perennial (USDA Zone 4). Slender, dark green leaves with sweet anise scent. Considered essential in many French dishes.
|Plant in well-drained soil in full sun. Propagate by root divisions. Space mature plants 3 feet apart. Subdivide every three years. Can be grown in containers indoors or out if roots given enough room. Does not like wet feet.
|Thyme (Thymus vulgaris)
|Perennial (USDA Zone 4). Small shrub with tiny, brownish-green leaves. The leaves have unexcelled aroma and flavor. Attractive to bees and butterflies.
|Plant small plants in well-drained soil in full sun. Clip back each spring. Space mature plants 10 inches apart. May be grown in containers indoors and out.