Extension Master GardenerSM Volunteers of Buncombe County

Herb Gardens

Oh Sweet Basil – Don’t let Basil Downy Mildew Spoil Your Harvest!

Healthy Sweet Basil

If you love pesto and other recipes that feature sweet basil (Ocimum basilicum) you may already be looking forward to growing your own plants this summer!

Growing your own
Basil is an herb with tropical origins, so wait until after the last frost to sow seed or transplant starts into moist, well-drained soils in full sun. After the first few sets of leaves form, pinch back the tips to encourage bushy growth. Remove any flower buds for best flavor and to keep the plants producing more leaves. Harvest stems of leaves as needed; harvest entire top growth before frost.

Basil problems
Although insect pests are not usually much of a problem—aphids and Japanese beetles can do some damage, especially if your plants are just getting established—diseases are a concern!

  • Basil Downy Mildew (BDM). Basil downy mildew (BDM) is caused by the fungus-like organism, Peronospora belbahrii that reproduces from spores spread by the wind and through seed saved from infected plants. BDM does not overwinter in Western North Carolina, but as the temperatures and humidity rise each spring, it is only a matter of time before winds bring it north.
    How to identify:
    – Leaf color changes—resembles nutritional problems that manifest as a yellowing or browning of leaves.
    – Dark spores on the underside of leaves—can be seen even without a microscope or hand lens.
  • Fusarium wilt. Fusarium wilt (Fusarium oxysporum f. sp. Basilicum) is a soil and seed-borne disease that affects plants after they have grown normally to about 6 to 12 inches tall.
    How to identify:
    – Growth becomes stunted or wilts.
    – Stems show brown streaks and bend like shepherd’s crooks.

Preventing Basil Disease Problems
Prevention starts with healthy seed! Some seed companies test basil seed lots for fusarium wilt to reduce the risk of seed-borne illness.

Resistant varieties. There are also fusarium-resistant and BDM-resistant basil varieties. NC Extension Master Gardeners conducted trials in 2022 to compare five BDM resistant varieties (‘Rutgers Devotion,’‘Rutgers Obsession,’‘Rutgers Passion,’‘Rutgers Thunderstruck,’and ‘Prospera’) with the popular ‘Genovese’ variety.

In this project all of the resistant varieties remained disease free, while ‘Genovese’ was infested beginning in many locations in August (note that in 2019 Buncombe County reported BDM began in July)!

The resistant varieties compared favorably to ‘Genovese’ in taste tests and the top varieties were described as follows:

‘Prospera’—Growing taller and more upright than other varieties, Prospera was the overall favorite among the BDM-resistant cultivars. Some thought it needed staking because of its taller stature and a few volunteers reported stems breaking during storms.

‘Rutgers Passion’—This variety received positive comments on its color, aroma, plant vigor, and good branching habit.

‘Rutgers Obsession’—There was overall satisfaction with this cultivar based on its color and slightly more compact growth habit. It proved to be a solid BDM-resistant alternative to ‘Genovese’ and was the highest rated variety in taste tests.

Extension Master Gardener Volunteers Recommend These Varieties

Cultivation practices.

  • Do not replant basil where soils may harbor Fusarium oxysporum f. sp. Basilicum, which may persist in soils for 8 to 12 years!
  • Avoid overhead watering, which may contribute to disease spread.
  • Fungicides that are available to home gardeners are not very useful in preventing disease.

Article by Barbara Hayes and Debbie Green, Extension Master GardenerSM Volunteers.

For more information:

NCSU Plant Toolbox:  https://plants.ces.ncsu.edu/plants/ocimum-basilicum/

BDM resistant varieties
https://emgv.ces.ncsu.edu/2023/05/planting-basil-extension-master-gardener-volunteers-recommend-these-varieties/
New Sweet Basil Varieties from Rutgers University

Basil diseases:
NCSU Basil Downy Mildew Fact Sheet:  https://content.ces.ncsu.edu/basil-downy-mildew
https://www.buncombemastergardener.org/?s=basil+downy+mildew
https://growingsmallfarms.ces.ncsu.edu/growingsmallfarms-fusariumbasil/

 

Gardening Video: Growing and Using Culinary Herbs

Gardening in the Mountains presents:
Growing and Using Culinary Herbs

Presenter: Phil Roudebush, Extension Master GardenerSM Volunteer

Herbs are commonly grown in gardens and containers for a variety of uses. This presentation will provide general information about growing and using herbs with a focus on those used for culinary purposes. You’ll get Ideas about how to process and use culinary herbs year-round. Recipes for making various types of herb pesto, vinegar, butter, rubs, and oils will be discussed and provided in a handout.

Video access:
To access this video on the Buncombe County Master Gardener website, click on the link below:

Growing and Using Culinary Herbs

Or go to www.buncombemastergardener.org , click on the ‘Gardening Videos’ tab at the top of the page and select the video from the list provided.

Fresh Herbs at Your Doorstep

I love having fresh herbs right outside my kitchen door to snip when I’m cooking. It is surprisingly easy to grow a large variety of culinary and tea herbs in a small space. Here’s how.

Herb Garden Near Door for Easy Snipping_by DWood
Herb garden near kitchen door for easy snipping

Which herbs to grow?
Perennials. Choose from many culinary herbs such as oregano, thyme, sage, chives, rosemary (‘Arp’ variety does best in WNC), lavender, and mint. A word of caution: to avoid mint invading your entire garden, plant it in a container.

Biennials. Parsley is a biennial herb that many gardeners replant every year. The first year you will have the delicious leaves and the second year it goes to seed.

Annuals. The most common annual herbs are basil, dill, chamomile, and cilantro.

Plants or seeds?
In general, perennial herb transplants are readily available. Most annual herbs start readily from seed.

Herb Garden in Container_by Frances Carter_CC_Flickr
Herb garden planted in container

Grow herbs in a container or in the ground?
Either! If you are limited on space or sun, consider containers. I have good success with metal tubs that you can find at most hardware and big box stores. You can pack lots of herb plants into a large tub. Just remember to punch holes in the bottom for drainage—a hammer and nail work great. You can also plant several herbs in a 14-16-inch round or square planter with drainage holes. Use 3 parts potting mix (NO fertilizer or moisture beads) and 1 part organic matter—such as compost or leaf mold—mixed into the top half of the container.

For in-ground growing, choose a space that drains well. A 3-foot by 3-foot area can easily accommodate 8 to 10 perennial herbs. Work organic matter into the top 4-6 inches of the soil and you’re ready to plant.

Herb Garden in Raised Beds_by Kyla Kae_CC_Flickr
Herb garden planted in raised bed

Growing conditions
Group herbs that have like growing needs together. Most herbs require 6 or more hours of sun a day, but dill and cilantro can tolerate partial shade. Perennial herbs prefer hot dry conditions. Biennial and annual herbs require more water and organic matter.

Fortunately, herbs have few pests or insects. 

Harvesting herbs
You can harvest up to 75% of a season’s growth at one time. Clip herbs in the early morning for best flavor. Cut perennial herbs for use until one month before the first projected frost date to avoid stimulating new growth that may not harden before winter. Harvest annual herbs right up until frost.

Harvest flowers, such as chamomile and lavender, before they are in full bloom. This maximizes flavor and shelf life. To encourage a second fall flowering of lavender, harvest the flowers in early summer, then cut back young plants by half their height and older plants by one-third. Do not cut into the woody, brown stem of lavender or it may not generate new growth.

Use fresh-cut herbs and flowers in cooking or diffused in water for teas. Use 2-3 times the amount you would use of dried herbs.

Preserving
Drying is the traditional way to preserve herbs. Use a food dehydrator, or tie a small bunch of stems together with string and hang upside down in a warm, dry spot, with good air circulation, out of direct sunlight. When the herbs are completely dry and brittle, store them in glass jars for up to one year.

Freezing chopped fresh herbs or flowers in water in ice cube trays is another great way to preserve the herbs. When you need herbs, just drop the cubes in soups, stews, sauces, or water for tea. 

Winterizing
Perennial herbs should survive the winter without additional protection, if planted out of direct winds and lightly mulched.

Learn more
Horticulture Information Leaflet, “Growing Herbs for the Home Garden”, NC State Extension Horticulture Publication.
https://content.ces.ncsu.edu/static/publication/js/pdf_js/web/viewer.html?slug=growing-herbs-for-the-home-gardener

Horticulture Information Leaflet, “Harvesting and Preserving Herbs for the Home Gardener”, NC State Extension Horticulture Publication.
https://content.ces.ncsu.edu/harvesting-and-preserving-herbs-for-the-home-gardener

Horticulture Information Leaflet, “Winterizing the Herb Garden”, NC State Extension Horticulture Publication.
https://content.ces.ncsu.edu/winterizing-the-herb-garden

Cornell Book of Herbs and Edible Flowers by Jeanne Mackin, Cornell Cooperative Extension, Ithaca, New York, 1963.

Article written by Debbie Wood, Extension Master GardenerSM Volunteer.

Contact Us

Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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