Maximizing Your Herb Garden - Maintenance

Formal Herb Garden (Photo from St Louis Mag, by JJ Lane)

If you've put in an Herb garden or started them up in containers - a little maintenance can really improve your harvest.  While I envy a large formal herb garden like the one shown on the right - I need to maximize a much smaller place. That means some work year round. Good news is that herb plants, general have low maintenance requirements. All one needs to do during the growing season is remove weeds, provide water, perhaps mulch or fertilize, and prune/harvest.  Below see more details on these steps and other considerations.

Plant movement - change placement  

Plant facts will say these herbs need full sun: Basil, Borage, Caraway, Catnip, Cilantro/coriander, Dill, Fennel, Lavender, Mustard, Oregano, Rosemary, Sage, Summer Savory, Tarragon, and thyme.  

Sunshine Lavender Farm

These herbs need partial sun: Beebalm (bergamot), chamomile, chervil, chives, echinacea, garlic, lemon balm, lemon verbena, marjoram, mint, Parsley.  That said, Beebalm grows just fine for me in part shade. And I've been successful with echinacea and garlic in full sun. 

Sometimes plants do not thrive because they are not getting enough light or the wrong amount of water. Assuming that you can fix the water situation - a little tweak to placement may make a big change in plant health.  You may consider moving the containers or moving the plants. I do not suggest moving a plant more than twice a year. 

Fertilizing  An outside (in the ground) herb garden may not need much fertilizer depending on your soil. However but herbs grown in containers will require a bit of extra care which is typical with container gardening. Container grown plants continuously use up nutrients and need a time-release organic fertilizer or a liquid fertilizer.  

Please consider - don't over-fertilize herbs. Too big of plants means more work for you pruning, harvesting, preserving. It may force them to flower sooner. And it may make dilute the flavor if the plants get too straggly. Avoid fertilizing late in the growing season.

Everyone loves Parsley

Guard against Insects and Pests 
Herb plants can be used as part of an integrated pest management program. The smell and oils from herbs can deter to garden insect pests. However, that doesn't mean that your herb plants will be pest free themselves! As you work around the garden keep an eye out for  pest problems on your herb plants.  Many insects like Aphids, leaf miners and spider mites will feed on the plants. You may not see the bug but you will see the result of their munching - that is  leaf spotting or stippling marks or leaf curling damage.  If you see signs of inset pests you can spraying the infected plant with insecticidal soap (or your own soap mixture). You need to make sure to get all sides of the leaves and plan including underside and inside leaves/stems.  Some pests, like caterpillars will become butterflies :)

Here is a listing of some common pests for popular herbs, treatment should be organic and appropriate for edible crops:

• Basil: Aphids and slugs love basil. Treat with chemical sprays. Reduce moisture and have good air circulation to reduce fungus.
• Chives: Sometimes gets aphids which can be hosed off.
• Cilantro: May be powdery mildew which is treated with fungicides 
• Marjoram: Aphids, spider mites are common. Treat with insecticidal soap. Prevent fungal problems with good air circulation and water so that leaves dry by evening.
• Oregano: Aphids, leaf-miners and spider mites are common on plants grown in containers. Treat with pesticide.
• Parsley: Watch out for caterpillars and fungal disease. Remove infected leaves and apply fungicides early.
• Rosemary: Whitefly and spider mites are treated with organic pest controls. Control water conditions to reduce botrytis rot. Remove rotting plants.
• Sage: Slugs and spider mites can be controlled with diatomaceous earth. Other issues include powdery mildew and verticillium wilt. Sage needs good drainage and air circulation.
• Tarragon: Powdery mildew and downy mildew may attack tarragon. Reduce this with  good air circulation and watering so that it to dries by evening.
• Thyme: Spider mites and aphids like thyme especially the underside of leaves (and they are small and hard to spot) I see the leaf damage. Knock pests off with a heavy blast of water or use insecticidal soap. 

Pruning Herb Plants 

Post pruning lavender - From LongCreekHerbs.com

For all type of herbs - continually inspect and remove yellowing leaves and those damaged by pests. Then determine what type of herb you have because that will determine how you should prune to maintain your plant. (Pruning is different from harvesting. Pruning is cutting back to maintain the plant.) There is a good article on lavender and sage here.  

• Perennial Herbaceous Herbs (that's funny to type!): these die back to the ground in winter. No pruning necessary  just chop it to the ground when when harvesting or to get rid of the flowers.  They can be decimated several times a year to reduce old and dead branches. This includes Bee Balm, Chives, Oregano, Sweet Fennel, Winter Savory, Tarragon, and (the evil) Mint. Maybe an all Herbaceous culinary Herb garden would be a good idea. Except for the mint. Keep it out of the garden and in a well confined area, like a pot suspended in mid air. This plant is invasive and should NEVER be planted in your garden.
• Perennial Evergreen Herb Plants: these stay green year round. Examples are  Rosemary, Thyme and Sage. They only require pruning at once a year. In early spring,  cut back old  branches without signs of new growth.  Also trim out branches to increase airflow (avoid lots of crisscrossed branches.)   Don't let the branches get too tall and woody - they won't produce the leaves you are after. If you can remove old in favor of shorter and leafier branches that's a good move. This will revitalize your herb plant. Prune only about one third of the foliage at a time. Always cut to a point that still has growth showing. 
• Annual Herbs (depends on your location):  These plants last only for one season and then must be replanted the next year.  Some annuals (in my cold climate garden) include Basil, Chervil, Cilantro and Dill.  These plants will "go to seed" each year before it dies.Once an annual starts to make flowers it is difficult to make get it to produce of leaves. If flowers/seeds are present, all the energy goes into seed production.  Also when an herb begins to flower the leaves can yellow or become change in flavor.  So by pinching out the growing tips of herbs such as basil (Ocimum), the plant bushes out. You may need to prune or harvest regularly to keep the plant growing leaves instead of flowers. See my blog post on preserving your fresh herbs. 

Weeding Your Herb Garden   It almost goes without saying - but I wrote it anyway. Yes, weeding the herb garden is a must, if only to make harvesting easier! You can take down weeding needs through application of straw, leaf clippings or mulch. 

Preparing for winter, aka Winterizing your herb garden 
In a cold climate garden some extra steps are helpful to put the herb garden to sleep for the winter. Herbs can have shallow roots that are easily damage by the freeze/ thaw cycle. Mulching in protects and keep herbs safer from the cold. After the ground is frozen, spread a loose mulch up to four-inches deep. Avoid material that will pack down and get mushy during the winter months - like grass clippings or shredded leaves. This gets too much moisture and may cause herb plants to rot.  If it gets too compacted, herbs will have difficulty growing up in spring. Remove the mulch after there are seen signs of new growth in spring. 

Happy Day
Teresa Marie

PS BTW the St Louis Botanic Garden and Chicago Botanic Garden have really awesome herb gardens