How To Fertilize And Water Herb Plants
Though most herbs don't require much fertilizer, at some point they will need it. Herbs produce the most oils when they are given a steady feeding of a slow acting fertilizer such as fish emulsion, bone meal, cottonseed meal or blood meal. Add it to the soil at time of planting or potting. These natural fertilizers break down slowly and provide herbs with nutrition, but at a slow pace, thus providing healthy growth and helping produce the flavors we look for.

Herbs do not like constantly soggy soil so make sure to plant them in well-drained soil. Soil conditioners or compost can be mixed in with poorer soils at planting time to provide better drainage and supply beneficial nutrients to the plants. To ensure good drainage, I usually plant herbs in a raised or mounded garden bed similar to the methid I use for planting annual flower beds. 

Feeding Tips and Instructions

First, evaluate soil conditions

There's usually not a need to perform a soil test before planting or fertilizing herbs; however, it may be a good idea to research the various types of herb plants you have growing in your garden to see if there are any specific nutritional needs. Some herbs like an acid soil while others like an alkaline soil.

Testing Soil pH  Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. If you're unsure about the pH of your soil, or whether or not it is suitable for growing your herb plants, it's a good idea to test the pH in the planting area. You can quickly test soil pH with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil at planting time and regularly as a mulch can also help to increase acidity and maintain acid soil conditions.

Feeding herbs in the garden

In general, herbs you grow in garden soil will not require much fertilization. Herbs can often get much of their nutrient needs from the native soil. Be aware that many herbs will produce poor quality flavors and aromas if fertilized too heavily, particularly when synthetic, fast-release fertilizers are used.

At planting time, you can fertilize your herb plants with a solution of fish emulsion, and then on an as-needed basis throughout the season. Well-rotted, or composted manure can be used as fertilizer early in the season as a slow-released source of nutrients.

Feeding herbs growing in containers

In general, herbs you grow in containers will need more fertilization because they have no other way to get additional nutrients once they've used up what's in the pot.

First things first, make sure you grow potted herbs in a light, well-drained, premium potting mix. Avoid those cheap, dollar-a-bag potting soils. Too, make sure the pot has drainage holes. If there is no hole(s) drill one at 3/4" diameter.

Be careful not to over-water! Allow herbs growing in pots to dry out a little between waterings.

Organic fertilizers are recommended over synthetic because synthetic fertilizers usually contain a lot of salts, and this can build up over time in potting soil.For efficiency, your potted herbs can be fed every two weeks with a liquid fertilizer such as fish emulsion, mixed at full strength as suggested on the product label.

Other Helpful Tips

Avoid late-season fertilization which can stimulate new growth that could be damaged by a frost, compromising overall health of the plant. A good rule of thumb is to cease fertilization two months prior to the average first frost date in your area. 

Pruning and harvesting of perennial herbs should be done during spring and summer; avoid excessively cutting of plants after mid fall. 

If you are really serious about growing herbs, the best thing you can do is buy a good book on herb growing. A book will not only introduce you to herbs you had no idea existed and provide specific growing and fertilization instructions, but you will also find important information on when to harvest each herb, and how to keep and store them. With some herbs, harvest time does make a difference, and if you wait too long, they may be past their prime.

How To Water Herb Plants

There are many, many types of herbs so, without going into details about each type, here's some general guidelines and tips for watering.

Many herb plants, such as basil and other leafy types, like a consistently moist or damp soil, but not one that is constantly soggy or wet, which can lead to harmful plant diseases and often death of the plant. Others, particularly the more woody-stemmed plants such as lavender, rosemary, sage, thyme, like the soil to dry somewhat between waterings. 

I often use observation to determine whether my herb plants need water. If the leaves of a plant are wilted, I check the soil moisture. If during the heat of summer wilting occurs while soil is still moist, it is a sign that there might be root damage from too much water previously. The herb plants I have growing in pots wilt more often than those growing in garden beds, which is common. If plants are not wilted chances are there is still sufficient moisture in the soil. 

If your herb plants growing in pots are wilting too much and require more frequent watering than you can handle, consider moving them to a location where they'll get some shade or filtered sun during the hottest part of the day. Or arrange some taller plants around them to provide some shade. Too much direct sun on herbs growing in pots can cause root temperatures to rise to a level where metabolism slows dramatically and water movement to the rest of the plant is seriously impeded. growing herbs in light colored containers can help keep soil temperatures down. Plants growing in cooler ground temperatures usually don't have this problem.

In general, whether you're watering herb plants in garden beds or containers, if you use the finger-test to check the soil to a depth of at least a couple inches each time before you water, you'll soon develop a feel for when water is needed. If the soil is dry, provide water. If moist, leave the plant alone...even if the leaves are wilting. 

 Err on the side of watering less, not too much, as it's much easier to kill an herb plant by overwatering than by underwatering.