How to grow Herbs in containers

In all the years I have been growing herbs I have only found a very, very few that cannot be grown in containers.

Containers:

Choose the container to suit the plant.  If it is a tall plant make sure the container has a base wide enough to prevent it toppling over, even if placed outside in a high wind.

A collection of containers is sometimes much easier to look after than a window box, and you can give each herb its own individual bit of tender loving care. If using unconventional containers (old watering cans, sinks, a half beer barrel: make sure they have drainage holes, and gravel or broken pots in the bottom of the container to stop the holes clogging up)

Herbs can suit Hanging baskets but the position is crucial.  They dislike high wind and full sun all day.  Also, they are mostly fast growers and if too cramped or ver-or under watered they will drop their leaves.  They also benefit from being picked regularly, which is not always possible in a hanging basket.  I can recommend the following:  double-flowered chamomile, creeping thymes, prostrate rosemary, catmint, creeping savory, golden marjoram, dwarf marjoram, pineapple mint, pennyroyal and maiden pinks.  

To prepare your hanging basket, line the basket with sphagnum moss followed by a layer of black plastic with holes punched in it. Then, fill the basket half full with compost.  Position the plants, trailers at the side, taller, more upright herbs in the middle.  Do not overcrowd.  Fill up with compost.  Water in well.  Let it drain before hanging on a secure hook or bracket.  Check hanging position for accessibility.  In the height of the season you will need to water at least night and morning.  Make sure that it cannot fall on anyone's head!!

Compost and organic fertilizers:

Choosing the right compost is essential for healthy plants.

Own Soil-Based mix:

If you wish to make a soil-based compost of your own this recipe is fairly reliable:

• 4 parts good weed-free garden top soil
• 3 parts well rotted garden compost
• 3 parts of either coir or wood fiber or composted fine bark, all of which must be moistened prior to mixing with the other ingredients
• 1 part sharp river sand.

Fertilizer:

When making your own compost you will need to add a fertilizer either in granule form or as a liquid feed.  Add at the rate that the manufacturers recommend.  You can buy organic fertilizers from garden centers and hardware stores.  The following organic fertilizers are ideal to be added to potting or seed-sowing composts:

• Liquid Seaweed: This contains small amounts of nitrogen, phosphorous, potassium and it is also rich in trace elements.  It not only makes a good soil feed but as the elements are easily taken in by the plant, it can also be sprayed on as a foliar feed.
• Calcified Seaweed: This contains calcium magenesium, sodium and numerous trace elements.  It is ideal for adding to seed compost.  Add according to the manufacturer's instructions.

Potting and Seed Composts:

• Multipurpose Potting Compost: This is usually a peat-based compost with added nutrients.  However, the nutrients are too strong for seed sowing and not enough for potting.  therefore I advise you to use a seed compost for seed sowing and a good peat-free potting compost for all your potting needs.
• Peat-free Compost: These are now readily available.  Over the past three decades the options have grown tremendously:

1. Coir:  This is a by-product of coconuts.  Its main advantage is that it is very light.  However, the main disadvantages are that it dries out very quickly, and it leaches the fertilizer.  For this reason it is worth looking out for coir mixed with clay, which acts as a buffer and stops the fertilizer from disappearing, and it also stops the compost drying out too fast.
2. Composted bark:  This is a byproduct of the wood industry.  It is available in many sizes and shapes.  For potting and container growing it is essential to get bark that has been properly composted for an adequate length of time.  This is because newly harvested bark will not only burn the roots and stems of young plants, it will also take the nutrients from the plant and the compost as it starts to decompose.
3. Composted wood fiber: This is another product of the wood industry and is now becoming readily available.  The advantages are that it is very light and absorbent and behaves well in containers.  The disadvantage is that it has to be heat treated, which puts up the cost and is not particularly environmentally friendly.
4. Green Waste: This is a byproduct of city waste.  Many local councils now sell green waste and many composts now include this.  The advantage is that it is environmentally friendly; the disadvantages are the consistency of the contents and if it has not been correctly composted, you can have an invasion of compost fly. There can be a certain amount of heavy metal waste within the compost, which can cause the plants to become distorted.

Maintenance:

Spring:  This is the time of year to pot plants if necessary.  A good sign of when they need this is that the roots are truly protruding from the bottom of the container.  Use a pot next size up.  Carefully remove the plant from its old pot.  Give it a good tidy up (remove any weed and dead leaves.  If it is a perennial, trim growing tip to promote new busy growth)  Place gravel or other drainage material in the bottom of the container and keep the compost sweet by adding a tablespoon of granulated charcoal.  As soon as the plant starts producing new growth or flowers, start feeding regularly with liquid seaweed.

Summer:  Keep a careful eye on the watering; make sure the pots do not dry out fully. Move some plants out of the midday sun.  Deadhead any flowers.  Feed with liquid seaweed, on average once a week.  Remove any pest-damaged leaves.

Fall:  Cut back the perennial herbs.  Weed containers and at the same time remove some of the top compost and redress. Bring any tender plants inside before the frosts.  Start reducing the watering. 

Winter:  Protect all container-grown plants from frosts.  If possible, move into a cold greenhouse.  If weather is very severe, cover the containers in a layer of sacking.  Keep watering to the absolute minimum. 

Thanks Jekka McVicar.