Growing Herbs in Containers - Planting Containers

We have discussed choose the container and designing the layout in previous posts.  Now it is time to talk about the actual planting.

Make sure that if you plant to use your containers outdoors that the plants you include have been hardened off.   “Hardening off” is the process of moving plants outdoors for a portion of the day to gradually introduce them to the direct sunlight, dry air, and cold nights. You start with a few hours in the shade, then a few in sun and shade then longer periods of time outdoors until they can finally tolerate the flexible outdoor temps.  If you spring the outside on them the plant will often die.  So give your plants a fighting chance by hardening them, especially of they came from your grow lights or from a greenhouse nursery.

Step to planting:

Preparing your containers -- Make sure your containers are clean and free of residue.  A mixture of 6 parts water 1 part bleach can be used to sterilize the pots and remove residual bacteria from previous seasons that can harm new plants.  Make drainage holes in the bottom if they do not already exist.  No holes means drowned plants. Cover the holes with broken pottery shards or coffee filters to keep soil from escaping. If planting a large container cover the shards with some bulky material, like recycled foam peanuts, crumbled paper or even torn folded pieces of cardboard.  The bulk will cut down on the weight.

Fill your container with soil mix.  The amount of soil you put in depends on whether you use seeds or seedlings to plant your herb garden. In general, if you are using seeds, fill your container to about 1 inch from the rim so that you will have room to cover your seeds with a little additional soil.
With plants fill 2 to 3 inches in the bottom, place the plants and fill in around the plants.  Make sure the soil  is well firmed down to give roots more hold.  Peat based soil (often times called growing medium) is better suited for growing seed, not large living plants.  It dries out more quickly and lacks much nutrient value.

Mix nutrients into your soil - It took me years to realize that I was starving my plants to death. Use a manure-based compost or a home made compost that you mix into the soil mixture you use in your pots to provide nutrients, then realize that the soil will become depleted over the season and feeding will be required.  You can make a compost tea or purchase a commercial fertilizer.  I water with compost tea once a week when we reach the height of the growing season in late June (see below for a link to a fertilizing post.)

Make your own potting mix by blending:

5 parts top soil; 2 parts cool compost or mixture of compost and peat moss; 1 part course (not play) sand.  The sand increases the oxygen and the compost provides the organic matter.  Later in the season I use a mix of 50% top soil and 50% compost to top off the pots as the soil sinks.  This adds more nutrients and replaces what is lost to watering.

I also found this recipe among my lecture notes.  I have tried both and have no opinion which is better.  I like using coconut coir instead of peat moss because it is more renewable.

Homemade Soil Recipe:

1 part pre-soaked Coir Peat 

1 part course sand / builders sand (or vermiculite)

2 parts sieved Compost / soil

1 Tbls to 1 cup* Worm Castings or Vermicast (humus) 

Mix equal quantities of pre-soaked coir peat and vermiculite (or coarse sand if using) together well in a separate container. Place the sieved compost Preferably home made but a commercial certified organic soil mix is an alternative if you haven’t got your own.  in your larger final mixing container have.  Add the blended coir peat and sand to this compost/soil, then stir in the worm casing/humus. Check the pH with a meter.  Most plants require a pH of between 6.0 and 7.0 but if you are growing veggies, from my experience, they grow best in the range of 6.2 – 6.8 pH. 

*this is an approximate quantity based on making 12 gallons  of potting mix using a 3 gallon (9 liter) brick of coir peat. Feel free to add more if you have it!  If you can’t access vermicast, you can buy worm castings or use some humus from the bottom of your compost pile that is most decomposed or use good quality compost.

Remove your plants from their nursery pots carefully - When I first started gardening, I would grab it by the stem and pull to get it out of its pot. Often I would just pull the top of the plant off sometimes killing it before I even got started. To avoid this, if you have a six pack of plants, that is made of flexible plastic, hold the plant close to the soil surface (I make a v out of my fingers and place them on either side of the stem) and squeeze the plants out of their holder from the bottom. If the plant is in a nursery pot, try pushing it out from the bottom. If it is root bound, you may have tear or cut any roots off that are sticking out the bottom hole of the pot and slide a knife around the inside of the pot, before the plant will slide out. In extreme cases, you may have to break the pot to free the plant.

If your plant is root bound, which is often the case, make sure to break up the plants roots, either by tearing them or cutting them. Some people simply rough up the roots on the outside by rubbing them, but I'm a little more aggressive and often tear or cut a compacted root ball so the roots will be able to grow freely, not in a circular pattern, which can strangle a plant.

Planting - There are two main things to know when actually planting a plant in a container (or anywhere else for that matter). You want to plant it at the same level that it sits in its nursery pot. So in other words, the level of the soil should stay the same and no more or less of the plant's stem or crown should be covered. You also want to make sure there are no air pockets and your plants' roots are surrounded by soil. In a crowded pot, sometimes it is difficult to put soil in between the plants, but you will need to make sure that you do, or the roots will dry out if they are in an air pocket, and your plant can die. Sometimes you just need to feel around a crowded pot and stuff soil into any holes you feel. It's also a good idea to water a pot right after you plant it, which settles the soil. At that point you can go back and fill in any holes or depressions with extra soil.

Give your containers a good watering!

Position pots of sun-loving plants where they will have at least 5 or six hours of strong light every day.  Without that number of hours stay with bay, lemon balm, mint, parsley, thyme and scented geraniums.

Watering - watering of container plants is a daily requirement if they are in the sun.  Twice a day (morning and evening is ideal).  About 1/2 to 2/3 through the growing season the soil will become depleted of nutrients so prepare in advance to have a fertilizer at the ready to add to your watering routine to keep the plants healthy.  For more details on fertilizing containers, check out this blog post from 2013.