vegetable garden with raised beds and containers
vegetable garden with raised beds and containers

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Growing Vegetables in Containers

Revised: 
4/26/2010

1.  Location, Location, Location – Where will you put your container(s)?
Choose your site first!  Consider the following before purchasing containers and plants:

  • Size of area for container
  • Height of plant material desired (will you need a trellis or other support structure?)
  • Single or multiple containers
  • Available light during the course of the day – full sun is needed for most vegetables

2.  Select the Container
Choose based on your site selection and the plants you want to grow; consider the size of the container relative to the area where it will be placed. Use whimsical planters for children’s areas. Match styles to the décor of your home. If you are using a recycled container, make sure it was used in its previous life for something food-safe.
If you are purchasing a large container that you plan on leaving outdoors all year round, make sure it is freeze resistant. Many ceramic and concrete containers must be brought into a protected area over the winter to keep from cracking.  
Plants will grow in most anything as long as there is enough good soil or soil-less mix and there is a drainage hole.  
Good Drainage is the Key to Successful Container Gardening
Resist the temptation to use a container without drainage holes.  Use “feet” to keep the container up off the surface whether it’s soil, concrete, brick or decking material. The pot will drain better and you will have fewer problems with staining of your patio or deck.

  • Clay – high frequency of watering;  great for plants that like dry conditions; very porous;  salts and sometimes algae will build up on the exterior and rim of the pot
  • Plastic – easy to use, easy to keep clean; retains moisture better than clay pots; new styles look like terra cotta or glazed ceramic.
  • Ceramic – glazed pottery works well, retains moisture longer than unglazed pots; make sure there is a drainage hole.
  • Metal – not recommended as primary container for growing plants, the metals can leach into the soil and cause toxicity problems;  water will rust the container; ok as secondary container

3.  Choosing and Mixing Soil for Container Gardens
Go organic!  By this I mean use a lot of organic matter in your mix!  More organic matter will result in faster growth and will help to retain moisture in the pot. Container gardens grow fast and furiously when provided with the right soil environment.  
Happy roots produce happy plants, beautiful blooms and more fruit!
Remember the container is a limited growth environment for your plants, it needs to be the best possible for the best growth. The soil mix will make the difference.
What is organic matter?

  • Good quality compost - has no odor, no recognizable “pieces”
  • Peat moss
  • Ground bark

What is added for drainage?

  • Vermiculite – heat-expanded mica, gold, compresses easily
  • Perlite – heat-expanded rock, white, crumbles to powder when pressed
  • Styrofoam pellets (looks like perlite, but is squishy)
  • Ground bark – although organic, adds more to drainage
  • Sand – not always used but can be added to container mixes at a rate of 50%; is very heavy – this can be a good thing (won’t tip over, difficult to “borrow”)

Soilless potting mixes are high in organic matter. Read the bag for ingredients before you buy.  Most “soil mixes” don’t really have soil in them. They are a mixture of compost, peat, ground bark, vermiculite and/or perlite. Soil adds a lot of weight to the mix, and can certainly be included in the mix for outdoor container gardening. If you are adding soil make sure it is sterilized so you don’t run the risk of contamination with a disease or insect problem. 

How Much Soil?            

  • 10 inch pot     ~ 2 ½ gallons of soil mix
  • 12 inch pot     ~ 3 ½ gallons of soil mix
  • 14 inch pot     ~ 4 ½ gallons of soil mix
  • 16 inch pot    ~ 5 ½ gallons of soil mix
  • 20 inch pot     ~ 6 ½ gallons of soil mix

NOTE:  Place container where you want it before filling with soil.  It will be heavy!
4. Care of Your Container Garden
Water – Absolutely Essential
Lack of water is the number one cause for demise of container gardens outdoors.
 (Number 2 is probably chipmunks – they can’t resist a newly planted container.)

  • Check containers daily to see if they are dry
  • Water thoroughly till water drains through the bottom of the pot
  • Do not let plants sit in water

Fertilizer Recommendations
Incorporate a timed release fertilizer with your soil mix when planting for best results over the summer.  There are many brands of timed release fertilizer, choose one formulated for “flowering plants”. In addition, fertilize once every two weeks with a balanced nutrient mix (e.g. 10-10-10 or 20-20-20) or a fertilizer formulated for flowering plants (e.g. 9-18-9 or 5-10-10).   This may seem like heavy fertilizer applications, but remember, your plants are in a confined, limited resource pot and will grow quickly.  In addition, with regular and frequent watering that outdoor container gardens require, many of the nutrients will be leached out of the soil.
Fertilizer provides the nutrients (chemicals) needed by the plants to make their food.  Nitrogen supports total plant growth, and is required for healthy foliage and root development.  Too much nitrogen can result in decreased numbers of flowers and fruit.  
Key to Understanding Fertilizers
    First Number – the % of nitrogen (N) in the fertilizer    
Second Number – the % of phosphorous (P) in the fertilizer
Third Number – the % of potassium (K) in the fertilizer

4. Vegetables for Containers – Seed Sources

http://www.raingardens.com/seedpage/garden.htm
http://www.seedman.com/baby.htm
http://www.penyaseeds.com/cat.htm
http://www.parkseed.com
http://www.jungseed.com
http://www.burpee.com
http://www.mailordergardening.com/
http://www.containerseeds.com

Garden Now

Prune summer flowering shrubs like hydrangeas, Japanese spirea, potentilla in early spring. For more info, click on the link below:
Cooperative Extension University of Wisconsin-Extension