Where I live, the first signs of spring come in the form of warm days in early February. By mid-March my local garden center is stuffed with cold season vegetables and flowers such as pansies and snap dragons. There are even a few tender, summer-growing like petunia and basil for sale as well.
Recently, as I wandered around looking at the selection, an employee caught my eye.
“Can I help you with anything?”
“No,” I said. “I’m waiting until after the last frost date to plant my garden. I just wanted to see what was out.”
“Smart girl,” she said. “Two years ago we had an ice storm in April.”
When is the best time to start a container garden?
When you garden in containers, the best time to plant your container garden isn’t always the same time as when you plant your garden in the ground. Small containers give a gardener the flexibility to move a plant indoors during a hard freeze to protect it. If you have a tomato plant in a 5 gallon pot on casters, this means that you can get it growing (and producing fruit) sooner.
There are several factors that may play into when you plant your container garden.
Seed and Plant Availability
Local garden centers will often stock transplants long before they can be put in the ground. Even hardy plants like oregano and thyme may be sensitive during this period. This is because they were grown in a greenhouse and are not hardened off yet.
Here where I live, the nightly temperatures will probably drop below 40 degrees at least twice more. These plants can be put in containers, but if the temperatures will drop below 40, they should be brought indoors or moved to a sheltered location until they harden off.
The number of days of cold temperatures is significantly fewer the further south that you go. The USDA recognizes this by dividing the country into hardiness zones. When you purchase a plant, it usually lists the hardiness zones that the plant can thrive in on the tag. Plants that are hardy to your zone can survive through the winter. Plants that are not hardy in your zone may live through the summer but will die after winter’s chill hits.
For example, in my garden I grow rosemary, lavender, chives, thyme, oregano and basil. Plants like the oregano and chives will die back to the top of the containers at the end of summer. But the roots survive inside the containers and new chives pop back up each spring. The basil, on the other hand, dies after the first frost and will not come back. Rosemary is one of those borderline plants where I grow. If I have a mild winter and keep the rosemary plant close to the house, it may overwinter outdoors. Just to be on the safe side, I generally move the plant into the garage once it goes dormant.
Most temperature zones also have a last and first yearly frost date attached to them. The time between these frost dates is a period in which you will probably not experience frost in your area. In Zone 1 (up in Alaska’s interior) the frost free time lasts only from June 15th through July 15th. Where I live in zone 7, the frost dates last from April 15th through October 15th. In Zone 9 areas which occur in the southernmost parts of the United States, the frost free dates last from January 31st through December 15th.
For a good idea of when your frost free periods of time occur, check with your local garden center or a county extension service.
If you are starting your garden from seed, keep in mind that seeds will not grow until the soil temperatures warm to a certain point to encourage germination. If your soil is not yet warm enough to encourage germination, you may wish to start the plants indoors early before moving them outside.
Some containers are too large to be moved. Rooftop gardeners sometimes use plastic swimming pools or tire rings filled with soil and porches may be set with cement planters. These types of planters may not be easy to move once they have been planted. If you own a planter such as this, you may cover the planter’s surface with a layer of straw and a layer of plastic to protect the plants inside.
A cold frame is like a mini greenhouse. Gardeners use it to start plants outdoors without exposing them to cold temperatures that might kill the plants. Most cold frames consist of a box with a window over the top of it to let in solar radiation during the day. At night the cold frame helps to keep out cooler temperatures. I have seen cold frames made out of cinder blocks, dug into the ground and lined with bricks, or even made of old hay bales. During cooler days and nights, a cold frame is a good place to put container plants to protect them. It’s also a great place to put tender seedlings until you are ready to harden them off.
The bottom line is that it is never too soon to start a container garden. Container gardens started early just require more work than container gardens started after the first yearly frost dates.