There is something alluring about planting in containers. Besides allowing for gardening in unlikely places, it invites a different level of creativity. However, there are some things to keep in mind to get optimal satisfaction.
1. Choose plants with similar light and water needs.
2. Make sure your containers drain. Ideally, buy containers that already have holes that will let water drain through enough for the size of the pot. You don’t want it retaining water like a pond. However, if your favorite pot does not have holes, you have a couple of options. You can find a way to drill them, keeping in mind that the right tools make a big difference for this job and some materials may be prone to cracking. There is also the option for planting in a smaller pot that has drainage, that will fit inside the other pot. In this case, you can either take it out to water it and let it drain a bit. Or you can set it up on something like a brick, making sure that when you water, you don’t let the water level in the bottom of the non-draining pot reach the bottom of the draining pot. On a side note, having water remain in the bottom of the non-draining pot can also harbor mosquito larva and smelly algae, so is best avoided. Also, check out this article from The Garden Professors if you’ve heard you need coarse material in the bottom of the pot to help drainage. It turns out that is wrong.
3. Be aware of placing plants at the correct level in the container, compared to their root zone. If you don’t know otherwise, assume the plants need to be in the soil just above where the roots flare out. If planted too deeply up the stem, some plants will die. Some of the soil from the original pot may fall off the roots, but that is easy to replace during the planting process.
4. Be careful where you hold the plants during replanting. Basically, avoid holding them by the stem. I generally use a two-step method. I place my spread fingers over the surface of the soil in the pot while I am hitting the bottom of the original pot to dislodge the plant. Then, if the root mass is very solid and stable, I will hold the plant there. If the roots are fairly small and/or I need to dangle them while I fill in around them, I hold the plant by a sturdier looking leave. The point being that a plant can grow even if missing a piece of root or a single leaf, but if you break the stem, it will die.
5. Consider foliage as much as blooms for combinations and contrast.
6. Remember that roots in containers are less protected from extremes. Hot is hotter, cold is colder. Any perennials need to be a zone or two below your average zone to have any chance of surviving winter. Containers in hot spots will be more affected by heat than plants in similar heat growing in the ground.
7. Containers don’t tend to get monitored during the winter, so that is another reason perennials might not survive winters. They might not get enough water because of being under eaves or lack of winter precipitation. Or they might get water logged from being out in lots of winter rain.
8. Pot size will affect whether or not a container can be easily moved, including being brought inside to overwinter. If you do decide to move a container, do it before watering since water adds a lot of weight.
9. Depth and size of the pot will affect growth potential of most plants, due to size, roots can grow and the amount of water kept available in the soil. Some plants naturally have shallower roots, but others will benefit from depth. Shallow roots make taller plants less stable, due to both their own weight above ground and any wind. The photo below is a container at the Idaho Botanical Gardens. It is a mix of plants that don’t need much water.
10. Have a watering plan in mind from the beginning. While you might be able to modify plans along the way, most plants cannot wait for water until you set something up. Keep in mind that while drip systems can be convenient, the watering needs can vary a lot during the year.
11. Think about whether you want color all summer long, a sequence of color shows, or some combination. Most perennials only bloom for about three weeks.
12. Even though annuals typically bloom for “the whole season,” many have a preferred portion of the season, doing best in the cooler or hotter times. Sometimes this can be manipulated by container location.
13. If plants are already flowering at planting time, consider pinching the blooms off so that the plant will be able to put more energy into establishing itself and give better blooms later.
14. Although plants can be planted closely in pots, it is still a good idea to leave them some room to grow, so don’t pack them in when they are small. As they grow, they will still need more water and nutrition to support their growth in their relatively tight quarters. When planted closely, they will not become as full as if they had lots of space to themselves. They are still in competition for water and nutrition.
15. It often works best to plant a container from the middle out, both for design and practicality.
16. You will want taller plants in the middle, going down in height toward the edges, and possibly trailing plants around the edges.
17. Hanging pots or containers on stands work best with low growing and trailing plants.
18. Don’t be afraid to mix vegetables and flowers in a pot.
19. If growing edibles, which may include some flowers, such as nasturtiums for salads, try putting the pot somewhere you will pass by regularly for remembering to harvest.
20. Keep in mind that potting soil specifically made for container growing is probably best due to things like water retention and ease of providing fertilizer.
21. Be creative with trellises to be able to use vining plants or support plants that might tend to flop or break. In the photo below, a trellis is in the middle to support the thunbergia vine, which will become very vigorous in the warmer months. Meanwhile, the salpiglossis, annuals which thrive in cooler weather, will be the main attraction around the edges.
22. Pruning and deadheading can be very useful in keeping a pot looking good throughout the growing season.
23. Remember that containers usually need more evaluation and maintenance than plants growing directly in the ground. Plants in containers can’t send roots as far out to get what they need and they don’t have the same reservoir of nutrients and water to draw from.
24. Overwatering is one of the most common reasons container plants die. When they are drowning in soil that is being kept too wet, they look like they are not getting enough water because their roots are rotting and they can’t absorb it.
25. Don’t be afraid to experiment with combinations. There are many things that will look good together and accidental combinations usually work well.
26. Direct seeding in containers is an option, but keep in mind that they need appropriate water and warmth to sprout. Just like with many seeds, you will have the most success if you plant more than you want and thin plants later as needed. I just planted sunflower seeds in the middle circle of two whiskey barrels.
27. Many times there will be volunteers in a container from the previous year’s plants. If you learn to identify seedlings, you can take advantage of that. I did not plant any of the petunias or snapdragons in the pots below.
28. Cats often think containers are litter boxes or refreshing places to lounge. They may be deterred by placing a few plastic forks, handles down and tines up, around in the soil.
If you would like some helpful hints for starting seeds for your own container plants, there are seed starting basics explained in this article. Read here for a comparison of the pros and cons of using containers. No matter what, have fun with the possibilities!