Tips for Growing Spring Bulbs in Containers
Each fall, we plant thousands of spring-blooming bulbs in our New Jersey trial garden. But we don’t have much experience growing spring bulbs in containers. So we asked Claire Jones, a gardener in Maryland, to explain how she does it. You can follow Claire’s gardening adventures on her blog The Garden Diaries.
If you don’t have a yard or garden for planting spring bulbs, like tulips, daffodils and hyacinths, don’t despair. Just plant them in pots. Planting bulbs into a nice loose potting medium is easier than digging holes in the soil. There are other advantages, too:
• Enjoy seeing the flowers up close and personal
• Add a cheery pot of bulbs to any flower bed that needs sprucing up
• Accessorize your potted bulbs by adding other spring-blooming flowers
• Experiment with new varieties and new combinations of colors and flower styles
• Grow tulips without worrying about deer. Keep the pots near the house where deer won’t dare to tread
What You’ll Need to Grow Bulbs in Containers
I started planting spring bulbs in containers because I wanted an easier way to enjoy them. If you live in a place that is colder than Maryland (hardiness zone 6), growing bulbs in containers may not be an option for you. But in zones 6 and 7 it’s easy to do as long as you remember a few rules.
- Growing Medium. Use a high-quality mix with lots of perlite or vermiculite for good drainage. Do not use garden soil.
- Pots. Use inexpensive plastic or terra cotta pots. Terra-cotta will need some protection from temperature extremes (I use bubble wrap); Make sure they have drainage holes in the bottom.
- Spacing. Plant the bulbs so they are close but not touching. Their tips should be just below the soil surface. Here is your chance to stuff them in and get a huge color show.
- Depth. For best results, try to stick closely to the recommended planting depths for each type of bulb, while leaving as much room as possible under the bulbs for root growth.
- Layers. To get a more abundant look, you can layer different types of bulbs on top of each other. For beginners, it’s best to stick with one type of bulb per pot.
How to Care for Spring Bulbs in Containers
Spring-blooming bulbs must go through a period of cold temperatures in order to bloom properly. This means they need to be kept colder than 48° for most of the winter. A basement is too warm, but depending where you live, an unheated shed, cold frame or garage can work fine.
It’s important to know that bulbs in containers get MUCH colder than bulbs that are planted in the ground where there is soil to insulate them. If the soil in the container is allowed to freeze, the bulbs will die. Read on to see how I provide extra insulation for my containers.
Water sparingly during fall and winter. The soil should stay slightly moist – never soggy. Check the containers throughout the winter to make sure the moisture level is correct. If you live in an area with rainy winters, you will need to cover the pots so they don’t get too wet.
Where and How to Store Potted Bulbs During Winter
I keep my potted bulbs outside on my patio until temperatures are consistently below freezing. In the mid-Atlantic region where I live (Maryland, zone 6), that can be as late as mid-December. Once freezing temperatures are here to stay, I move the pots to a more sheltered position. Since temperature is critical for success, you need to store the pots in an area where the bulbs will get cold enough, but the soil will be protected from cycles of freezing and thawing.
For me, the ideal winter storage space is an unheated mud room attached to my house. I wrap the pots in insulating bubble wrap and place them next to the wall of the house where they get a little warmth. My cold frame is another good place to store pots. I have heard of gardeners who store their potted bulbs in galvanized trash cans with some burlap or other filler stuffed around them. Storing them in cans protects them from the great bulb destructors: squirrels, mice and voles.
Storing bulbs in your garage can be a good option. But the exhaust fumes from an idling car contain ethylene gas, which will kill the flowers inside the bulbs. You’ll get wonderful pots of nothing but foliage. Keeping the bulbs in a backup refrigerator is another option. But unfortunately, ripening fruit also emits ethylene gas. Store the fruit elsewhere or protect the pots in impermeable plastic bags to avoid contamination.
Check on your pots monthly and water only if/when the soil feels dry to the touch. Towards February, you’ll probably start to see the first green shoots. At this point you can ramp up the watering and move the pots out into a protected area (don’t let them freeze). Start with partial sun and gradually acclimate them to full sun for good flower development.
Step by Step Instructions for Planting a “Lasagna” Pot
Lasagna-style planting means layering different types of bulbs to get a 6 to 7-week display from one container.
• Choose a deep container (at least 16″).
• Plant your bulbs almost as deeply as you would in the ground; for instance, 6 or 7 inches deep for tulips and daffodils, and 3 or 4 inches deep for little bulbs such as crocus and miniature iris.
• Put about 4” of high-quality potting mix in the bottom of the pot and firm the soil. Position the first layer of bulbs on top with the growing tips up. Cover each layer with more soil before placing the next layer of bulbs.
• For my layers, I started with 10 daffodils. The second layer was 10 hyacinths; third layer 16 tulips, last layer 50 assorted small bulbs (20 muscari, 20 crocus, and 10 iris reticulata).
What to Do After the Bulbs Finish Blooming – Two Options
You can either compost all of the bulbs or replant some of them in your garden. If you replant, do it right after the flowers fade. Cut off the spent blooms and gently tuck the bulbs and their foliage into the ground at the correct planting depth. Apply a liquid fertilizer to help replenish the nutrients used during flowering. Second-year flowers are never as spectacular as the first year, so I usually compost the bulbs and start with a fresh batch in the fall.