Gardening with Gardner: The In and Out of Bulbs in Autumn

Gardening with Gardner: The In and Out of Bulbs in Autumn

When the flowers are fading and the leaves are falling, it’s time to turn our attention to bulbs. Some come out of the ground, some go in, and others might even be planted indoors.

Dig ‘Em Up 

In New York, and much of the northeast, winters are too cold and wet to leave summer bulbs in the ground over the winter. Most of the things we plant for summer blooms are native to warmer, even tropical, climates.

As it gets cold, and frosts start, these bulbs go dormant. The foliage begins to yellow or turn brown and die back. As the roots go to sleep, they’re ready to be stored somewhere safe until the warmth of spring returns. Bulbs to dig up now include calla lilies, gladiolas, and dahlias.

If you have oriental lilies, you can leave those in the ground over the winter.

Row of calla lilies in bloom
Calla lilies in bloom during summer

Calla lilies grow from roots called corms, and may multiply over time. As you dig them up, pull the leaves off, and you can break off the thick spaghetti-like roots. You may notice that a corm has multiple sprouts, or that a center or lower portion seems separating. It’s fine to gently break them apart.

A box of gladiolas next to a box of calla lilies
Freshly dug gladiola and calla lily corms

Gladiolas tend to come out of the ground easily – yay! They have bulbs that are also called corms. You may notice that the corm the leaves are coming from is on top of a thinner, soft, or rotten looking corm. That’s normal– it’s just the previous year’s corm. If it’s firm and strongly attached, you can leave them connected. If it’s soft, shriveled, or barely hanging on, break it off and toss it. You might also notice that there are many tiny little bulbs attached by thin strands to the corm. As they multiply, gladiolas form “cormlets” or “cormels”. You can leave them attached without harm. Eventually these little babies will grow up to become larger corms that can produce flowers. Cut off the leaves (the papery husks can stay on the bulb), and be sure the corms are firm before storing them.

Dahlias are the last summer flowers that I dig up each year. I have a whole post about them. Dahlia roots are known as tubers, rather than bulbs or corms, and they have thin skins similar to a potato. After a hard frost that kills the foliage, they should be dug up (unless you’re somewhere that doesn’t have risk of freeze or rot) and rinsed. Rinsing isn’t mandatory, but helps if you have sticky, heavy clay soil. It also helps me send the worms and bugs back into the garden and makes it easier to check them for diseases like leafy gall. You can divide large clumps into smaller clumps or individual tubers if desired. Finally, allow them to dry before storing them somewhere cool with balanced humidity.

Generally, calla lilies and gladiolas can be stored in open trays, but dahlias need to be stored in a container (box, tote, bag) with a medium (wood shavings, mulch, vermiculite) to make sure they don’t dry out or get moldy.

Put ‘Em In

Autumn is the time to plant for spring! Bulbs for flowers like tulips, daffodils, crocuses, hyacinth, and allium need to be planted before the ground freezes. Generally, these need 12-14, even 16, weeks of cold temperatures (around 40°F or less) to grow and bloom properly. 

I planted a lot of bulbs this year!

Plant all of these bulbs with the pointy side up, but how deep? Think about thirds – one third of the hole is the bulb, and two thirds is the soil. In other words, bury a bulb with twice its height. You can layer smaller bulbs above larger ones, if desired. This is sometimes called “lasagna planting.”

You won’t have to dig up spring-flowering bulbs for storage, or replant them. You can simply leave them in the ground. If you’d like to have your collection grow over the years, look for varieties that “naturalize” and be sure to give them a little space to multiply. Flower farmers usually pull up the entire tulip – leaves, bulb, and all– to ensure long stems and get the longest storage life for sale. The bulbs are then composted – without leaves to feed the bulb in the ground for the rest of spring, they won’t regrow properly. 

If you have issues with pests (I have “evil” squirrels in my neighborhood), you can place chicken wire in the soil, purchase deterrents that are sprinkled into the soil, use a layer of small sharp gravel or stones, or try scattering onion greens on the surface. Squirrels don’t like the onion and garlic family– luckily for me, that includes allium! They dig up my tulips bulbs, chew on them, and will chew the flowers off in spring! I’ve opted to plant lots of daffodils and allium instead. They occasionally dig up a bulb in the fall to see whether I hid treasure for them, but they don’t damage it. I just pop it back in the ground, and they leave the flowers alone. I’ve decided to work with nature, rather than against it.

Amaryllis in bloom

Forcing Bulbs Indoors

The holiday season often comes with bulbs in bloom in florist shops. In winter – but how??! Bulbs can be forced to flower out of season. If you plan far ahead, you could have tulips for Valentine’s Day! You’d need about 3 months of cold storage, and about another month until flowers bloom. Amaryllis bulbs do not need a cold period like tulips and daffodils do.

Paperwhites are in the same family as daffodils. They do best if placed in a cool, dark location for 2-3 weeks after potting. You may see paperwhites “potted” in vases and pebbles, without soil. They will do fine this way! To stunt their growth a bit and keep them from getting too tall and leggy and falling over, Cornell researchers have found that a little alcohol helps! Stems may reach about half of their normal height, but will flower normally.  Once the green shoots are an inch or two tall, pour off the water and water them with a 5% alcohol solution (note: “proof” is twice the percentage of alcohol). You can use any hard liquor (vodka, tequila, whisky) or rubbing alcohol.

With proper storage of summer corms, planting spring bulbs now, and forcing others in winter, you can have blooming bulbs all year long.