By Jim Leser
When it comes to autumn garden chores we almost always think of cleaning up our gardens, a dump trip or two and adding to our compost pile. While these are all worthy activities when our gardens are generally shutting down with the onset of cooler weather, I like to think ahead to when spring-blooming bulbs kick off a colorful spring season in my garden.
Spring-flowering bulbs are planted in the autumn because they’re hardy in colder temperate climates, and they require a cool dormant period of at least eight–12 weeks before they can produce flower buds. The recently planted bulbs will develop roots until the ground freezes.
The many spring blooming bulbs can be planted until the ground is frozen or no longer workable. These include the ever popular crocus, daffodils, narcissus and tulips. But don’t forget the alliums and the hyacinths. Daffodils and narcissus should be planted earlier (early September to late October). Other bulbs, especially tulips, can be planted from early September through to mid-December, as long as the ground is not frozen solid, which would be a rare event in our area. When purchasing bulbs, look for firm ones. These will produce the best blooms. Discard any that show signs of rot, are soft, or crumble when squeezed.
The majority of bulbs prefer well-drained soil that’s neutral to mildly acidic (pH 6.5). But even in our alkaline soils I have had no problems growing spring flowering bulbs. But beware that our heavy clay soils aren’t suitable unless they’ve been amended with organic matter to improve drainage and to provide air space. Bulbs are highly susceptible to fungus and mildew diseases, which spread in excessively wet conditions. Bulbs planted in poorly drained soil are likely to rot or develop botrytis blight. Tulips are especially susceptible.
Planting holes can be dug with an ordinary trowel or spade, but there are a variety of specialized tools available. A garden auger that attaches to a hand drill is useful for mass plantings. A bulb planter is a cylindrically shaped tool that removes a core of soil at the correct planting depth. Many trowels have a “ruler” on their blade to help with correct planting depth.
Bone meal or slow-release bulb fertilizer can be placed in the hole before planting. Lightly mix the fertilizer with the soil. Be sure to follow the package directions, which vary depending on the planting area. I have found that our soils are pretty fertile and generally don’t require a lot of babying with special fertilizers.
I recommend planting larger bulbs like tulips, daffodils and hyacinths 6 inch deep and 6 inches apart. Smaller bulbs like crocuses (which are really corms) and grape hyacinths should be planted 3 inch deep and 3 inches apart. Planting at the maximum recommended depth helps to protect bulbs from moisture loss during intense summer heat and also helps deter digging predators such as squirrels.
Planting your bulbs in the right direction is very important. For pointed bulbs such as tulips, daffodils and hyacinths, ensure the pointed part faces up toward the sky, and the flat part faces down into the ground. If you can’t tell which end is which, plant it sideways — this makes it easier for the plant shoot and roots to grow in the right direction.
Generally, bulbs are left in the ground for the next season. Even when the plant is in decline, its leaves continue to process food; therefore, it’s important not to disturb the leaves until they have died back naturally and the bulb goes into dormancy. Until then, you should cut only the spent blooms.
Planting bulbs among other perennials will give you some color and interest before your later flowering plants are ready. Mass planting of bulbs is another option and provides a great visual impact. When I plant for this affect, I don’t dig a hole for each bulb but rather dig one wide hole to fit all my bulbs in. You can even plant crocus bulbs in lawns with warm season grasses. They will emerge and flower before your grass “comes alive” in the late spring.
If the garden space will be used for annuals, bulbs can be dug up (with their foliage intact) and stored in a garden shed, garage or secluded area of your garden until their foliage dies back naturally. They can then be cleaned and stored somewhere cool and dry for planting in the fall. It’s good practice to dig up and replant spring bulbs every third year.
One last caveat if you live in deer country. Don’t plant bulbs such as tulips without some protection from deer browsing. Deer consider tulips a delicacy. And while I’ve never had deer actually eat crocus, they seem to delight in pulling them up. So they need protection too. Both daffodils and alliums are generally deer resistant. But remember, hungry deer will try to eat almost anything!
Jim Leser retired to Cedaredge in 2007 after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a Colorado Master Gardener.