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Bulbs: A Seasonal Cycle: Successful Bulb Cultivation

Tulipa 'Perestroyka' (foreground) at NYBG; photo by Danielle Colburn


Bulbs produce glorious flowers in a wide range of colors, shapes and sizes. Some have luxurious, velvety flowers; some are intricate and strange; others are just bright and cheerful.  Everyone is always happy to see early-season bulbs emerge through the snow.

Bulbs look wonderful in both naturalistic plantings and formal displays. The easiest way to create a naturalistic planting is to throw a handful of bulbs on the ground and plant them where they land. Groups of 12 bulbs or more tend to work best. In a mixed-bulb planting, plant groups of 5-7 bulbs in drifts, making sure different varieties intermingle and overlap. Formal displays should be laid out in advance to ensure a uniform structure.

In the New York City area, some bulbs, such as daffodils (Narcissus), come back year after year, while others, such as tulips (Tulipa), tend to be short-lived and can be treated as annuals. The best way to increase their longevity is to provide optimum growing conditions.

Most bulbs thrive in free-draining, sunny locations in the garden. Others, such as wood anemones (Anemone nemerosa), dog-toothed violets (Erythronium) and snowdrops (Galanthus), are woodland plants that need humus-rich soil (rich in organic matter), and shadier conditions.

The rule of thumb for most bulbs is to plant them three times their height and space them three times their width. Be sure to plant bulbs right side up--that is, the pointed end where the leaves and flowers will emerge next spring. If you are not sure, lay the bulb on its side and it will find its way to the surface. Other general rules are to plant bulbs deeper in the North than in the South; plant deep in light sandy soils, shallow in heavy clay; and sink larger bulbs a little deeper than three times their height, while keeping small bulbs closer to the surface.

Spacing is a personal preference and will depend on the look that you are trying to create. Remember that many bulbs, such as daffodils (Narcissus), multiply quickly and should not be planted too closely. Bulbs should never touch each other when planted--if one rots, it may cause others to deteriorate.

In a cultivated garden, loosen the soil with a garden fork and rake the soil level. Hold your trowel so the front is facing you, stick it in the ground, and pull it toward you to create a hole. Place the bulb in the space that you have made behind the blade. Then pull out the trowel and firm the soil. Alternatively, use a bulb planter or spade to make small holes and drop the bulbs in. When planting bulbs, incorporate a bulb fertilizer or balanced fertilizer into the soil mix and amend the soil as necessary (see below in tips).

When planting bulbs in a lawn, cut a large strip of grass and pull it back. Then proceed as instructed above.

Plant your bulbs immediately after receiving them. Most spring-flowering bulbs can be planted in September or October. Wait until October to plant tulips (Tulipa) and lilies (Lilium). Bulbs should be firm and plump. If they cave in when you squeeze them, are full of mildew (a little is fine), are soft or rotting then throw them out.

Photo of Galanthus elwesii blooming in the lawn at NYBG; photo by Ivo Vermeulen

Galanthus elwesii (snowdrops) blooming in the lawn at NYBG; photo by Ivo Vermeulen

Growing Tips

  • Plant bulbs in areas with good drainage. Poor drainage will increase the chance of rotting.
  • Let the foliage die back on its own. Once the foliage starts to yellow it can be cleaned up. Bulbs need a six-week period for the foliage to photosynthesize and put energy back into the bulb for the following year's flowers. Remember, if your bulbs are planted in the lawn, do not mow the area during this six-week period.
  • When using bulbs for cut flowers, remove as little foliage as possible.
  • The best time to fertilize bulbs is in the fall when you are planting, using a bulb fertilizer or a balance fertilizer. Mix the fertilizer into the soil before placing the bulb in the hole.
  • If you would like to fertilize an existing planting to give it a pick-me-up, use a diluted foliar feed and apply it once the foliage has emerged and then one more time following flowering.
  • Amend the soil before planting. Aged compost, Sweet Peet™, or well-rotted organic matter are ideal for amending soil. For improved drainage add grit or sand (sharp sand, not builder's sand, which compacts).

Strategies for Protecting Bulbs from Squirrels, Chipmunks, Voles, Deer, and Humans

  • Plant pest-resistant bulbs such as "Tommy" crocus (Crocus tommasinianus), daffodils (Narcissus), hyacinths (Hyacinthus), fritillary (Fritillaria), grape-hyacinths (Muscari), snowdrops (Galanthus), and ornamental onions (Allium).
  • If planting just a few bulbs, build a mesh wire or cage to prevent them from being dug up or eaten by squirrels and voles.
    Use 1/2-inch hardware cloth for the bottom and sides of the cage and larger chicken wire for the top.
  • Add a handful of sharp grit to the holes when planting tulips and other bulbs to prevent voles from tunneling up.
  • Plant bulbs in large leftover plastic pots from plants purchased at a nursery. Add three inches of soil to the bottom of the pot, mix in fertilizer, sink the pot and bulbs into ground just below soil level, and fill in. This will protect tulips and other bulbs from voles and prevent you from slicing through them when digging in your perennial garden.
  • Cover newly planted beds with plastic bird netting, window screens, or hardware cloth to prevent squirrels and other animals from digging up newly planted bulbs. Alternatively, spray the newly planted area with hot pepper sauce.
  • Plant bulbs that are susceptible to vole damage among patches of Narcissus. Voles hate daffodils and will stay away from the area.
  • Spray newly emerging shoots with deer repellent or hot pepper sauce, or surround the area with blood meal.

Erythronium americanum (yellow trout lily); photo by Jody Payne

Erythronium americanum (yellow trout lily), a woodland native; photo by Jody Payne

If you would like to expand your bulb collection but end up destroying existing bulbs by slicing through them as you plant, here are a few helpful tips

  • In the spring, when the bulbs are out, inter-plant them with summer-flowering bulbs such as gladioli or annuals. At the end of the season, pull out the summer-flowering bulbs or annuals, and replant the holes with more spring bulbs.
  • Find creative ways of marking bulbs, so when the foliage disappears you know where they are planted. Suggestions include marking with golf tees, surrounding spring bulbs with fall-blooming crocuses, or marking the area with perennials. Fall bulbs include autumn-crocus (Colchicum), or autumn-flowering crocus (Crocus speciosus), cyclamen (Cyclamen), snowdrops (Galanthus reginae-olgae), and nerine (Nerine).

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