The best time to plant hardy spring-flowering bulbs in New York is late summer to early fall, though the time frame varies around the state:
- In Zone 4 and 5, plant by late September to early October.
- In Zone 6, plant by mid-October.
- In Zone 7, plant by early November.
- In protected areas in the New York metropolitan area, plant by early December.
Plant hardy fall-flowering bulbs (such as colchicum) in August. Treat tender summer-flowering bulbs like annual flowers. Plant them after the danger of frost has passed in late spring.
When purchasing spring-flowering bulbs, size matters. Bigger bulbs produce bigger plants. Avoid bulbs that are soft, moldy, bruised, or show other signs of damage or disease. If the papery skin (like an onion's) is loose or torn, it usually won't affect the bulb unless the bulb has been otherwise damaged. In fact, removing skin from the bottom of tulip bulbs may help them root faster if you are late planting them. If you can't plant your bulbs soon after purchase, store them in a cool (60 degrees F to 65 degrees F) place to keep them from drying out.
Before planting bulbs, carefully note which end is up. It's usually pointed, compared with the root end which looks like the base of an onion. (Even bulbs planted upside-down usually come up.)
Plant tulips and daffodils so that their tops are about 5 inches below the surface of the soil. (Plant tulips slightly deeper in sandy soils.) Plant smaller bulbs (such as scillas, chionodoxas, grape hyacinths and snowdrops and any others that are 1 inch or less in diameter) so that their tops are about 2 to 3 inches below the soil surface. (As a general rule plant bulbs so that the soil above the top of the bulb is about twice the diameter of the bulb.)
Space large bulbs about 4 to 6 inches apart. This provides them with enough space to grow for two or three years before they need to be divided. Space crocuses and grape hyacinths about 2 to 3 inches apart. Space smaller bulbs 1 to 2 inches apart. For naturalized plantings, space daffodils at least 10 inches apart and set small bulbs at a rate of about 20 per square foot. Smaller bulbs are much more effective when planted in masses rather than individually.
In light sandy soils, you can use the dibble method to plant: Make a small hole with a pointed stick, press the bulb down into the hole, and cover with soil. But with heavier clay soils it's important to loosen the soil beneath the bulb so that the roots can easily penetrate the soil. To plant individual bulbs, use a trowel to dig a small hole to the appropriate depth and loosen soil in the bottom of the hole. For group plantings, excavate a larger area to the correct depth with a shovel and loosen the soil. Gently snuggle the bulbs into the loosened soil at the bottom of the hole, then cover with soil.
Some gardeners add fertilizer to the bottom of the hole. If you do, work it in well and add a layer of soil above this before planting the bulbs so they do not come into direct contact with the fertilizer.
Water thoroughly after planting. Cover plantings with 2 to 4 inches of mulch to protect the bulbs from cold and keep the soil from heaving or drying out. If mice are a problem, place wire mesh over beds until the ground freezes to prevent them from digging out bulbs. To discourage squirrels, place chicken wire over plantings. The bulbs will grow up through the chicken wire in spring.
Tender summer-flowering bulbs are planted in much the same way, only in late spring. Spacings vary depending on species.