Fall is the best time to plant hardy, spring blooming bulbs and properly preparing the planting site is a must. Good soil drainage is important to healthy bulb life so if your soil contains clay, amending it with some compost, peat moss or other organic material into the top 12-18 inches will help. Sunlight requirement is also something to consider. Check the package label to see if your bulbs need full sun, partial shade or full shade. Keep in mind that bulbs planted on a south slope will bloom earlier than the same bulb planted on a north slope.
Planting bulbs in September through early October will allow time for the bulb to become well rooted before freezing weather arrives. In general it is recommended to plant a bulb two to three times as deep as the bulb is tall and the planting depth is measured from the bottom of the bulb. The planting depth for summer bulbs vary, so check the package label for instructions. Lightly press the bulbs into the prepared soil with the root plate facing down. Water the bulbs once they are planted. This will help to settle the soil and provides moisture so the bulb can start growing roots.
Bulbs need phosphorus to develop a good root system. Note that research has shown that phosphorus from bone meal is only available to plants in soils that have a pH below 7 (www.ext.colostate.edu/pubs/garden/07410). Refer to or have a soil test done for this information. Mix bone meal or superphosphate into the soil just below where the bulbs will be located when preparing the site. In an already established bed it is important to supply the bulbs with additional fertilizer. For spring flowering bulbs, in the fall mix into the soil five tablespoons of a 10-10-10 soluble fertilizer plus two cups of bone meal for a 10 sq. ft. area. In the spring as soon as you see the shoots breaking the surface of the ground, apply the same mixture. Do not apply fertilizer to spring flowering bulbs after they have started flowering. For summer and fall flowering bulbs, fertilize monthly from shoot emergence to the time that the plants are in full flower. For a 10 sq. ft. area, apply seven tablespoons of a 10-10-10 soluble fertilizer split into two or three applications.
One of the issues I have with bulbs is the ugly dying off of the foliage. The foliage should not be cut or mowed off until it turns yellow and dies off on its own. The plant needs its green leaves to make food that is stored in the bulb for the next year’s growth. I like to plant my bulbs under the roots of chrysanthemums or another perennial. As the perennial grows it hides the fading foliage of the bulb.
As always, Happy Gardening!
The Purdue University Cooperative Extension Service can be reached at 499-6334 in LaGrange County.