Tulips and other bulbs usually bloom spectacularly the first spring following planting. But if their flowers aren’t quite as bountiful the next year, it’s usually because they lacked the proper nutrition the previous year.
I’ll refer to tulips, but all spring bulbs react in the same way. It’s fascinating to know what goes on inside a tulip bulb, and that holds the key to future bloom.
When you buy tulip bulbs in the fall, located within the dormant bulb is next spring’s flower bud. It’s already formed deep inside the bulb.
If you cut a bulb in two, you can actually see the tiny formations of both leaves and flower buds, waiting. Following fall planting, the bulbs produce roots, then receive their necessary winter chilling. In spring when soil and weather warm, the pre-formed leaves expand and grow. Shortly the pre-formed flower bud expands and emerges.
Each spring, after tulips produce foliage and flowers, the bulb must re-energize itself and form flower buds deep inside the bulb once again for the following spring’s growth. Each year the tulip bulbs must have the strength to pre-form next year’s tiny interior buds. That takes energy, and for that energy the bulbs need nutrition. If the bulbs lack nutrition, the buds formed interiorly might be small and skimpy, resulting in future flowers that aren’t as robust as well-fertilized tulips.
To provide the necessary nutrition, soil around tulips should be fertilized every spring about the time they’re blooming. Use a well-balanced flower and vegetable fertilizer. (Well-balanced means the 3 numbers on the analysis are roughly equal. The nitrogen, phosphorous and potassium levels will be about 10-10-10 or 12-18-12.) Special bulb fertilizers are also good.
Granular fertilizer can be applied to soil surface and then cultivated in shallowly. Water well to activate. Water-soluble types like Miracle Gro can also be used. Apply the water soluble types about once a week while the tulips still have foliage.
To further conserve bulb’s energy, remove “spent” flower heads after petals wither to prevent seed head formation, which saps strength.
Allow leaves to remain on bulbs as long as possible, because the leaves feed the bulbs and are responsible for the photosynthesis that produces next years buds inside the underground bulbs. Let leaves turn yellow and dry down naturally. After they are crisp-brown, the foliage can be removed.