Established bulbs tend to be strong growers that typically only require water when needed, occasional fertilizing and routine inspection for pests and diseases. If you had applied fertilizer to your bed when preparing it for planting, you’ve provided all the necessary nutrients to get your bulbs off to a good start. Now regular applications of nitrogen, phosphorus and potassium, plus micronutrients and trace minerals, are essential for root, foliage and bloom development.
A hand dibber is a good fertilizing tool for feeding naturalized bulbs once they’ve sent up first sprouts. It gets the fertilizer down to the root zone.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Work granular fertilizer into the soil using a hand fork or a garden rake to mix it with the soil. If you’ve applied mulch to your bed, rake it aside, apply the fertilizer and work it in. Water thoroughly immediately after you apply the fertilizer to carry its nutrients down into the soil and dilute it, preventing foliage burn. Then you can replace the mulch.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Always carefully read and completely follow all package directions when applying fertilizers, wear protective clothing, and safely dispose of all empty containers and unused fertilizer solutions as directed. Water thoroughly before and after applying fertilizer to dilute, dissolve and spread the nutrients it contains.
Feed spring bulbs with a 10-5-5 dry or granular fertilizer, work an enriched organic compost into their mulch, or spray their foliage or flower shoots with a foliar fertilizer that will be absorbed directly. Apply fertilizer once a month until flower buds begin to open.
Fertilize summer, autumn and evergreen bulbs monthly during periods of active growth, using a balanced 10-10-10 dry formulation, liquid organic fertilizer or foliar plant food. Withhold fertilizer from the bulbs once they’ve formed flower buds.
In most cases, it’s a myth that spring bulbs require predormancy fertilizing. (The one exception is in beds with naturalized bulbs.) Instead, it’s best to apply a fresh layer of protective mulch to the bed. The mulch will decompose slowly, releasing its nutrients into the soil and be available for the bulbs’ use when they begin to grow new roots and foliage.
For most bulbs, it’s important to fertilize during the period of active growth (instead of during predormancy), stop when flowers form, and leave the bulbs’ foliage in place after all their blooming has finished. The leaves of these plants will manufacture nutrients and store them underground in the bulb, new corm or tuber, allowing it to grow and bloom the following season. After a month or so, the foliage will yellow and wither away. Trim away any spent seedpods and flowers after bloom, leaving the foliage to do its work.
For naturalized beds that contain bulbs that remain in place from year to year, withhold water beginning in autumn. In spring, or when shoots or flower stalks first emerge from the soil, apply a 3-10-10 formulated liquid fertilizer and immediately water to carry it deeply into the soil. Phosphorus and potassium quickly bind chemically to soil mineral particles, remaining fixed at the surface. Watering helps carry them to the bulbs’ root zone. If the bed can be cultivated and the location of the bulbs is certain, cultivate carefully around the plantings to mix the fertilizer into the soil.
Give your soil a boost annually – especially container plantings. Decomposed kelp extract contains few nutrients but holds many enzymes that foster root development and activate growth points on bulbs. Apply it every year in springtime.
Bulbs that are lifted after they bloom require fertilizing only when active growth begins; use lifting as an opportunity to cultivate your soil and work in amendments for the following season. Again, naturalized bulbs that remain in the ground should receive annual fertilizing as they begin their growth cycle, as shown in the following techniques, plus a post-bloom fertilizing with 3-10-10 fertilizer. So gather the appropriate fertilizer, a shovel, rake (or hand fork) and gloves, then take the steps shown for each technique in the following pictures and described in their captions.
