Almost all of the flower bulbs in our collection must be planted in the fall prior to the onset of winter. This 3-month period of consistently cold temperatures enables bulbs to fully form flowers (embryos) within, develop mature root systems and avoid premature top growth. Without a winter hibernation, many bulbs do not yield fully formed flowers, and are prone to flowering short within the neck of the stem, if they flower at all. Sad but true.
For most flower bulbs, like Tulips, Narcissi, Hyacinths and Crocus, the winter is referred to as a period of vernalization, a required resting period provided by prolonged, consistent cold temperatures. U.S.D.A horticultural zones help gardeners determine which flower bulbs are good for their gardens based on a range of minimum temperatures. Many flower bulbs are good from horticultural zones 4 through 8 which would indicate minimum temperatures generally under 32°F yet above -25°F. These horticultural zones provide us with direction as to whether or not flower bulbs would successfully experience the vernalization and bio-chemical trigger to ensure mature spring flowering.
For most flower bulbs, in warmer climates a period of simulated vernalization or precooling is required for spring blooms. However, there are flower bulbs that do not require a period of precooling in the warmer climates of horticultural zones 8 through 10.
Happily, everyone can experience the beauty of bulbs!
Flower Bulbs for Warmer Climates without Prechilling
These types of flower bulbs may be fall planted in horticultural zones 8 through 10 without being precooled:
*Allium cowanii, A. karativiense, A. neapolitanum, A. siculum bulgaricum, and A. sphaerocephalon
*Anemone Giants (Anemone coronaria)
*Fritillaria persica, F. Maxima Lutea and F. Rubra Maxima
*Iris hollandica (Dutch Iris)
Select a planting site with partial or dappled sunlight and plant them at least as deep as specified to prolong the bloom period. Apply a light 2” layer of mulch to help retain moisture and to trap cool temperatures in the soil. If rain is insufficient, give them a little drink after planting. Treat the bulbs as annuals.
Now for how to grow Tulips, Narcissi, Hyacinths, Crocus and other types of flower bulbs in warmer climates.
To successfully grow these flower bulbs in horticultural zones that are too warm for an adequate period of vernalization, one must create a simulated vernalization period by prechilling the bulbs. In horticultural zones 8 through 10, this means that the bulbs should be prechilled at a dark 35°F to 45°F starting in mid-October for up to 16 weeks, depending on the bulb.
Flower Bulbs Best Chilled for Warmer Zones
Here is a brief summary of the flower bulbs best-suited for prechilling and planting in horticultural zones 8 through 10.
Tulips should be prechilled for ten to 14 weeks. Never less! The very best Tulips to prechill and plant in horticultural zones 8-10 are:
*Species Tulips Tulipa bakeri Lilac Wonder, T. clusiana Lady Jane, T. clusiana var. chrysantha, T. clusiana var. chrysantha Tubergen’s Gem, T. linifolia, T. orphanidea flava, T. saxatilis and T. sylvestris
*Single Early Tulip Flair
*Giant Darwin Hybrid Tulips
*Parrot Tulips Blue Parrot and Flaming Parrot
*Triumph Tulip Negrita
*Fringed Tulip Burgundy Lace
*Lily Flowering Tulips Mariette, Purple Dream and White Triumphator
*Single Late Tulips Avignon, Belle du Monde, Blushing Beauty, Blushing Lady, Dordogne, El Niño, Françoise, Maureen, Menton, Queen of the Night, Renown, Temple of Beauty, Yosemite, and The Scheepers Hybrid Tulip Mixture
Because of temperature fluctuations and changing temperature patterns, we encourage gardeners in horticultural zone 7b to prechill their Tulips too.
Generally, Narcissi should be prechilled for 16 weeks. Here are some of the varieties that are known to perform best prechilled and planted in horticultural zones 8 through 10.
*Trumpet Daffodil King Alfred
*Large Cupped Narcissus Fortissimo, Fortune, Ice Follies and Pink Charm
*Double Narcissus Cheerfulness, Tahiti and Yellow Cheerfulness
*Triandrus Narcissus Moonlight Sensation, Starlight Sensation, Sunlight Sensation, Thalia and Yellow Ocean
*Cyclamineus Narcissus February Gold and Tete a Tete
*Jonquilla Narcissus Baby Moon, Hillstar, Pueblo and Sundisc
*Poeticus Narcissus Actaea
*Tazetta Narcissus Avalanche, Cragford, Falconet, Geranium and Silver Chimes
*Species Miniature Narcissus canaliculatus
*Scheepers Gold Medal Southland Mixture
*Van Engelen's Southland Grand Mix
There is a host of Miscellaneous Bulbs that must be prechilled and planted in horticultural zones 8 through 10. They need to be prechilled for longer periods, perhaps because they are planted more shallowly and are more prone to feeling the immediate heat once planted. These include:
Chionodoxa: prechill for 15 weeks.
Crocus: prechill for 15 weeks.
Eremurus: prechill for 12 to 15 weeks.
Galanthus: prechill for 12 to 15 weeks.
Hyacinth: prechill for 12 to 15 weeks.
Iris reticulata: prechill for 13 to 15 weeks.
How to Prechill Flower Bulbs
First, let us know that you intend to prechill your bulbs when you place your order with us. We will ship your order to you so that you may begin this process in mid-October. Open your order when you receive it. Remove the inner boxes and bags from the cartons. Keep the inner boxes opened for air circulation.
The best way to prechill flower bulbs is in a refrigerator that is only used for bulbs, not mixed in with food. Just to be hygienic.
The refrigerator should be a dark 35°F to 45°F. Never put flower bulbs in the freezer. (If you do have to share a refrigerator with any food, make sure that there are no apples or pears because they emit ethylene gas that can damage embryonic flower formation as well as encourage flower bulbs to decompose.) Some bulbs may develop a blue-green mold during the process of precooling. A firm bulb is a viable bulb. Discard any that are soft after precooling. Once planted, the soil wicks away excess moisture and the mold disappears.
Before removing the bulbs from refrigeration, prepare the planting site fully. Remove only the bulbs needed for immediate planting. Do not remove them from the refrigerator and leave them out in the sun in advance of planting. They could lose their cool. It’s all right to prechill the bulbs a little longer than specified, but never shorter.
Can We Prechill Bulbs for You?
Sorry to say, but we do not prechill bulbs here for later shipment. Each of our clients must prechill the bulbs themselves. The reason for this is that bulbs can easily lose all of the benefits of prechilling if they are in a delivery truck without refrigeration that travels through or stops overnight in a hot area.