Daffodil bulbs can be obtained in different grades, as well as standard dry bulbs or pre-cooled bulbs. The standard grades of daffodils are: Double-Nose I (DN I), Double-Nose II (DN II) and round bulbs. DN I bulbs promise the most flowers, but flowers vary greatly among the different cultivars.
For forcing, I rely on DN I bulbs while smaller grades are an economic alternative for dry bulb sales. We are fortunate to have plenty of cooler space, so we can work with standard dry bulbs, which are more economical than pre-cooled bulbs.
For forcing early in the season, coolers are indispensable. But for late-season growing, cold frames will do just fine in regions where temperatures approach freezing. Inconsistent cooling due to weather will result in uneven crops and poor flowering.
One of the most important decisions you’ll make is choosing a reliable supplier. It took me several years and some patience to find the right companies. Particularly challenging for the companies working with me is the fact that the Longwood Gardens’ forcing program consists of more than 100 daffodil cultivars for an average year.
Frequently, displays consist of small numbers of pots. So I need only a few hundred bulbs for each cultivar. In these instances, I am below minimum order and my suppliers not only tolerate me, but they support our program.
Many suppliers are set up to work with you to find the right selection of cultivars, so they are happy to provide you trial samples to promote their cultivars. Each year, I plant some extra pots of new cultivars. This gives me an opportunity to practice with these product lines and see how they perform and fit into my program.
Because commercial operations generally focus on fewer cultivars, they avoid some challenges I have experienced. Good suppliers will help you identify suitable cultivars as well as make sure you’re getting quality bulbs for a fair price.
Bulb quality is also essential. You need to inspect each bulb crate upon arrival. Dispose of any soft or diseased bulbs. If something goes wrong during shipping or bulbs are infested with fusarium, tell your sales representative. You should be informing your supplier as soon as possible to get a refund or a substitute shipment. I have found combining orders and storing bulbs in a cooler will save on shipping costs. Bulbs can be stored for several weeks in a cooler with a set point of 63Â°F.
Vernalization & Forcing
Pots are watered in well after planting and placed in coolers for a cool treatment. Most daffodils require 15 to 17 weeks cooling. Some cultivars, such as ‘Early Sensation,’ are fine with just 12 weeks cooling. Pots should stay evenly moist. The quality of the crop can be affected negatively by uneven moisture during cooling. Crops should be checked at least weekly for watering and to determine their developmental stage. Cooler temperatures are reduced at certain intervals. The developmental stage governs the timing of decreasing temperatures.
Stage 1: 48Â°F. Roots begin to show at drainage holes of the pots.
Stage 2: 41Â°F. The shoots start growing. Then, move pots before they are 1-inch tall.
Stage 3: 33Â°F. Maintain this temperature for the remainder of the cooling period.
Once the chilling requirement is completed, pots should be moved to a forcing compartment in your greenhouse. Choose a well-lit growing area (2,500 footcandles) and maintain a temperature range of 63Â°F to 68Â°F. Manipulating day and night temperatures can alter plant height. The bench time or forcing time varies greatly among the cultivars but ranges generally between 15 and 30 days. If you have time, you can grow plants at lower temperatures like 55ÂºF or 60ÂºF.
Forcing at a lower temperature usually results in more compact and sturdier plants with stronger flowers. One has to weigh the prospect of better quality product with the cost of the bench space.
Often, people ask me when to plant bulbs and when to take them out of the cooler. This all depends on the display date, or for a commercial greenhouse operation, the ship dateâ€“and for a person trying to win a blue ribbon at the flower show, the date of the show. Determining the proper planting date is a basic equation and simple to calculate. It is best done using a spreadsheet.
Subtract from the display date (DD) the time it takes to force (FD) the crop in the greenhouse and the time crops need to vernalize in coolers (VD). The result will be the potting date (PD). So again: PD = DDâ€“(FB+VD).
Plant Health & Crop Quality
Harvest & Sale
Make sure you have arranged for swift distribution of your crop. Daffodils are highly affected by temperature. At a temperature range of 45ÂºF to 55ÂºF, daffodils exhibit a remarkable longevity of two and sometimes three weeks. At temperatures above 65ÂºF, flowers may last only a few days.
Therefore, the shelf life of a crop is limited and flowering pots can be held for only a limited amount of time in coolers. Infrequently, I have held crops for about 14 days in a cooler with a set point of 32ÂºF. When holding crops longer in the cooler, plant quality will deteriorate. Please note that plants held for some time in the cooler have a shorter lifespan on display or on the shelf. They do not last nearly as long as plants that were never held in a cooler.
Speed of distribution and temperature control during transportation to the sales shop are essential. It would even be worthwhile to have several potting dates with fewer pots per succession. So when delivering plants to the store, a smaller number is delivered on subsequent delivery dates, providing fresh merchandise over several weeks.