Over the last few years, the Longwood Gardens lily program expanded to include an assortment of lily cultivars: Easter lilies, Asiatic, Oriental and hybrid lilies. Next year, Longwood will be growing lilies almost 10 months of the year, and its visitors are always delighted to see such amazing lily displays.
This year's OFA Short Course was a busy event filled with meetings so Longwood could plan its major event next year: Lilytopia. As part of Lilytopia's planning, I was tasked with growing lilies to be displayed at a New York City promotional event in September. The event commemorated the founding of New Amsterdam 400 years ago.
I had worked with a large number of forcing bulbs over the years, but I had never been tasked with summer lily production. And for the New York event, I had a time frame of just 50 days to finish a crop. The deadline was troubling, but I planted the bulbs July 15. The crop turned out great, and Longwood made a good impression in New York City.
You can make a good impression, too, if summer production of Asiatic lilies makes sense for your greenhouse operation. In this article, I'll offer tips for summer production of Asiatic pot lilies - essentially sharing Longwood's success story for our 50-day deadline earlier this year.
How It's Done
To start, it is best to order bulbs with a delivery date a couple days before the potting date. It takes a couple of days to get the frost out of bulbs, and it often is impossible to break up frozen blocks of peat and bulbs without injuring the plants. Make sure you order just enough bulbs for your project. Bulbs will start sprouting once thawed, and they should not be refrozen.
When working with bulbs, including lilies, the quality of the bulbs is critical. In my experience, cutting corners and saving a few cents here and there by going with a cheaper supplier often leads to problems later. Find a supplier that works for you, and you will find your job to be a lot easier.
Check your bulbs upon arrival and reject damaged or diseased bulbs. Do not plant them, because you are likely to invest a lot more resources then the crop may be worth.
Order the appropriate grade of bulbs that fits your program. Lily bulbs are offered in a range of grades, corresponding to the circumference in centimeter, starting at 10/12, 12/14 and 14/16, which is common for Asiatic lilies. The same goes for larger grade Oriental bulbs, which are offered as 14/16, 16/18 and 18/20 grades.
A grade indicates how many flower buds to expect on a single stem. Larger bulbs will yield more buds, and the potential number of buds varies greatly among cultivars.
As a Longwood grower, I am interested in the biggest bulbs possible for the extra blooms. But if you're producing crops for a box store, a smaller grade might suffice.
If it is important for you to work with a specific cultivar, order early. Certainly, one can order last minute and bulbs may be available. But popular cultivars sell out. When ordering late, be prepared to negotiate for substitutes. This can be time consuming and frustrating.
I have been working with bulbs for many years and have made the following observations: Good suppliers have dipped their bulbs in fungicide and systemic insecticide before distribution. The bulbs have been programmed and pre-cooled before they have been frozen for storage. And, generally, a wide variety of cultivars can be obtained year-round.
Good suppliers will work with you in selecting the best cultivars suitable for your location. In my experience, suppliers often can give you advice with products that may work well within your market segment. Still, you need to hold your sales rep accountable.
Potting Media & Fertilizer
Longwood owns its own soil-mixing machine. Longwood uses a special lily mix that consists of 40 percent peat moss, 20 percent coarse sand (for extra weight), 25 percent pine bark compost and 15 percent vermiculite.
A good pH range of the media is 6 to 6.5. Frequently, I have to increase the amount of lime added to the medium when batches of pine park compost are particularly acidic. In general, it can be stated a potting medium for lilies should have good water retention yet provides for sufficient aeration.
Another recommended medium used for commercial greenhouse production is as follows: 25 percent peat, 60 percent pine bark and 15 percent composted pine bark. I do not apply fertilizer when mixing media. Pelleted fertilizer release is controlled by temperature. Too much fertilizer may get into the medium during summer growing conditions.
In a few instances, crops were burned. I have had good experiences with complete soluble fertilizers applied via the irrigation system. A complete liquid fertilizer is applied at a rate of 350 ppm every watering.
On weekends, the pots are flushed with clear water to prevent salt accumulation. Once the stems sprout, the media should have an EC of 0.5 millisiemens (mS) to 0.75 mS. Anything over 1.5 mS will cause trouble, and the pots should be flushed with clear water to get the EC down - and I mean down very quickly.
I chose to add coarse sand to my mix to add some extra weight to the pots because I was growing the crop outdoors. Especially toward the end of the crop cycle, wind can cause damage to the plants when pots are blown over.
Shipping and weight of the pots are issues relating directly to crop quality. There is a lot of emphasis on reducing weight of the crop for shipping. Consequently, extremely light potting mixes are used, including for lilies grown in smaller pot sizes.
These media may not provide sufficient weight to support the plant. Shuttles work well on benches to hold up the pots. However, once the crop reaches the consumer level, pots are often taken out of shuttles. Crops at this stage are prone to get damaged because the weight of the pot does not hold up the plant.
Economic reality is tough, but so are your commitments to customers. If the promised value of your product does not deliver, your customer base will erode very quickly.
It is important the potting media retains water to ensure consistent moisture during a day in the summer. Aeration is a must. Waterlog or overwatering will result in phytophthora, pythium as well as other root rot pathogens attacking the crop. Keeping pots dry is not an option, either. Keeping them dry in the summer is likely to damage the root system - the roots quickly desiccate and plant growth will be impaired, resulting in a poor crop.