Even with the rise in first-year flowering perennials, it can still make sense to overwinter crops for early spring sales.
July 11, 2011
Paul Westervelt of Saunders Brothers in Virginia gave a great presentation on scheduling perennials, as part of a day-long perennials production track at the OFA Short Course on Saturday. He explained the pros and cons and ins and outs of producing perennials in the spring for spring sales, in the summer for fall sales and overwintering in the fall for spring sales.
Vernalization, or having the plants experience a cold period by overwintering or simulating winter, can create beefier plants with more flowers. While some can be cooled in the plug stage, others must bulk up to a certain size before cooling.
For growers who are planting in the fall and overwintering for spring, advantages include free heat, high light, plants going dormant at the natural time and getting a jump on the spring season. One disadvantage is the longer a crop is in production, the odds increase for problems to arise, like root rot and botrytis.
If you're growing and finishing crops in the spring, vernalization still matters and it's better to choose plants that don't need to be bulked first. Many perennials, like gaillardia 'Arizona Sun,' don't need vernalization and can be grown alongside annuals. Although the turn is shorter, plugs do take time to root and low light levels can make bulking slow. Crops also may need to be heated for an early finish.
Advantages of producing another turn in the summer are the space is available along with high light and free heat. The drawbacks are increased pestilence and disease pressures and the fact that the fall market is not spring and demand is not as strong.
In terms of liner sizes, Westervelt uses 128s in quarts, 72s in gallons and 30s in 2-gallons. He also has been rethinking bare root as an input form. For instance, coreopsis 'Moonbeam' produced from bare root are much fuller than the wiry plants that grow from plugs. Conversely, he prefers astilbe plugs over bare root.