Can We Prevent “Club foot” Celosia?
Well-grown crested celosia should form a spade-like triangular shape topped by a wavy edge. Under Ithaca (Zone 5) summers in both high tunnel and field, we frequently got irregular, misshapen flower heads that remind one of a club foot rather than a crest. This disorder is particularly prevalent among varieties that were selected for the well-regulated conditions of greenhouse culture, such as the Bombay group.
Research indicates that the crest shape can be influenced by daylength, but the occurrence of this disorder is too sporadic to be explained by the regular progression of the duration of light. Temperature fluctuation are a more likely causal factor, and they widely in our growing season. Accordingly, we chose to manipulate the temperature under which the celosia seedlings were being raised, to see the effect on crest shape.
Beginning 2 to 4 weeks after sowing, we transplanted seedlings of ‘Bombay Sunshine’ into 4 in. pots and placed them in either a growth chamber set at 60 F day and 50 F night temperature, or left them in a 72 F greenhouse. At the same time, we looked at the growing points of the seedlings under a microscope, to see if the growing point had changed from a round dome producing leaves, to the distinctive rectangle of the flower initial. We thought that by exposing the plants to the cold shock at the time the flower head was forming would produce the distortion we often saw in our plantings.
With our first try, we thought we had hit the jackpot: the warm-treated plants had regular combs, and the cold-treated plants looked really ugly (see photo 1). We should have quit while we were ahead. In the second run, in the warmer growth conditions of later spring, the plants had already formed flowers by the time we started the cold treatments, and none of the plants showed the malformation. In the third run, although we timed the cold treatment exactly to coincide with flower formation, even the warm-treated plants were malformed (see photo 2).
Although it is tempting to say that experiments should never be repeated, it appears that there are factors other than temperature fluctuations causing the disorder. In particular, we think that irregular watering in the period before the temperature treatments were started were another factor. For celosia growers, the results reinforce the advice that careful variety selection, avoiding lines poorly adapted to your growing conditions, is of key importance.