Adapted from Effect of Transplant Age on Yield by Elsa Sánchez1
Planting of transplants may be delayed because fields are too wet. This article summarizes research that describes how transplant age affects yield of bell peppers, tomatoes and summer squash.
Summary: Suggestions for transplant age reflect what is found in the literature. They are generally midranges accounting for the difficulty of removing young transplants from cells and minimizing production costs for producing older transplants. One suggestion is to aim for the lower end of the range. That way, in the event that it is not possible to transplant when planned, plants can still be field planted for several days without yield being affected. The suggested age ranges of transplants for ideal growth are 8-10 weeks for bell pepper, 6-8 weeks for tomato and 2-3 weeks for squash.
Study 1: (Weston, 1988) Transplants were 30, 40, 50 or 60 days old (about 4.3 to 8.5 weeks old) when field planted. At the end of the growing season yield was not different, regardless of the age of the transplant; however, the 60-day-old transplants (about 8.5 weeks old) produced larger early yields that the other transplants.
Study 2: (McCraw and Greig, 1986) 11- and 8- week-old transplants of 4 cultivars were field planted. The 11-week-old transplants were 12 inches tall with open flowers and small fruit while the 8-week-old transplants were 6 inches tall without flowers or fruit. Flowers and fruit on the 11-week-old transplants were either left on the plant or pinched off. The 8-week-old plants were left alone or the growing tip was pinched off to stimulate growth. In the first year of the 2 year study, yield was not affected by any of the treatments. In the second year, the 11- week-old transplants on which flowers and fruit had been pinched off, produced the highest early yield, but yields from the 8-week-old transplants with the growing tip pinched produced the greatest number of large fruit. The conclusion was that while cultivar played a role, 11-week-old transplants generally produce more, but smaller fruit than 8-week-old transplants, regardless of whether pinching was used.
Vavrina and Orzolet (1993) reviewed over 60 years of research on tomato transplant age. They determined that overall yield really depends on cultivar, environment and the management techniques used. Because of that, transplants of 2 to 13 weeks old can produce similar yields. As far early yields, they were larger with older transplants.
Even though a 2-week-old transplant generally ends up producing comparable season long yields to a 13-week- old transplant, removing a young transplant from its cell can be difficult because the root system is not extensive enough to hold the container soil which is a problem. On the other hand, it costs more to produce an older transplant and older transplants have a higher possibility of exposure to disease and/or insect problems in the greenhouse.
Conclusions were to use a transplant in the 4- to 7-week-old range so that removing the transplant from its cell is not difficult and transplant production costs are not too high. Also, hold onto any extra transplants. They can be used to replace any in the field that have died and their age should not greatly affect yield.
In a study on summer squash (NeSmith, 1993) 2 cultivars of 10- to 30-day-old transplants (about 1.4 to 4.3 weeks old) were field planted. Some differences between cultivar were observed. In general the age of the transplants affected growth and establishment; however, total yields were not different based on transplant age. Early yield was also not affected by transplant age.
The researcher also mentioned the difficulty of removing young transplants from cells. A 21-day-old transplant was recommended because in the event that it could not be planted right away, it could keep for at least about 10 more days without compromising yields.
Some themes are evident from these studies:
- Different cultivars respond differently to transplant age.
- Environmental conditions and management practices play a large role