Michigan ornamental growers extend season with greenhouse vegetables

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Looking to take advantage of the increased demand for locally-grown and a better quality product, ornamental plant growers in Michigan are adding a variety of greenhouse vegetable crops.

Ornamental plant growers in Michigan are looking to extend their selling season by producing greenhouse vegetables. Many of these growers are looking to take advantage of the increasing interest in locally-grown produce.

Michigan State University Extension greenhouse and floriculture outreach specialist W. Garrett Owen said he works with ornamental growers who produce bedding plants, vegetable transplants for field production and retail sales and who also finish vegetables for retail sales.

“A lot of the growers who I work with who grow vegetable transplants grow cole crops, including cabbage and kale, which are then field transplanted,” Owen said. “Few ornamental growers who I work with produce vine crops of tomatoes and English cucumbers. There is also a grower who is experimenting with peppers and eggplant. The majority of these growers also produce field vegetables.

Michigan ornamental plant growers are using a variety of production methods to grow greenhouse vegetables including using large nursery containers filled with the same substrate used to produce ornamental crops.
Photos by W. Garrett Owen, Mich. St. Univ. Ext.

They grow the ornamentals in the spring and then produce field vegetables. They had the available greenhouse space and felt they could earn additional revenue by adding vegetables.

“In general the smaller growers I’m working with may have as few as one or two hoop houses or greenhouses. The larger growers may have up to an acre of greenhouse vegetable production. I work with a lot of small grower-retail operations. They grow spring ornamentals and also have a vegetable farm as well. They typically sell the vegetables through their retail garden centers. After the spring bedding plants are sold they focus on the vegetables. Some also sell at farmers markets and some have contracts with local restaurants and grocery stores. The product for these growers, who are located in southeast Michigan, is based on what they’re comfortable growing and what their customers are looking for.”

Owen said the growers are marketing their produce as an early crop ahead of what would be field grown.

“These growers can provide fresh tomatoes and other produce earlier than what can be field harvested,” he said. “They also have better control in regards to quality. It’s the early harvest, meeting the early market demand and having a superior quality product.

“When I was visiting these growers in April and May they were already harvesting tomatoes. After the annuals are sold then they are growing the greenhouse tomatoes. That goes all the way until the fall and then they rip those out and give the greenhouses a rest period. They can clean up the greenhouses and prepare them for the next spring production. They make sure that no pests or diseases are carried over through the winter. There is also one ornamental grower producing tomatoes year-round in conjunction with growing ornamentals.”

Adding vegetable production

Owen said some of the growers started producing vegetables because they had empty greenhouse space and wanted to get another turn to increase their profits.

“For many it was a trial-and-error project,” he said. “They wanted to see if they could grow greenhouse vegetables with the inputs, including substrates that they were already using for their ornamentals.

“The vegetables are separated from the ornamental crops. The crops are separated in the greenhouses whether it is a separate greenhouse used for vegetables or the greenhouses can be closed off with automatic doors or plastic curtains.”

Owen said the ornamental growers are using different production methods to grow the vegetables. Some are using large containers, including 2-, 3- or 4-gallon nursery containers filled with a commercial growing mix.

This Michigan ornamental plant grower is producing cherry tomatoes in flower bulb crates filled with a commercial substrate.

“The smaller growers who are doing finished vegetables are using bag culture with a commercial substrate,” he said. “They lay the bags out in the greenhouse and grow the vegetables in the bags.

“Some growers are using flower bulb crates that are filled with a commercial substrate. They plant in the substrate and then cover the crates with the bags the substrate came in. Some are also growing in Bato buckets. The substrates include commercial peat-perlite mixes, coir and some are using a bark-based coir mix to provide more drainage.”

Challenges of greenhouse vegetable production

Even though these ornamental growers were growing vegetable transplants for field production and retail sales, Owen said they faced some challenges when trying to finish the vegetables under greenhouse conditions.

“Since these vegetables crops were being grown in a protected environment and they are edible crops, some of the chemicals that can be sprayed on greenhouse ornamental crops or what can be sprayed on outdoor vegetables weren’t labeled for greenhouse crops,” Owen said. “They had to find out what they could use to control pests and diseases indoors. The growers are using conventional production methods and are not growing organically. They do try to implement organic practices when possible such as pest and disease control.

“The majority of pests and diseases that they are trying to control outdoors are the same as the ones they are trying to control indoors. Some of those pests and diseases are also the same ones they are trying to control on their ornamental crops.”

In this Michigan hoop house, the ornamental plant grower is using bag culture to produce tomatoes to extend the production season.

Owen said one of the biggest challenges these growers faced was trying to grow greenhouse vegetables in the same growing mixes they were using for ornamental plants.

“The crop time for the ornamentals is anywhere from four to eight weeks,” he said. “Trying to grow a greenhouse crop like tomatoes for months in the same ornamental growing mix caused some issues. For example, with a peat-perlite mix settling occurs and the particle size degrades over time. The chemical and physical properties are going to be altered, including air space and container capacity. Some of the air space in the substrate is lost from settling or compaction. Just because a substrate can be used to grow ornamentals in a short crop time, there are challenges using the same mix for longer-term greenhouse vegetables.

Owen said none of the growers who added greenhouse vegetables changed substrates. One grower did add more peat in order to increase water retention.

One of the biggest adjustments the growers had to make for greenhouse vegetables was related to pH management and keeping the pH within the recommended range during the longer crop cycles.

“To make pH adjustments some of the growers did alter or chose a fertilizer based on the crops,” he said. “Blossom end rot on tomatoes was a challenge for one grower. That was helped by altering the pH and changing the fertilizer that was used.

“Irrigation was another issue, including how they were watering and how often they were watering. This also varied based on the age of the crop, the substrate they were using and how they were growing the crop. There wasn’t just one answer for these growers because they were growing different crops, how they were growing them and at different stages in the production cycle. We had to tailor the changes based on their method of growing.”


For more: W. Garrett Owen, Michigan State University Extension, East Lansing, MI 48824; (248) 347-3860 Ext. 202; wgowen@msu.edu; http://msue.anr.msu.edu/experts/garrett_owen.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

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