Growing Greenhouse Vegetables: Timing The Gaps

For ornamental growers looking for a new product for the gap seasons between traditional crops, vegetables can make a lot of sense. Many of the necessary structures, equipment and techniques are familiar. But there is plenty to learn as well, from nutrition to irrigation strategies to variety selection — a lot of which revolves around timing.

We talked with Paul Gallione of Johnny’s Selected Seeds to learn more about the steps he recommends for growers getting started in vegetable production.
 
GG: A lot of the details for adding a crop like vegetables are obviously going to vary for every grower and his own situation. How does timing impact these decisions?

Gallione: There’s more to it than just saying, “OK, I’m an ornamental grower and my greenhouse is empty and I’m going to grow vegetables.” Don’t get me wrong — there’s probably a lot of equipment, labor and infrastructure that can be utilized for vegetable production and therefore make the whole farm more profitable, because you don’t have infrastructure or equipment sitting idle. But there are some really important considerations before you jump into vegetables.
 
If you’re going to grow vegetables in the gaps between ornamental crops, it’s really important to understand the transition or gap time — how long that period is. When are the bedding plants out of the greenhouses and other structures? When can I do that transition?

If you only have two months between crops, you may only grow certain types of crops — maybe leafy greens. If you have four months or six months or even more, you could think about fruit crops.
 
GG: Are growers going to need to consider adjustments with their structures to get into vegetables between ornamental crops?

Gallione: Tomatoes are probably one of the easier fruiting crops to grow. Cucumbers and peppers may be a little more difficult just because of insect pressures and environmental concerns in terms of temperatures and such in the greenhouse.

When it comes to growing vegetables in summer temperatures, growers may want to think about either applying shading compound to the structures or utilizing a shade cloth of some sort — or increase ventilation or evaporative coolers. That’s one thing they need to be aware of, because I would have to think a lot of your bedding plant growers don’t grow things through the summer unless it’s a fall crop of mums or something, and a lot of that is only started in August. They may be used to having three months with nothing in the greenhouse. And those are the three months that we have our most intense sunlight and the longest duration of sunlight.

In a lot of crops, tomatoes for example, pollen can be damaged over 90°F. You can have fruiting issues. Same thing with peppers — you can have blossom drop. Cucumbers can take a little more heat but then there are some insect concerns there.

Also, unfortunately, some of the shorter season crops like lettuce and spinach will not tolerate those hot temperatures growers may find. But something like lettuce or spinach could be a fall crop.

GG: Are there pest issues in moving back and forth from ornamentals to vegetables?

Gallione: That’s one thing that’s really important when you’re growing multiple crops in the greenhouse or any kind of structure. Your Greenhouse Grower readers are making money from selling ornamental bedding plants. The last thing they want to do is jeopardize that.

If a grower is growing a fall/winter crop, they want to make sure that every bit of green matter is out of that greenhouse or structure for at least two weeks before starting the next crop to eliminate what we would call the green bridge. That’s a situation where a disease or an insect is able to survive to get to that next crop.

Say, for example, you have a winter lettuce crop and unfortunately that lettuce crop has two-spotted spider mite. If you’re not considering the timing, you may not get the lettuce out of there when it’s done and leave enough time before you plant your crop of bedding plants. All of a sudden, you’re noticing your bedding plants are going down hard from two-spotted spider mite.

So you have to pay close attention to the timing and eliminate that green bridge. That’s an important consideration.

GG: Are there differences in marketing ornamentals and vegetables growers need to consider?

Gallione: It is different. The most disappointing thing a grower can face is not losing a crop, but having a bumper crop and not being able to get rid of it. So, right from the get-go, you have to think about marketing. Where’s this product going to go?

[Before you start] there has to be some market research and some thought put into the process to determine what vegetables you have a demand for and how you are going to market those vegetables.

It happened to me because I’m a part-time grower with fresh market vegetables, along with my role at Johnny’s. And it’s really discouraging when you put the time and effort and resources into producing a crop and then you can barely give it away.

It’s one thing if you’re not really concerned about the return but your readership is definitely going to be concerned about that. I’m sure they could find other things that are more enjoyable to keep busy if they’re going to lose money at it.

GG: Have you seen any cool examples of ornamental growers making use of their space for a vegetable crop?

Gallione: I read a story about a bedding plant grower in Connecticut that had taken one of their tunnels, and instead of hanging baskets with fuchsia or petunias — because they’re all done at that point in the season — they filled up hanging baskets with cucumbers. They grew cucumbers in a vertical method. But instead of the way most vegetable growers would plant cucumbers in the ground with trellises going upward, they put them in hanging baskets and let gravity help out with the trellis. And that worked out really nicely for them from what I understand.

I believe they had a retail operation so they were easily able to incorporate that extra product. Here they were, taking a structure that was not in production and bringing in money.

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