I can't tell you much about dahlias, as they are much more difficult here and we have such a short season, they behave differently, but I think I can answer the glads questions. Glads are heavily dependent on variety for their bloom time. Bigger and smaller corms of the same variety will bloom at about the same time, or the the big ones might bloom slightly earlier, but the flower stalk will be smaller on the small corm than the flower stalk on the bigger corm. For consistent flowers over a longer time period, succession-plant them. For the very earliest bloom, get earlier varieties and plant them in your warmest spot. If your place is like mine and has two different microclimates, just planting the same glads in both areas will result in a longer bloom time. I succession-plant for longer bloom, though, because that's a lot more reliable.

How tall is your greenhouse ceiling, i.e. from the surface of the soil to the roof? Is it less than five feet? The glads might get taller and more stretched-out in the greenhouse, so take that into account, but if you have five feet or more of growing space, I doubt it will be a problem. You might want to consult another Midwesterner on that. Flowerfarmer, do you grow glads in the greenhouse?

Also, did you realize that glads continue to get taller even while they're blooming? If you cut them in a timely manner, i.e. when just one or two florets are open, or even when none are open but some colored and are sticking out from the stem sideways, they never will reach full height in the greenhouse, so that saves you some space problems.

Do you have a plan to deal with or avoid the thrips that plague glads? I don't have that problem, thrips don't handle this climate well (I think they don't like the cold mountain nights), but a lot of people lose a lot of glads to thrips.

Jeanne

Jeanne,
Yes, I have grown glads before and been totally wiped out with thrips. I have a bunch of bulbs that were sent me free to replace those that I thought came with thrips last year. I'm thinking of planting only a couple hundred in the greenhouse to see if they do anything, or else the bulbs will just wither up and die if not planted this season.
I had hoped they'd just give me a credit so I could order something else, but they said, "Glads, or nothing." So, I'm thinking it's worth a try. I believe glad thrips are species specific so they won't get into other crops. Anyone know?
Greenhouse is about 7 feet high, or 6 feet from the soil level in the beds, but that's in the middle of the greenhouse, so I'll have to plant them mostly near the aisles, and put lower growing things closer to the edges.
Ann

The dahlias would probably be happiest with greenhouse film that blocks the UV rays and dispurses the light throughout the hoophouse. You don't get burn spots with this type of film. If the temperature doesn't get over 90-95 in your hoophouse, the dahlias will be fine. They will need plenty of water. I'm assuming you use fans for air circulation. We have dahlias from cuttings in one of our hoophouses. We planned these for early production cutflowers before the field crop starts producing. Now, we are cutting both from the hoophouse and the field. The dahlias in the hoophouse sustained some pretty high temperatures for two weeks straight without any adverse affects on them. They just kept on producing many, many blooms.

I have not grown glads in the hoophouse; but, I can't think of any reason not to try. Large growers force them in the fields by putting plastic over the plantings. Good air circulation in the hoophouse -- top requirement for disease and pests. Even a cheap box fan if you don't have greenhouse fans helps move the air. If you use drip irrigation, this would probably help control alot of those issues. Planting them closer to the aisles also sounds like a good plan. Are glad thrips species specific? We had signs of thrips on the dahlias. I assumed they were the same; but, honestly cannot say for certain. I can say I despise those nasty things; but, more than anything the Japanese Beetles put us over the edge.

Are you planting the dahlias and glads directly in the ground in the greenhouse, or in pots or crates? Is it a regular greenhouse, or a hoophouse? I'm curious because I grow many dahlias in the ground, but am trying to come up with something for much earlier blooms. I am putting in 2 more rows that will be left in the ground this winter. Most years they keep over just fine. The ones I left in the ground last year have been blooming for a couple weeks. I did grow a few in pots in the greenhouse, but they weren't the taller varieties, and most started getting powdery mildew because of poor air circulation, so have now moved them outside.

Teresa

CRDahlia,
I think you addressed your question to ff, but I'll tell you what I am thinking. I have raised beds in the greenhouse, some 6 inches high and others 12 inches. I'd think the taller one would be good for both dahlias and glads for support. But I like the idea of doing them in crates. Thanks.
Ann

We find dahlia flower production drops off a lot in October as the days shorten, regardless of the weather. Our Thanksgiving weekend ( second one in October)is the last weekend we count on having a lot of dahlias, although it's only about 80% or 90% of what we have at the end of September. By the end of the month we have relatively few flowers, even though we haven't had frost. As you're farther south than we are the days will shorten less dramatically, but I'm not sure how much farther south you actually are. We're in the Greater Vancouver area. Good luck.
Chris

I don't think thrips of any kind are species-specific. They happen to be most attracted to light-colored flowers, like white, pale yellow, pale pink, but they'll go for the dark ones also. They just happen to be really in love with glads, but they'll hit roses, and I don't know what all else. I had a problem with them in my previous garden.

Jeanne

I forgot to mention that thrips especially thrive in hot weather, so they going to really love the greenhouse. That's why I asked whether you had a plan for prevention.

Jeanne

In a greenhouse environment it is possible, in principle, to completely eliminate insect pests. With field grown flowers this is not possible. This is one of the reasons that conventional flower growers frequently produce crops in the hoophouse that could equally be produced in the field. The hoophouses are used somewhat for climate control; however, pest control is one of the major reasons we grow in the hoophouse. Pests were observed when it was cool and rainy -- not hot. We have also installed large screened doors on each endwall of the hoophouses for pest control. The only crop we have found that does not do well in the hoophouse environment are zinnias.

Teresa, I don't know if your question was directed at me or what. However, the dahlias are planted directly in the ground. The dahlias we grow in the hoophouse are bred specifically for hoophouse crops. These plants do not get as bushy as the field dahlias. Space is at a premium when growing in a hoophouse. In one 8'x92' bed, there would be 368 plants. We have no problems with powdery mildew even planted so close together. These new variety plants may well be bred for mildew resistance. The hoophouses/hightunnels are actually called cold frames by the greenhouse industry. Generally, they are unheated structures. One thing I didn't mention earlier, but is important: We had 5' extension put on all the side anchors when we ordered our houses. So, the hoops don't go all the way to the ground on the sides as would normally be the case with a hoophouse. We, therefore, have 5' sidewalls. We can grow tall crops in all the beds in the hoophouse -- not just down the center bed. These houses are normally 12'6" in the center.

You can eliminate thrips in the greenhouse? How, when they're so tiny, I'm sure they can go through a screen? Don't they fly? I have no idea whether they have a flying stage or not.

Jeanne

I have no idea if thrips fly. Or, if they do whether they fly first class or coach. You are aware there are beneficial thrips? Anyway, I believe Ann mentioned her glads arrived infected with the pests. Therefore, the free glads. The percentage of pests in our hoophouses is so minimal. There are absolutely no Japanese Beetles in any of our houses. We battle them constantly in the field. We also have no aphids, no thrips in the hoophouse environment. We're not organic; and, we not opposed to spraying for pests if necessary in the field. We never have to spray in any of the hoophouses.

I didn't know the bulbs themselves could carry thrips. I thought the thrips showed up from somewhere in the hotter days of summer, but I've never had a real thrips problem so I've never looked into it. I've only gardened in a cool-and-foggy-summer climate and in this cold-nights climate. Thrips don't seem to like either climate.

I have a severe aphid problem in the greenhouse, but the thrips are minimal. I only see a few on the white snaps but they aren't enough to cause any kind of a problem. Even the white snaps they're on are just fine. They don't seem to be interested in anything else in there, but I don't have glads in there.

No, I didn't know that there are beneficial thrips. How are they beneficial? Maybe those are what's on my white greenhouse snaps.

Jeanne

I am happy to report that I ignored all the advice to totally gt rid of my glads last year when I had the major thrip invasion. I worked in a little systemic rose treatment just around the glads, and did it again this spring when they were coming up. My glads that I left are starting to open, looking great! Since I Planted new ones too jsut incase I am going to have to find a way to sell lots of glads! And since the systeemic only has about a 3 month life to it, the systemic that I Put on in early MAy should be just about out of them now. We had one 3 day heatwave early on but after I had put on the systemic and so I am very happy. Cut blue ones and peach ones for tomorrow's bouquets.