Hybridizers: It can be fun to breed your own zinnias - Part 5, 2 by Zen_Man

Zen_Man wrote:
Hello again, Sharon,

OK, I have a software update download going, so I have some time to talk about growing zinnias indoors. It isn't particularly hard to start some zinnias indoors a few weeks early to set them out in your garden after it safe to do so in the Spring. Although that usually does require fluorescent lights, pots, growing medium, and possibly some soluble nutrients, it isn't nearly as hard as actually growing the zinnias indoors from seed to flower to seed to complete the cycle.

As far as I know, no book discusses growing zinnias as a house plant. And there is good reason for that. Houseplants usually have minimal light requirements, are relatively slow growing, and have modest requirements for water, nutrition, and care in general. Zinnias are not like that at all, in that they require a lot of light, grow rapidly, and use a lot of water and nutrients.

If you take the time, effort, and expenditure of money, you can grow zinnias indoors successfully. It can even be gratifying to meet and overcome the challenges of growing zinnias indoors, just as people who grow orchids indoors enjoy doing that, despite the challenges. Zinnias are probably at least as difficult to grow indoors as orchids. My zinnias are my orchids.

I am not an organic gardener, although I use some of their methods, particularly soil improvement by composting. It's hard to get too much organic matter in garden soil. But I have no compunction against using "chemicals" along as they are handled safely. I don't understand some of the organic gardening dogmas. Organic gardeners seem to approve of using Epsom Salts to provide some much needed magnesium (a component of chlorophyll). Epsom Salts, which is Magnesium sulfate, is somehow organic, although Potassium sulfate fertilizer is somehow a dreaded chemical. That seems inconsistent to me, particularly since both substances could come from the same chemical plant. But that is irrelevant to the discussion here, except to explain that how an organic gardener could grow zinnias indoors is beyond my expertise. It might be possible, but I have no information on that.

If you are breeding zinnias, growing them indoors has some good advantages. It lets you make progress much faster, because you get more generations per year. And it turns out that cross pollinating zinnias indoors is particularly easy and effective. You no longer need to worry about the bees stealing your pollen or applying unwanted pollen. Since your indoor zinnias are portable, you can move the pollen donor zinnias next to the female zinnias for your own convenience.

Adequate light for the zinnias is a requirement. You might succeed in starting a few seedlings early on a sunny window sill, but that won't work for actually growing zinnias indoors. That doesn't provide enough light. Even if the window sill were very sunny or there is a sun room or greenhouse available, there simply aren't enough hours of sunlight in the Winter to meet the "full sun" requirements of zinnias.

So you have to supply some light. I use T8 4-foot fluorescent lights in inexpensive shoplight fixtures. I got most of mine from Home Depot, and paid about $8 per 2-bulb fixture. I think that prices have since gone up significantly, because inflation continues. I think that inexpensive shoplights are still cost effective. I put the shoplights as close together as I can, and get four shoplights over each 2 foot by 4 foot shelf. That gives 8 fluorescent tubes per shelf. I have overdriven some of my shoplights for more light output. I try to adjust the hanging chains to keep the bulbs about 3 inches above the zinnia plants. Occasionally I forget and a rapidly growing zinnias gets a little "scorched" by contacting a bulb. The shoplights are on a timer, set to turn the lights on and off for a day length of 16 to 17 hours. The shoplights and T8 bulbs are one of the necessary expenses, but I use the economy priced cool white T8 bulbs. They cost less in boxes of 10 bulbs. I don't think the special plant spectrum bulbs are worth the extra cost. I try to keep my bulb cost to about $3 per 4-foot T8 bulb.

You also need pots, growing medium, and trays for the pots. I use Premier Pro-Mix BX as my "sterile" growing medium. I don't use soil indoors, because that can cause problems. The Pro-Mix contains a very limited amount of nutrients, just adequate for two or three weeks of seedling growth. Because the sterile growing medium doesn't contain the soil bacteria necessary to break urea down into available nitrate and ammonium ions, I use urea-free nutrient formulas, like Better-Gro's soluble nutrients for orchids.

Because you aren't growing in soil indoors, you probably have to add soluble calcium in your nutrients. It might be helpful to get an analysis sheet for your water supply. Most municipal water departments will supply you an analysis sheet on request. Your water might contain usable amounts of calcium, magnesium, and other elements, and then again, it might not. When you are using soil-less growing, you are in effect growing your plants hydroponically, even if you are using a growing mix as a support medium in lieu of the gravel, sand, rock wool, or just plain water that are used in hydroponic gardening. Plants need a lot of calcium, so hydroponic growers almost always add soluble calcium to their water. I purchased some calcium nitrate and I add some of that to the water that I supply to my zinnias.

I will touch on problems with pests, such as aphids, fungus gnats, thrips, and the dreaded spider mites in subsequent messages. You may not have them, but you could, and you have to be prepared, and possibly take preventative steps. One year I lost my entire indoor zinnia garden to thrips, and my very first indoor zinnia garden involved an ongoing war with aphids that I had inadvertently brought indoors from the garden on zinnias that were transplanted from the garden to pots. I used a small vacuum cleaner intended for computer keyboards to suck many of the aphids off of my zinnia plants. Pests that are normally kept in check by natural enemies outdoors can have catastrophic population explosions indoors.

This year, even before a killing frost, starting the 12th of October, I began bringing green seeds indoors and planted them to start a new generation of zinnias, rather than prolong the current generation via indoor cuttings. I took a few pictures yesterday. The first picture shows a zinnia plant in the process of being re-potted. The second picture shows some of my indoor zinnias that are budding. I have a lot of re-potting pending, and it's time to start some cross-pollinating as well.

ZM