Zinnias Won't Stop Blooming If You Do This

Zinnias, native to many parts of North America and Central America. These flowers make the ideal annual for any pollinator garden. In this video, we're gonna go over how to plant, how to fertilize, how to prune, how to water, potential disease issues, and so much more. Hi, I'm Dr. Tom Warren, and you're watching A Plant Doctor. Let's get started. Zinnias tend to do best in full sun, like you see here behind me. They can take a little bit of shade. However, if we get them in too much shade, they'll get very long, they'll get leggy, they'll tend to fall over more often, and they'll also be more susceptible to diseases that we'll talk about later. Zinnias can be anywhere from, say, four to eight inches tall in some dwarf varieties, all the way up to over four feet. I've got some flowers up here touching five feet tall in some of the larger varieties. The flowers on zinnia, they can be single flowers, so just a single row of petals all the way around the flower. They can be double flowers. They can be semi-doubles. But regardless of the flower type, all of these have composite flowers. So what we consider the whole flower here is actually several dozen flowers in one. And so when the petals fall off this and it goes to seed, there'll be several dozen seed heads at each one of these flowers. There's two main groups of zinnias that we need to discuss. So we have our taller ones. These are known as elegans. So zinnia elegans can get four foot tall plus. And then there is a dwarf variety called zinnia ingustifolia. So ingustifolias are gonna be 12 inches all the way down to about six inches in height. In general, the elegans will be more susceptible to diseases. I'm gonna show you here later. These actually have some powdery mildew and they have zinnia blight as well. We'll talk about both of those and I'll give you some closeup shots. The dwarf varieties tend not to get it as often. So, but there's a trade-off here. These will bloom more prolifically than the dwarfs, but they tend to get a little more disease. The dwarfs, less disease, but not as many flowers. Now there is a third kind we've crossed. Breeders have crossed ingustifolia with elegans. And we've kind of got this mid-range selection where we've taken some of the height out of elegans, some of the disease resistance out of ingustifolia. And so you get a plant with little disease, lots of flowers and minimal disease pressure as well. And speaking of disease, there's really two things you need to look at at your zinnias to be aware of. There's powdery mildew and there's also zinnia blight. There's some cultural things that you can do with your zinnias to lower the chances of seeing this. One is plant in full sun. Second is going to be plant in the area where there's a lot of airflow. Don't plant in a corner. Don't plant right up against the house where if the wind's blowing a certain direction, there's no wind hitting it. For example here, this wall over here to my left, it faces south. So if I was getting a north wind and this plant was right up against that wall, it would get no air movement at all. We want air movement, we want full sun, and that's going to help our zinnias not get as much disease. If your powdery mildew becomes significant enough to the point you're seeing leaves begin to wilt, you can spray them with copper sulfate. So that's an organic fungicide that you can use or you can use daconil as well. I'll leave some links down in the description below for both of those products. It's just general fungicides. I've elected not to spray these even though they have a little bit of powdery mildew on them. It's not to the point that it's been detrimental to the plant. The other thing is going to be zinnia blight. So zinnia blight is going to be little round circles on your leaf and most of the time it'll be brown black on the outside with white in the middle and that's zinnia blight. Here again, it's not something that we worry about too much. You can see how healthy and happy these zinnia are behind me and I haven't sprayed them with anything. Here behind me, I try to keep this insecticide free, herbicide free as much as I can. I don't think I've sprayed anything in here in five or six years because all this is a pollinator garden and so we're trying to keep this as chemical free as possible for all of the insects, the butterflies, the moths, even the hummingbirds. We have a lot of hummingbirds come in and feed on these zinnia as well. Trying to keep it all clean for the animals that come through here because we enjoy what the flowers bring in terms of the insects and we don't want to put anything out that's detrimental to them. So how do we use zinnias in the landscape? If you're using dwarf zinnias, the ones that get six to maybe 12 inches tall, you can use those as borders in between your turf and your planted areas like you see here behind me. These larger ones can be planted as specimens. So I've got a few here. This is elegans. You can see here this tallest flower stalks, maybe five feet tall or so. And I'll let them grow, maybe groups of two or three as specimens. And then I have some cross hybrids as well that I'll shoot some B-roll of. And so this is perfusion. And perfusion is that hybrid I was talking about earlier where we're crossing some angustifolia features with some elegans features. So the plant's not as big, but also we don't see near as much of zinnia blight. We don't see near as much powdery mildew either as well. So specimens, we can use them as a border. You really can't use them for a hedge or a screen. They don't get big enough. So specimens and borders are the primary uses for practicality in your landscape. The easiest way to grow zinnias is from seed. They have an extremely high germination rate. You should easily get over 90% germination rate with growing zinnias from seed. And we can start them indoors. You can start them before your last frost, say a month before your last frost. So for me, my last frost on average is April the 11th. So mid-March, we can start these indoors and you can have them in a south-facing window. And once they've germinated, so they'll germinate within a week, easy. Most of them are going to germinate within three or four days. In the afternoons when it's warm, you can take them outside. And if you're not getting cold that night, you can just leave them outside. But if you're gonna get down below like 40 degrees, you'll probably need to bring them in for the night. Slowly acclimate them to the outdoors, never exposing them to temperatures below 40 degrees. You never want to expose them to a frost with them being annuals. They're going to die very quickly if you do so. So what's my recommendation for how to start these? I do not like starting these in something like a humidity dome that is one of these 72-tray cells. And the reason being is there's really not enough volume for zinnias in one of these little cells here. So these might be okay for starting a few things. I love seed trays, don't get me wrong. They're fantastic humidity domes. But what I prefer is something a little larger. So I've got two examples here. I'll start them in old six-pack cells. You can notice the volume difference here between that 72-count tray we were looking at earlier. Much more area for the roots to be able to grow. Or four-pack cells. Either one of these is very sufficient. Zinnias are not gonna be particular about potting mix. Whatever you have on hand, use it. Keep the soil moist and your zinnias will germinate. Another way that you can start zinnias if you do not have seed trays, you can start them in milk jugs. You can cut the tops of the milk jugs off and put some potting mix in there. Or you can plant them directly into the ground. Simply rake back your mulch, put the seeds down on the ground. You may want to incorporate some potting mix or some sort of soil amendment, some compost in your native soil. Put your seeds down, rake the mulch, pine straw, pine bark, whatever you're using for your mulch, rake that back over the top. And your germination rate will be just as high as if you started them in seed packs. The only downfall to doing it that way is you need to wait until after your first frost. So I'll get to April the 11th, which is my average last frost date. It doesn't mean that it's always my last frost date, it's my average. So that means like 50% of the days will be after April 11th, 50% will be before. I'll get to April 11th, I'll look at my 10-day forecast. And if we're in a warming trend, I'll go ahead and plant some zinnias seeds in the garden, direct sow into the ground. Rake back the mulch, seeds down, mulch back over, they come up, no problem. If you're seeing a downtrend in temperatures, a threat of a frost, get past that time period and then go out and plant your zinnia. When and how should you water and fertilize your zinnia? Zinnias are extremely drought tolerant. I have not watered these zinnias one time this summer. Now I have had above average rainfall this year. I do not want to be misleading here, but on a general rule of thumb basis, if you don't get rain for a week, water your zinnias. Now they do not like wet feet. I would not encourage you to water these every day, every other day, unless they're in a pot. If they're potted, use the finger check rule, stick your finger down in the soil, and if your finger is wet, don't water. If your finger's dry, go ahead and water. But in the ground, like these are, once a week is more than enough water. In terms of fertilizing, oftentimes just mulch decomposition is more than enough for your zinnias to thrive, just like you see here. I have not fertilized these this summer at all. I have extremely sandy soils here. There's very low nutrient value in my soils. Most of the fertilizers that you're gonna put down will leach out through the soil layer over time in these very sandy soils that I have here. And you can see how well these zinnia are doing. Now, if I start seeing some symptoms of some nutrient deficiencies, like interveinal chlorosis, which is just yellowing of the leaves or anything like that, I will come out and fertilize. I may put a tablespoon of Osmocote down along the roots of these plants. Osmocote is a slow-release fertilizer. It has all of our macros, the nitrogen, the phosphorus, the potassium, but it has all of the micros as well. So there's things we don't think about that plants really need, things like magnesium and manganese and iron. It has it all in there, and it's releasing it out very slowly so that it does not leach out into the soil. And when it rains, it just goes away. It controls the release of the nutrients to where your flowers are going to get more nutrients than they would otherwise. Pruning zinnias. You can get a strong second flush out of your zinnias if you prune them mid-summer. So early summer, they start to bloom. They're putting on some flowers. You can come in, cut these off a third of the height. I wouldn't go much past half height, and they're gonna make a thicker, fuller zinnia, and it's going to produce more flowers than you would have otherwise. Me, personally, I do not come out here and cut these down to a third or a half. My wife actually does flower arrangement stuff, and she's doing enough selective cutting of these really tall flowers, coming in here and cutting them. And wherever she cuts, we'll have more branching coming out. So these are constantly branching and filling out. So if you're doing these for cut flowers, for indoor flower arrangements, there's really no need to come in and whack them back really hard. But if you do elect to cut them back by a third, what I would encourage you to do is if you have several places where you have zinnias, like I have here, only do one group at a time. So I would do this group here. I would wait maybe 10 days, go do the second group, wait 10 days, go do the third group. So by the time that I get to the last group, these have already flowered back out. I'm trying to keep my pollinators as happy as possible. My pollinators absolutely love the zinnias. It's late in the evening here, so they've kind of gone away. But if you come out here in the afternoon, there's just tons of moths and butterflies and bees and hummingbirds. It looks like the sky's dancing with all these insects that come in here. It really is amazing. So we're trying to do our part to keep the pollinators happy as well with our zinnias. To me, companion planting with zinnias is very important, especially in early spring. Oftentimes when I first plant these zinnias, especially these tall elegans like you see here, they're kind of leggy. If we get a thunderstorm, they'll blow over and eventually they'll grow back upright. But what I found out is this, if you have the right companion plants, they're less likely to blow over. So what I have here, this is lantana. This is a mounding lantana. And so I planted lantana and zinnias interlaced with each other. And what I found out is that the lantana will hold up the zinnias. So if we get a strong storm early on in the spring, they're not gonna get blown over near as much as if they didn't have something else to lean up against. Now, as you progress through late, all the way to late summer, like we are now, these get really woody. I mean, I can shake that right there. It's not going anywhere. But early on, they do have some very tender vegetation and they want something to lean up against when those winds kick up. So lantana's good. I have black-eyed Susans here. You can probably see just off to my left here. Beyond those, we have some Shasta daisies and there's some Russian sage in here as well. So just anything that your zinnias can lean up on. Now, I would not do it with something that's taller than your zinnias. So like a Nellie R. Stevens or a Yopon Holly or something like that, because you're never gonna see the flowers on your zinnia because those plants would be taller. But some of these lower growing perennials are ideal for companion plants with zinnias. If you have a tip, trick, or hack that you use with your zinnias in your garden that we did not talk about in this video, please leave those down in the comments below. Here on the channel, I like to think of us as a community of learners and I would love to learn something from you, the viewer. Guys, as always, thank you for watching The Plant Doctor. And until next time, happy gardening.