Starting petunias indoors

idloveamochaJanuary 6, 2014

I've been scouring the forums, but haven't found an answer yet on this.

I plan to start petunias indoors this winter. I want to start a wave variety, and another 'standard' type. I am unsure about when to start these.

I would be transplanting outdoors around mid-May. I would really like to have blooms on the plants at transplant time.

I've read that they grow quickly, but how quickly?

I was burned last year by seedlings (different type of flower) that I began in early February, only to have teeny tiny plants by May, and no blooms until July.

Any guidance? Thank you!

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ken_adrian Adrian MI cold Z5

without any info on how you grew them.. i can not give you ideas how to have more vigorous plants to take out around 6/1 .... or whenever your last frost date is ...

but one thing i can tell you is.. lack of vigor.. and lack of bloom .. in the appropriate time period equals lack of proper light intensity ....

what is your light source.. how many hours.. how cold at night .. etc ...

frankly .... blooms by july is probably NORMAL .... presuming you arent running a high quality greenhouse.. with perfect temps all day long.. including night... perfect humidity ... and intense sunlight ...

all those things are hard to perfect in a house ... especially if you have a forced air furnace [humidity].. and your house cools down at night ...

when i grew hosta seedlings .. my light ran 16 hours a day.. at night to offset heat loss ...

tell us more aobut your setup.. if you want to move beyond speculation ...

again.. frankly ... i think you won.. growing a hot season plant indoors.. and getting bloom by july ... the only failure you had.. was your 'expectations' of growing them to perfection.. like the pros do ... you know.. those ones that are shipped in .. in bloom ... were probably grown in the deep south or mexico ... so as to perfect the growing process ...

i think you ought to be happy with your result ... though of course.. there is always the need to want to do better ...


    Bookmark   January 7, 2014 at 9:18AM
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Setup is in heated basement. Ambient temperature mid/upper 60's. Seeds are sown in potting mix, and tray is on a heat mat (which gives a boost of around 10 degrees). Germination is quick with this method.
Lighting is a T5 bulb (Jumpstart light system) 16 hours per day. Initial watering is spray mist...then moving on from there.
I've grown other flowers that have done well and have grown quickly. Examples: pansies, shastas, snapdragons, columbine, black-eyed susan, etc. Those had excellent growth and flowering shortly after planting in May.

What threw me last year? Vinca. Germination was alright, but they were soooo slooooow. Light was still 16 hours until I moved them to a southern exposure window. They just didn't grow very quickly/didn't become nice, full plants.

I'd almost rather start the plants a smidge early than a smidge late. I think I saw 6 weeks before planting as a guide for petunias, but that seems very short.

    Bookmark   January 7, 2014 at 8:44PM
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I've grown petunias for years in my greenhouse and it's only for a few years I've had my light set up. It's much the same as yours. I find the 2 are much the same with the same plant growth and germination. In fact I think the lights are a bit better.

I start my petunias the middle of April and set them out the end of May and they are budded out and ready to bloom and the odd one is blooming. I don't want them blooming any more than that so I get a longer bloom time in summer before they get long stems that I call leggy

As you can see 6 weeks like they suggest is the timing I use and for me that's perfect. Petunias tend to germinate and then just sit there for a while. You think they are not growing but they are setting down roots. You may think they will never be big enough to set out. Then overnight they start growing and just don't quit and they are always at the stage I want them for planting out.

    Bookmark   January 7, 2014 at 11:39PM
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Edie(5 NY (Finger Lakes))

Blame the plant. Vincas are slow for me too. I've started them indoors the past two years. Starting them earlier than recommended helped a bit. The early-started seedlings bloomed indoors, which was nice for sorting out colors from the mix, but they were still small. They love heat. They do not love normal house temperatures. They do not love our normal spring temperatures either. I think I'll leave vincas to our friends in warmer climates. There are so many other plants that do like it here.

    Bookmark   January 11, 2014 at 8:08PM
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Thanks, everyone! Sounds like I will start them around the beginning of April. However, I'll be trolling the local seed stores soon.

edie_h, it had to be the coolish temperatures with the vinca. They never looked sickly...they just were not gaining ground at all. In fact, the vinca didn't even bloom until almost August, which was a full 2 1/2 months after I transplanted them outside. We had a mild summer and an extremely wet spring, and I am sure that contributed to it. We didn't get true heat until mid-July.
*sigh* I think I'll just hit the garden center to get my vinca fix!

    Bookmark   January 11, 2014 at 10:41PM
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mxk3(Zone 6 SE MI)

I find both vinca and petunia quite easy from seed, although the petunia seeds aren't easy to handle since they're so small- but you can buy pelleted petunia. Vinca always do beautifully for me under the lights, but have to be careful not to over-water - they hate too much moisture and the growth may be stunted if over-watered; same thing when planted outside - avoid too much moisture. If that means waiting a week or two for the May rains to pass, then I wait.

I usually sow both ~8-10 weeks before planting out date.

    Bookmark   January 12, 2014 at 11:50AM
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I have been starting petunias indoors for several years now with great success. I usually start them earlier than recommended. At about 8 weeks you can take cuttings, and start more plants from those. With the expense of the wave type seeds, working from cuttings can easily quadruple your plants per dollar.

I started these Jan 19th last year - this pic is from April 27th

    Bookmark   January 17, 2014 at 6:33AM
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Mandolls, those look wonderful!

That is around the stage I'd like to see them by early/mid May. So, you'd say maybe the second week in February to start them?

I've never regenerated from cutting on petunias. How did you do that?

    Bookmark   January 19, 2014 at 2:09PM
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Petunias are easy from cuttings. I use a 50/50 pearlite and vermiculite mixture, in a clamshell box. You can cram 20-30 cuttings into the box. Take your cuttings so that you have at least one node submersed in the mix. I don't bother with rooting hormones, the petunias don't seem to need it. Within a couple of weeks roots will begin to form, and they are ready to pot up.

People will tell you not to start petunias so early, to keep them from getting to leggy to quickly, but if you take cuttings, that will encourage them to branch out. Even the types that I am not trying to propagate from cuttings get cut back fairly regularly.

Also - once they are growing, petunias prefer it cool, so your basement temps will be fine. The plants in the picture have all been potted up into 9oz plastic cups, that seems to be just about the right size to hold them for quite a while.

    Bookmark   January 19, 2014 at 6:56PM
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Please tell us about your lights. There seems to be a hundred choices out there , some cheap and some almost out of reach for the regular gardener.. What works and at what price please

    Bookmark   January 23, 2014 at 12:25AM
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Ken - I use the most inexpensive 4ft. "shop lights" I can find, with a mix of cool and warm 40 watt fluorescent bulbs. Over the years the fixtures have ranged from $10-$15, the bulbs about $5 a piece.

Here in WI, t-12's are being phased out and t-10's substituted. The t-10's are smaller, so I can fit 3 lamps (6 bulbs) per shelf which each hold 4 standard trays of seedlings (sometimes I squeeze in 5 trays when I have to) I keep the lamps on timers, 16 hrs on 8 hours off.

For the past 4-5 years I have added a few more shelves and a few more lamps every year in my space. My shelves are spaced 18"-24" apart, with the lamps hung on chain, so that they can easily be raised/lowered as needed.

Here is a pic from early last year - I use the sheets of Styrofoam as reflectors.

    Bookmark   January 23, 2014 at 8:47AM
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I didn't know there was such a thing as a T10. I am using 48-inch T8 tubes in my fluorescent shoplights. I get them in packs of 10 for about $30.


    Bookmark   January 23, 2014 at 12:18PM
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oops - I am not sure why I named them t-10s - they are t-8's. I am better with plants than with numbers :)

    Bookmark   January 23, 2014 at 4:46PM
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ken_adrian Adrian MI cold Z5

the pic above is much like mine.. in theory ...

note the hardware chain on the sides of the lights.. to adjust light height ...

technically ... all you need invest in.. is two standard.. 4 foot shop light fixtures.. with standard bulbs [read that.. the cheapest ones you can buy] ... and the hardware chain ..... just about EVERYTHING else can be common recycled summer garden stuff.. cleaned with 10% bleach ...

again.. the key is LIGHT INTENSITY ... not foo foo lights.. not a foo foo stand .. not foo foo pots..

but a good sterile media also helps with water management ....

you can make this as expensive as you want.. but there is no need ...

ken .. the other ken????

    Bookmark   January 24, 2014 at 5:41PM
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mnwsgal 4 MN(4)

A friend over sowed petunias one spring and gave me some seedlings, all in one small square container. I transplanted them as they got large enough to move. They grew on well under lights until they could be moved outside during the warmer spring days.

I also use the standard 4 foot shop lights and buy bulbs 10 at a time, cheapest I can find. Usually run between 1 and 2 dollars each. I've never had a problem with overwintered plants not flowering because of the cheap bulbs. One year (early on) I used different type bulbs but found it made no difference for my plants or seedlings.

Also use chains to lower and raise lights. Some of my lights are high on one end and low on the other to keep the light closer to shorter plants. The shelving is left over wire shelving
and the chains hang from the shelf above.

Haven't started seeding this year yet but set up is ready.

    Bookmark   January 25, 2014 at 9:57PM
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Thank you one and all, the info is of great help. I was ready to buy expensive "grow lights" as I am having a reall tough time growing "WAVE PETUNIAS". Maybe this info will help
Thanks again

    Bookmark   January 28, 2014 at 1:31AM
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runswithscissors(MT 4/5)

I do not know if my input would be helpful, but I just started my Petunias (January) which is too early, really, but here's why I start so early. I like to grow them cool/cold (55 at most) and very slow and as they grow I keep them pinched. If they mass produce roots, I prune those too. My goal is to have squat, wide little plants by April. Then I start with lots of light and heat and fertilizer. They take off! Keep pinching. By June 1st I have fully branched, large, blooming (4" Pots) petunias ready to fill out patio pots or for planting right in the flower beds. I like the idea of cuttings too, but I pinch too often to have viable cuttings.

    Bookmark   January 29, 2014 at 8:14PM
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mxk3(Zone 6 SE MI)

I use regular fluorescent shop lights, a mixture of warm and cool light bulbs.

This post was edited by mxk3 on Sat, Feb 1, 14 at 12:33

    Bookmark   February 1, 2014 at 12:31PM
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RWS - "I pinch to often to take cuttings"

If you just wait a little longer - those "pinchings" are cuttings. They don't need to be long, just a couple of leaf nodes will do.

    Bookmark   February 1, 2014 at 3:13PM
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Glad I found this forum, some good info here. My wave petunias are doing great, even though they do grow very slow. Not used to that.
Thanks again all

    Bookmark   February 21, 2014 at 12:55AM
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Congrats, glad to hear they are doing well, now the trick is keeping them happy until spring. I suspect your spring is earlier than mine - I finally started mine 3 days ago, but they won't go outside until Mid-May at the earliest.

    Bookmark   February 21, 2014 at 7:22AM
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