Growing seeds in Perlite

joannacalaAugust 8, 2007


I am a recent gardener and am about to try my hand at growing some perennial flowers from seed - echinacea, rudbeckia, helianthus, helenium, agastache. I have read that Perlite is a good medium for germinating seeds. Since I live in zone 10 and have a only a very mild winter (never any frost), I was planning to leave the seeds in a semi-shady spot on a balcony outside about Jan-Feb. time.

Could someone please advise how to use the Perlite method? I guess I should cover the seeds with a thin layer of the perlite? Should I also cover with cardboard until they germinate? Do I need to use liquid fertiliser? If so, at what stage? When should I move the seedlings to a soil-based mix? Can they go straight from the perlite to the soil in the ground?



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calistoga_al ca 15 usda 9

Using straight Perlite you may have difficulty keeping enough moisture to germinate the seeds. I would cover with clear plastic to prevent evaporation. Seeds that require darkness you can cover with black plastic. Fertilizer used where there are no roots does no good. For most plants transplanting is best done when it has produced the first set of true leaves. The first leaves are cotyledon or "seed leaves" the next set are "true" leaves. I would pot most seedlings instead of directly into the garden. Al

    Bookmark   August 9, 2007 at 9:49AM
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Perlite is expanded volcanic rock, and there contains nbo nutrients to nurture the seedling. May i suggest a mix of cactus soil (for fast draining), perlite (for drainage) and some vermiculite for retaining moisture) The balance between the draining properties of the perlite and the absorbing properties of the the verimiculate make the mixture hold the right amounf of moisture. Make sure you use sterile soil and materials as not to intoruduce baterial and fungus (namely damping off fungus) to the seedlings

    Bookmark   August 9, 2007 at 5:01PM
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origami_master wrote: Make sure you use sterile soil and materials as not to introduce bacterial and fungus (namely damping off fungus) to the seedlings

I'll tell you, for as much as people make fun of me and tell me it's overkill, I'll never stop pasteurizing my seedling mixes before using them...I've not had a case of contaminated seedlings since.

    Bookmark   August 10, 2007 at 4:56PM
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Fungus and mold are the bane of my seed growing experience. If I do use a mix that has any organic matter, I spray with a .1% solution of hydrogen peroxide after watering.

Perlite is so light, I would use washed (salt-free) sand with the perlite for solidity and fertilze lightly after germination, or just follow Oragami Master's advice.

    Bookmark   August 10, 2007 at 5:29PM
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calistoga_al ca 15 usda 9

Considering that many plants self sow themselves in your garden soil every year, how do you suppose the garden soil manages to sterilize itself? Damping off is NOT pre-ordained because you are not using sterile soil. Too much moisture and too little air circulation, plus low light levels encourage the growth of the fungus. This combination is never present in the garden and even with a large population of fungus spores damping off is not a problem. Al

    Bookmark   August 11, 2007 at 8:51AM
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rhizo_1 (North AL) zone 7

I agree with Al. I never sterilize my seeding flats. Problems with disease are almost always due to excess humidity, moisture, and not enough circulation.

I've never heard of anyone using 100% perlite for seed germination, but I do use it for rooting cuttings. I prefer a perlite/peat moss combo for seeds.

I sow seeds in flats, in rows. After they develop their first set of true leaves, I transplant them into cell packs or 4 inch pots, filled with a coarse textured potting mix. Here, I will grow them on until they fill the pot nicely with a substantial root system. As long as the potting medium is very coarse (full of perlite and bark), that won't take much time at all.

    Bookmark   August 14, 2007 at 12:53PM
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tommie_jo(z8b TX)

Using straight perlite for seed starting is not the norm, it is used for cuttings. Instead start with a quality "seed starting mix"; it will be free of pathogens and of the correct particle size for starting seeds  fine, with the ability to hold moisture until seeds have sprouted and pushed through the surface.

This link to RichterÂs Herbs, Seeding Demonstration and Why Seeds Fail may help you a lot. "If at first you donÂt succeed, try, try again."

The problem most folks without a greenhouse or indoor shelf & shop light fixture system have is that once germinated seedlings require very bright light or they will stretch and fall over. I have a metal bakerÂs rack, seedling heat mat and shop lights equipped with full spectrum daylight bulbs (set 4 inches above the flats) for starting my perennial and veggie seeds indoors. Once they have true leaves, if the weather is right, I move them outside for more natural light either in the flat or transplanted to cell packs, protected from overly hot sunlight with floating row cover or shade cloth to continue the growing out phase.

There are simple, cost effective systems one can set up  just experiment and youÂll find one that works for you.

The most important pointers I can give is to do a little research BEFORE you plant those seeds; find out what that particular seed requires BEFORE you waste your seed, time and resources ($$$) trying a method that may not work. If those are rare or expensive seed don't plant them all at once, see if the method works first; start a notebook, keep track of methods used, dates and results. Also learn how to properly STORE seeds so they remain viable.

So many seeds, so little time...

Happy Gardening!


    Bookmark   August 16, 2007 at 12:05PM
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calistoga_al ca 15 usda 9

Tommie the last paragraph of your message should be printed on every seed package. Al

    Bookmark   August 17, 2007 at 9:54AM
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Perlite and vermiculite are the Kings of certain crucial things, especially soil aeration. I buy perlite in bulk forms and till it into my flower beds even though I have the best of black dirt where I live. Tomorrow, yet two more boxes of perlite will be delivered in boxes almost big as me, so my wife will sigh and say: "Your Mother warned me before the wedding in 1972, but she never told me you'd become another "potty-trained Martha Stewart. What's next? A chicken coupe full of hens that lay green, pink, and blue eggs?"

I grow MANY seeds both indoors and out. (I forget WHY) I almost NEVER use just perlite or vermiculite as the potting mix for seeds. I add peat moss at around 50%, to help retain the moisture. Yes there is no nutritional value in that mix, but until the seeds become plants with say 2 sets of leaves, my experience tells me that seeds benefit far more from other conditions such as constant temperature, light, water, humidity or say the correct music. One time I accidentally left the TV on MTV after an Eagles concert, and half an acre died from the subsequent RAP!

I DO more heavily use vermiculite and/or perlite for cuttings, but even then I usually add some peat, so that there is better soil contact. It seems logical to me anyway, but then again... I'm the guy who thought it logical to build and put a greenhouse in the living room!

My plants are most always doing well, but I'd appreciate any prayers you can offer for my wife.

jim Palmer

    Bookmark   August 27, 2007 at 6:36PM
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