HELP with encouraging substantial roots on seedlings

[Anthony_Toronto]

Not sure where I have gone awry. I usually try to have larger, more advanced 'seedlings' to at least try to take best advantage of my shorter growing season (I'm just north of Toronto). Several years back I would sprout seedlings, transplant into a small cell/pot when they had a few true leaves, then transplant again to a medium sized or larger pot (up to 8 inches or so). Plants were usually 8 weeks or so old, and 2 to 3 feet tall, with stems about as thick as a pinky finger at the base, and looked good. When it came time to set out, I remember grabbing the plants at the base of the stem and pulling them out of the pot, and having the entirety of the material in the 8-inch pot come out in a ball, all held together by the roots. That is what I am looking for.

However, for the last 5 or 6 several seasons, I have had tremendous difficulty getting any substantial root development. I germinate in seed starting mix, usually with good to great success. Once the plants have 2 (or more) sets of true leaves I transplant, sometimes into smaller cells (like the 4-cell packs that most annuals come in), sometimes to 3 or 4 inch pots, sometimes to larger pots. Sometimes I pot up once from the initial starter cells, sometimes twice, sometimes thrice. I use potting mix, sometimes (always, recently) using moisture control mix, which seems to make watering easier (absorbs well, rather than floating on the surface forever before absorbing). I generally let the pots dry out before re-watering, and water from the bottom when I can, and when I fertilize it is with something like 10-50-10 (varying over the years...sometimes a lot of fert, sometimes very little fert), all of which I understood to be things that would promote root growth, or in any event not suppress it. I've even tried doing some deliberate damage (as well as unintentional damage) to the tap root to encourage more fibrous roots. And every year in the last 5 or 6 years I have had the same result, no matter what I did or changed...crappy roots, with the main roots being maybe 3 inches wide in total (on a 3-foot tall thick great looking green leafy plant), with a few stringy roots that grow out to the side edges and bottom of the pot, but basically fall away when I unpot the plants while setting out in the garden. More or less watering, more or less fertilizer, smaller or bigger pots, more or fewer pot-ups...none of it seems to make any difference.

Don't get me wrong, my plants do ok in the garden eventually (usually), but don't do well with early stress in the garden (presumably because lack of roots means lack of ability to take in enough water/nutrients to withstand a little heat or dry), but I want to once again get seedlings with a a little more of a strong base of roots.

Sorry for the long post...does anyone have any suggestions that are any different from everything that I have already tried? On thing I can't recall is the medium that I used way way back in my pots...but I can't imagine that it was potting soil or there is no way that I would have been able to pull out the entire root ball from the pot by the stem, so it must have been some sort of lighter potting mix (definitely not moisture control though...maybe that is the culprit? controlling moisure so much that roots don't need to branch out? given how much I let the pots dry out between waterings I don't see how). I believe I made some inquiries on this a few years back, but not sure anything that I came away with had any change in results. I have seen older research on how roots change with potting up (branching out more/becoming more fibrous, vs. having a deep tap root for plants without many pot-ups, sowed into field from seedlings for example) so I know what I should be trying to achieve, but its not happening, even with up to 8-week old seedlings.

Thanks,
Anthony

[Barbee]

I think you need to look for a potting up mix has plenty of larger bark fines in it. This is just my opinion mind you ..but I have noticed that if I use a very finely ground mix for potting up the roots do not get enough air to make those nice fat roots that I like to see on my transplants. I like the fine stuff for seed starting then when I pot up I switch over to a much coarser product. FWIW, I do not care for the moisture control type potting mixes. I think you can do more harm than good by keeping the roots too wet.
Anyway, theres something for you to ponder

[Anthony_Toronto]

I'll try anything, and that sounds like a reasonable suggestion, thanks. Might try a few different methods this year and see which works best. No more moisture control mix for me, even though I'm not sure it was the culprit, and I know I had the issue before I started using that mix.

[mdvpc]

I have used this before and it works.

http://www.npktechnology.co.uk/produ...rator-additive

Its quite expensive, but you dilute it an awful lot. Most hydroponic shops will carry it.

[Doug9345]

My gut call is that the MG moisture grow is holding so much water that the roots don't have to grow very far to get all the water and nutrients they need.

[b54red]

It sounds to me as if you may be keeping them too well watered. To encourage root growth it is best to let the plants dry out good. When I am getting mine ready to go into the garden it is not uncommon for me to allow them to dry out to the wilting stage several times or about once a week. If on the other hand I keep them well watered and never let them dry out they will have many fewer and more delicate roots which makes transplanting more difficult and the plants also get more of a shock when planted out when the roots are less developed.

I take a good potting soil and add some bark fines (preferably well aged), some UltraSorb, and some Optisorb and add it to the potting soil along with a small amount of cottonseed meal. I give them a little fertilizer when first potted up then only again if they start looking a bit paler than they should. Down here where it is so hot I frequently add a bit of water absorbent crystals so that I don't have to water them every day; but I think that would be entirely unnecessary in your cooler climate. The crystals will hold a little bit of moisture for longer in the pots so they don't need to be watered as often and it takes them longer to dry out to the wilting stage also.

Any time you have a day nice enough to set them outside I think you should because the wind and sun will encourage the plants to be stronger and develop a better root system. Tomato seedlings develop into stronger plants even though they may not be as pretty when they endure a little stress.

Bill

[Hermitian]

Use a water-soluble iron supplement. You'll find them chelated in both inorganic powder form and organic liquid form.

[ScottinAtlanta]

After some experimentation, I now pot up to PRO‐MIX® BX MYCORRHIZAE™ - it seems to encourage growth from 1 inch to 8 inches without any problems.

[Anthony_Toronto]

Originally Posted by b54red

It sounds to me as if you may be keeping them too well watered. To encourage root growth it is best to let the plants dry out good. When I am getting mine ready to go into the garden it is not uncommon for me to allow them to dry out to the wilting stage several times or about once a week. If on the other hand I keep them well watered and never let them dry out they will have many fewer and more delicate roots which makes transplanting more difficult and the plants also get more of a shock when planted out when the roots are less developed.

I take a good potting soil and add some bark fines (preferably well aged), some UltraSorb, and some Optisorb and add it to the potting soil along with a small amount of cottonseed meal. I give them a little fertilizer when first potted up then only again if they start looking a bit paler than they should. Down here where it is so hot I frequently add a bit of water absorbent crystals so that I don't have to water them every day; but I think that would be entirely unnecessary in your cooler climate. The crystals will hold a little bit of moisture for longer in the pots so they don't need to be watered as often and it takes them longer to dry out to the wilting stage also.

Any time you have a day nice enough to set them outside I think you should because the wind and sun will encourage the plants to be stronger and develop a better root system. Tomato seedlings develop into stronger plants even though they may not be as pretty when they endure a little stress.

Bill

I always let them dry up to wilting or to the point that the pots are light as a feather before watering again, so that's not it. Hardening off in the weather for a few weeks vs. bringing them from inside straight into the garden has made no difference in roots for me so far, though the foliage/stems have been a little stronger after being outside than being inside with a fan on them. However its windy where I am so the wind damage from hardening outside for the last few weeks always seems to negatively outweight the controlled use of a fan inside.

[Anthony_Toronto]

I use Pro-Mix as my seed starter. Maybe will give that a try for potting up for a portion of plants and see how it goes.

[bughunter99]

Here is a pretty good article that you might find useful.

http://www.soilandhealth.org/01aglib...10137ch26.html

In your case I would try the following.

1. Go back to whatever seed starting mix you used to use, without the enhancements.

2. Cut back on the transplanting activities to just once. Injuring the roots can slow things down.

3. Use a more balanced fertilizer that is a liquid, not granules. Use it at 1/2 strength. Nothing more than an 8:8:8 for sure. I've read that over-fertilization can stunt growth. I go less than that with mine.

Stacy

[RJGlew]

http://www.waynesthisandthat.com/pottingsoil.htm

[Father'sDaughter]

I would also suggest staying away from the moisture control stuff. A few years ago I accidentally bought a bag and nothing I planted in it did very well. I dumped the rest of the bag in my garden just to get rid of it. After a heavy rain a few days later, I ended up with jelly-fish like blobs of about one to two inches all over the area where I dumped it. I'm guessing they were the moisture holding product that was added to the potting mix. I'm thinking of few of those jelly blobs in a small pot will really cramp the root growth.

[Anthony_Toronto]

RJGlew great link, thanks, will take a closer look.


Stacy that is the older article that I was referring to, great find!! But when I decreased the number of transplantings (based on the results of better production noted in the article) I did get a heavy tap root like those in Figure 70 on the right, but transplanting into the garden with that root system versus the one on the left seemed to cause some problems. So I was willing to slow things down by adding transplanting, but something else aside from what I have been doing is clearly needed. And every year I do transplant some plants more times than others (just out of sheer laziness), but still the same results with all...ugh

Unfortunately at this point I have no clue what potting soil I was using way back when the roots were good, so I'm stuck experimenting . Back then I knew a little from reading the assorted forums etc. but didn't really track anything or look for any particular products like I have since...and although I have had excellent plant top growth since then the roots continue to be lacklustre...its like when you throw together something great in the kitchen, but can never replicate it because you were just going by feel with what was on hand!!! Very frustrating.

As for changing the fert, the only reason I use the 10-52-10 plant prod plant starter fertilizer is because it has more phosphorous and is touted as a fertlizer that is formulated for encouraging a vigorous root system, which is the one thing that I'm trying to adjust/resolve. I don't know how decreasing the phosphorous would increase the root growth but that's why I'm here asking questions...would a more even blend work better to accomplish better root growth?

[RayR]

You need more than NPK if you want good root structure. Plants do not live by NPK alone.