What's going on with my portulaca seedlings?

I planted portulaca seedlings in mid April. Here it is over 2 months later, and this is all the bigger they are. Is this normal???? I planted them in windowboxes mostly filled with professional compost (bags branded by our local garden center). But I put seed starter mix on the top two inches. I think over time the seed starter washed away. I put them out in the sun as soon as they sprouted and only brought them in when cold threatened.

Anyway, they seem to be going in slow motion and don't look like they'll be ready to plant outside this season. Anything I can do differently next year?

TIA
LAS

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LAS14, I wished I knew to assist you. The only problem I figured it may be is that the seedlings could use some high nitrogen fertilizer? I'll leave this note. Hopefully others who has more experience with this type of plants will chime in.

The soil looks pretty wet--if you just watered them then maybe that's not the problem, but if you're keeping them consistently on the wet side that could make them struggle. I also don't think that compost is a good medium for pots...it's great for amending garden soil but for a window box you need something that's intended for pots and will drain better.

If you do repot them, consider adding lots of medium pine bark to your usual soil mix (for more aeration).

You can buy expen$ive orchid bark, or a 2-cubic-foot bag of medium pine bark mulch and screen it yourself. Crummy mulch can be had for $3 per bag, but I splurge for the $8 brand at a good nursery, so it doesn't smell like old socks soaked in stale beer or be mostly big chunks of wood or useless powder.

Two cubic feet of pine bark will fill a LOT of pots! That's 7.5 gallons, or 25 cents per quart.

I think bark for pots should pass through a 1/2" screen, and it's OK if you have to rub them around to get them to pass.

But mostly they should NOT pass easily through a 1/4" screen (especially if you add other things to the mix that are fine or small).

Buying "medium mulch" from a good nursery, instead of "fine" will mean you don't have to get rid of a lot of too-fine stuff.

From Home Depot or Lowes, "fine" and "medium" mean little, since you will get a lot of powder and a lot of big chunks and wood in either one. (They should call it "random lumbering waste product".)

I think that REAL nursery-supply wholesalers have "double screened pine bark" - but it might cost more.

Small particles will quickly fill up the gaps, voids or channels that could have allowed water to pass through and air to enter. I think it is best if the "fine" part of the potting mix is less than 1/4 of the total. Maybe less than 1/5.

(Crummy, old, wet, smelly bags of mulch from Home Depot may have started to ferment, perhaps anaerobically, and be too acid and have somewhat toxic breakdown products that baby roots won't like. Flush it, add some lime and leave it in a loose pile to aearate to disperse some of the the crud ... or use that bag AS mulch or walkway-dressing, and go buy some nice clean dry chunky bark to pamper your roots with.)

(I got most of these ideas from Al in the Container forum, but they've held up in practice as I've used them.)

Roots can't have too much air. Especially baby roots that can't suck a pot dry in order to get some air. Don't water-board those roots!

And if a pot drains so fast that you have to water too often, you can probably slow it down by top-dressing with some of your current mix, and letting that seep down into the pots.

Corey

Wo! Thanks RickCorey_WA

Just guessing, but what ecrane3 said sounded right.

And I have become a real nut about shredded, screened pine bark. I used to drown all my seeds in powdery, soggy peat-based commercial mix. The improvment was like night and day - and I still haven't got a really "chunky" blend.


Corey

ecrane3 is right, the soil looks wet. Portulaca is a succulent and thrive in hot sun in welldrained soil that is kept on the dry side. In other words, allow the soil to dry out somewhat between watering.

I think that most likely the plants have lost many roots from rot, the reason for the color and slow growth. Next year, use potting soil with sand added. Or cactus/succulent soil.

Thanks to all. Will definitely change the soil and watch the watering.

LAS

I planted some more seed on June 11 to see if early planting was just not good for portulaca. Then I got the idea that maybe they weren't getting enough nutrients, so I watered thoroughly with Miracle Gro a little over a week ago. My April portulaca have finally taken off, but my June portulaca are ahead of where the April ones were two weeks ago. But I still don't know if it's hot days or nutrition. But next year I'm just not going to plant them so early. Along with keeping them well drained.

Here's a picture of the April portulaca today.

And here's a picture of the June 7 portulaca.