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Two days ago I had soil of pH 5.5. I impatiently planted my lavender and now I'm worried because lavender needs a pH of 6.5 to 7.5.

I did mix the soil with about 1/4 (volume) of quartz sand and some small stones, but I guess that only avoids the soil being soaked and doesn't influence the pH value.

Tap water, which is what I use for watering, has an average pH of 7.6 over here (Berlin, that is) - might that help?

1) How badly did I mess up? I really want this lavender to thrive and to survive the winter. I already killed a whole balcony full of lavender last year because I didn't know about the importance of avoiding soaked soil, and I just can't live through that again cue dramatic gesture.

2) Is there a somewhat easy way to increase the pH value at root level now that they're planted?

  • I read somewhere that limestone takes years to permeate the soil when added to the top of it
  • .. or should I add baking soda into my water (ratio of baking soda per liter [gallon] of soil anyone?)
  • .. or should I get "pH up" solution for hydroponic growing equipment (I think they're mainly sold for people who homegrow weed)
  • .. or should I dig the plants back up, mix in limestone and replant them? After two days the roots probably haven't grown into the added soil yet and it wouldn't bother the plants (?). It would just be annoying for the human involved.

These are my beauties

  • Can you not just buy some new multi purpose potting soil, unplant the lavender, empty out the window box, fill up with new potting soil and plant into that? Multi purpose potting soil should have a neutral ph, which is fine, though if you can get hold of John Innes No. 3 potting soil, that's the best, also with a neutral ph. Lavender grows perfectly well in the ground here in my part of London, where the soil ph is just on the acid side of neutral. Biggest risk where you are is surely winter freeze of the soil and roots, which will kill any plant – Bamboo Jun 26 '17 at 18:22
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If you want to use the mix you've made (probably more fun than buying new), go ahead and taker the plants back out - since they were planted 2 days ago, there will be no setback. Take 1/4 lb of agricultural lime and mix it thoroughly into the soil (I think that should be the right proportion for the soil you have), to bring the pH back up to 6.8-7.0.

Shouldn't take more than 10-15 minutes from start to cleanup, the plants can go right back in. I see it's an option you listed, and it's definitely the one I'd go with, if you think it's worth the time. After a month or so, I'd check the pH again to check if it's in the range you want. If it needs adjustment after that, it'll probably be very minimal and not require removing the plants.

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I'd be more concerned about your lavender not making through the winter because of temperature. I looked up climate info for Berlin to get a better idea how lavender would fare unprotected in winter. I don't know what sort of numbering system you use, but your zone is a little colder than mine but not much.

Now no matter what perennial you're growing in the balcony planter, you can drop the zone by 2 or 3. In other words, if the lavender cultivar you're growing is hardy to zone 5 and you live in zone 6, your balcony soil would be more like 3 or 4. Your lavender would have no hope of surviving. If your zone is 8, the lavender should survive winter unless you get a particularly bad cold snap in the late fall or early winter before the plants have acclimatized to colder weather.

Soil in containers doesn't have the residual heat that's stored in the ground to protect perennials through winter. Do you have any place you can keep your planter through winter where it's cold but not freezing? I don't know how else you could protect it to cold exposure.

As for soil pH as you originally asked, I used to stir limestone (powder) into the soil around lime-loving plants like pinks, lilac and baby's breath. Please DON'T use baking powder! If you want, you could put limestone in a container with water and let it sit for a few days. Use that for watering.

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How did you test your soil? I am impressed that you've done this. Is this a mix of your own or was this from bagged potting soil? Bagged potting soil is all that should ever be used in pots...no sand, gravel or other amendments that haven't gone through a sterilization process. Sand and gravel do not increase drainage, in fact if there is a layer of sand or gravel or rocks at the bottom of the soil you will have created a perched water table.

Your lavender look very healthy. Yes, you can easily transplant each of these plants with no problem. Think about the size each of these plants will eventually try to be; 3'X3'. They will survive just fine in this pot because they are indoors and not getting enough light nor room to grow to their natural size...for awhile.

Using your tap water will help to raise the pH. Lime sprinkled right on top will help raise the pH. What are you using for fertilizer? The green of your plants looks anemic but it could also be the photograph.

Let us know how you planted, what soil you used before adding sand, if there is only soil in that rectangular pot, anything else that you have added. If you've not added any fertilizer; go get Osmocote 14-14-14. Use at the most 2X per year for indoors.

Keep in mind that these plants will fill this pot, very pretty. Think about selecting a new type of plant and relocating this lavender to the out of doors landscape. Make sure you acclimate them. You will have to use a knife to slice between plants and plant each chunk separately...hopefully together with 2 feet between each plant. Do this in the early spring. If you like your lavender indoors you could try larger pots that sit outside on a covered porch for the summer, bring them in for the winter.

We could talk about how to prune these guys. Very important for lavender. With a little fertilizer and hopefully we hear that no rock or gravel was installed between the soil and the drainage hole...this pot should be just fine until next year. Glad you see that allowing the soil to dry is important for this plant!

Just get some dolomite lime to sprinkle on top of the soil. Make sure that soil is potting soil. Do not add anything else; just soil in that pot. I really like the gravel below the pot and the saucer! Keep pouring out the excess water. Water deeply but only when that soil is dry. And a little fertilizer. This Osmocote (I hate promoting any of their products...except for this fertilizer) is extended release. Just enough, not too much, lasts for 4 to 6 months depending on light and volume.

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