Kelly Osborn

Let it bolt the peeled stalk is called celtus and is fantastic stir fried.  They actually have varieties designed just for that purpose but I find my regular lettuce does just fine.

Yes, correct ph, correct zone, correct water, multiple years to get a crop.  I have tried but failed miserably to get it to work in my house.  There are commercial greenhouses that have now figured it out though and at ~$90 per pound it would be nice to figure out how to grow it for the fancier restaurants in the area.  Horseradish no longer produces viable seed but I have gotten Wasabi seed up but I would not be surprised if you need a root section of Wasabi for a quality crop.

Horseradish and Wasabi are in the same family so I just grow horseradish.  Most of the Wasabi in the typical restaurant is just horseradish with a little food coloring and other mustards combinded.

One of your pictures also showed flowers and since horseradish is in the Brassicaceae - brassica/mustard/cruciferae family it will have 4 petals, 4 sepals, 6 stamen (2 shorter than the others), 1 pistil like all in the family.  For example look at any mustard, radish, broccoli, cabbage flower they all are in the same type flowers.  For wild foragers out there this is one family you need to recognize.  The entire plant of this family are technically edible from roots to flowers, some are just not very palatable.   Cabbage roots for example are edible just too tough and woody to eat.

Most farms grow horseradish for three years then harvest during the fall.  I harvest when I need some.  The roots in my clay soil do not get as large but they are awesome one little root ground up is a lot of flavor and sinus clearing.

During tomato season I like to ferment my own ketchup with horseradish, ie cocktail sauce, so that is usually when I harvest.  I also love to ferment my horseradish for the season.  Right now I have a jar of garlic scapes fermenting on the counter top and a little left over in the fridge from last year after it is done I will do a quart of horse radish.

I will caution you it is very prolific plant and will take over a garden bed.

That is Horseradish scratch and sniff either the leaves or root will confirm it.  Dock comes up in basil around a central stem, horse radish in random clusters from the roots.  One of my favorite perennials a brassica family with roots, leaves and edible flowers.

Weeds tend to do fine.  Amaranth purslane have zero issues.

I agree with your caution of the compost before using any I test on a few broad leaf seadlings like beans which die quickly especially for grazon herbicide which is persistent for years.  It is nice having sources nearby where I can source organic compost and manure from ranchers who grow their own feed.  The mushrooms are certified organic so the compost should not have too many nasties and my plants seem to love it.  Until I can establish my own compost crops I am going to have to rely on others. Trying to get a decent garden year one is difficult, my current soil has been a grass yard for 20 years and is solid compacted clay with very low NPK in soil tests.  I have been bitten in the rear before trusting municipal composted manure which had pesticides in it so I am very careful.

I just moved to a new house so my personal resources are very limited.  Luckily there is a mushroom farm close by that sells an entire pickup load of mushroom compost for $20 and I am having very good luck with equal parts perlite, coconut coir and the compost, it comes out as a very loose starting mix.  It is working well for the seedling starts and as potting soil once my sprouts have true leaves.

For the poster who said they have a hard time sowing seeds in a row because they use plastic trays try moving to larger wooden boxes made from scrap wood mine are 14" x 20" x (3" and 6" Height).  They are large enough to separate the varieties by about an inch and do not collapse catastrophically.  As the sprouts get larger I move the best looking ones to the deeper boxes or to individual pots / solo cups.  Try to keep the roots from bottoming out in your seedling containers, it has a tendency to send many into bloom which slows their growth once out in the garden.  When plants are putting energy into reproduction they stop putting energy into growth.  This is one of the reasons many people prefer to plant directly in the garden for the faster growing plants.