Ask This Old House S24E19: Nursery Arches, Houseplant Myths, and a Pea Stone Patio That Needs 72 Hours Off

Season 24, episode 19 of Ask This Old House splits three ways: a nursery repaint, a myth-busting conversation about houseplants, and a budget patio in a freshly leveled backyard. What holds the hour together is that none of the three jobs is really about the finish. Mauro Henrique's arch wall lives or dies on layout marks and tape technique. Jenn Nawada's plant advice keeps landing on the same word, quantity. Mark McCullough spends most of his segment underground, in gravel, fabric, and a drain pipe nobody will ever see again.

Nursery Paint and the Arch Wall

Emily just moved in, is due next month, and has a dog named Waffles. The room she wants repainted is, in her words, a little too pink. Mauro starts by asking what the room is for, which is the part most of us skip. A nursery wants calm, so the green goes on the walls and the accent wall gets two arches in a second green and a beige. Three colors total, all in the same soft family.

The painting itself is deliberately ordinary, and that's the useful part. Curtain rods come down, cover plates come off, floors, baseboards, and outlets get protected. Emily immediately hits the windowsill and the ceiling with her brush. Mauro's response is not a technique, it's a rule: get a wet rag and clean it now, before the paint dries. That's the same instinct he brought to a paint spill earlier this season in the wet paint rescue episode, and it's the single most repeatable thing in the segment.

Emily asks why they're not priming. Mauro's answer is refreshingly narrow: over an already-painted surface, you don't need it. Over bare or fresh plaster, you do. He also shows how to cut in around something like a thermostat, where the brush goes in on just the tip and dances a little. Two coats on the walls, then the accent.

The arch layout is where the television edit makes it look effortless. It isn't complicated, but it is fussy. Mauro and Emily settle on 26 inches wide, and roughly 38 to 40 inches tall so the arch clears the slanted ceiling line above. Marks go down, a level confirms them, and a string with a pencil at the center of the 26-inch span traces the curve. Two arches, both drawn freehand off the same string.

Taping is the hard part, and Mauro says so out loud. Low-tack tape goes on the outside of the line, because it won't lift the existing paint. Around the curves, he rips short sections of tape and works them around the reference line a few inches at a time. Then they roll green on one side, beige on the other, and give it a second coat. The tape comes off while the paint is still wet, which is the detail people get wrong when they wait overnight and end up with a jagged edge bonded to the wall.

One gap needs filling at the end. Mauro freehands it. He notes that you can use tape there, but only if the arch paint is fully dry first. That's an honest distinction between what a pro is comfortable doing with a brush and what a first-timer should do with tape and patience. Mauro says he uses a paint brush all the time, so he's comfortable freehanding. If you're painting an arch at home, tape it and wait.

Jenn Nawada on Houseplant Myths

This segment is Kevin O'Connor asking whether things he's heard are true, and Jenn Nawada giving short, unglamorous answers.

Myth one: houseplants purify your air. The claim traces back to a 1989 NASA study, and Jenn doesn't dismiss it outright. It holds, she says, if the entire room is full of plants. One or two plants won't clean your house. She says she'll keep plants anyway, for the mental-health side of it, which is a nice bit of honesty.

Myth two: plant citronella around your patio and mosquitoes stay away. They won't. A couple of plants in a garden bed isn't enough oil in the air. A citronella candle works better because the oils are concentrated, and lighting it cooks those oils off along with the smoke. Scented geranium with lavender and citronella can deter insects, but again, mass quantities. This is the second time this season Jenn has sorted real plant advice from wishful thinking; the earlier edition in the houseplant doctor segment was about pests, and this one is about claims.

Myth three is the one I had wrong. People are afraid to cut roots. Jenn pulls a rootbound plant out of its pot, shows the circling roots that have been hunting for somewhere else to go, and fans them out. You can also trim the long ones. It stimulates growth rather than killing the plant. Then it goes into a bigger pot with fresh soil at the right depth, backfilled. Kevin calls it teasing the roots, then does a bit where he teases the plant like a schoolyard bully.

Pea Stone Patio: Retaining Wall, Drain, and Binder

Michelle and Greg live in a newer build. They leveled a slope for a swing set, the kids have a place to play, and the adults have a deck that's small and up high. They want somewhere to sit and watch, and they want it cheap.

Mark measures 18 feet from the first step to the end of the deck, then proposes a 16-by-14 pea stone patio, held back from the edges. The yard still drops off in front, so the plan includes a short retaining wall along the leading edge to hold the stone level, plus stepping stones from the concrete to the patio and to the shed. Materials: pea stone, landscape fabric, landscape block, a binding agent, and aluminum edging.

The base depth is the reason pea stone qualifies as budget-friendly. Mark digs down 4 or 5 inches, not the 8 inches a typical hardscape assembly needs. The digging is rocky and slow, and both men say so.

The wall is built the way a wall is always built: dig 12 inches down, compact, add gravel for drainage, compact again, then set blocks. Masonry adhesive goes between courses, caps go on top, and Mark checks them with a bullet level in both directions. He pitches the cap slightly so water runs off, and he skips glue on the upper lip because it oozes out and looks bad. When the gravel base is right, he says, the blocks barely need fiddling.

Then the invisible work. They compact the soil and wet the whole area first, to keep dust down as Greg stays ahead of Mark with a hose. Landscape fabric goes down starting from one end so the overlaps shed water toward the porch instead of letting runoff sneak underneath. A 4-inch perforated drain pipe, wrapped in fabric, runs the length of the wall and pokes out at a corner so gravity can carry overflow away. Aluminum edging holds the surrounding dirt back from the stone. Only then does the pea stone go down, a couple inches at a time, with Mark using a 6-foot level as a screed to get the top coat flat.

The binding agent goes on last. It's the answer to the obvious worry with pea stone and small kids: loose rounded stones that get picked up and thrown. The stepping stones are set by tracing each one, digging twice its thickness, compacting crushed stone for drainage, adding wet stone dust, then wiggling and tapping the stone down and packing the edges. Mark calls it rock solid, which is the correct dad joke for the moment.

He asks for 72 hours off the patio so the binding coat can cure, and points out that the new retaining wall creates a planting ledge out front. Mark has compared walkway materials and base depths before in the paver pattern segment; pea stone is a different animal with a shallower dig and a curing window.

What the Edit Leaves Out

The arch wall looks quick because Mauro is comfortable with a brush and has done the layout before. The taping alone is slow, tedious work done on a stepladder. The patio edit compresses two things worth naming: the rock-filled digging and the compaction passes, which are what actually keep a pea stone surface from rutting. The 72-hour cure is also real; the binding agent needs time to set before foot traffic.

DIY Confidence Scale

• Painting the nursery and taping an arch accent: 4/5. Prep and rolling are beginner-friendly. The arch layout takes patience, and the low-tack tape around curves is genuinely fiddly. Tape the final gap instead of freehanding it.
• Houseplant repotting and root pruning: 4/5. Forgiving by nature. If you cut a root, the plant generally responds with new growth. Use fresh soil and plant at the same depth it grew before.
• Pea stone patio with retaining wall: 2/5. The spreading and raking is approachable; the wall base, drainage, compaction, screening, and binder put this in hire-it or bring-an-experienced-helper territory.

Additional Resources

• Watch on PBS
• Official This Old House episode page

The gap between the three segments is really a gap in what we notice: a painted arch shows its flaws immediately, a rootbound plant forgives you, and a patio fails quietly from underneath months later. Which of those three would you rather find out about the hard way?