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Happiness is a potting shed

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“I am always happy to be in my potting shed. It is a retreat from the cares of the world and yet a place for quiet, concentrated work.”

— Monty Don, “The Complete Gardener,” 2009

British gardener, television host and author Monty Don says he propagates thousands of plants in his potting shed every year. Lately I’ve been spending a lot of happy time working in my “potting shed,” which is actually a bench set up in my 10-by-20-foot greenhouse. Although I start only a few hundred plants, I get immense satisfaction out of watching all of those tiny green heads poke through the growing medium and search hopefully for the light.

In recent years, I have had low germination rates for seeds sown directly into the garden beds, so this year I’m starting almost all of my seeds indoors. I don’t believe there is only one right way to successfully start seeds. I enjoy experimenting, so I thought I would share what I’m trying out this year.

I’m using netted coir pellets to start some of my vegetables and annual flowers. Coir is an organic material made from the fibrous interior portion of coconut shells, thus it’s considered a renewable natural resource. The thin netting that holds the coir in place is made from biodegradable material.

The pellets are tightly compressed until they are submerged in water, and then the coir expands to about 2 inches tall. I’ve found that it’s important to do this ahead of time, so the pellets have fully expanded and the coir is evenly moistened throughout, otherwise, it’s difficult to sow seeds in the hard-packed coir.

When the coir pellets are ready, I place them in trays with holes in the bottom for drainage. As my old plastic seed trays are wearing out, I’ve been replacing them with sturdier trays and drilling holes using a 3/8-inch bit. These trays are placed into larger shallow tubs without holes for bottom watering.

I like to use wooden shish kabob skewers for seed sowing. I use the blunt end of the stick to make a hole for the seed, and then I shake out some seeds onto an index card folded in half and use the pointed side of the stick to guide the seed into the hole. The goal is to get one or two seeds into each planting hole. This will avoid having to prick out extra seedlings later on, which could damage fragile roots of the plant you want.

I use the skewer again to tuck the seeds into the coir, and then I use an old kitchen sieve to lightly cover the seeds with a bit more coir.

The big advantage of using coir pellets is that I won’t have to lift seedlings from the medium when I plant them into the garden, which may reduce transplant shock. I do wonder, though, how fast the netting will break down in the garden soil.

Another potential advantage is that seedlings grown in coir pellets will produce healthy root systems through air pruning. When roots make contact with air that comes through the porous netting, the roots can self-prune and produce more branching. On the other hand, coir doesn’t provide any nutrients to plants, so I’m using the pellets only for annuals that will be transplanted or potted up fairly quickly.

It will be interesting to observe how seeds in the coir pellets germinate and grow compared to the seeds I’m starting in “soil” blocks. I bought a galvanized steel blocker that makes four 2-inch cubes at one time. I’ve learned that the growing medium for soil blocks must be more moist than usual; the medium should clump together like playdough. I’ve been using a mixture of one-third compost, one-third moistened coir, and one-third perlite.

The blocker is pressed into the growing medium, then the blocks are ejected onto a tray with drainage holes, and the tray is placed inside a larger shallow tub without holes for bottom watering. Each block has a narrow space in between for roots to air prune, and so the block can be lifted from the tray later on without disturbing other plants. The blocker makes a small indentation in the center of each block where I sow the seeds like I described with the coir pellets.

I’m using the blocks for some of my vegetables and annuals, but mostly for perennials and other plants that will take longer to grow root systems before they’re planted outdoors. The compost will provide nutrients to plants that will spend more time in the growing medium.

Making “soil” blocks certainly takes more prep time and is a bit trickier than plopping a coir pellet into a tray. On the other hand, I like the fact that I can use my own compost for the growing medium and I don’t have to worry about transplanting the seedlings so quickly. (I tend to fall behind in the mad rush of spring planting.) Also, the seed blocker is a one-time purchase, whereas coir pellets must be replenished.

I’ve learned that labeling each tray or row as I go is essential. I include the species and cultivar name and the date the seeds were sown on each label. I splurged this year and bought an electric labeler so I can attach the labels to sticks and, hopefully, the plant names will not smear or disappear after watering. I can reuse the sticks by peeling the label off.

The real challenge for successful indoor seed starting is to avoid too much heat and too much water; they can produce weak plants and attract fungal diseases. I use heating mats for my early spring indoor seed sowing, initially set at 65-70 degrees, and then I fiddle with the settings based on what my soil probe says is the actual temperature of the growing medium (it’s usually higher than the setting). I cover the trays in my unheated greenhouse on cold nights, but take the covers off during the day.

Bottom watering usually works better for seedlings, but I do mist the top of the medium with water from a spray bottle (I add diluted chamomile tea if green algae forms on the top of the growing medium to help prevent damping off). I’ve learned there is no universal formula for how much to water. I observe closely and use my skewer to probe the medium. If it comes out clean, then I add more water to the bottom tub so the seedlings can draw up moisture through their roots as needed.

Monty Don describes his happy place — his potting shed — as a highly organized environment where everything has its own place and is easily accessible. I wish I could say the same for the potting area in my greenhouse, but I can say that I’m never happier than when I’m in the midst of starting new life by planting seeds.

Rhonda Nowak is a Rogue Valley gardener, teacher and writer. Email her at Rnowak39@gmail.com. For more about gardening, check out her podcasts at https://mailtribune.com/podcasts/the-literary-gardener and her videos and blogs at www.literarygardener.com.

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My garden to-do list this week

  • Sow more seeds indoors: second round of peas, radishes, lettuce
  • Cut back old growth from perennial herbs and flowers
  • Build raised beds in new hoophouse

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Peat moss or coconut coir?

Many gardeners avoid using peat moss because it develops in bogs over a very long period of time, so most people consider it to be a nonrenewable natural resource. In addition, extracting and processing peat moss for commercial use releases a lot of carbon dioxide into the atmosphere, and transporting peat moss (mostly from Canada for the U.S. market) leaves a significant carbon footprint.

Coconut coir has been recommended as a more environmentally friendly alternative to peat moss because coir is a recycled waste product. However, most coir for growing purposes has been washed and processed to reduce its naturally high levels of sodium and potassium. Not only does washing the coir use up a lot of water (80-160 gallons per 1.3 cubic yards), processing the coir is carbon intensive. The majority of coir is processed in India and Sri Lanka, so transporting it across the globe increases its carbon footprint.

Using coir plugs for seed sowing