The waiting is the hardest part: Hardening off seedlings

I have three weeks to go until our average last frost date.

coldframe full

I did really well this winter, getting seeds sown and potting things on. Now, I’ve got to hang on until the tender things are safe to plant. The cold frame is jammed full.

Hardening off seedlings, though, is too important a process to skip. I skipped it all the time until I built my cold frame–mostly because I didn’t want to spend half the morning bringing trays of plants in and out of the house–and my plants performed correspondingly poorly.

Hardening off is a process of gradually exposing seedlings and tender plants to larger temperature variations and stronger light levels than they experience indoors. The process produces slower, sturdier, more resilient growth, preparing plants for life in the open garden. Without a cold frame, gardeners place plants in a sheltered location outside–maybe in a shaded site, close to the warmth of the house–for a short period of time, lengthening the exposure to outside conditions every few days.

Using a cold frame–basically a tiny greenhouse–makes the process far less tedious. It’s not quite a matter of set-it-and-forget-it, but it frees up lots of the time and space other parts of life demand. My cold frame, which I constructed myself from recycled materials for about $30, faces south and backs up to my house. I start hardening off my seedlings in mid-February, when we begin to see a few 50-degree (10C) days. I start with the hardy perennials, then move in the hardy annuals. Tender plants come last. Space permitting, I sow vegetable seeds in flats directly in the cold frame.

During the first few days in the frame, I place plants on its south side so they sit in slight shadow from the frame’s front wall. They gradually move towards the back as more plants come in. On unusually warm days, I vent the cold frame by propping open the glass doors, made of discarded windows. This keeps the temperatures inside from getting too hot–such fragile plants can quickly dehydrate and die if the temperatures climb too high. Sometimes I’ll prop open the windows entirely, but cover the opening with a bit of horticultural fabric. This practice lets the light in but keeps hungry foraging birds and squirrels and early insect pests out.

coldframe full 2

The second quadrant of the cold frame.

We’re getting close enough to the last-frost date that I may move out some of the plants with the longest tenancy–particularly the perennials–into permanent locations. They’ve withstood some cold nights already, so a late frost won’t likely bother them.

Believe, gardeners! The digging season is nearly here.





Garden log, 6.13.14

The tomatoes overgrew their stakes, and it’s only mid-June. I removed the stakes and replaced them with a trellis. The trellis uprights are two 1-inch bamboo poles, and the laterals are the tomato stakes I had been using. Lashed everything together with Boy Scout knots (feeling very proud of my handiwork); it looks quite nice, if I may say so.

How big are these ground cherry plants going to get? They’re 3′ x 3′ now and we have quite a long summer to go. There’s lots of real estate underneath those leaves so if it gets out of hand I will try putting some lettuce underneath.

Planted seeds of ‘Blue Hubbard’ and ‘Waltham Butternut’ squash yesterday, plus more shiso  (first seedlings died) and eggplant ‘Listada di Gandia.’ Today I’m getting in ‘Contender’ bush beans, ‘Yellow Pear’ cherry tomatoes, and some ‘Lazy Housewife’ shelling beans.

Working away on trying to get the new garden spaces in the back under control. Transplanted Rosa ‘Darcey Bussell’ to a new spot near the deck, replacing ‘Sophy’s Rose,’ which died. Also moved the massive English lavender to this bed. While it doesn’t get quite the full sun it got on the south side of the house, it is close. It’s sitting high and dry just off the deck stairs, and should get reflected sun from the stairs and the brick patio beyond. Absurd downpours and high humidity the past few days have left it looking quite depressed, but perhaps it will rebound soon. Planted seedlings of nicotiana, transplanted a Nepeta ‘Walker’s Low’ and weeded. Oh, the weeds.

The transplanted Rosa ‘Generous Gardener’ cl. has put on vast amounts of new growth, all of it fresh and healthy looking. I am impressed with what I believe are the results of feedings with nettle compost tea. If the nettles aren’t themselves working, they’re a brilliant placebo.

I need to move the Japanese maple before it gets too big  but it doesn’t make sense to do this before fall; it will just be too hot, and who knows what kind of moisture we’ll have this summer. I’ve also got to get rid of a rangy ash tree first; the only place for it to come down is right where I want the maple to go. If only I could find a money tree in a nursery catalogue.


Seed viability, part 3: Planting seedlings embedded in paper toweling

The easy sprouts have been potted up, and now it is time to tackle the ingrown ones.

seedlings embedded in towel

Now, the good thing about seedlings growing through their germinating substrate (the paper towel) is that, if you can be trusted with a pair of scissors and have sharp ones to hand (does anyone besides tailors ever have sharp scissors?), you can trim yourself a little seed mat by which to handle the seedling, making transplanting relatively risk-free. Or you can use a box cutter, if you have a sharp blade and clean it first with a bit of rubbing alcohol.

How to Pot Up Seedlings That Have Grown Through Paper Towels

1. As before, prepare a seed flat with moistened, sterile seed-starting mixture. This flat, incidentally, is an upcycled Chinese food take-out container, and it is perfect for such a task.

prepared seed flat

2. Taking care not to cut off the root (which may have tiny root hairs emerging from it), guide the blade of the knife or scissors between the sprouted seeds. Cut a small section of towel to support the seedling:

seedling embedded in paper towel

3. Carefully cut individual seed mats out of the towel. Hold the towel up to a light to help you find the space between the roots.

hold up the seeds to the light

4. Plant the seedlings, giving adequate space to each one. Don’t overcrowd the flat. Gently firm the roots against the soil.

fully planted seed flat

The seed capsules on the soil surface fell off during the planting process. These are not additional, fresh seeds planted in the flat, which would overcrowd the plants.

5. Top the seedlings off with fresh seed-starting mix, up to the base of the seed leaves.

top-dressed flat

6. Water gently, using a rose on a watering can or the spray function of a faucet or squirt bottle, and set in a bright, warm space.

Keep an eye on the seedlings, in whatever form they were potted up, and do not allow them to dry out. Bottom-watering is best: Set the flat in a shallow dish of water and allow the water to wick up through the drainage holes in the bottom of the flat. Once the seedlings have developed one or two sets of true leaves, they may be potted up again.

Garden log, 6.13.13

Blazing hot and sunny weather until 5 pm, then a thunder shower. This is the summertime weather I remember from childhood. The daylilies are blooming spectacularly.

I dug up a 3-gallon bucket of daffodil bulbs from the south side of the house. They will be in the way of heavy machinery whenever work begins on the house addition, and our builder, David, tells me we must do some regrading on that side of the house to correct an emerging drainage problem. Either the bulldozer will move the bulbs or I must.

Dug up and potted the Hydrangea quercifolia that has been looking so forlorn this spring. My theory is that its water-to-sun ratio is dreadfully out of whack this super-soggy season. It has mostly defoliated itself but the wood is still green. I pruned back hard and put the pot on the deck near the potted fig. Lots of baby figs on the tree; I hope they hang in there.

Transplanted more coreopsis and Campanula persicifolia from the winter sowing project. I hope to get everything transplanted before it is time to gather seed for next year’s sowing. I am getting there, but very slowly. Collected some seed pods from Paeonia ‘Festiva Maxima’ to see if I can grow those from seed. I understand I should not expect flowers from such plants for at least four years, but it will be a fun experiment if I remember not to throw out what will look for a long time like a forgotten pan of dirt. Imagination is such an essential companion to gardening.

High, 92.

Helleborus experimentalis

I recently read Gayla Trail’s post about her fear of growing hellebores. I was surprised to learn that many people seem to feel trepidation about growing these plants. They are pricey, certainly, but for me they have been so easy as to be almost ridiculous. I have given mine absolutely no coddling and while my soil isn’t the worst in the world, I think, it isn’t going to win any “Best Tilth” awards, either.

I am conducting a little experiment, then, to see just how tough a hellebore can be. My only expectation is that at least one of these clumps should thrive in spite of me.

I dug up a few clumps of seedlings with my beloved garden knife. Note the exemplary growing conditions.

Experiment methodology:

  1. Dig a hole the same size as the transplant (no larger).
  2. Plop it into the hole (do not amend soil).
  3. Mash with foot.
  4. Do not water.
  5. Do not feed.
  6. Do not tend.
  7. Return periodically to assess progress or demise.

playhouse site

Test Plot A: The kids’ playhouse.  Just above the concrete block on the left of the photo is a window from which the children pretend to sell ice cream. It gets plenty of foot traffic. This is also the landing site for the bucket on a pulley, which hoists things to the fort’s lookout level. The soil here has never been amended, unless you count the occasional covering with a wood chip mulch to cut down on the mud. This site is in deep shade and grass can’t grow here. Assuming similar conditions to neighboring undeveloped garden spaces, the pH here is 4.8.

water meter, west facing

Test Plot B: West-facing gravel scree atop the water meter. This site receives neither foot traffic nor love. The most human attention it gets is a scowl from me as I leave the driveway, thinking “I have got to do something about that space.” May occasionally receive attention from dogs being walked. There are lots of neighborhood dogs.

barren south facing site

Test Plot C: South-facing, against the concrete foundation. The soil here is completely untended, rock-solid clay. I expect it to receive some foot traffic as it is in the access path for any people and equipment who will be working on the addition to our house this summer.

living above ground

Test plot D: No-man’s land behind the shed. Test Subject D, slightly more mature than its counterparts, will live above ground, simply in the clod in which it was dug up. This is in a shady site behind my shed, where large pots and leftover bricks are stored.

These test plantings were established and photos taken on March 28, 2013. We’ll check in periodically and see how they fare.