September in the hoophouse: sowing spinach, replacing bubble foil insulation, removing shadecloth

Two jars of sprouted spinach seeds and grits to prevent the damp seeds clumping.
Photo Pam Dawling

Sowing Spinach

We sow our first hoophouse spinach in the ground around September 7. Because it’s too hot in the hoophouse at this time for spinach seed to germinate, we pre-sprout the seed for a week in the fridge before sowing. This is very easy, much easier than growing beansprouts!

We measure out the amount of seed we’ll need and soak it overnight in a jar of water. We use 1oz (28 g) of seed per 90ft (27.4 m) row. We use a cup measure or a tablespoon that we keep in the spinach seed bucket. 7T = ½ cup. 1T=15 ml. It’s very roughly ½ cup per row. We use Mason jars and replace the flat metal lid with a piece of screen of some kind, metal or plastic, with holes smaller than spinach seeds. The Mason jar lid band holds this in place.

In the morning we drain off the excess water, and set the jar in the fridge on its side. Once a day we rotate the jar to even out the moisture and therefore hopefully the rate of growth of the shoots. After about a week the seeds have grown a short white root 1/8” (3 mm) long and are ready to sow.

Spinach seedlings from pre-sprouted seed in the hoophouse in September.
Photo Pam Dawling

When there is extra moisture with the seeds they can tend to clump together. One solution to this problem is to mix in a dry inert material like corn grits, as in the first photo, to make the seeds easier to sow individually. This year I tried a different approach. I spread out a scrap of rowcover on the ground and spread the seeds out on that to dry the surfaces. This made the seeds easy to sow, but I noticed that several white rootlets were left behind on the rowcover. I don’t know if the rowcover Velcro effect caused this or if it was a higher rate of damage than the grits treatment. It wasn’t a significant amount.

Replacing bubble foil

Beyond time to replace this torn and crumbling bubble foil insulation.
Photo Pam Dawling

We have a 3 ft (1 m) length of a foil and bubble-plastic roll material along the base of the north wall in our hoophouse. The north side is the coldest, and not a lot of direct light comes in there, that low down, so we decided to insulate from radiation losses and also get some light reflection back there. I think it works well, although I have not measured anything to see if my impressions are backed up by reality! We put the hoophouse up in 2003 and we have replaced this “bubble foil” once since. Definitely we left it too long since we last changed it. As well as big rips, we had micro-crumbs of plastic flaking off. Not what we want in our food!!

An office staple remover is the perfect tool for removing the batten tape (old driptape).
Photo Pam Dawling

I pulled off the old stuff, using an office staple remover to extract the old staples. I reused the scrap driptape we had been using as batten tape (still years of life left for it in that role!) My approach to agricultural plastics is to buy the most durable and treat them gently to make them last as long as possible. We had two partial rolls of the bubble foil material in the shed, so I used those, but found myself 14 ft (4 m) short, so we had to buy some more. I don’t know about durability, but the Reflectix product was the sturdiest at the start. How long would this stuff normally last? Two changes in 2003-2019 = 16 years. 8 years is too long! 6 or 7 seems like it might be OK. Ask me in 2025!

A quick crop of Tokyo bekana Asian greens for salad, in front of the new bubble foil.
Photo Pam Dawling

Removing the shadecloth

The 15 year-old shadecloth on our hoophouse is still serving us every summer.
Photo Pam Dawling

In the summer we cover our hoophouse with a large sheet of shadecloth. We pack it away in the second week of September. (It helps if the first bed of winter crops (planted September 6-7) has had a chance to germinate before we make it hotter in there by pulling off the shadecloth.) Our shadecloth is 50% knitted polyethylene. I think 45% would be better than 50%, next time we buy. And I think buying 100 ft (30 m) would be better than just the 96 ft (29 m) length of the hoophouse. See the way the shadecloth pulls away from the ends in the photo.

Our hoophouse in 2008 when the shadecloth was in better condition.
Photo Pam Dawling

We are still using the shadecloth we bought in 2004, 15 years later. It has a few mouse holes that happened in storage, and the fabric is starting to lose its strength and rip. We used to fix  snap-on grommets to the center-line of the shadecloth at the ends and tie with ropes onto the end wall structure. But nowadays the shadecloth is too weak to withstand the firm pull we need to give to get those ends in place. So we get a hot spot at each end of the hoophouse. We’ll need to buy new shadecloth in the next couple of years. Probably we can cut the old piece up into 7 ft (2 m) strips to use over beds of lettuce outdoors. It won’t need much tensile strength for that task.

We use snap-on grommets, big hooks in the baseboard and a long piece of rope, to hold the shadecloth along each long side of the hoophouse.
Photo Pam Dawling

Fall hoophouse bed prep and shadecloth removal

Our hoophouse is covered mid-May to early-September with a large shadecloth.
Photo Twin Oaks Community

Today we’re removing the giant piece of shadecloth that has been over the top of our hoophouse since mid-May. We’ll unclip the ropes, roll them up, then pull the shadecloth off onto the ground, roll and bundle it up. It’s important to store it so mice can’t get into the bundle and make holes. We already have a few of those!

The shadecloth is held on by ropes zig-zagging between snap grommets on the shadecloth and large hooks on the baseboard.
Photo Twin Oaks Community

We’ve just finished preparing the first of our 7 hoophouse beds for the winter greens. Crops grow so fast in the hoophouse, and the organic matter in the soil is consumed at a rapid rate. Every new crop requires a fertility boost. In the fall, we prepare our beds by removing all the summer crops, and spreading four or five wheel­barrows of compost per 4′ × 96′ (1.2 × 29 m) bed. This is a generous 46 gals/100 ft2 (or 680 L/36 m2 bed)or more. A full wheelbarrow generally holds six cubic feet (44 gallons or 170 liters). 1 ft3 = 7.5 US gals. An inch of compost is about 8 ft3/100 ft2, or 60 gals/100 ft2; 20 gals/100 ft2 is 15 tons/acre (8.6 L/m2). Other professional growers use any­where from 12–40 gals/100 ft2 (5–17 L/m2). Some use much more.

There are 3 concerns about using too much compost: high phosphorus levels, raised salt levels and nitrate accumulation. Some growers like to do two years of high compost rates (40 gals/100 ft2, 17 L/m2 or more), then reduce the rate to half that and add fish or kelp, at only 5 oz–8 oz/100 ft2 (15–24 gm/m2) per year. Sustainable alternatives to compost in­clude organic pelleted chicken manure, alfalfa meal, etc.

Broadfork from Way Cool Tools.
Photo Way Cool Tools

A few years after we put up our hoophouse,  we noticed that despite our best efforts, we were walking on the edges of the beds and compact­ing them. Initially we simply loosened the edges of the beds with a digging fork. We then noticed that the plants on the edges grew better, and we realized the whole bed width needed loosening. If you have designed your hoophouse to use trac­tor equipment there, that will deal with soil com­paction. We wanted our hoophouse to be free of internal combustion engines and fossil fuels, and the broadfork has provided the solution. Ours is an all-steel broadfork from Way Cool Tools. We do an annual broadforking each fall, before planting our winter greens.

We set nylon twine to mark the bed edges, holding it in place using sod staples. The string alone has not been enough to stop us walking on the bed edges. Loose soil is important because our winter crops grow all the way to the edges of the beds. After spreading compost, we broadfork the beds, then vigorously work the compost into the top of the soil with scuffle hoes and rakes. We learned the hard way the importance of raking the soil to a fine tilth immediately after broadforking — you don’t want to let the broadforked clumps dry out into bricks before you rake! See the photo below and imagine what could happen!

Hoophouse bed broadforked to aerate the soil without inverting.
Photo Pam Dawling

I wrote about our bed prep method and tools, and also our outdoor sowings for transplanting into the hoophouse, with a special focus on suitable lettuce varieties in my post Sowing hoophouse winter crops here in Sept 2017.

We have just started planting our late fall, winter and early spring crops in the hoophouse. We are  pre-sprouting our spinach for a week in a jar in the fridge. Soak the seed overnight, drain it in the morning, fit a mesh lid on the jar, and lay it on its side in the fridge. Once a day, give the jar a quarter turn to tumble the seeds and even out the moisture. If the seeds are a bit wet when you need to sow them, and clumped together, pour them out on a cloth to dry a bit before sowing.

We will sow five crops in our first bed on September 6 and 7– spinach, tatsoi, Bulls Blood beet greens, radishes and scallions. On September 15 we sow lettuces, chard, pak choy, Chinese cabbage, Tokyo Bekana and Yukina Savoy, in an outdoor bed to be transplanted into the hoophouse in a few weeks, after we’ve prepared another bed.

We plant crops closer in the hoophouse than outdoors, and closer to the edges of the beds. We don’t have many weeds in the hoophouse, and the paths are marked off with twine, to keep us from stepping on the beds. We find that the soil does slump and compact some of its own accord, even if we don’t step on the edges (and of course, some feet do find themselves on the bed edges), hence the once-a-year broadforking.

Young spinach plants (and henbit!) in our hoophouse in December. This is our second sowing, not the early September one.
Photo Pam Dawling

Step-by-step guide to hoophouse fall bed prep:

  1. Remove the summer crops to the compost pile,
  2. Spread a generous layer of compost over the whole bed surface.
  3. Gather the soil staples and move the drip tape off to one side or the other,
  4. Broadfork the whole bed, but not all at once. Only broadfork the amount of space you have time to rake immediately, otherwise the warm hoophouse conditions dry out the soil and make it harder to cultivate into a fine tilth, which is the next task. We tackle 1/3 bed each day.
  5. To use a broadfork, go backwards working the width of the bed. Stab the tines into the soil and step on the crossbar, holding the long handles. Step from foot to foot until the crossbar touches the soil, with the tines all the way in, then step off backwards, pulling the handles towards you. This loosens a big area of soil, which hopefully crumbles into chunks. Lift the broadfork and set it back in the soil about 6” (15 cm) back from the first bite. Note: you are not inverting the soil – this is not a “digging over” process. Step on the bar and repeat.
  6. Sometimes we use a rake, breaking the clumps up with the back of the rake, then raking the soil to break up the smaller lumps, and reshape the bed. More often we use a wide stirrup hoe very energetically. This isn’t the job stirrup hoes were designed for (that’s very shallow hoeing), but the sharp hoe blade does a really good job of breaking up clumpy soil.
  7. We’ve found it important to lay the drip tapes back in place in between each day’s work, so that the soil gets irrigated when we run the system and stays damp. We don’t want dead, baked soil.
  8. When the bed is prepared, we measure out the areas for different crops and mark them with flags.
  9. Next we use our row-marker rake (bed prep rake) from Johnny’s Selected Seeds.
  10. After the rowmarking, we deepen the furrows if needed (often it’s not needed), using a pointed hoe, then sow the seeds.

For more on winter hoophouse crops, see

Planning winter hoophouse crops for our step-by-step process for hoophouse crop planning

Cold-tolerant lettuce and the rest, our January 2018 assessment of the varieties we grew that winter and which survived the unusually cold spell we had.