It’s the middle of April, so time for my second post on native pollinators. This year I again purchased a handful of mason bee cocoons to get a jump on pollinating until the bumblebee and honey bee populations can find the roof. I should mention that last year several of the tubes in my bee houses were filled and sealed by the mason bees introduced at that time. Unfortunately I didn’t properly take care of them over the winter, though I intend to do so this year if I’m given a second chance. For anyone else in a similar situation, here’s a handy guide to harvesting your mason bee cocoons at the end of the season: https://crownbees.com/harvest-cocoons
The Good. As mentioned above, the cocoons we set out last year hatched (not all, but many of them) and were seen happily pollinating the flowers across our roof. After a few weeks I started to see a few of the tubes closed off with mud. All in all perhaps a dozen tubes were closed in this fashion.
The Bad. First, I noticed many small insects around one of my bee houses in particular, this being the one housing the leaf-cutter bee cocoons. They were almost certainly predatory wasps, and looked like this. Their presence might explain the very low hatch rate for the leaf-cutter cocoons that I’d purchased. Also, as mentioned above I didn’t properly harvest the mason bee cocoons, and instead left them outside over the winter. Fortunately for me, almost all of the plugged cocoons appear to have hatched this spring, and I’m seeing bees buzzing about the bee houses even though the newly purchased cocoons haven’t yet emerged.
The Ugly. While most of the bees I’ve seen up close this spring have looked healthy, I’ve encountered a couple that were absolutely INFESTED with mites. If you look at the photo at the top of this post, you’ll see 6 mites hitching a ride on the bee’s back. In one instance there must have been HUNDREDS of mites on the poor bee. As such, I will be absolutely sure to properly harvest the cocoons this year, and will at minimum continue to replace all tubes with new bamboo, and possibly replace the houses themselves.
As I mentioned previously the soil in the planters that we use is less than ideal. We’ve taken to amending it with purchased compost and manure each spring, which has had a noticeable effect on production. While purchasing soil amendments is fine, we’ve also set up a worm composter on the roof to provide additional, free nutrients to the soil.
First, we don’t have the smaller, apartment worm composter that is provided by the city following their composting courses. We’re currently using the Worm Factory 360 Composting Worm Bin which we were lucky to pick up on Craigslist. This bin has 4 separate trays that stack one inside the other which lets you build your compost in stages, and makes separating the worms out easier. Additionally, there is a final, lower tray used to catch the compost tea, and a spigot to let you drain it when desired. Using the Worm Factory 360 has come with learnings that I will share here.
Keep the compost bin in a somewhat sheltered location. The trays aren’t sealed, and water hitting from the side will get into the trays. We live in Vancouver, and it rains A LOT. To prevent the trays getting too wet, we’ve positioned out bin where it is open from above to allow some moisture to hit the composter, but where it is protected from the sides.
Keep the composter’s spigot open. I know, this robs us of the compost tea, but we’re not diligent enough to keep it drained enough to avoid the lower tray from getting soaked. If you’re checking on the bin daily, then maybe closing the spigot is fine, but otherwise consider keeping it open. It also helps that our bin is on a grassed area, so the tea doesn’t cause any mess.
Do not compost large pieces of bread, and any meats/cheeses. We don’t have rodent pests on the roof, so the typical rodent risk related to meat/cheese isn’t an issue. That said, we do like to avoid smells, and further we’ve found that any dense break/cake etc tends to not break down and instead just mold.
Rotate the compost trays. We keep the trays with the freshest material in the bottom, and the oldest/most ‘ready’ tray at the top. I’ve found that the worms in that top tray, once they’ve finished the available organic matter start to migrate down to lower, more nutritious trays, making worm extraction much easier.
So far we’ve made due with a single Worm Factory 360 Composting Worm Bin but given interest from others in the building, we’ll be looking at purchasing additional, or some other, larger bin to accommodate the available vegetable waste. At this point I’m thinking about either a tumbler / rolling composter, or one of the more pleasantly designed aerobins like the ones on offer at Amazon.
What’s the problem with pollinators? There aren’t enough of them… and they sleep in.
My second year, I added berry bushes to the roof, and added to the count this past season. What I found is that the berries bud and flower much sooner than vegetables in this climate, and apparently much sooner than bumblebees and honeybees surface to help with pollination. As a result, I’ve had very limited fruit production, though this past year I was able to get some improvement by manually making the effort.
I don’t know if the issue is that local pollinators aren’t emerging at the same time, or whether the location, and relatively limited flower options means they don’t visit until blooms are more abundant. Regardless, it’s a problem that I’m trying to deal with on a couple levels in 2019.
First, I scattered wildflower seeds in some beds reserved for non-edibles in hopes that they will emerge and flower to provide additional options for any pollinators that do emerge and visit early in the year.
Second, I’ve purchased a number of solitary bee homes and will be seeding them with mason bees in March, in hopes that the early-emerging mason bees will bridge the time between early flower emergence and the arrival of the pollinators that service the broader pool of fruit and vegetable plants.
If anyone has other ideas I’m all ears, as I’d like nothing more than to have bushes loaded with berries through the spring/summer of 2019.
One topic I wasn’t prepared for during year one was the increased impact of wind on the garden. Ground-level gardens benefit from natural barriers in the form of trees, buildings, hedges and the like. On the roof, most of these aren’t present, and in our case winds from the west are uninterrupted as far as the eye can see. The implications?
Risk of toppling for any non-woody plants.
Lower ambient and soil temperatures due to the cooling effects of wind.
Arrival of foreign seeds from who-knows-where.
Risk of toppling non-woody plants. This issue became clear almost immediately as after transferring seedlings to the outdoor beds. Despite having staked them, the first windy day saw them lashed about their stakes to the point of death. Over time I’ve come to realize the obvious danger to young plants, but that this extends also to larger plants later in the year as well. A number of large tomatillo plants found themselves significantly damaged as a late summer wind caught the row and toppled those poorly staked, and even snapped some of the stakes themselves.
We’re still testing, however we’ve found the following to work:
Choose locations with wind & temperature consideration in mind when planning your garden. For example, our pepper plants are now bordered by a protective glass barrier (conveniently already present on the roof) which both limits wind exposure and allows light through to heat the soil.
Stake all plants, large and small. We used bamboo of various lengths and diameters, affixed with twist ties which required adjustment as the plants matured in order to avoid impairing growth. Note that we affixed both stems, and branches where necessary, and revised placement of supports through the season to provide adequate support and protection.
Protect the most exposed areas with additional barriers. For some beds the exposure was just too great for anything other than strawberries, or low herbs like thyme, or woody plants. Here we affixed supports to the beds themselves and used strips of burlap to break the wind. This worked well to block the wind, however I think it was too effective and may have lead to powdery mildew on some plants as they dried more slowly after rain, and there was limited circulation. This burlap on Amazon comes in narrower sheets which should allow introduction of gaps which should help with circulation.
Lower ambient, and soil temperatures. This one’s pretty straightforward, but cool wind will cool plants, so constant wind will bring down the temperature around the plants, and of the soil itself. My guess is that this will be more of an issue for plants like peppers, but I could be wrong. This year I’ll be trying black plastic sheeting on the soil prior to seeding, and then retaining it around the plants to raise temperature for those plants that need it.
Arrival of foreign seeds. This one I hadn’t considered, but it quickly became evident. Each spring we see the evidence as weeds of all types start to sprout in our planters, and each year we see new varieties showing up. Some of these may arrive with birds (a particularly irritating example being climbing nightshade which has taken root in the far corner of a non-cultivated, and hard-to-access planter… right at the precarious edge of the roof), but I’m completely convinced that many are brought on the wind and deposited randomly.
These challenges aside, I do think the plants benefit from the additional circulation afforded on the roof, especially given I tend to plant more densely than recommended given the limited square footage.
The soil selected for our rooftop containers is miserable. I’m guessing this is to limit weight as the “soil” looks to be about 25% crushed lava rock. Regardless it seems a safe bet that its not much good for growing. Rather than haul a ton of sand up to the roof we decided to pursue other approaches.
Fertilizer & Bone Meal
Cow & Sheep Manure
Winter Cover Crop
Fertilizer & Bone Meal. Starting with fertilizer & bone meal, we’ve used it, but we’ve used very little of it. Generally just something added at the start of the year. The main reason we haven’t used it much is cost. No question it works… but it costs, and I’m cheap.
Compost. We’ve got a worm composter set up and churning through kitchen scraps on the roof. We try as much as possible to keep any remnants of meat or cheese out of the mix, and over-index on fruits, vegetables and egg shells. Further, over the winter while the worms are in slow motion I’ve been blending fruits, vegetable and egg shell scraps and digging them into the soil. Does it work? Who knows… but it doesn’t seem to hurt.
Cow & Sheep Manure. This one’s pretty simple. I buy several bags each year and dig it into the soil in our planters before planting seeds and starts.
Winter Cover Crops. These are a new approach starting last winter. I went with winter peas and rye grass… and it worked great. Let it grow over the winter, and in the spring cut it and dig it under. It seems to compost pretty quickly, and the legumes fix nitrogen for the season’s crop. My one learning from the first year is to start the seeds before winter arrives, so they have a chance to get to a decent size before the cold weather stalls them. This year I decided to repeat the winter peas and rye grass, but also added some crimson clover. Wish me luck.
Aaaand, that’s it. At least that’s it for our roof thus far.
Transitioning the rooftop from the original lambs ears, creeping thyme and various others to fruits and vegetables has been a gradual transition. The original plants showed mixed levels of success, and where they faltered, unsightly weeds quickly took hold. While we have attempted to pull the weeds as they arrived, they were quick and plentiful, so this year we took a different approach.
After an initial clearing of vegetation (both what remained of the original plantings, and the early weeds) we scattered wildflower seeds in the most visible, and not yet tackled planters. What resulted was better than we’d hoped with bursts of colour presenting all season long.