Growing in Your Greenhouse: Berries

Brian Bill

Brian Bill | April 13, 2022

Growing in Your Greenhouse: Berries

April is here in full force, at least that’s what the calendar tells me. The frost on my windshield this morning isn’t exactly a harbinger of spring, but the blooming tulip fields offer some reassurance the date on my phone isn’t wrong. This Sunday is Easter after all, and while I was going to write a blog about the flowers we typically see in holiday based decorations, I’ve already written a blog on flowering bulbs (link here) so I felt it may be bit redundant. However, the chilly weather of late has put in mind a few cool weather fruits. Berries, to be exact. Strawberries, blueberries, raspberries and blackberries are all fantastic greenhouse crops and to sweeten the pot, they grow well in cooler temperatures. As with anything you plan to plant in your greenhouse, you’ll likely need to do some research and careful planning before you get started. Berries in particular require some forethought, these seemingly simple grocery store staples can be more complicated than they let on, don’t be fooled! First off, the variety of berry you plan to grow can vary drastically and I’m not just talking about choosing strawberries over blueberries. Though that is an important question to ask. As it turns out, there are quite a few varieties of each individual berry. Perhaps you’re a fan of the Ac Valley Sunset variety strawberry that fruits later in the season or maybe you prefer the Ozark Beauty, a much more common variety that boasts ever bearing properties. I won’t and probably couldn’t go on and list all other varieties and their qualities, I’d still be writing this blog 10 years from now were that the case. The point being, choosing the type of berry you wish to grow is just the first step of many when planning your berry patch.

Once you have chosen which berry to plant where, it’s time to decide upon variety. When making this decision, take into consideration when you want to harvest your fruit and what climate you can keep inside your greenhouse. Strawberries, raspberries and even blackberries have ever bearing varieties, though the later have proven to be insufficiently productive. Ever bearing berry bushes, generally speaking, don’t exactly have a season. These plants will continue to bear fruit all year round, but will produce less fruit per. However, more plants can be put in the ground per square foot, so if you do things correctly, you can have plenty of berries all year long. There a plenty of other differences between ever bearing bushes and those that abide by the traditional growing season, but that is generally the most important when it comes to choosing between the two. Once you pick between the two major categories, it’s time to make more refined decisions. What kind of berry do you want? Some varieties produce larger fruit with a more bland taste, others can produce a sweeter and smaller fruit. If you’re starting from seeds, you’ll likely have a wider option of choices but you may have to wait longer for your plants to mature and actually start bearing fruit. Do some research and find your desired berry, or pick a few different ones and find out for yourself which you like best. The good thing about an abundance of varieties is you can really customize your garden!

When you are planting, keep in mind what you are growing, and what they require. Strawberries are going to be your best friend if you are looking to plant as many as possible in a small space. You can get pretty creative with strawberry alignments. Tiered planters work well, some people make holes in PVC pipe in attempts to maximize space. You can also plant them individually in pots or use one of those pots with “multi-pockets” or stacked offset tier pots. Like I said, strawberries offer a lot of options in small amounts of space. Blackberry and raspberry bushes should be planted in individual pots, about 2 foot in diameter equipped with 6 foot stakes, leave enough room to walk through between each plant. Blueberry bushes require the most space, needing around 5 feet between plants if planted in beds. They can be potted, so long as the diameter is anywhere from 2 to 4 feet depending on which variety you go with. Again, ensure there’s enough space to walk between the pots.

Once you’ve figured out what and where you want to plant, it’s time to worry about temperature. Specifically for blackberries, raspberries and blueberries. These plants, for most varieties at least, require a decent amount of time spent in cool temperatures. Night time temperatures that drop below 40°F is the best case for a lot of varieties, but there are some that have low-chill requirements as it were. Both black and raspberries need to spend about 200 hours in below 40°F temperatures before they can start producing fruit. Blueberry varieties tend to range anywhere from 500-1000+ hours. If starting from seeds, it is alright to germinate your plants indoors, but as soon as they are hardy enough to survive life outside, place them outdoors until their required cool temperature time is achieved. If you bought already started plants from a nursery, they more than likely have spent enough time out in the cold, but I would double check before buying so you know what you’re getting into. Once your plants have gotten the right amount of cool weather, feel free to move them back inside. Keep your greenhouse in the range of 60-70°F. Strawberries are pretty different and don’t really require cool temp time. Perhaps the others do because they are bushes and strawberries are more vine like in structure, I’m not sure, that’s a bit above my pay grade.

Now that you’ve gotten a handle on the temperature component of growing berries, now you get to deal with pollination. Given that you are going to be moving your plants inside once they are able to develop fruit, you will likely pull them from the natural world before pollinators can do their jobs. This means that you are pretty much in charge of pollinating your plants. There are some products out there that you can order, pollination wands in particular come to mind. But you can just as easily do this with a soft bristled paint brush or potentially even by finger, assuming you’ve washed your hands. This is a step you will need to take unless you start taking your plants outdoors daily. The former would likely be easier on your knees and back as it would keep you from picking up and moving pots on a daily basis, however, the latter is good for the environment as it helps feed the many pollinators in our ecosystems. You can try an alternative and just let bees and butterflies lose inside your greenhouse, but that just seems like a bad idea to me. By all means, experiment as you will, but don’t blame me when your greenhouse becomes a large scale beehive. Hey, at least you’d have fresh honey.

If you are planning to grow strawberries and don’t plan to pot individually, beware of runners. Strawberries are notorious for propagating via runners which can lead to overcrowding in planter boxes. Thinning over time is a very necessary process to ensure that your strawberry plants can grow to their full potential. These runners often seek spots with more nutrient rich soil or even greater access to sunlight so any bare spaces in your planter boxes will be occupied by a runner at one point or another. If the runners have begun to mature a little bit, you can clip them and propagate them elsewhere. Clip all but two or three leaflets from the new runner plant and then move them to a new bed or pot. This is a great way to get more plants from your original without sacrificing the original. If you wish to take cuttings from either black or raspberry bushes, wait until later in their growing season. Once ready, snap a stem off the main bush, one that snaps easily without much resistance. Trim the cutting down to about 3 to 6 inches and ensure each cutting has at least two leaf nodes intact. Remove the lower leaves and place the cuttings stem in a cup of water. From here you can leave them in the water until roots begin to form, or alternatively you can remove them from the water and dip into rooting hormone powder and then plant in a mixture of perlite and soilless mix, once the roots are sufficient in size, transplant to a quart sized container. Pot up or transplant to a permanent location come spring time. 

Now, you’ve probably made your decision as to what you want to grow and how you’re going to go about doing so. However, you are not quite done yet. Different plants are going to require different types of soil if you truly want them to thrive. Strawberries for example, generally want a pH range of anywhere from 5.5-7.0 whereas blueberries want 4.5-4.8 but will tolerate up to 5.2. Do some research as to what soil type and pH level your plants want, just as each plant variety is subtly different, so too are its requirements for optimal growth.

As always, keep an eye out for pests. I’ve said it once, I’ll say it again; greenhouses are basically the perfect environment for pests. It’s warm, moist and filled with fresh vegetation. Keep your vents open and fans running to make sure fresh air is circulating throughout your greenhouse. Heating and lighting will likely not be necessary given the time of year, but it’s never a bad thing to have them on hand just in case. Keep your greenhouse walls wiped down and the floors free of clutter and dead leaves. Remove dying and yellow leaves from your plants and avoid splashing water on the foliage when hydrating your plants.

Soon enough, your berries will be blooming and you’ll be surrounded by fresh fruit. Keep track of how many plants you actually plant, you don’t want all these berries going bad before you get a chance to use them! Enjoy your week, thanks for reading and I’ll be back next week for the next blog!

-Brian Bill