May in Your Greenhouse

Brian Bill

Brian Bill | April 29, 2022

May in Your Greenhouse

April has come and gone and while we didn’t get noticeable change in weather, we did get a few sunny days scattered about. Mornings can still be a bit cold as we desperately await the, “last frost of the season”, an ever illusive date that grows more unpredictable by the year. While we may never know exactly when that day will come (I was fully in summer clothing this time last year, I write this wearing a hoodie indoors this year), it is an important date. The last frost signifies our ability to be able to plant outdoors in earnest. Thankfully, for those reading this, you probably own a greenhouse. Why wait for the weather outside to cooperate when you could (and should) have started this year’s gardening journey months ago! This month, at least the early part, the big issue you should be dealing with is a lack of space inside your greenhouse. Things should be getting pretty busy in your greenhouse as your seedlings should be reaching near maturity and will be ready to be hardened off outdoors soon enough. Yes, that means you will soon free up some much needed bench/shelf, once you start transplanting outdoors that is. If you are growing tropical plants and plan to keep them in your greenhouse, you might not get any extra space this month, but you should still have plenty to do!

Regardless of what type of plants you’re growing in your greenhouse, you should have a compost system set up. If not, there’s no time like the present! This time of year your plants should have plenty of off-shoots and suckers that will need to be pinched off to promote optimal growth. If you don’t have the space or time to try and propagate these cuttings, add them to your compost pile! A healthy mix of older decaying plant matter and newly clipped, green plant matter will create a nice fertilizer for you once the process is said and done. Too much green will not work as well as a good mix, it will also take a lot longer to fully decay. Adding enzymes and other material to aid in the breakdown of the organic material can help you along the way, but be careful what you’re adding. Do your research and make sure the additives you choose are in accordance with your gardening methods. You don’t want to use a lot of heavily processed chemical products if you are trying to have an organic garden. Watering your compost pile, if kept outdoors and exposed to the elements, is also a good idea. Don’t over water, but make sure your compost pile is evenly moist to efficiently speed up the decomposition process.

May is a great time of year for gardening. The weather is warming up, but we still get plenty of rainy days and gray skies. Outdoor gardening can begin in earnest and greenhouse gardening begins to ramp up. You might not be ready to harvest anything just yet, well maybe if you started tomatoes back in January, but let’s just assume you didn’t. This month you will have a lot of work tending to growing seedlings, checking on maturing/fruiting plants and ensuring your microclimate is perfect for your chosen plants.  Two things that might make your life a little easier this month are crop covers and down-up pulleys. Crop covers will make sure that the unpredictability of the last frost is not a bother for your growing plants. These covers essentially work as small scale greenhouses for outdoor plants. By allowing 80% of sunlight to penetrate, crop covers retain the heat of the day well into the night protecting your plants from any cold spurs. Ours protect from frost down to 26° F so you can rest easy. Not only do they protect from adverse weather, but they can also keep pesky insects and birds from destroying your crop. In fact, ours are so sturdy you can reuse them many years in a row and are made from UV stabilized material. Down-Up Pulleys are simply a gift from above, quite literally in fact. Attach these to hanging baskets to make watering a breeze! Once attached you can simply pull down on the basket when you need to water it! Our pulleys can hold up to 20 pounds and have a vertical adjustment of 31”. Hanging baskets are meant to hang, but you shouldn’t have to get out a step stool every time you need to water your flowers. Sorry for the shameless advertisement, but these products really are incredible and can save you a lot of time and heartache!

Temperature and humidity needs in your greenhouse really begin to change during May. Up until now you’ve been trying to figure out how to keep your greenhouse warm without spending an arm and a leg in electricity bills. But now, you may need to figure out how to keep things cool. Generally speaking the optimal temperature range for May is 75°-80° F to keep your plants nice and happy. This range may vary depending on what you’re trying to grow, so just make sure you do your research on how to keep your specific plants happy. If you are trying to keep things cool in your greenhouse, first consider shading. We carry a wide variety of shading cloth, ranging from 55-87% sun blockage. These percentages tell you how much sun the cloth is going to block from coming into your greenhouse. Keep in mind that they will still let the sunlight and heat associated with it into your greenhouse, but they will cool things off considerably. Make sure you are shading on the exterior of the greenhouse as shading is proven to be 40% more effective this way. Take inventory of the plants you are growing, what their needs are and keep in mind your local climate as well as greenhouse sun exposure. All of these factors should help you decide what amount of sun blockage you need out of your shading cloth. Heating in your greenhouse should be taken care of by the exterior climate. Outdoor temperatures and sun exposure should be taking care of it for you at this point, but I wouldn’t throw your heater in deep storage just yet. As mentioned before, the climate is getting less and less predictable as the years go by, so you never know if you’ll need a heater to keep things warm this month. Make sure you’re always prepared and you won’t have to deal with the negative repercussions of cold weather. Along with increased temperatures in your greenhouse, you will also need to increase the amount of humidity. Make sure you are staying on top of venting and air flow. Open vents equals loss of humidity so make sure they are only open when necessary. If your humidity levels have dropped, there’s a few steps you can take to get them back up. Spraying the floors and benches in your greenhouse in the morning will allow for extra water to get trapped and evaporate as the heat of the day increases. This way you can insure that there is a steady source of humidity in your greenhouse all day long.

Speaking of water, the need to feed your plants is going to increase this time of year as well. Both the amount of water and fertilizer will need to go up. If you keep a list of the plants you have and their watering/fertilizing schedule you can easily track how much water and fertilizer you are using. Water only during daylight hours to make sure you are minimizing risk of mold and fungal growth. The sunlight and heat of the day will help evaporate any excess water you may have used. Be careful when watering not to splash on the leaves of your plants as that can easily lead to rot and disease. Once your fruiting plants begin to show swelling fruit, it’s time to increase your fertilizing. You do need to be careful when fertilizing your plants. Too much is not good for your plants as it will flood their systems. A general rule is to add a little bit, often. Fertilize plants around once a week but use a minimal amount of fertilizer per feeding.

This month you should be seeing a lot of growth out of your plants. Any vertical growing veggies, such as cucumbers and tomatoes, will need to be trained around supports. Supports will help keep your plants from falling over once the fruit gets too large. Pinch out unwanted growth on your plants so they can focus on the good stuff. Keep some Neem Oil on hand for unwanted pests and fungus. Warm weather, while being very beneficial for gardeners, brings with it multiple threats to your plants. There are, in fact, two sides to each coin.

Harvesting this month is possible, though only if you were entirely on top of things in the previous months. If you were active in your greenhouse during the winter, you have the potential for a very productive harvest this month. The best thing about greenhouses is really that you can ignore the seasons outside and make the growing season whenever you want! So long as you have the heaters and artificial lighting necessary to create a hospitable climate during the colder months. If you’re smart about it and diligent in planning and execution you can supplement your grocery bill all year round by growing your own produce. You can also just grow and keep plants that make you happy! Not everything has to have a monetary driving factor.

However you use your greenhouse, this should be a busy month! Stay on top of things and you should have a very productive May. Don’t forget to check in and thank the various mother’s in your life, I’m sure they’ll appreciate it. Until next week, thanks for reading!

-Brian Bill