A mini or small greenhouse garden is the best way to garden for individuals who do not have much space.
Unlike a permanent greenhouse garden, they are highly portable, meaning that you can move them around your property so that your plants can get enough sunlight in different seasons if you choose.
Growing in a mini greenhouse can be much fun for both beginner-level and experienced gardeners. But before you buy some of the plants you fancy growing, you have to know the basics of growing plants in small greenhouses.
This guide will help you get started.
Setting Up Your Small or Mini Greenhouse
A little greenhouse allows you to extend the growing season. You can plant early in spring or summer and grow some vegetables throughout the year.
However, installing the greenhouse is the first step of your indoor/enclosed growing adventure. You have to consider several things such as lighting, temperature, watering, humidity control, sanitation, and the types of benches to install.
Here are the major items your mini greenhouse will require.
Greenhouse gardening items include mixed growing mediums large containers, pots, seedling flats, and hand tools and a watering can.
Some greenhouse hobbyists opt for biodegradable pots, and if you prefer them too, you will have to store them in watertight containers.
I personally like just reusing plastic from containers, RX bottles, and things like that to start my plants. That way you don’t have to worry about the pot molding and you find another use for things that would normally end up in the trash.
You can mix the growing mediums in buckets with lids or store them in plastic tubs with lids. The containers protect the home-blended mediums from pathogens and insect eggs.
While benches are nice, shelves are can be cost-effective. However, depending on what you want to grow you can just leave plants right on the ground.
One of the best benefits of having benches or shelves is to have multi-layer growing. So that way you can pack more growing into a small space.
Sanitation is vital for any mini greenhouse. Nothing can be as frustrating as bugs, bacteria, or fungus infiltrating your greenhouse garden and causing problems or even ruining your entire season of plants.
Make sure you remove all clippings, leaves, and other plant matter from the greenhouse after you have trimmed them off.
You also want to make sure you remove any plants that become infected or molded as they can spread to other plants.
Irrigation and Drainage:
For the plants to stay healthy and grow throughout the year, they will need enough water. That means you have to invest in drip irrigation or simply watch things closely and water when needed.
For a small greenhouse garden setup, you can use a hand watering can.
Drainage is essential, meaning that you have to ensure that all benches are slanted slightly so that any excess water can drain properly.
Alternatively, you can design the benches with slats or holes to allow dripping of excess water.
If your greenhouse is in a perfect place with lots of south-facing light, you should be all set with the lighting you will need.
However, if your greenhouse does not receive enough light naturally during the day, or the plants require light for more hours than it is naturally available in your place, then you have to invest in grow lights.
You will have to raise them as the plants grow. Greenhouse lights are a better choice but they might be cost-prohibitive for mini and small greenhouses.
When planting shade-loving plants, you will have to invest in the artificial shade when the bright sun of summer starts appearing on the horizon.
A shade cloth will keep the hottest sun rays out of your greenhouse throughout the day.
A small evaporative cooler, fan, or heater might be necessary if you plan to use the greenhouse throughout the year.
Greenhouse heaters are inexpensive but there are also some off-grid options for keeping a greenhouse garden above freezing in the winter. Be sure to check out my post on How To Heat Greenhouse In Winter Without Electricity.
Fans can cool help to cool a greenhouse in a mild climate as well as provide muchly needed air circulation.
One of the biggest things to keeping the right climate conditions in a small greenhouse is to make sure you have ventilation as well as air circulation.
Other than a fan as we mentioned, depending on the type of greenhouse garden you have, I highly recommend investing in an Automatic Vent Opener.
Use a thermometer and a hygrometer for precise control of your climate control system.
What to Grow in a Mini Greenhouse
Before you start the plant selection, you have to understand the type of mini greenhouse you are working with as well as the size greenhouse.
Understanding the capabilities of your structure will allow you to provide a favorable growing environment for your plants.
There are two types of greenhouses, which are standard greenhouses and cold frame greenhouses.
Standard Mini Greenhouses:
Standard mini-greenhouses offer a warm climate to allow maintenance of an ideal temperature (to some degree) regardless of the outdoor conditions.
Depending on your location, you can use this type of greenhouse to start plants and then transplant young plants to your outdoor garden after the outdoor temperatures have stabilized.
Unfortunately, some places may experience temperature fluctuations even in summer, meaning that you have to grow the plants throughout the season.
Cold Frame Greenhouses:
Cold frame greenhouse garden is different from traditional greenhouses. The mini-greenhouses use insulation and solar energy to make a microclimate in the garden.
That means they are ideal for starting seedlings or transitioning some greenhouse plants before they are planted outdoors.
People mostly use them to grow tender plants during winter and keep the planting soils warm. You can extend cool-season vegetables or sow seeds earlier in spring in these greenhouses.
They provide shelter from weather and wind without overheating the plants.
So, Which Plants Should You Plant in Your Greenhouse Garden?
While mini-greenhouses are small, they should not limit you on what you can grow in them. However, the season will dictate the plants you can grow in it unless you have a full climate control system set up.
So, with that in mind, let us look at some of the crops you can grow in your greenhouse garden at different times of the year.
Winter to Early Spring:
At the start of winter, sow frost-tolerant plants like leafy greens, cabbage, spinach, lettuce, and broccoli if you have an unheated greenhouse.
The plants can endure low temperatures. If you will be moving them outdoors, you can do so after the evening lows are above 30 degrees Fahrenheit.
Mid to Late Spring:
After spring and the official planting season arrive, plant the tender plants inside your mini greenhouse. The plants require a warm and controlled environment with over 8 hours of direct sunlight to thrive.
Sow the tender plants like cucumbers, melons, and squash indoors to transplant in early summer if that is necessary. Ensure that the plants are not exposed to frost before the transplanting because frost will kill them.
Summer to Late Summer:
Transplant the plants sowed in the previous season outdoors to make more room for the mid-summer crops in your greenhouse.
As the internal and external greenhouse temperatures increase, grow the heat-loving plants like tomatoes, eggplant, and hot pepper varieties.
Too much heat in a mini greenhouse is not good for some plants. It can also invite mildew, mold, and dry out some plants.
When applicable, include ventilation systems in the structure to allow more air to flow into the greenhouse and keep the plants comfortable including on the hot summer days.
Autumn & Late Fall:
As the heat of summer reduces and the cool weather returns, it is time to use your greenhouse to finish off the summer plants and plant cool-season vegetables.
And because cool-season crops are the hardiest, you do not have to heat the mini greenhouse for them to grow unless you live in a super cold area.
Some of the options to try at this time include snow peas, kale, and turnips. The growth might be slow but steady. Furthermore, you will have many plants to eat and enjoy during the winter greenhouse months.
Starting Seeds in Your Mini Greenhouse
Starting seeds happens in plain seed trays, single plug trays, or hydroponic trays and people prepare them according to their needs.
After planting seeds, record the label and the planting date for easier recognition of the plants. Planting seeds and allowing them enough time to flourish is a good idea.
That will help you review their germination rate to know how many seeds you need to get the needed seedlings. Here are the types of seeds to consider.
By starting seeds in the greenhouse it also allows you to get a head start on your outdoor garden as well.
Hybrid seeds are a healthy choice because you can buy them from any local garden store. The seed companies identify them as F-1 seeds, meaning that they are crossbreeds of two similar plants.
The seeds grow into big and healthy plants that look identical and they have a highly consistent production. You can also harvest earlier than expected.
Unfortunately, the seeds are more expensive and you cannot store them for a long time.
Heirloom seeds are a great idea. Many people grow them for their awesome flavors. They also produce genetic varieties for future cultivation and they adjust to the local environment easily.
These types of seeds are hands down my favorite because you can keep the harvested seeds for another year, meaning that there might be no need of buying more seeds each year.
Disease & Pest Control:
Disease and pest outbreaks in your small greenhouse garden can be a serious pain and the problem can easily get out of hand if you do not address it properly.
Diseases and pests in greenhouses require three key factors, which are the susceptible host plants, the presence of diseases and pests, and a favorable environment to proliferate.
A good pest management program will address all the factors simultaneously. Here is how to control some of the common pests.
Aphids are small sap-sucking insects with soft bodies. The insects reproduce very fast because they do not need a mate and they give birth to live aphids.
There are various types of aphids that feed on plant sap. Each type has a different color but you will mostly see the fully-grown aphids in your mini greenhouse.
Unlike the other types of aphids, the fully-grown aphids do not fly – they crawl – and you might not see them on the sticky cards.
You will have to examine the plant leaves, particularly the underside, to identify the leaves. Further, aphid skins and ants will tell you that aphids exist. Ants feed on the “honeydew” produced by aphids.
There are ways to Get Rid Of Aphids Naturally.
Fungus gnats are another type of pests to expect in greenhouses. They are small winged and long-legged insects that graze on organic matter and algae in the soil media.
While they do not cause any damage to the plant directly, they can be a nuisance in your greenhouse and they can carry soil-borne diseases like pythium, which can affect your crops.
You will see them flying around the base of your greenhouse plants and other wet areas. White fungus gnat larvae may also exist in the soil medium.
One of the best ways to control these is to use sticky traps to catch them around the base of the plants.
Whiteflies are among the commonest pests expected in greenhouses. The pests are related closely to aphids and they are of the same size.
However, unlike aphids, they are winged and white, meaning that they will fly away when you disturb them. Like aphids, they feed on the plant sap and they can produce “honeydew” residue at different stages of their lifecycle.
You will mostly find them on the sticky traps in your greenhouse and around the plants. Failure to control them will lead to fruit and leaf damages, which can cause stunted plant growth.
Use insect screens to keep them out of your greenhouses. Besides, you have to keep your greenhouse clean from excess plant material, debris, and weeds to keep aphids and whiteflies away.
Some people also use blasts of water to knock them off the plant or spray neem oil, on the plants to kill them. Yellow sticky traps are a good choice for small greenhouses too.
Slugs and Snails:
Slugs and snails will only increase if the humidity levels in your mini greenhouse are high. The nocturnal, fleshy, and slimy creatures are easy to control because you just need to keep your greenhouse clean.
Ensure that the greenhouse is free of uprooted weeds, used boards, leaves, rocks, and bricks because they can give moistened hiding spots and cooling.
If you do run into an issue, check out our post on How To Naturally Control Slugs And Snails.
While mites exist in many types, spider mites are the most common in greenhouses. They are small and they may have a green, brown, or red color.
You will mostly see them on the underside of your plant leaves and fuzzy webbings may appear on the leaves as the population increases.
You can release predatory mites as an early action or preventative method. Monitor the climate to ensure that the greenhouse is not very hot and dry.
Spider mites are a big problem in dry greenhouse climates or the warmer microclimates such as closeness to the heat source.
Over-fertilizing of plants can make the plants more susceptible to spider mites too. Use safer soaps or insecticidal soaps like neem oil to control the spider mite population.
Powdery mildew is fuzzy white fungal spores that appear on plant leaves. It can affect any plant, including those grown outside the greenhouses.
But it shows up first on the broadleaf plants. Powdery mildew fungal spores can flourish in any greenhouse but it requires humid conditions to damage the plant leaves.
Use circulation fans to boost the airflow in the greenhouse and prune out any excess old plant leaves in the dense plantings to boost airflow into the plant canopy.
Reduce the humidity in the greenhouse by increasing ventilation. Further, you can invest in a dehumidifier or boost the nighttime temperature with a heating system.
Use products like potassium bicarbonate (baking soda), sulfur burners, or commercial potassium bicarbonate-based sprays such as foliar spray to prevent and respond to powdery mildew infestation.
Thrips are tiny winged insects that you can only see with the help of a magnifying glass or a hand lens. Besides, there are many thrips species, but western flower thrips are the most prevalent.
They mostly cause patterned silvery patches, which contain small black specks, on plant leaves. The pests primarily scrape and suck chlorophyll from leaves, therefore, damaging the leaves and reducing the ability of plants to photosynthesize.
Flower deformation and stunted plant growth might also be signs of thrips infestation. Use blue or yellow sticky cards to monitor the thrips population because they will trap the adult thrips.
Also, look out for thrips damages on the plant leaves or grow small flowering crops like petunias that attract thrips naturally.
An established thrips population can be hard to control. Therefore, prevention through screening is the only choice.
Alternatively, you can use predatory mites to kill the thrips at various stages. Beneficial nematodes are also effective.
The above tips will help you grow healthy plants in a greenhouse garden and stretch the harvest season into fall and winter.
You can grow herbs indoors, grow some sensitive plants, and start seeds for various seasons. Remember to monitor the greenhouse temperature and humidity regularly. In case of a pest infestation, use the above tips.
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