Greenhouse Vegetable Gardening (2015)
What gives the greenhouse its special atmosphere is its cultivation. Plants, water, and earth emit a wonderful smell and provide high humidity, but cultivation can be done in many different ways.
By deciding on which plants to grow and how much of the year to devote to them, it’s possible to set up a practical and easily cared for greenhouse. Plan for what’s most important to you: the pleasure of gardening, the seating for a leisurely coffee break, or for the economic benefits of cultivating vegetables and plants.
A common design is to make a narrow border along the length of the greenhouse where tall plants, such as tomatoes and cucumbers, can be set. You can install shelves for seeds and small plants along the opposite wall, or perhaps along the width of the greenhouse. To maximize the use of space even further, you can grow dill, lettuce, and basil in the soil between the tomato plants. Pepper and paprika planted in larger pots can line the path. You can even do all the cultivation in pots, the benefit being that plants are easy to move as needed, although they do need more care with watering and fertilizing.
If the greenhouse is a larger model, the short wall furthest away can be set aside for seating space for coffee breaks, in combination with a workbench. Very narrow shelves fastened to the house construction can hold a row of pots, which you can fill with favorites such as geraniums, fuchsia, and myrtle.
How to grow
In a greenhouse you can cultivate plants and flowers in many different ways simultaneously.
You can raise plants in pots placed on the ground. You can also sow seeds directly into shallow boxes that contain soil. Dill, parsley, and lettuce grow well in boxes, too, if you harvest them as they grow.
It’s also possible to grow plants and flowers directly in the ground in the greenhouse, in what are usually called beds. Larger plants such as tomatoes and cucumbers are typically grown in beds. First they’re seeded in pots, and when the plants are big enough they’re transferred to the growing area, either in the ground or in a bigger pot.
What to grow
Most people grow tomatoes and cucumbers in their greenhouses but there are many other options, some of which are suggested in this book. To simplify cultivation and plant choice, plants that are treated the same way are all collected into growing groups. Regardless of whether it’s a tomato or a cucumber, they grow very similarly, so instead of repeating the instructions for each plant, consider them applicable to all plants within the group. When it’s time to increase the workload, make it simple on yourself by choosing plants within the same growing group—you’ll have fewer details to keep in mind. As your joy in gardening increases, you can add other plant groups to your greenhouse.
Carnation, one-year annual.
Summer flowers for outdoor plantings (chap. 5)
Some plants don’t reach the flowering stage before the first frost arrives, or flower extremely late if they aren’t first started in a greenhouse. We like early flowers in beds and flowerpots. Petunias, Mexican marigolds, lobelia, and similar plants do flower even if direct seeded, but it won’t be until late summer or early in the fall. If they can spend a month or two in the greenhouse beforehand, they will delight with flowers throughout summer. Even many bulbs and tubers risk freezing before flowering. Plants in hanging baskets and big planters are many times more beautiful if the plants are given a chance to fill out to their proper size in a greenhouse before they are hung in place.
Nasturtium, a great choice for flower beds.
Wide bed sowing for bountiful flower beds (chap. 6)
It’s very simple to pre-cultivate seedlings in the greenhouse for transplanting later into the ground and in flower beds. It’s a very gratifying and easy way to grow flowers for bouquets and lush, colorful flower gardens. A greenhouse is the ideal place to get the most out of seeds and grow as many plants as possible. And if the seed is very expensive or rare, you don’t want to sow it directly outside—in a greenhouse you don’t run the risk of the seed rotting or birds and snails enjoying it as a snack. In a greenhouse, more seeds will probably germinate than in the ground outside.
Tomatoes prefer the greenhouse.
Growing vegetables in the greenhouse (chap. 7)
The most common greenhouse vegetables are the ones that don’t have time to ripen outside—tomatoes, melons, eggplant, and hothouse cucumbers, for instance. In Sweden the summer season is simply too short, so you need to grow plants from seed to harvest in the greenhouse. During long hot summers they might grow in the ground, but this may not work reliably every time, and not in the country’s northern parts. Depending on where you live, there will be other plants, like cape gooseberry (physalis), bell peppers and peppers, that also need to grow in a greenhouse to ensure that they will have time to ripen.
Bean seedlings to transplant outside.
Vegetables to plant outside (chap. 8)
Vegetables are delicacies we enjoy in the summertime. Start growing vegetable seedlings in the greenhouse to transplant outside to ensure an earlier harvest. It also makes for less work weeding and thinning, even if the plants are very small when transplanted. Plants that require a lot of warmth to germinate, such as basil and pickle cucumbers, need to be started inside to ensure even germination and plenty of seedlings, and only then will they be ready to be transplanted outside. It’s even good to start traditional herbs (like dill) in this manner to decrease the risk of fungal attacks.
Tender lettuce for early harvesting.
Early harvests in the greenhouse (chap. 9)
Greenhouse cultivation can bring a very early harvest of plants that you grow outside later on in the season. You can enjoy your own lettuce, delicate green onions and crisp radishes in early spring.
The early spring sun heats the greenhouse quicker than the ground outside, so if you grow seedlings in flats and then transplant them into the greenhouse soil, you will be harvesting those plants several weeks earlier than from the outside vegetable patch. Being able to harvest heat-loving herbs early adds that little something extra at mealtimes.
Seedlings and early potatoes in a cold frame.
Hotbeds and cold frames (chap. 10)
A hotbed is a good complement to the greenhouse. There is a centuries-old tradition of growing early vegetables—primeurs—in hotbeds. Starting in a greenhouse and transplanting into a hot or cold frame is an additional way to increase cultivation possibilities. Gherkins, squash and dill are examples of plants that need the greenhouse warmth to start growing before being transplanted to a cold frame. During the summer, melons like its warm soil. Also, beets, carrots and other primeurs can grow to an early harvest.
Geraniums thrive in a greenhouse.
A greenhouse in flower year-round (chap. 11)
It’s necessary to mix different kinds of plants in the greenhouse if it is to become a green oasis year-round. Small hardy trees like peach, apricot and nectarine are in bloom so early in the year their flowers will freeze if they’re kept outside. These can be grown in pots or directly in the ground. A mature grapevine will give summer shade and bunches of sweet grapes. Annuals, perennial Mediterranean plants and traditional plants such as roses contribute to the beauty.
Plants that are not hardy and need to be kept cool and in proper light during the winter will flourish in the greenhouse during the summer. These are plants like camellia, citrus, and olive trees, bay leaf, rosemary, and myrtle that cannot be kept in homes. Many plants, among them bougainvillea and passion flower need a warmer climate in order to develop and flower.
Pansies can be made to bloom early.
Overwintering plants in a greenhouse (chap. 12)
The greenhouse can be used to overwinter (hibernate) less hardy species—which ones depend on where you live. Plants grown in pots year-round are more cold sensitive. Thus, a greenhouse environment is beneficial for them, too.
Spring flowers, bulbs, and perennials (chap. 13)
To produce early blooms outside, it’s possible to plant bulbs in a pot and let it overwinter in the greenhouse, thus forcing an earlier flowering. Even other spring flowers like primulas and pansies can be sown in the fall, transplanted into a pot, overwintered, and then forced into an extra-early flowering. If you want to grow your own perennials, sow them during the summer and let them overwinter in the greenhouse before transplanting them the following year. This way you’ll succeed in growing new gems and difficult plants that do not like cold or wet winters.
Spring flowering nectarine in the greenhouse.
Houseplants—cuttings and seeds (chap. 14)
Houseplants or indoor plants, which we keep inside our homes, flourish in a greenhouse. If you want to take cuttings or plant seeds from houseplants, the greenhouse is the right place to do it. Treasured favorites like geraniums grow more handsomely in a greenhouse, and many other plants benefit from a rejuvenating cure in the greenhouse’s light and airy atmosphere.
It’s even possible to multiply plants such as potentilla (cinquefoil), roses, and other ornamental shrubs yourself. Plants prefer an area that’s a little warmer and more protected while they’re developing roots, even though these plants are meant to be outside year-round.