Greenhouse Vegetable Gardening (2015)

By sowing flowers in flats in the greenhouse you’ll soon have small plants ready for the outside. Even diminutive plants that take their time in reaching the bloom stage will still flower earlier if started inside than if they’re only direct-sown outside. They can be planted exactly where you want them, and also in the desired quantities.

Tall, late summer-flowering asters, together with snapdragons, painted daisies and brightly hued marigolds are but some of the flower options that delight the senses. Lately, many of the flower beds in public spaces have been planted with a handsome variety of different flowers. Some, like the annual royal knight’s spur, require a long growth period before they flower; others, like nasturtiums, reach the flowering stage very quickly. But no matter what type of flowers you use, in order to achieve a dazzling display in your flower beds, all the flowers need to bloom simultaneously. While petunias are lovely to plant out and enjoy, if the nasturtium next to them won’t bloom until later in the season, then a big part of the overall visual effect is lost. The possibility of starting plantings indoors to hasten the production of even the simplest plants is one of the great advantages of owning a greenhouse.

Some store-bought seeds certainly don’t come cheap—that special kind of calendula, old-fashioned sweet pea or black nasturtium can set you back several dollars per seed packet. What’s more, there’s no guarantee that all seeds will emerge when they’re direct-sown in the flower bed. Therefore, it’s highly recommended to start these kinds of plants inside. Sowing seeds in a flat or a box increases your control over the end result—there’s no risk of slugs or birds feasting on the fragile shoots, or that a sudden downpour will wash away the soil. The content of the seed packet is usually meager, especially if the seed is expensive, so in order to coax the most plants from the packet, the seeds should be sown in the greenhouse.

As it is such simple and quick work, it is no great bother to wide bed sow many of the garden’s flowers. Besides, the plants are certain to grow in their assigned space once you manually plant them out. If you are planning to keep a vegetable patch edged by nasturtium, it would be quite irritating to see a bald spot because, for whatever reason, three seeds didn’t take. It’s also impossible to buy many of these plants as seedlings, at least of the rare varieties. An unusual white nasturtium or a creamy marigold, for example, makes for a delicate display along with a full-bodied grey violet opium poppy. By wide sowing in flats or boxes, you have the possibility of creating many of your own imaginative combinations in the garden.

It’s easy to wide sow Mexican Zinnias.

How to’s—Wide sowing

♦ Fill shallow flats/boxes with planting soil. Use a mini-frame with a plastic lid if you have it. Fill the flats/boxes generously with commercial planting soil that is weed and disease-free.

♦ Pat down the soil firmly, paying special attention to the corners, and continue to add more soil until the flat/box is nearly full.

♦ Water with a watering can fitted with a fine nozzle; the soil should be soaked.

♦ Sow the desired seeds on the soaked soil, leaving ample space between each seed. Cover the seeds with soil according to the directions on the packet and lightly pat it down with the palm of your hand. The damp will rise up through the layer of soil.

♦ Place the flat/box directly in the greenhouse. Any plants that need higher temperatures for germination can stay inside the house until shoots appear. They can then be moved into the greenhouse as soon as they turn green.

♦ Water the seeded flat/box carefully, preferably using bottom-up irrigation if the flat/box has drainage holes at its base. If there are no holes, be extra careful when watering—don’t water to the point where the flat/box becomes water-logged; in fact, water so sparingly that the flat/box nearly dries out. If you have sown in planting soil, start watering with liquid fertilizer when the shoots reach about 1 cm (1/3”) high, and continue doing this. See p. 36.

Transplanting outside

When the weather turns warm enough and the seedlings have reached 3 - 5 cm (1 1/4-2”) high, it’s time to move them into the garden. They can be used in many ways: in flower beds together with other flowers that needed an advanced start in-house; as fillers where a plant failed to grow or where the spring bulbs have started to fade; or as colorful accents among late-flowering perennials. These kind of small plants are perfect for making beautiful combination plantings in large hanging baskets. They’re also good for the vegetable patch, where their rows can provide cut flowers for bouquets. (Don’t underestimate the thrill of having easy access to cut flowers for wonderful summertime hostess gift bouquets.) Many of the plants are also edible and make delicate garnishes for salads, drinks and cakes.

Provisional flower beds

If you run out of containers and flower beds in which to put your plants, there is an easy fix: Cover the ground with a layer of newspaper and add an edging. (The edging can be made from a pallet collar, of wood or plastic, or untreated railway ties). Fill the space inside and along the edges up with store-bought, bagged planting soil mixed with some long-acting fertilizer. Insert the plants and wait for flowers to appear. These kinds of flower beds are good for areas where it’s difficult to grow anything, such as areas under big trees or in front of a hedge. If the bed is set up under a tree or on a hard surface, it is advisable to put down a liner like a plastic cloth, root barrier, garbage bags or other material that will prevent water run-off.

Suitable plants for wide bed sowing in flat/box

Snapdragon, Antirrhinum majus

Calendula, Calendula officinalis

China Aster, Calistephus chinensis

Painted Daisy, Tri-Color Daisy, Chrysanthemum

California Poppy, Eschscholzia californica

Sweet Pea, Lathyrus odoratus

Rose Mallow, Lavatera trimestris

Common Toad Flax, Linaria maroccana

Love-in-a-mist, Nigella damascena

Common (Opium) Poppy, Papaver somniferum

Clary Sage, Salvia viridis

Pincushion/Sweet Scabiosa, Scabiosa atropupurea

Signet Marigold, Tagetes tenuifolia

Indian Cress/Nasturnium, Tropaeolum majus

Canary Creeper/Nasturnium, Tropaeolum peregrinum

Mexican Zinnia, Zinnia haageana

Everlastings of different types, such as Sea lavender, Giant Strawflower, Paper Daisies and others, Xerochrysum bracteatum

Wide bed sowing for the summer flower bed, and its outcome.