Hobby Greenhouse Growing Tips

Posted on January 14, 2021 | Categories: Donna Balzer, greenhouse gardening, Greenhouse Planting, grow your own food

Before you Order Seeds for your Hobby Greenhouse, Read the Fine Print

seed catalog

I like to get a head-start on cucumbers by growing them in my greenhouse. I have learned to use only parthenocarpic varieties.

When I started growing in my hobby greenhouse a few of my favourite plants stopped working for me. That’s when I learned to read the catalogue fine print and adapt my shopping for better hobby greenhouse growing.


  • the bugs we rely on to pollinate our cucumbers are not usually buzzing in our greenhouses in summer.
  • the heat we get in the early greenhouse is sometimes too much for plants that prefer cool air.
  • growing taller plants makes better use of the entire greenhouse growing area.

Tips for ordering seeds and supplies


Before you grow anything in your greenhouse check how your favourite plants are pollinated. Lemons, tomatoes and strawberries grow without insect pollination but fruit better with insects or a little help from the gardener.  Small bees, a soft paint brush or an electric toothbrush to vibrate pollen loose will boost fruit numbers and quality on different plants.

greenhouse tomatoes

Tomato flowers, for example, have both male and female flower parts on every bloom but with heat above 90 F or 32 C, pollen dies and fruits never form. Catalogs list heat tolerant (greenhouse) types of tomatoes such as Marbonne and Margold. But all you really need are indeterminate (also called vining) plants because they keep growing up and producing new blooms as they grow. Add a little summer shade to keep temperatures lower on the hottest days and touch bloom clusters lightly with a vibrating electric toothbrush to help the male pollen fall and contact the sticky female bits.


This one word is key to success in a  hobby greenhouse.  It is important to look for it in catalogues especially under listings of cucumbers and zucchini.

A parthenocarpic plant makes fruit without pollination and, if grown with other parthenocarpic types, the fruit is seedless. The other fancy cucumber terms Monoescious and greenhouse cucumbers

Gynoecious mean pollination is needed by insects moving pollen from male to female flowers on the same plant (Monoescious) or male to female flowers on different plants (Gynoecious.) Unless you are willing to wield a paintbrush to move pollen between the sexes, fruit will be limited with these seed-producing types grown in your greenhouse.

Parthenocarpic cucumbers like Sweet Success do not need pollination or pollination help of any kind. Other William Dam parthenocarpic cucumbers include Lisboa F-1, Piccolino F-1, Salad Bush and Iznik.

“Greenhouse” cucumbers in catalogues are Parthenocarpic varieties needing warmer conditions. You can grow these in your greenhouse earlier than May if you are willing to heat.  Since I also grow cool tolerant arugula and spinach at the same time, I stick to using parthenocarpic seeds and I don’t aim for greenhouse parthenocarpic seeds.

Johnny’s Seeds lists parthenocarpic cucumbers like Corinto, Diva and Nokya as well as specialized, warm temperature greenhouse types Quirk, Excelsior and Picolino. Rare Seeds lists Beit Alpha, China Jade and Muncher as parthenocarpic.

parthenocarpic cucumbers

Successful cucumbers on Week 19 in the Greenhouse


Short Days/Bolting

Old-school spinach like my old favourite Bloomsdale, usually needs short days and a cool climate. In northern climates this means September to April in a cool greenhouse. This makes them perfect in your late fall, winter or early spring greenhouse. (Although in really cold climates they do appreciate an extra fabric cover to keep them alive in winter.)


greenhouse spinach

Slow bolting and cold tolerance are two important descriptions of spinach grown in a greenhouse. This spinach is perfect plant in the greenhouse.

But the trouble with cool season short season plants is once they get big enough to produce a bumper harvest, they suddenly bolt as the days get longer in spring. This means they get tall, flower and set seed. Newer cold tolerant varieties, less dependent on short days (in the Johnny’s catalogue) include Space and Corvair. Vesey’s also lists Space and Esalade as bolt resistant and William Dam lists Olympia as slow bolting and reflect as heat tolerant. If you are growing in your greenhouse and your spinach fails to delight, try these newer varieties.

Bolting spinach

It is devastating when spinach bolts and goes to seed. This spinach – Bloomsdale – couldn’t tolerate the heat in my April greenhouse so it bolted quickly in April.

Spray on Fertilizer:

Green plants need nitrogen. In cold soils in the early spring greenhouse, the microbes that release nitrogen to the plants can’t function. Products like fish or seed meal need warm soil before they trigger green plant growth. This is why specialty fertilizers like the ferticare products work so well. They are instantly available because they can be sprayed on leaves for faster uptake, making cold soils irrelevant.

I have been growing in my greenhouse for over fifteen years now and I am still learning to read the fine print.  I still see new varieties of plants being introduced.  If you are new to greenhouse growing, I strongly recommend to read the fine print in your catalogues. You’ll be sure to discover a new plant or plant type to suit you and your greenhouse to perfection.

greenhouse arugula

One of my favourite cool-season crops in my greenhouse is Arugula. I let it grow tall and keep picking individual leaves off the plant all winter. I grow potatoes and beets outdoors in the garden and store them in the house over winter. Here is a photo of one of my favourite new recipes: potato crusted white fish with beet and arugula salad.


P.S. January is the perfect time to start your main onion crop. I suggest starting Spanish onions (also called yellow onions) in an open tray in your house over a heat mat. As they get bigger bring the tray out to your warming hobby greenhouse in March and keep growing them in the same tray until it is time to plant them in your garden in May.


For more great tips from Donna, visit www.donnabalzer.com.

You can also read Donna’s gardening books: No Guff Vegetable Gardening with Steven Biggs and her just released Gardener’s Gratitude Journal:  Part Diary, Part Personal Growing Guide.

donna balzer