Growing vegetables in polar climates: the trouble of early bolting, due to 24 hour daylight

If it was not enough the challenges of growing vegetables in polar climates: strong winds, short summer and erratic weather, even ash fall from volcanoes (because I am living in Iceland), there is yet another to mess up with the growth of vegetables: positively in some cases, negatively in others: 24 hours daylight.

Some plants flower depending in the amount of daylight hours. Long-day plants will flower always when the day is longer than a threshold number of hours of daylight. Such vegetables will not produce well in Iceland (or other polar climates such as Sweden, Norway, Canada or Alaska) because they will bolt (early flower) even when they are very young seedlings. So, you cannot expect spinach to make large leaves, because the plant will flower almost after sprouting from seed. You cannot expect radish to make a radish, because the plant will flower very fast, and skip the part of creating the nice edible bulb. This will also happen with lettuce.

Lettuce, spinach, fennel, radish, turnips (and to some extent other brassicas) will bolt if grown during the polar summer, due to the excessive amount of hours of daylight. Therefore it is not possible to grow these plants, unless in shadow or later in the summer, when the daylight is reduced from 24 to 16 hours. By then, the first frosts are rapidly approaching, and so this makes growing them very complicate.

I am not worried with the turnips: I can still eat those greens like that, but for the spinach I would like to see some nice big leaves, not young flowering seedlings. The same goes for the radish: from a whole bunch of plants, only one gave a bulb. All six fennel plants bolted. I will not even try again, as fennel can only grow without cold, and the summer is already finishing here. But I will seed now (as it is 1st August) new seedlings of spinach, radish and turnip, to see if they don't bolt so easily during early autumn (August to October): there will be already some frosts, but still no snow.

Swiss chard also bolted, but it was growing since May, and so it already produced a nice crop of leaves. The swiss chard growing indoors, in shadow did not bolt yet. This demonstrate the value of growing plants indoors to accelerate growing, and protecting from the excessive bolting-inducing sunlight. With lettuce, the case was different, some plants bolted, others they strangely stalled in growth.

The positive side was for the indoor tomatoes: with so much daylight, I was surprised to discover how sweet the tomatoes taste! The extra sunlight increases even more the level of sugar in the fruits. It's unbelievable.

Permaculture advises: shadow tolerant vegetables

A full day of sunshine is about 14-15 hours However, some vegetables can do with less time of sunlight.

This is very useful if you plan a garden in the shadow, if you grow a garden in a urban setting for example, in a location not facing south, or under trees such in a forest garden.

Tolerant of 4-6 hours of sun

Herbs: Bay, chives, horseradish, mint and parsley

Vegetables: Broccoli, swiss chard, cress, kale, kohl rabi, lettuce, leafy perennials, radish, spinach, welsh onions

Fruits: Gooseberries, red currants, rhubarb, loganberries and morello cherries

Tolerant of 6-8 hours of sun

Herbs: Fennel, rosemary, sage, thyme (also lovage)

Vegetables: cabbage, beets, cauliflower, carrots, leeks, onions, parsnips, peas, potatoes, runner beans, broccoli and turnips. Celery and chicory also do pretty well, but chicory prefers full sun. Even perennials such as Yacon can crop perfectly (in a good soil) with as little as 4-5 hours of sunlight. And as I showed you in 2009, tomatoes and cucumber can crop enough with even less than 6 hours of direct sun. Tomatoes yields will of course have reduced yields, but cucumbers can produce good if they have good soil and warm weather. 

Fruits: Strawberries, blackcurrants, kiwi, raspberries and white currants.

It might be good, if you are growing your vegetables in part shade, to cultivate them in raised beds, to avoid excess humidity in the soil. Take care also with slugs, as they love crawling in the shadow. Protect  your vegetables with  two effective slug barriers! Either by putting cut plastic around your plants, or by spreading sawdust.

The vegetables that would need the most sun and warm would be sweet peppers, eggplant and pumpkins, squash and zucchini.

Remember to click here to be notified of future new articles at the Green Spot!

And click here to read more articles about permaculture gardening

Permaculture advises: growing a minimalist garden (that requires the least amount of work!)

If you are those kind of people that prefer to start the garden and then do nothing, this is for you.
This is a list of plants to make a permaculture edible garden, made of perennials, that once you start, there is almost no further work required. Some vegetables are perennials, other are self-seeders.


Some plants for a minimalist garden:

Perennials for greens (spacing indicated)

• 9-star broccoli .... 100cm
• Daubenton's kale ... 60 cm
• Good king henry (bitter taste) .... 30 cm
• Sea beet (tolerates sandy soils) .... 30 cm
• Tree collards .... 100 cm
• Skirret .... 25 cm
• Sea kale .... 90 cm

Perennials for salad use

• Ḿitsuba (can grow in part shadow) .... 15 cm
• Musk mallow .... 30 cm
• Pink purslane (acid soil, and shadow) ... 15 cm
• Salad burnet (alkaline soil) .... 20 cm
• Chicory .... 20 cm
• Garlic cress ... 30 cm
• Ramsons or wild garlic (for shadow) ... 10 cm
• Sorrel ... 25 cm
• Turkish rocket ... 50 cm
• Watercress ... 15 cm
• Everlasting onions ... 15 cm
• Tree onions .... 20 cm
• Welsh onions .... 20 cm

Perennial 9-star broccoli, can give many crops if you keep cutting them.

Self-seeders for greens

• Fat hen 
• Swiss chard ... 25 cm 
• Alexanders .... 50 cm

Self-seeders for salad use 

• Chickweed (can grow in part shadow) ... grow without thinning
• Lamb's lettuce ... 10 cm
• Winter purslane (tolerates sandy soils) ... 15 cm
• Bittercress ... 10 cm
• Land cress ... 15 cm
• Nasturtium ... 15-20cm
• Rocket ... 10 cm

The following table can help you calculate how many plants do you need to get full ground cover with perennials. The recommended spacing is described later below.

Spacing, cm ---- Plants

100 ................... 1

60 ..................... 3

30 ..................... 11

25 ..................... 16

20 ..................... 25

15 ..................... 44

10 .................... 100

Remember to click here to be notified of future new articles at the Green Spot!

And click here to read more articles about permaculture gardening

Permaculture advises: increasing biodiversity

Biodiversity is a very much sought goal nowadays. Increased biodiversity is good for most species, and creates more sustainable habitats, and also gardens. Not only creates fun in growing and observing many species growing together, but it also reduce pests, help in fruit pollination, and can increase soil fertility and balance.

Increased wildlife will gain from different habitats in your garden, such as ponds, grass, cornfield flowers and trees and shrubs. Cornfield wild flowers attract butterflies and bees and provide much color.

Some species will work as service stations for passing wildlife such as birds and butterflies, such as buddleia (supports a big number of butterflies and bees), cotoneaster (abundant berries), evening primrose (food for moths), muscaris and lunaria (early nectar flowers), guelder rose, hawthorn, ivy, chaenomeles, willows, michaelmas daisy (late autumn nectar plant) and teasel, dipsacus (pollen plant, birds).

For birds, nest boxes and drinking water (such as in ponds) is very useful. Edible native herbs include chickweed, sorrels, nettles (good for butterflies), ramsons or wild garlic and several types of berries. These might be a preferred choice.

Some of the trees that are associated with increased biodiversity (in UK) are willows, oaks and birches. A single tree of these can harbor more than 300 different species of insects. Other trees good for biodiversity include poplars, hawthorn, alder, crab apple, hazel and beech. Native species such as these, naturally harbor much more biodiversity than exotic species. Exotic species can also harbor many insects such as Norway's spruce, but others will generally contain little insect life such as black locust, walnuts and chestnuts. Therefore, for other countries, it might be that other trees will be better for increased biodiversity, most likely their native species.

Another word of caution with exotic species is if they become overly invasive. Invasive species are second only to habitat destruction as a contribution to extinction and the alarming loss of biodiversity! These are likely to be species which can adapt very successfully to the local climate and propagate by runners, rhizomes or aggressive seed dispersion. Often it can be nitrogen fixing species such as lupins and mimosa. Be careful with other species such as rhododendron, eucalyptus, acacia or black locust.

Remember to click here to be notified of future new articles at the Green Spot!

And click here to read more articles about permaculture gardening