How much sun do veggies need?

 

Robin Gale-Baker, from Sustainable Macleod discusses how much sun your veggies need. This is one of a series of articles she has written about growing various veggies (see right hand sidebar). She has also written a number of articles about growing various herbs, growing various fruit trees and general growing techniques.

Expert gardeners often bandy around certain terms as though we will automatically know what they are talking about. But do we? When it comes to terms like full sun, partial sun, partial shade and full shade, what do these really mean? And is afternoon sun the same as morning sun? As discussed below, the answers to these questions are a little more complex than at first might be expected.

The first point is that some people use the terms ‘partial sun’ and ‘partial shade’ interchangeably. However, drawing a distinction between the two is important because some plants in this broad category need more sun and are more heat tolerant and therefore need afternoon sun whilst others do poorly in afternoon sun and need the less intense morning sun. So, in this article:

  • Full sun means 6-8 hours of direct, unfiltered* sun per day.
  • Partial sun means 3-6 hours of full, unfiltered* afternoon sun per day.
  • Partial shade refers to 3-6 hours of morning sun as opposed to afternoon sun.
  • Full shade means less than 3 hours sun per day (according to some definitions) to no direct sunlight at all (according to other definitions).

*Unfiltered means that there is nothing in the way of the sun’s rays such as tree branches or shadowing.

There is also a nonsense term – full sun, partial shade. It’s one or the other! What it really means is that the plant will survive in partial shade but will not thrive or produce ripe fruit.

Because the rays of the sun pass through more of the atmosphere in the morning, sunlight is less intense before midday. In the afternoon, the sunlight is hotter than in the morning. Around midday, when the sun is directly overhead, it is strongest.

How hot the sun appears also depends on our latitude. Information from gardening books written for the UK and Europe will reflect their conditions not ours. Top temperatures in these regions in summer are usually 10 degrees below what we experience in Melbourne and this needs to be factored in along with the actual hours of sunlight. Local conditions are important!

While drought-tolerant and heat-tolerant plants, such as silver and grey plants and tough woody herbs, can tolerate hot sun for 9 hours a day, most veggies would burn in those conditions. Blistering, sunburn and heat stress are serious problems when we experience extreme summer heat, especially when temperatures hit the 40s. But all vegetables need some sun to grow so none will grow well in total shade.

Within these two extremes:

  • Vegetables which produce fruits generally like full sun, as the sun is an important element in producing the starches and sugars that give these vegetables their flavour. This includes tomatoes, eggplants, capsicum, chilli, cucumber, zucchini, pumpkin, sweetcorn, beans, peas and rockmelons. If you do not have sufficient direct sunlight for tomatoes, choose cherry tomatoes which because of their small fruit, will ripen with 3-4 hours sunlight. Plant eggplant in the hottest part of your garden, then capsicum in the second hottest and tomato in the third hottest area. Rockmelons do well if planted above fresh manure which acts as a heat bed early in the season when they require warm soil temperature to get an early enough start to produce fruit later in the season. Eggplants and capsicums, which need soil temperatures in the 20-30degC range to germinate, are best bought as seedlings, unless you have a heat mat, otherwise, like rockmelons, they will produce fruit too late for it to fully mature. Sun-loving vegetables will not produce a good, fully ripe crop with less than 6 hours direct sun per day, and can tolerate 8 hours. Beans and peas need full sun early in their season but do badly in the height of summer when it is too hot for them.
  • The onion family also likes full sun. This includes onions, garlic, spring onions, shallots and leeks.
  • Vegetables that produce roots grow best in partial sun – that is afternoon sun and morning shade. This includes carrots, parsnip, turnips, beetroot, radishes and potatoes.
  • Vegetables where you eat the stems, buds or leaves generally prefer partial shade – that is morning sun and afternoon shade. These include brassicas such as kale, cabbage, broccoli, Brussels sprouts and cauliflower, and leaf crops such as silverbeet, spinach, cress, rocket and lettuce. It also includes celery, kohlrabi and globe artichoke. The darker the leaves, the less light the plant needs to grow (with silverbeet, spinach and watercress being examples). Be careful not to overwater vegetables growing in shade as there may be insufficient sun to dry the ground.

  7 Responses to “How much sun do veggies need?”

  1. Hi Luke,

    I’m afraid that in the winter months with only 3 hours sun you are unlikely to be able to grow veggies. 3 hours and less equals full shade and no veggies grow in that – only things like ferns. If you think there is any leeway with the amount of sun, you could try dark leafy greens such as spinach, rainbow chard and silverbeet, and the herbs Guy mentioned such as parsley, coriander and also chervil. Veggies like lettuces need to grow quickly or they are tough so they won’t work as the lack of sun slows their growth. Hope this helps.

    Robin

  2. Thanks for this article.

    I have surrounding taller buildings that cast long shadows in winter over my apartment terrace (it is not a covered balcony). If the terrace gets 6.5-8.5 hours of sun from August to April, but during May-July may only get 3 hours, and some places on the terrace will be in shade for most of the day, does that mean I cannot grow full sun plants? There seems to be conflicting information, and I am hoping someone could clarify.

    I was hoping that the amount of sun for most of the year would allow this to be possible, but the shade/low sun in winter would impact the ‘yield’ of the plants and limit their growth, or will the lack of sun in winter mean they will die/fail to produce fruit?

    It is a shame, as outside of the winter months being shaded by these taller buildings blocking the winter sun, the terrace gets ample sunlight for full sun plants for most of the year.

    Any info would be deeply appreciated.

    Thanks

  3. Thanks, very useful information.
    Where would basil, coriander and parsley do best?

    • Hi Ariel,

      Basil, coriander and parsley will all grow best in partial shade.

    • Thank you – this has really clarified things as I gave a decent garden space, but I want to utilise it all and the west side of the yard is going to waste currently.

  4. Thanks for this informative and straight-forward article. You’ve just answered some very long standing queries of mine!

    • Yay! At long last!
      Straight forward, common sense answers re sun/shade requirements and, more particularly, ‘why’ for different plants, which helps in better understanding. Thank you!
      Others (info) focus on general info.
      I can now move forward and sow/plant in areas where I was questioning/doubtful!

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