Successional sowing, interplanting, relay planting and thinning

Be sure to read the section on basic growing techniques first

<aside> 💡 The basics section of this book covers all of the fundamental skills and techniques of gardening. This section covers a few of the more advanced techniques. It's best to get the hang of the basics, get familiar with how long plants take to grow and how fast they grow before you move on to using some of these at scale. Start small and experiment.


This section provides an overview of the main techniques for growing more and sometimes healthier, food from the same space. These are the basic techniques of high intensity growing. The rest of this chapter provides lots of examples of how to do this for specific crops. My individual growing guides provide detailed instructions for each fruit/vegetable.

The techniques I'm going to cover are:

  1. Start seeds in modules
  2. Successional sowing
  3. Interplanting
  4. Relay planting
  5. Progressive thinning

Let's dig into a little more detail:

Start seeds in modules

For all the details of sowing in modules see my chapter on sowing seeds!

Many gardeners start off sowing seeds directly into the ground. This appears to be easier and quicker, but it's often a false economy. Direct sown seeds take longer to germinate, germinate erratically, are more exposed to pests and diseases, need thinning out and occupy valuable bed space for longer than module sown seeds.

Module sowing just means starting seedlings in pots of some sort and transplanting them when they are about 30-60 days old. Modules are just the most efficient type of 'pots' to use.

<aside> 💡 Carrots and parsnips are the exception here, they do better sown direct.


When you sow in modules, you can germinate indoors, grow seedlings in ideal conditions away from pests and disease, optimise watering etc. You plant you modules out when conditions are ideal and the plants are strong and healthy, better able to respond to pests and disease. Often you will be sowing in early spring and planting out in late spring, so those extra 30-60 days in ideal growing conditions makes a huge difference.

Having trays of module sown seeds all ready to plant, means that as one crop finishes, you have another all ready to grow strongly. You don't have seedlings occupying ground for as long, so you have plants that are ready for harvest occupying the ground for longer.

The bottom line is that you get a much bigger and healthier harvest and can squeeze more successions into the same ground, see the next section.

Successional sowing

Successional sowing is the simplest of the advanced growing techniques, basically it just means sowing seeds regularly, often multiple sowings of the same type of seed. Radish is a great example here, radish matures - in late spring - in just 30 days from sowing and it spoils after a few weeks. So to have a continuous supply of radish you need to sow a small batch every few weeks for months on end.

There are a few things to consider about successional sowing:

  1. The time from sowing to harvest varies depending on the time of year, so while radish might only take 30 days to reach maturity when sown in May, it might take 60 days when sown in March. Similarly a sowing in a polytunnel will grow much faster than a sowing outside. It helps to sow in modules, germinate at home and grow for a few weeks in a greenhouse before planting, this means that the first half of a radishes life always takes 3-4 weeks, even if the second half varies.
  2. It rarely makes sense to grow the same variety for every succession, different varieties have been optimised for different times of year. Even at the same time of year varieties will take different times to harvest, early carrots and early potatoes for example grow to maturity much quicker than main-crop varieties. My individual growing guides explain all this for each crop.
  3. It rarely makes sense to grow the same type of plant for every succession, for example purple sprouting broccoli is very productive in spring, but green broccoli (calabrese) is much better in summer and early autumn. My year round growing guides explain all of this for each type of veg.


Remember, interplanting is not just planting two random plants in the same area of ground, the main reason for this type of interplanting is aesthetics. True interplanting means carefully selecting two - or more - plants that do better together than they would alone. There are several criteria to bear in mind:

<aside> 💡 In most situations when I interplant I don’t reduce the planting density of the primary crop by much, but I do reduce the planting density of the interplant


  1. Does one of the plants enhance the others access to nutrients
  2. Does one of the plants help protect the other from pests and/or diseases
  3. Do the plants draw water and nutrients from different levels of the ground, i.e. one being deep and the other shallow rooted
  4. Do the plants grow at different rates, allowing one to be harvested, before the other one needs the space and not get in the way of harvesting
  5. Does one of the plants provide shade or protection from the wind to the other plant
  6. Does one of the plants act as a backup to the other, in case of failure, i.e. if one fails the other will succeed
  7. Does one of the plants deter pests or attract insects away from the other (most of these reasons turn out to be myths)

Relay planting

Relay planting is similar to interplanting, but has a different objective. Whereas interplanting is focused on two plants that grow better together, relaying planting is about using up space when one plant is fading, to get the next plant started early.

The two plants need not complement each other, because the established, but fading, plant doesn't really care about the small relay plants. The relay plants don't really care much about the fading plants either, because they will be gone soon.

I find relay planting most valuable when I have a looming surplus of the fading plant. This normally happens in early spring and autumn. At these times I really want to get the relay plant established as early as possible, but I still need the established plant for a few weeks, but not for long as harvest volumes are picking up.

A classic relay plant is radish/turnips in gaps between over-wintered spinach, or calabrese and cauliflowers in gaps between winter lettuce. Carrots and parsnips take a long time to germinate, so they can be sown a few weeks before the existing crop finishes.

My individual growing guides explain all this for each crop

Progressive thinning

Thinning takes advantage of the fact that when plants are small they can be planted very close together, as they grow, they take up more space. That space can be created by harvesting every other plant, then perhaps a month later, every other plant again.

This works for plants where the thinnings are a valuable harvest. For example onion thinnings can be used as salad onions, garlic thinnings can be used as green garlic.

My individual growing guides explain all this for each crop