Modular sowing – starting your plants off in small groups of thin-sided pots instead of sowing the seeds directly into the ground or a seedbed – can be a very useful way to save space and increase the productivity of a kitchen garden or allotment.
What are the benefits of growing plants in modules?
- You can get an early start in your kitchen garden in the Spring if you start some module plants off indoors.
- Module-grown plants will be a decent size when you plant them out – their stronger roots and bigger leaves can help them grow faster and be more resistant to pests and adverse weather conditions.
- Modular sowing causes much less root damage than transplanting seedlings from seedbeds.
- It’s a great way to make your garden more productive, as there’s less time waiting for crops to be ready once they’ve been planted.
- Planting out new modules as soon as the previous crop’s finished means that there are no bare patches of soil from which nutrients can be lost.
- Modules can be grown in a relatively small space, so they won’t take up too much room before you’re ready to plant them out.
- You can easily fit different types of modules onto windowsills, greenhouses and outdoor shelves, depending on what you want to grow, and when.
- If a few of your plants fail to thrive after planting, you can quickly replace them with spare plants from modules.
What grows well in modules?
Most herb and vegetable seeds can be grown in modules, it’s just a matter of getting the right size of module for the type of seed.
- Large modules are best for brassicas such as cabbage, kale, broccoli, Brussels sprouts etc, and also sweetcorn
- Tall modules are best for legumes (peas and beans) with long, fragile roots
- Medium sized modules are good for things like onions, leaf beet and fennel
- Smaller modules are best for hearting lettuces and other salads, basil, and companion plants
Plants such as carrots and parsnips don’t tolerate having their roots moved, so these are best sown straight into the ground. Fast growing radishes and rocket don’t need to be sown in modules as they will give you a quick crop wherever you put them.
Seeds of vigorous plants such as pumpkins, cucumbers and courgettes are best sown into larger pots, so they don’t get too cramped. This is often the case with tomatoes and aubergines too.
How to start off plants in modules
Some seeds are best sown directly into their modules, but others (chillies, sweet peppers, tomatoes, aubergines and so on) may do better if sown into trays of seed compost and then pricked out into individual modules once they’re a bit larger.
There are a few rules to remember:
- Use the right size module for each plantlet – small, slow-growing plants are fine in smaller modules, but plants that grow quickly and reach a larger size when mature need to be in bigger pots.
- Use fine textured, good quality compost as the plants will be growing bigger than the small seedling stage in their modules, and will need more nutrients.
- Sow sparingly to prevent overcrowding, and be prepared to thin out modules where there should only be one plant or a small number of plants growing.
- Make sure that there is good drainage, otherwise plants may be prone to ‘damping off’ or other problems.
- The cheap plastic sheets of modules that you find in pound shops are often too flimsy to support and protect plants properly. You may find that spending a little extra on reusable module containers is more cost effective in the long run.
- Remember to label carefully, ideally with something waterproof, so you know exactly what the plants are (many types of plants look similar at the seedling stage).
- Sow a few more seeds than you think you’re going to need. This gives contingency for bad weather, pests, failure to thrive and so on – and if they all do grow well, you can give away, sell or swap some of your spares.
You can make your own module containers for some seedlings using egg boxes and the cardboard tubes from inside kitchen and toilet rolls – these can be planted straight into the ground without being removed, which is ideal for plants with very long and delicate roots such as peas and beans. If you have problems with cardboard going mouldy, you can buy commercial long, thin reusable plastic modules called Rootrainers, although they aren’t cheap.
How to keep your module-grown plants healthy
- Start your modules off in a spot where they will receive enough sunlight for strong growth.
- Modules can dry out relatively quickly, so remember to keep them watered regularly.
- If possible, use a fine rose or spray on your watering can or hose when watering, or water into the tray below, to prevent mechanical damage to smaller plants.
- Plants that have been growing in modules for more than six weeks will benefit from a little multi-purpose liquid feed every now and then.
- Check regularly for pests and diseases, which can spread faster between plants that are grown closely together.
- A few organic slug pellets scattered around your modules can help keep slugs and snails at bay.
- Growing module plants under a fine net or garden fleece is a good idea – it can protect against aphids, flea beetle, cabbage whitefly and cabbage butterflies.
How to transplant modular plants
- An hour or so before transplanting, give the modules a good watering with some very dilute plant food or plain water.
- Be very gentle with the roots of the plant, and hold by the leaves rather than pulling on the stem, to prevent damage.
- You may wish to add some chicken manure pellets, compost or multi-purpose plant food granules to prepare the soil before planting, especially if you’re growing plants from the allium, brassica or cucurbit families.
- If the plants are a type that’s likely to need some kind of support, such as canes or netting, add supports at the time of planting to prevent damage to the roots.
- Water in well once the planting out is complete, and make sure the newly-planted crops don’t dry out over the next few days.
- Try not to grow the same type of crop over and over again in one area, as this can deplete the soil and encourage certain pests and diseases.
Have you tried sowing in modules? Do you have any top tips to share?