Pots, Bags or Border Growing? Which is best?

Although the question of whether pots, grow bags or border growing is best in the greenhouse seems simple, the answer isn't clear-cut. It depends on what you are growing and your circumstances.

Growing in the Greenhouse Border

The main advantages of growing in the greenhouse borders are that they provide:

1. Virtually unlimited growing media for the roots to spread out in.
2. A good water reserve so if you forget to water for a day the plants are ok. Especially important with tomatoes that are very sensitive to irregular watering.
3. You can underplant cordon tomatoes with salad crops, force early carrots and courgettes etc.

The drawbacks to growing in a border are:

1. With both hot and sweet peppers, they can tend to produce more foliage than crop because of the available growing media.
2. Water can pool around the stem of cucumbers which will rot and kill the plant, you can prevent this by mounding the base of the cucumber and watering to the side.
3. It can be difficult to judge the amount of additional fertiliser required.
4. The soil in the border, or at least the top 15cm (6”) of the soil, should be changed annually to avoid the build-up of disease, which is quite a task.

Grow-bag growing

The grow-bag is a simple but clever idea. The compost, being contained in the plastic bag, doesn't lose water through evaporation and at the end of the year the used bag of compost is easily removed from the greenhouse and can be used as a general soil improver.

Financial pressures have driven prices down and many suppliers have compromised on the quality and quantity of the compost to compete so, unless you can find a good quality grow-bag, we're in the silly position of having to either insert bottomless buckets filled with compost on top of the bag or to cut out the base of one bag and the top off another to combine them into one decent sized bag!

Most grow-bags will have markings for cut-outs into which you plant. In my experience, they suggest you can plant three tomatoes but in reality, you will be better off just planting two plants per bag.

There's no doubt that they are convenient and easy to use but my own preference is to fill giant reusable grow bags with a good quality multi-purpose compost. These bags tend to collapse but it's easy to knock-up a wooden box to hold the sides up.

Growing in Pots

For peppers, both sweet and chilli, I've found 20 cm (8”) pots are the best. Because they don't grow too tall, I double stack them with some at floor level and some on top of the staging.

Small cucumber varieties such as Picolino, Zeina and Cucino do well in pots, usually on staging and allowed to trail. Larger varieties such as Carmen or Tiffany can be grown in pots but you'll need a large one. I've used builder's buckets with holes drilled in for drainage as large pots. Ideally, the large varieties go in the border or giant grow bag.

Aubergines need a large pot to give of their best, as with the large cucumbers go for the border or giant grow-bag.

All the cordon types of tomatoes will do well in pots, just a little larger than those for peppers. I find 25 cm (10”) pots perfect for them. Cherry bush tomatoes will also do well in pots or hanging baskets. They can be started in the greenhouse and put outside for the summer and brought back into the greenhouse as the season cools.

The drawback with pots is that they need washing before re-use which is not the most pleasant job on a cold winter's day.