Posted by: sweetpea | May 29, 2008

Tomatoes – Indeterminate or Determinate? (Or, to pinch or not to pinch?)

Apparently tomatoes fall into one of two groups (with a third inbetween group for those that are awkward!), they are either Indeterminate or Determinate (or Semi-determinate).  Ever since I started growing tomatoes I have come across these two terms in the descriptions of the tomatoes but never really known what they meant.  I have also known that you are supposed to pinch out the side shoots on some tomatoes but not others, but knowing which ones has always been a mystery to me so I have always just let them do their own thing.

This year I decided that I’d make it my mission to get to the bottom of these two issues, and as it happens they are one and the same, i.e. knowing whether your tomato is a determinate or indeterminate variety will determine whether or not you pinch.

So what’s the difference?

Indeterminate tomatoes are varieties whose growth is pretty much continuous, the fruit trusses being produced from the leaf axils, so if you leave them to it they will just keep on growing.  If you do let them do their own thing you will still get fruit but they will tend to be small and won’t all necessarily ripen.  So these are the types that we need to control by pinching out the side shoots (which by the way can be rooted easily to make new plants).  By doing this we make sure that all the plants energy goes into producing the fruit.  It is also a good idea to pinch out the growing tip of the main stem when 4-5 trusses of tomatoes have formed so that these will have a chance of ripening on the plant before the end of the season.  Indeterminate varieties are also refered to as cordon or vining types and are usually tied to canes or string for support.

Determinate tomatoes are varieties that form compact plants because they have some control over their own growth, they produce many sideshoots, but these will only grow so long before terminating in a cluster of flowers. Because of their nature these varieties do not need pinching out, but the main stem should be tied to a cane for some support.  These varieties are also refered to as bush varieties.

So just to recap:

Indeterminate (Cordon, Vining) need pinching

Determinate (Bush) don’t need pinching

Of the varieties I have grown this year:

Indeterminate – Gardeners Delight, Sunbelle, San Marzano, Broad Ripple Yellow Currant, Purple Calabash, Orange Banana, Principe Borghese

Determinate – Red Cherry

So looks like I have a lot of pinching out to do!


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