When is it going to get warm?

I spent most of this morning transplanting my tomatoes from their seed pots up into individual pots. They need it to allow them to grow on faster but, I wondered when it was going to get warm.

Those of you who have looked at the Raspberry Pi part of this site will know that I’ve been measuring and recording various temperatures (outside, in the polytunnel and in a barrel of water in the polytunnel) to see whether a barrel of water in the tunnel can improve (i.e. raise) the temperature in there.

However, what it shows is that, even in the warmth of the polytunnel, temperatures are really struggling this year. Not only did we have various “Beasts from the East” during March, but the weather in April has been damp and miserable. Wet and little or no sun. Whilst I haven’t got any data for previous year, what’s obvious from the figures for this year is that rather than trending upwards, the average daily temperatures for early April are on a downward slope and, unless we get some decent sun in the next few days, it doesn’t look as though its going to get any better.

This affects my tomatoes. Normally, by now, I’m sure I’ve stopped taking the plants in and out of the greenhouse, relying on the daytime sunshine to leave residual heat in the greenhouse to keep the temperatures above 10C without adding any extra heat. However, in the past week, the temperature in the polytunnel hasn’t crept above 10C even in the daytime and the nighttime temperatures have drifted towards 5C.

Tomatoes don’t like being cold and not being adequately warm at the start will affect them throughout the year. So I’ll have to continue bringing them in and out of the house for a few more days yet. This could mean that I’ve got lots more trays to carry through but I’m afraid I’ve identified the strongest plants and only those will be molly-coddled, the rest will have to tough it out in the greenhouse.

Posted in Allotment, Greenhouse, Growing Tomatoes, Raspberry Pi, Vegetables | Tagged , , | Leave a comment

When should I sow my Tomato Seeds?

I ask myself this question every year. The seed packets say “sow in late winter” (when’s that?) or “late January to March” (more understandable) and, in different years, I’ve tried sowing from early January through until early April.

I think the answer depends upon a lot of variables some of which you can control and some of which you can’t. So lets look at them:

  1. The Weather
    The weather plays a part over which we have little or no control. Tomatoes originate from Mexico and grow best when the temperatures are always above 10C but below 35-40C. They also like light but not too much direct sunlight so juggling the seedlings/plants to give them the best conditions in the variety of external environments that we try to grow them in is a challenge. So knowing when the last frost is in your area and how much sunlight falls on your greenhouse whilst there are no leaves on the trees is something that you need to bear in mind and varies from yer to year.
  2. When/Where are you going to plant them?
    When and Where are related. Tomatoes suffer if their nighttime temperature stays below 10C for more than an hour or so and certainly don’t want a frost (they go purple, struggle and may not every recover). So you shouldn’t plant your tomatoes into their final place until after the last frost. Now when that is depends upon whether you’re planting them outside, in an unheated greenhouse or in a heated greenhouse and where in the world you live. (For me at home, the last frost is the end of May so planting outside has to wait until June, my allotment is on the other side of a north facing hill and the last frost is a few days later). An unheated greenhouse protects the plants and they can be planted a couple of weeks earlier. If you’re lucky enough to have a heated greenhouse temperature is not the issue.
  3. What are you going to do with them after they’ve germinated?
    Germinating tomato seeds is easy. Put them somewhere warm (20C) in decent compost and (depending on the age of the seeds) they’ll germinate in a week or two (the older the seeds the longer they’ll take but if they haven’t germinated in two or three weeks I think you can assume they’re not going to).
    However, once they’ve germinated, they need light and reasonable warmth to encourage them to grow strongly. I’ve found there are three steps:Seedlings:
    Seedlings are from when they first germinate until they’ve got their first true leaves. I sow my seeds in 7cm pots with about five seeds in a pot (perhaps more if they are old seeds which may not germinate). A seed tray will hold 15 pots and so 30 varieties (which is what I aim to grow) can be easily handled. Assuming the weather is reasonable (light & warmth), the seedlings can be carried out to the greenhouse every day and back in every night.

    Once the seedlings have their first true leaves, they should be separated into individual pots/plugs. At this point I carry out the first “cull” of my tomatoes, reducing the number of plants to about three/four of each variety. So now I have 90/120 plants. If they are in 7cm pots, this is 6-8 trays which is less convenient to move in and out of the greenhouse. However, I usually use plug trays which halve the number of trips.
    The plants will stay in the plugs for two – three weeks (its now five weeks since they were sown) and there will be nights when it will be warm enough for the tomatoes to stay out overnight in the unheated greenhouse.

    Small Plants
    Once the roots have filled the plugs, the plants need to be moved to larger pots (7-9cm) where they will stay until they are planted out. I cull them again, leaving myself with twice as many plants as I will need and, at this point, the plants need space & height, as well as warmth and light. However, by late April/early May the overnight temperatures in an unheated greenhouse are unlikely to fall below 10C for very long, so I tend to divide the plants, one set that will stay in the unheated greenhouse no matter what the nighttime forecast and the other half (30 plants) that will be brought in overnight if its going to be bad.

Tomato Seedlings 3 days after sowing


There’s no right answer, only what works for you. Your tomatoes will need about eight weeks from germination to planting out so seeds to be planted outside should be sown later than those in a cold greenhouse which in turn are later than those in a heated greenhouse.

How long you can look after the plants before they have to be planted out depends upon how much space you’ve got that can give the necessary warmth and light.

For me (in the middle of the UK and planting in unheated greenhouses) the answer that works seems to be early to mid March with a period of time molly-coddling the seedlings over night.

I’d be interested in your comments.

Posted in Blog, Greenhouse, Growing Tomatoes | Tagged , , , | Leave a comment

Recipe: Sweetcorn Chowder

This is a fantastic recipe. A rich and creamy soup that's quick and easy to make, using fresh or frozen ingredients.

Its so quick, it's not really worthwhile freezing, you can make it from scratch in the same time as it would take to defrost it.

Ingredients (for 2)

  • Sweetcorn Kernels from one sweetcorn cob
  • 1 medium courgette
  • 1/2 Onion
  • 400ml vegetable (or chicken) stock
  • Oil & 50g butter for frying
  • Optional - double cream to serve
Sweetcorn Chowder


  1. Chop the onion & courgette - they don't need to be too small as you're going to whiz it with a stick blender when its cooked;
  2. Heat up the oil & butter in a saucepan and fry the onion until its soft (not coloured);
  3. Add the courgette & sweetcorn kernels and fry gently for 3-5 minutes;
  4. Add the stock and cook until the vegetables are tender;
  5. Season - we don't add salt, the butter has enough in our opinion;
  6. Blend with the stick blender until its rich and creamy. The texture is up to you, if you want texture don't blitz it for too long.

There you go, 15 minutes from start to end and a rich, creamy, warming soup.

Posted in Recipe, Vegetables | Tagged , , , , | Leave a comment

Waterbutt in the Polytunnel – A final conclusion

As I’ve said more than once (here and other places) I’ve been intrigued by the question of whether putting waterbutts filled with water into the greenhouse/polytunnel can beneficially affect/improve the temperature in the polytunnel. To try and come to a conclusion, I built a Raspberry Pi temperature sensor with four sensors (see here). I put one outside the polytunnel, one inside the polytunnel, one in a small watering can of water and one in a waterbutt. For security I then copied the resulting file to a centralised Raspberry Pi over the network (like this) and finally copied the file to Dropbox so that I could read it elsewhere (like this).

All of this was done through a series cronjobs on the various machines.

These sensors have given me the ability to accurately measure all the temperatures and make some observations which go like this:

  1. The temperature in the polytunnel is most affected by sun. When the sun is shining on the tunnel, the temperature rises rapidly. If there’s no sun, the temperature in the polytunnel is the same or perhaps up to 0.5C warmer than the temperature outside the tunnel;
  2. The rate of water temperature rise is more affected by sunshine than the temperature in the polytunnel (this is a bit more difficult to prove as the main cause of rises in the polytunnel temperature is sunshine);
  3. The temperature of the water rises and falls more slowly than the temperature in the polytunnel. The water temperature changes proportionally to the difference between the temperature in the polytunnel and the temperature of the water.
  4. The temperature of the water becomes static at -0.3C, regardless of how much colder the polytunnel gets;
  5. The watering can (5L changes temperature more quickly than the waterbutt (200L).
  6. The temperature of the water is (in general) higher than the temperature in the polytunnel from 16:00 to 08:00 (when the sun is not shining)


  1. Having a waterbutt of water in the sun in the polytunnel must make a difference. The water will give out heat when the polytunnel is colder than the water;
  2. However, the effect is primarily driven by the number of hours of sun.

So, overall, the conclusion is (at least for the months of December, January & February, putting a waterbutt in the polytunnel has no appreciable of beneficial effect. The days are too short and there are to many sunless days.

This doesn’t mean that March and April won’t benefit as the number of sunny days increase and the nights get shorter. Let’s see.

Posted in Greenhouse, Raspberry Pi | Leave a comment

Recipe: Chicken, Swiss Chard & Noodles

This recipe is a new one for us, because I'm wheat free(ish) and my better half isn't, we're always looking recipes that can be created as both.

The original recipe called for spinach. Swiss Chard is easier to grow and available from early in the year and (in our opinion) better.

Ingredients (for 2)

  • Noodles (egg or Rice Noodles if you're Gluten/Wheat Free);
  • 2 small chicken breasts thinly sliced;
  • 100g mushrooms;
  • Small Bunch Spring Onions;
  • 1 Clove of Garlic;
  • 3 tbsp Oyster Sauce;
  • 100ml Chicken Stock;
  • 100g Swiss Chard (or more - as much as you like);
  • 0.75 to 1.5 tsp black peppercorns crushed (for heat);
  • Salt & pepper to season (optional).


  1. Cook the Noodles;
  2. Fry the chicken in the oil over a high heat to brown and cook through. Add the onions, garlic, mushrooms, crushed peppercorns and cook for about two minutes stirring as you go. (The quantity of peppercorns defines the heat of this dish, we don't like it too hot so 1 tsp is enough. Also remember to crush them up properly, finding -and chewing - bits of pepper in your teeth after you've finished isn't entirely pleasant).
  3. Add the Oyster Sauce and stock;
  4. Add the swiss chard and cook until wilted (1-2 minutes);
  5. Add any seasoning you think you need (we don't add any extra at this point);
  6. Serve on the noodles.
Posted in Recipe, Vegetables | Tagged , , , , , , | Leave a comment

Starting the Year

Right, first day this year when the weather seems to have been good enough to think about being out in the garden. The ground seems to have been so soggy this year that walking around will do the grass harm and there’s no point in digging the ground as it will be in clods and never do anything.

Anyway, today was sunny, warm and just windy enough to feel that the ground will benefit from working a bit. I decided that the polytunnel was the thing to do. What I wanted to do was to till over the ground but the Mantis objected, its completely jammed up so I think I’m going to have to send it away to be serviced. However, the ground in the polytunnel was friable and hoeing was all it seemed to need. So I tidied it through and the result was:

Tidied Polytunnel

A few strawberry plants on the bench at the end, waiting to be hung from the framework and some swiss chard which is showing new growth and will be good for the early part of the year.

I also sowed the first of the lettuces and tidied up the outdoor strawberry be in which I found:


Which shows that the bugs and beasts are still about and being a nuisance.

The birds were active all the time I was outside with Blue Tits looking in the birdbox and lots of things eating from the bird feeder.

The spring seems to be starting in the wrong order, we’ve got crocuses up and showing before the snowdrops are established. I don’t remember that ever happening before. Anyway, the year feels like its starting.


Posted in Blog, Greenhouse, Vegetables | Tagged , , , , , , , | Leave a comment

Raspberry Pi: Integration with Dropbox

Dropbox is a Cloud Storage area that’s free to use for private individuals for relatively large quantities of data. I like it for my Raspberry Pi network because it allows me to move files to devices that are not on my home network without having to open up either the home network or the distant network too much (one has to rely on Dropbox’s security but one would hope that they are relatively secure.

The Dropbox_Uploader is a BASH script, written by Andrea Fabrizi and allows you to upload/download/delete and otherwise manipulate files in the designated Dropbox area either directly or with Python programs. Details are available here and I have not intention of duplicating it because it would mean that I’d have to keep it up to date as there are changes either to the Uploader or to Dropbox.

Dropbox_Uploader is simple to call from a cronjob, so I use it to back-up the files shared to my “network master” Pi from the “slave” Pis on a daily basis so that I’ve got additional levels of security. There are a few things to remember when setting up the cronjob, and the one that I forget most easily is making sure that Dropbox_Uploader is available to the user executing the cronjob (i.e. if you load dropbox-uploader in the pi user, the cronjob must be created by the pi user otherwise it won’t be found and the cronjob will fail.

To upload a file, the cronjob command is:

/path/to/dropbox-uploader.sh sourcedir/file destdir/file

Scheduled to run as often as you like.

One example of repeat uses is that if you’ve set up a camera that triggers on movement (for example) you can run a cronjob every minute that checks for files and moves them up to Dropbox for security or examination from a remote device (such as your smartphone).

Posted in Raspberry Pi | Tagged , | Leave a comment

Raspberry Pi: Moving Files in a Network

I’m gradually building a network of Raspberry Pis for different things and, I suppose, its the way that an Internet of Things (IoT) would get built.

At the moment, what I’ve got is a couple of Raspberry Pi Zeros with temperature sensors connected to them in different locations (one in the house and one in the polytunnel which measures the temperature inside the polytunnel and outside). My initial plan is to measure the temperatures and plot them out as graphs (just for interest) but, you could see how this could evolve into a central heating control system maintaining the temperature in various rooms by turning pumps on and off but also using knowledge about the outside temperature to influence the turn on/off times as the rate at which the house cools/heat is affectedby the outside temperature.

Anyway, at the moment, the simple thought is to use a single, more powerful, Raspberry Pi3 to plot the temperatures over time.

In order to do that, I have to move the files containing the temperature from the sensors on the PiZeros to the Pi3. It turned out to be easier than I initially thought. A simple command:

rsync -avz -e ssh /sourcefile pi@target.local:/targetdirectory/

will move “sourcefile” to the targetdirectory on the target machine (.local specifies its on the local network rather than having to know the IP address).

By putting that command into a cron job, the file is moved every time the cronjob is scheduled on the source machine. I’ve set it to run once a day so my temperature files (taken every 10 minutes) are uploaded to the target machine once a day.

The only additional issue is security. The rsync command is running on top of SSH and SSH is secured and requires the password of the target machine every time it runs. So it can’t be run as a cronjob.So what we have to do is to make the source machine an authorised user on the target machine. This again is relatively simple:

  1. Generate an Authorisation key on the host machine: ssh-keygen following the prompts without a passphrase
  2. Copy this Authorisation key to the target machine:
    ssh-copy-id -i ~/.ssh/id_rsa.pub target.local
    Note this will ask for the password for the target machine. Its also recommended to look at authorized_hosts on the target machine to make sure that no other authorised hosts have been added accidentally.

From then on you should be able to use ssh and rsync over ssh without being asked for a password. If you want to make your target machine secure again, delete the file authorized_hosts within the directory and that will do it. This will remove all authorised hosts and the hosts will have to re-authorise themselves.

Security is a thing you should think about at an early stage so I would recommend

  1. That you change the username of your Raspberry Pi;
  2. Use a non-trivial password;
  3. Make sure that your other machines on the network are firewalled from the Raspberry Pis

Security is a problem with the IoT. Networked central heating systems are becoming common (as are fridges, etc.) but the issue is that they are being connected to home networks which contain important computers by people who don’t (and shouldn’t need to) understand the complexities of networking security.

Posted in Raspberry Pi | Tagged , , , , , | Leave a comment

Tomatoes: Determinate, Indeterminate, Semi-Determinate, Cordon or Bush: Pruning & Harvesting

Over the years I’ve been growing tomatoes, I have learned more and more about them and have a better understanding about how they behave so I thought I would write what I know about the three different growth habits of tomatoes and how to grow them.

There are three different types of tomato plants:

  • Determinate;
  • Indeterminate; and
  • Semi-Determinate.

These words describe the way in which the plant wants to grow.

Other words and phrases are also used to describe the way in which we train the plants to grow:

  • Cordon;
  • Bush;
  • Compact Cordon.

These descriptions are related as you will see from the more detailed descriptions.


Determinate plants have lots of shoots and they flower at the end of the shoots. The shoots grow to approximately the same length, the flowers all come at about the same time and the fruit on a plant all ripen together over about two weeks or so. Because of the way they grow, the plant looks like a bush. Once the fruit have set, the plant diminishes in vigour and little new fruit will set. They tend to be smaller plants (up to four or five feet), sprawl about and shouldn’t be pruned (if you prune them it will reduce your crop). Depending upon the weight of fruit on the plant, they may or may not need support. Plants with standard sized fruit (e.g. Heinz H9129) will need some support to keep the fruit off the ground, plants with cherry sized fruit (e.g. Sweet Pea Currant) are much less likely to need support as the total weight of fruit will be less.

Determinate tomatoes are ideal if you want a lot of tomatoes all at the same time (e.g. for making batches of sauces) and if you are growing tomatoes on the patio where they are ideally suited to growing in pots. Commercial growers in places where the weather is suitable for outdoor growing tend to grow Determinate varieties so that they can harvest them mechanically all at the same time. For this reason, there are lots of different Determinate varieties available from the USA.


Indeterminate plants have fruit over a longer season. They grow as a vine and fruit trusses appear along the length of the vine over the season ceasing only when the plant is killed by the weather. Sideshoots (new vines) grow out from the leaf joints along the main vine. These sideshoots themselves can have trusses of fruit and will generate more sideshoots, etc., etc.. Under the right circumstances vines can grow huge, sprawling and spread all over the place. The early set fruit will ripen, but the later setting fruit will probably not ripen on the plant before the plant dies in the cold.

When grown in commercial greenhouses, multiple sideshoots from a single plant can be trained through the greenhouse and, providing they are kept at the right temperature and with sufficient light and food can go on producing almost indefinitely.

When grown outdoors (particularly in the Southern USA) they tend to be grown in cages and the fruit is individually picked over a long period of time.

However, when grown in less clement places (such as in the UK) recognising that lots of fruit will not ripen before the plant dies of cold, we tend to grow them as a small number of vives in a Cordon, removing sideshoots as they appear to focus the plants energy into producing less fruit and clearing the leaves to allow the sun to ripen the fruit that has set. For this reason, the plants are usually “stopped” when they reach the top of the greenhouse to encourage the set fruit to ripen.

Most of the different sizes and colours of heritage and hybrid tomatoes are available as Indeterminate varieties. Examples of Indeterminate plants are Pink BrandywineRed Berry and Ailsa Craig).
Indeterminate tomatoes are good in the greenhouse (where there is plenty of support) because they take up less floor space than determinate varieties. For this reason, commercial growers who grow under cover will generally grow Indeterminate varieties (many hydroponically) and heat and light their greenhouses to get a long season and large crop.


These are actually better described as “Semi-Indeterminate” as they behave more like Indeterminate plants with fruit trusses being created along the length of the vine. However, like Determinate plants, the vine tends to stop growing when a small number of trusses have been set along a vine. As a result, the plants they typically grow to only three to five feet tall. They will need staking and some pruning to limit the number of stems. The best solution is to allow the sideshoots on the main stem to develop, but to remove any sideshoots on the subsequent vines. That way the total amount of fruit is increased but the set fruit has a good chance of ripening. Semi-Determinate are alright in the greenhouse (although you will need more space than for Indeterminate plants) but are less suitable for pots. An example of a semi-determinate plant is Gold Dust.

Choosing which varieties suit you best depends upon how much space you have and what varieties you are happiest with. We tend to grow Indeterminate and Semi-Determinate beefsteak, standard and cherry varieties in the greenhouse and Determinate cherry varieties in pots outside where we can move them around to catch the best of the weather to ripen them and provide snacks for the grandchildren.

Rules for Pruning and Harvesting

In summary:

  • Determinate: Don’t Prune and allow the plant to create a bush. All the fruit will be ripe over a couple of weeks and should be harvested when ripe;
  • Indeterminate: After deciding how many stems you want to grow (usually between one and three cordons) remove all subsequent sideshoots and stop the vines when five or six trusses have set on each cordon. Fruit will ripen over the season, should be picked when ripe and all fruit removed before the first frost kills the plant and unripe fruit stored and allowed to ripen or used green.
  • Semi-Determinate: Allow all the sideshoots on the main vine to grow (secondary vines) but remove all sideshoots on the secondary vines. Each vine will set a small number of trusses (two or three) and , like Indeterminate cultivars, the fruit will ripen gradually over the season and will have to be removed before the first frost kills the plant.

If you go to (here) you’ll find a full list of all the tomatoes we describe and each description includes the growth habits of the individual tomato.

Posted in Growing Tomatoes, Questions & Answers | Tagged , , , | Leave a comment

Should you grow Multiple Stems on Indeterminate Tomatoes?

There are essentially three different types of tomatoes, Indeterminate, Semi-Determinate and Determinate. They are defined by their growth habits. In this article we are going to consider growing Indeterminate tomatoes on a non-commercial scale.

Indeterminate tomatoes are usually grown in the UK as cordons.  A single stem is trained vertically upwards, either up a cane or strings, and all sideshoots taken off.  There is no fundamental reason why Indeterminate tomatoes have to be grown as cordons and This article considers whether there are other ways of growing and the advantages and disadvantages of them.

When growing as a Cordon, the major disadvantage is that the quantity of fruit is limited by the number of trusses that can grow on the single stem and the number of tomatoes that grow on an individual truss. The number of trusses is limited by the height of the plants (which is set by the height of the greenhouse or polytunnel) and the separation of the trusses on the stem (which varies from cultivar to cultivar but is usually around 12 inches (30cm) but often more. So in an average greenhouse one can expect to get somewhere between four and six trusses per plant.

An alternative is to grow multiple stems from a single plant. Indeterminate tomatoes naturally grow sideshoots, usually at the leaf nodes and, the additional stems can be grown up separately. The advantage of growing in this manner is that these additional stems will create extra trusses of fruit (usually slightly later than the main stem) and therefore you will get extra trusses of fruit within the same height as the single Cordon that would be formed if the sideshoots were not removed.

So far, so good. Logically it would seem sensible to grow as many sideshoots as possible from the single plant but obviously this isn’t the case, otherwise the tradition of growing cordons would never have developed.

There are three disadvantages associated with growing multiple stems.

First, whilst the plant is growing strongly, it can see no reason to set large quantities of fruit. Indeterminate tomatoes are tender perennials. Given the right growing conditions of light and warmth, they will grow on indefinately. We want them to produce lots of fruit and less growth so we stress the plant by limiting its growth which makes it set fruit for seed so that it will survive to the next generation. Limiting the number of sideshoots and stems increases this stress and makes the plant fruit more quickly. At the same time, we feed it with potassium rather than nitrogen fertiliser so that it also tries to produce more fruit and less growth.

The next disadvantage of having lots of stems is light. The UK is not an ideal place to grow tomatoes. Its too cold in the autumn, winter and spring for the plants to survive without additional heat (tomatoes grow best between 20C and 30C) so we grow tomatoes as annuals setting fresh seed each year. Also, the sunlight is not very intense. Tomatoes are natives of Central America where the sunlight is stronger than in the UK. We therefore have to minimise the amount of shading that the plants experience by growing them in places that are not shaded by other plants or buildings and keeping the glass of the greenhouse clean.

The additional stems grow additional leaves and these shade the plants and have to be removed. But the leaves that create the most sugars to ripen the tomatoes are the two leaves above and below the truss, so we don’t want to remove these otherwise the truss of fruit will not ripen well. However, the additional stems on the single plant will have leaves at different heights to the main stem and these will shade the trusses on the main stem.

Finally, tomatoes are susceptible to airbourne diseases, in particular moulds and fungal diseases. Therefore we want to maintain a good airflow through the greenhouse to make sure that the leaves and plants are kept dry, even in the humid conditions that occur in the UK.

So, essentially, there is nothing that stops you growing multiple stems on a single plant. If you intend to do so, increase the spacing between plants so that the additional stems can be separated both from the main stem and the adjacent plants. You will increase the amount of fruit on the single plant but possibly not by as much as if you had grown more plants in the same space and grown them as Cordons. You will, however, have grown fewer plants in the first place and therefore perhaps been able to give them more care at the early part of their growth meaning that you have stronger plants which in themselves will grow more fruit.

A final advantage of growing multiple stems is that the single root can be grown in excellent soil and some of the greenhouse may not need to be as well tended, in other words (for example) you could grow a single plant with a number of stems with the additional stems supported over an area where it would not be possible to grow plants.

Posted in Greenhouse, Growing Tomatoes, Questions & Answers | Tagged , , , , | Leave a comment