The Vegetable Garden in May

The Vegetable Garden in May

I was looking back on my diary and, while we are still probably behind by a couple of weeks, this Spring is nowhere near as cold as last year where we had hard frosts well into early May. Thankfully, the weather in my garden has been good for the past couple of weeks leaving me with a soil that has warmed sufficiently and is nicely drained and ready to work.

For various reasons (mostly, but not all, out of my control), I am way behind in my garden in terms of planting but I did get a full day on Monday to clear and weed the majority of my paths and beds; you wouldn't think it when you look around the place but I actually like hand weeding, especially the vegetable garden where the soil is loose and crumbly. As you probably know, a bacterium in healthy soil (mycobacterium vaccae) has been found to trigger the release of seratonin so, apart from the satisfaction of tidying your beds, hand weeding with a trowel may directly soothe an addled mind (very welcome these days).

Man kneeling on the ground examining soil

Working your way though your beds down at ground level also gives you the opportunity to have a good look what's going on and to appreciate the variety of life in a healthy soil. My weeding marathon helped me appreciate just how far my soil has come from the sticky clay I started with to it's present pleasing state after 12 seasons of adding manure, seaweed or compost.

I needed to be careful to avoid the many earthworms and composting worms (who are feasting on the manure and seaweed). I am always very pleased to see the earthworms as they were a rare sight in the beginning and are a tell tale sign of a good, balanced soil. As for the soil life I can't see, I can tell it is there from the fresh and sweet smell which is another marker of a happy piece of ground.

The sweet small comes from aerobic bacteria and tells me there are plenty of air spaces whereas a wet, compacted soil has a completely different (sour) aroma due to the anaerobic bacteria which operate in airless conditions. So, if you want to do a quick soil test on your garden, check for worms and give it a good sniff.

Trays of vegetable seedlings growing in a polytunnel

Anyway, the point of that little ramble is that early May is the time to sow or plant out nearly all outdoor vegetable crops and that you should have your beds ready to go. If not, as I said in previous mails, the quick all purpose solution is municipal compost (4-5cm layer) and 'Seafeed' seaweed and poultry manure applied at 200g per square metre. The exception will be carrots or parsnips where you should forego the Seafeed but deep rake the municipal compost and Blood, Fish & Bone at a rate of 150g per square metre into the top few inches of soil. Make sure it is very well mixed.


You can either sow direct in May or grow seedlings (baby plants) in trays to plant out later. I much prefer seedlings as they have a number of advantages, principal avoiding poor weather and pests but also because you will be 4 weeks ahead of the season if you started them off in April (seedlings are typically 4 weeks old when planting out).

The text below is from last year, I'm not being lazy (I don't think) as all is relevant in my garden this year (except the cat is a bit bigger now) so I hope you don't mind me including it again. I will write some fresh content next week after a weekend of garden work.

Trays of pea seedlings and other vegetable seedlings

What to sow and plant in May

For direct sowing outside in May, you have the choice of beetroot, early carrots, chard, parsnips, spinach, perpetual spinach, radish, turnip, peas and runner beans. I think I would hold off on parsnip and runner beans until the middle of the month.

If you are sowing indoors for planting out later, you can also sow Brussels sprouts, calabrese, chard, kale, kohl rabi, swede, turnip, lettuce, spring onions, sweetcorn and winter cabbage. It is a little late to sow tomatoes (although you might get away with some cherry tomatoes) cucumbers of chillis but if not done already you can also sow courgettes, winter squash or pumpkins.

The benefits for starting plants off in modular trays in April becomes very clear in May as the garden can get off to such a quick start if you have a stock of healthy seedlings ready to go in.

Cauliflower seedlings in modular trays

When should tray grown seedlings be planted out? 

As a rule of thumb, most plants grown in modular trays will be ready to plant out 4 weeks after sowing. The photo above is a tray of cauliflower plants sown at the beginning of April which are now entering their fifth week in the cell. I sow most of my early April cabbage family sowings in trays using a large 5cm module instead of the usual 4cm to allow them an extra few days in the cell if early May is cold, naturally I am glad I did it this year.

If I remove one of the plugs we can see a nice looking root system that hasn't become pot bound yet but is just about to get cramped, this really needs to be planted out by the end of the week. You can see by the colour of the leaves (nice and green) that the plant has not run out of nutrients yet, to my eye they are about perfect for planting now but by early next week they will start to struggle if I don't get them in the ground.

Cauliflower seedling roots

Remember, the majority of plants can be planted up to their first set of true leaves to strengthen them up but this is particularly beneficial for the brassica (cabbage) family which usually have a lanky lower stem when grown in a tray. You can see the seed leaves of the cauliflower in the photo (they are the first two with the long stalks and rounded ends) the true leaves begin just above them which is where your soil level should be when you plant them out.

When planting out any seedling, make sure to firm the soil in well around the root to get a good seal with the surrounding soil, you don't want big air spaces around the root or the plant can't take up moisture efficiently. Also make sure to water well after planting, it is better to take the rose off a watering can and make a little puddle around the root to ensure there is plenty of moisture deeper down and not just on the soil surface.

New radish seedlings

This photo shows radish seedlings ('French Breakfast', who has radishes for breakfast?) sown outside on the 23rd of April and just starting to come up under fleece. The little blue pellets are a natural slug killer which I use around most early outdoor sowings as a single slug or snail can wipe out the lot overnight. This is one of the reasons I start off so many vegetables in modular trays but radish, carrot or parsnip don't transplant well and need to be sown direct. In general I avoid any 'killer' products in the garden but do make an exception for these slug pellets which kill the slugs but are harmless to pets, birds or other wildlife even if the slug itself is eaten.

Shallots growing in raised beds

This image shows shallots looking very happy in the Saturday morning sunshine. Unfortunately, a prolonged period of frosty nights (we have just had a week of frost) in late April will make it more likely for onions or shallots to bolt in the summer. Thankfully we didn't have a warm March (followed by a cold April) which is the worst possible scenario so we shall see what happens. I think I mentioned it in an earlier mail but it is better to delay planting onion sets until the third week in March to minimise the chance of bolting.

As per the previous mail, the reason for bolting (going to seed) is that onions are biennials so are programmed to produce a flower (and seed) in year 2 of their lifecycle. If an onion set goes through a early spring followed by a cold period it chalks up the cold spell as winter and goes into the seed producing part of its cycle.

Cat under fleece

Frost damage under fleece I should have mentioned in the previous mail about fleece that if you have a prolonged period of heavy frost, particularly if the fleece has got wet in the daytime, the parts of the plant that are touching the fleece will freeze. To avoid this, use hoops or battens (or a cat) to raise the fleece above the foliage. The photo shows the first early potato sprouts after a -2 night and all is well with no damage.

Asparagus Jakmar Purple in the vegetable garden

Asparagus Spears

This is Asparagus Pacific Purple coming up though a layer of garden compost. The asparagus picking season runs from late April to early June but, like rhubarb, you should not harvest all the stems as the plant needs some to go into leaf and make energy for the following season.

Asparagus is a long term project with the first harvest coming 3 years after planting crowns or 4 years after sowing seeds (my plants are coming into their 6th year). The upside is, once established, it will crop every year for at least 20 years. I suppose it's like a pension, not that appealing as the reward seems so far away but something you will be very glad of when it starts bearing fruit.

It is too late to plant Asparagus crowns but, for next year, choose a hybrid all male variety if you are thinking of growling as they are much more prolific.

Soil temperature thermometer

Planting tomatoes or other warm climate crops in the polytunnel As we said, May is the busiest time in the garden but it is also a busy time in the polytunnel when most of the warm climate crops are planted into their final positions. Normally I would plant now but, as it has been so cold, the polytunnel soil is not as warm as I would like. If possible, I would hold off for a week or more, especially with very tender crops like cucumber or melon but if tomatoes are close to getting pot bound you may not have any other option.

The minimum soil temperature for tomatoes is 14˚C and, if you look at my thermometer above, you will see my soil is exactly 14 degrees so, while on the limit I will go ahead this week. I will be planting them in the morning to give them the day to adjust before the cooler night and will wrap with fleece at night to be as a precaution.

Tomato plant growing in a pot

Remember, when planting tomatoes, they need a lot of feed to produce the bountiful crops we are hoping for. Your soil needs to be in top condition with plenty of well rotted garden compost added but, even if this is the case, I would also add a slow release poultry manure pellet to bolster the nutrient store, the more fertile the soil., the less frequently you will need to add liquid feed later on.

When applying feed, avoid concentrating around the planting hole as this will make roots reluctant to leave this small, fertile patch. You want the roots to spread out and take nutrients and water from as wide an area as possible. The planting distance is a good rule of thumb, it is 50cm all round for tomatoes, therefore you need to feed 50cm all around the plant.

Stawberries growing in the polytunnel

Strawberries in the polytunnel 

We don't even sell polytunnels so this is not a sales pitch but a polytunnel or greenhouse really is a fabulous thing. Not only can you grow warm climate crops like tomatoes chillies and cucumbers but it is also a far superior propagation area than a windowsill (3 times the amount of light) so becomes the engine room for the whole garden.

At this time of year I really fall in love with it. I have been harvesting crops since late January with overwintering salads, calabrese, beetroot and spring cabbage just finished. I have garlic coming close to harvest and early baby carrots (below) which will be pulled at the end of the month. Strawberries are bulking up now and will be ready to pick in a week or two, all way ahead of anything outside. They are big investments, fair enough, but pay for themselves several times over with what they offer directly and for their support role to the outdoor garden.

If you have the room and don't have a covered area already I would strongly recommend one, it will transform your growing year.

Early carrots growing in the polytunnel

That's about if for this week, I hope you found something in there relevant and helpful to your own garden.

See you all next week!

Andrew