We are now very close to being able plant out seedling plants outdoors or to be able sow directly in the garden soil. Please be aware, however, that despite the recent sunny weather, it has been a cold April so the soil temperature may not be as warm as we think.
I probably mentioned it before but while the air temperature warms quickly in good weather, the soil will lag behind; on a warm April day the air temperature may be 20˚C but the soil may still be 6 or 7. A good rule of thumb is how much grass or weeds are growing or, to be a little more accurate, a soil thermometer is a very handy piece of equipment. For most cool climate crops the soil temperature should be 7˚or above for germination and growth, preferably 10.
I think it is generally accepted that starting seeds off in modular trays for planting out in 3-4 weeks will give the best chance of success. There are a number of reasons including protection from slugs and weather and the fact that you can choose the strongest plants from your trays to plant out in the garden.
In the image above you can see some trays in my tunnel which will be planted outside in early May including peas (in the foreground), broccoli calabrese and lettuce. The larger plants in the background are sweet peas (which I need to get on with planting), the white box is a fish box containing leeks which will be planted out at the end of April.
The most common reason for failure with seedlings is poor watering, either too much or too little, usually too much. Bear in mind that a freshly sown seed or new seedling sprout draws virtually no moisture from the compost. If you over water, the compost may not drain quick enough to prevent the seed from rotting or the young roots from suffocating from lack of air. Roots need air to breathe, if the compost is saturated all the air is forced out and while a large plant may be able to handle this for short periods, a tiny root system of a week old plant will not.
In the early stages it is better to water heavily and let the compost nearly dry between watering rather than little and often. Leaving a little dry will encourage a larger root system as the plant searches for moisture, frequent shallow watering leads to a shallow root system as there is moisture tends to me nearer to the surface and doesn’t make its way down to the bottom of the tray or pot.
In most cases, vegetable seedlings will be planted out in 2-3 weeks so, as long as you don’t neglect them, under watering is unlikely to be an issue. If you have fast growing seedlings like French or runner beans or plants that need to stay in pots for an extended period (tomatoes or peppers), they will need to be watered more often.
The large tomato plants above are an extreme example but, bear in mind potted plants with significant foliage will suck their pots dry in jig time.
Remember, with an emerging seedling, the only ways for the compost to shed excess water is through evaporation or escaping through the bottom of the pot. In a developed plant water is also being drained through transpiration by drawing moisture up though the stems and out through the leaves.
The photos above and below show garlic planted at the same time (last October) in my outdoor beds and in the polytunnel. It is hardly a surprise but the tunnel garlic is much further ahead and will hopefully be harvested in late May when it makes way for the cucumber and squash plants I sowed 2 weeks ago (you can see the cucumber in the header image). Outdoor garlic is harvested in late June or mid July.
The reason I mention them is, again, an irrigation point. The best garlic growing weather will be plenty of moisture until mid June followed by warm and dry conditions towards harvest time. If May and June are dry and garlic struggles to find moisture, the leaves will begin to yellow and maturity will be brought forward. The resulting bulbs will be significantly smaller and, because you weren’t expecting them so early, can get overripe and begin to split apart.
As we seem to be seeing a pattern of dry weather in early summer I am just saying keep an eye on outdoor crops and water if needed. If outdoor watering is difficult and your garlic has been dry, look out for yellowing leaves and harvest if the plants are dying back. It is better to harvest firm small garlic rather than burst bulbs which won’t store.
Obviously there is no rain in the polytunnel so, if growing indoors, make sure to keep well irrigated in April and May. I’ll let you know what the garlic looks like towards the end of next month but so far it is looking very good.
Potato Frost Damage
I know I mentioned frost and potatoes before but we are in the danger zone now when early potatoes are breaking through and are likely to be damaged by frost. Either I left my potatoes uncovered on purpose so I could show you what frost damage looks like or I forgot, I will let you decide.
You can see in the image above that the leaves are showing dark patches from frost damage and will likely die back. This isn’t a bit deal at this stage, the plant will not be affected too much, but if your potatoes are further along it will be a significant setback and will result in a later harvest.
To protect emerging foliage you can earth up soil around the leaves, as above, which will protect them from a light frost. The disadvantage is that you will need to do this every day or whenever frost is forecast. The better solution is fleece because, once it is down, you can cross the issue off your ‘to do’ list altogether.
My tip for laying fleece is to staple it on to timber battens either end to make it easy to lay and remove (you just roll it up around the battens). You will also need to weigh down with bricks or rocks, I am not a bit fan of pegs or clips as they tend to lift and let the fleece flap about which can do a lot of damage to tender new growth. For the same reason fleece is better laid with a little bit of tension, it can be let out as the plants grow and won’t do them any harm.
Just like garlic, if we have a dry May and June, make sure early potatoes get plenty of water, they need more than you think, especially in the few weeks leading up to harvest time.
This is more for next year if you have a poytunnel (sorry for all the tunnel stuff this week if you haven’t got one). The photo above is of beetroot seedlings planted inside late last October which I harvested today as they were beginning to go to seed. I will be honest and say they were the dregs of a seedling tray that had become pot bound and nearly ended up on the compost heap, I didn’t like to throw them out so stuck them in to see what happened. They have done surprisingly well and got off to an early start in late February to produce very nice tennis ball size beets bang on time for the tomatoes to follow them in early May.
The photo above is their replacements in another bed, these were sown in early March and are really starting to get going now. I have no other reason to show them other than they looked so happy with the morning sun illuminating their leaves and to mention, yet again, to keep crops well watered as beetroot gets woody if it dries out.
I think that will do for today. I will end with some tulips, in this case, White Triumphator. I guess it’s just a reminder to also leave room for flowers in your vegetable garden. A well ordered vegetable garden is a thing of beauty in its own right but the addition of some flowering plants bring it to the next level both for us and the many pollinating insects that depend on them.
That’s about it for now, see you next week!