Thursday, 21 January 2016

Problem Area - Physiological Disorders ... Frost!

Good Morning!
I had planned to post this much earlier in the week, but due one thing after another I've only been able to post it today. Next week the following post in the series will be published earlier!
Just a Note - You can find all of the posts on Plant Pests under a tab at the top of the page if you ever need to take a look.

Following on with the Problem Area series this next part is moving on from Pests. Due to the weather we have had recently I thought today's subject would be of interest ... FROST!

Frost is known as a 'Physiological Disorder'.
This is a disturbance in the normal function of the processes within a plant i.e. involving the cells of a plant and the processes which take place within a plant. These are direct results of the natural environment, are not infectious and cannot transfer plant to plant.
It's a bit of a long post, but I hope it gives you all the information that you need.

Frost can affect many tender and newly planted plants, during late Spring and early Autumn frost causes the most damage in the British Isles. However intense Winter cold can also cause damage to less hardy plants.
Ground Frosts occur when the temperature of the ground drops below freezing point and Air Frosts occur when the temperature of the air drops below freezing point.
'Frost Pockets' are caused by cold air flowing down to the bottom of sloping ground, collecting at the lowest point or a barrier. It is beneficial to know if you have any of these areas in your gardens before you begin planting.
Once the temperature has dropped strong winds can make a frost more damaging, the cold winds remove moisture from the leaves faster than it can be replaced, leading to browning at the leaf tips. Constant thawing and re-freezing can also be particularly damaging.

If you are unsure on how to tell if your plants have affected there are a few signs to look out for.
- Flowers, Buds, Shoots and Leaves may become distorted or blackened.
- Tender young growth may be damaged by Spring frosts, resulting in scorches and pale brown patches between the veins on foliage. This tends to be mostly on the top edges / most exposed areas.
- Dahlia and Canna leaves are blackened by the first Autumn frost, which often leads to the stems collapsing.

There are a few things you can do to limit the amount of damage.
- Evergreen shrubs that are prone to frost attacks should be planted in sheltered areas or moved there if grown in pots and protected with suitable sheeting.
- Choose plants that can cope with frost. Ensuring that they are reliably hardy and suited to your growing conditions. If you do have frost pockets make sure you choose your plants wisely.
Also if you plant in areas that is exposed to early morning sun, avoid Camellia's and Magnolia's as the quick thawing can ruin the flowers and young growth.
- Don't plant out tender summer bedding until the risk of frost has passed and they have been 'hardened off'.
- Slightly tender plants should be grown in warm sunny areas, e.g. a south facing wall which will provide extra warmth and some protection during winter.
- Lift and move tender plants under cover e.g. into a Greenhouse to protect them over winter.
Make sure the Greenhouse has suitable frost protection and heating for the specific plants.
If this isn't possible with larger plants then wrapping them with fleece to form a blanket is ideal.
- Cover plants which are vulnerable to frost with fleece when it is forecast.
- Mulching in Autumn and Spring helps prevent the ground becoming frozen and helps protect the root areas of plants. Make sure when you do mulch that the ground isn't already frozen or dry, ideally mulching should be done when the soil is moist.
- Avoid cutting down the foliage of tender plants such as Penstemons until the risk of frost has passed. The foliage helps protect the plant.
- Avoid planting Apple Trees in frost pockets as frost is particularly damaging to blossom flowers. Apple blossom can be protected scrim netting.
- Avoid giving plants a nitrogen rich feed late in the season as the plant will produce soft, sappy growth which is vulnerable to frost.

Here's a few things you can do if your plants have been affected.
- Once the risk of further frosts has passed, prune out affected foliage cutting down to an undamaged sideshoot or bud. Apply a top dressing of fertiliser to the ground to encourage strong growth.
- Newly planted shrubs can be lifted out the ground by frost so check them over and firm back in if needed.
- Many plants can recover from frost damage so be patient, if re-growth hasn't happened by Summer then only then should you replace it.

I hope you have found this interesting and helpful!

1 comment:

  1. With our fickle British weather, we can have all four seasons in one day, never mind a week, so it is always a challenge for gardener's to try and protect against weather related damage! I try to just grow hardier varieties and a bit fo trial and error to see what plants can withstand our extreme frosts, when we get them. I've lost a few of my favourite plants due to the cold over the years - a white dicentra and a well established artemisia Powis Castle to name just a couple, but I did find a small clump of my Cape Daisy which I thought was obliterated in the harsh frosts a few years ago and managed to propogate some new plants! Hopefully, we won't get too much more in the way of cold weather and Spring might be on it's way...with any luck! Keep warm, hugs, Lisa x