I write this on June 30th as we approach sun baked July (it is currently raining heavily). At least that means that I should not have to water our tubs of plants and recently planted trees and shrubs today - this is perhaps the single most important job in the garden for this coming month. Here are some tips for watering your plants most efficiently this month, along with some other garden tasks for July.
How to water pots and planters correctly
Irrigation will occupy a lot of gardening time this month, but it is easy to get it wrong. Here are a few pointers:
It never seems to rain into pots and planters - even after heavy rain your garden tubs may still have dry soil. This is because the foliage will have sheltered the soil from the rain or because the tubs themselves are sheltered by trees/awnings/eaves. Check pots daily and when you water them make sure the water is directed at the soil and not over the foliage. This is why well designed watering cans have long spouts.
Do you water in the morning or evening? Either will do, but never across the middle of the day as you will lose a lot to evaporation and water splashed onto the leaves can cause them to scorch. Evening watering gives the water the entire night to penetrate down to the roots, but it can also be argued that the damp soil creates a humid microclimate which can encourage mould. Morning watering has to be done early and the water either evaporates or is rapidly transpired through the plant and back into the air as the day progresses. On the other hand this encourages the passage of nutrients through the plant and gives it nourishment and water when it most needs it. Take your choice - I prefer early morning, but will water in the evening if I need to.
How often to water plants in pots? That depends - small pots will require daily watering, but I find that bigger pots and pots containing drought resistant plants can be watered every two or even three days, depending on the weather, the planting medium and where the pot if located.
Plants in pots also need feeding.
The compost you plant them in will provide nutrients for a limited period - a few weeks - and then it is up to you. Think of them as a bit like hamsters in a cage. if you don't give them food and water they will die.
Irrigating plants which are in open ground is a tricky topic.
Ideally your garden contains plants which are naturally suited to the environment so that, once established, they do not need artificial irrigation. This is the philosophy behind the current move to drought resistant gardens. Plant the right plants, mulch them deeply and they should survive. But life in not like that and plants which you are asking a lot of - fruit and vegetables for example - will need watering regularly if they are to remain productive. We tend not to water our potager every day but prefer a good water every couple of days - however, if the weather is exceptionally hot daily watering is required.
Newly planted trees and shrubs also need help in the first year or more as they need time to establish an effective root structure. In all of these cases you are trying to help the plant survive while establishes itself but you also want to encourage the roots to dig deep into the ground to search for water. If you water lightly and daily then the roots will be inclined to remain close to the surface, as water is easily available there, and they will continue to be dependent upon you for a ready water supply. Water very thoroughly every few days, leaving the water to soak into the soil and the roots to dig down and search for it.
So the answer to this conundrum is water as seldom as you can get away with but when you do water, water well. And watch out for drooping leaves - this could be a sign that the plant is trying to conserve its water because it does not have enough. Then you need to step in.
Keeping flowers going by deadheading regularly
Throughout the late spring and into the first frosts, the key to keeping plants in flower is to dead head them regularly. A plant flowers in order to get pollenated, set seed and then disperse those seeds to create the next generation. Once this has been achieved then its task has been fulfilled. If it is an annual or biennial (has a two year growth and flowering cycle) it will die. If it is a perennial it will cease flowering, or flower at a reduced rate, until next year. If you want your annuals and perennials to keep their flower filled vigour, you do need to deadhead before the plant sets seed. In this way you fool the plant into thinking its work is not yet done.
Shrubs and trees are slightly different. As a rule they flower once each year for a specific period, so deadheading will tidy them up and stop the plant expending energy on seed head production. But note - I am not including repeat flowering roses in this category as you need to deadhead them all summer to keep them flowering.
Feed plants in pots to keep them healthy and productive
Another way to encourage plants to flower more prolifically is to feed them a plant food which is high in potassium (the "K" in fertilisers which are sold with NPK ratios displayed on the side of the packet). Not everyone in in agreement about this, but it is generally felt that potassium promotes flowering and subsequent fruiting, so ensuring that your plant food is rich in potassium can help with flower production. Tomato plant food tends to be high in potassium for this reason. They will, therefore, will work equally well on other flowering plants, such as roses, and can be more cost effective to use.
You can also make your own potassium rich plant food from comfrey leaves. It smells terrible, but is very effective and better for the environment.
One reason for not cutting off spent flowers is because you want to collect their seeds for future use. Allow the plant to flower, set seed and then develop mature seed pods. Choose a dry sunny day when seed pods are at their peak maturity and then snap the pods off into a dry container. Bring them indoors (out of the wind) and shake the contents onto a white sheet of paper. Separate the seed from the chaff. This can be tricky as the actual seed may be hard to identify and/or tiny - I have found Google to be invaluable when trying to identify unusual seeds. Put the seeds into a LABELLED envelope (don't delay labelling - I have a few envelopes containing "who knows" or "can't remember"). Store in a cool dry place until ready to sow. I keep them in a sealed plastic container in the fridge if they are to remain unsown for any length of time. Ideal candidates for this treatment are the annuals and biennials Cosmos, Nigella, poppies, Cerinthe, hollyhocks, Verbascum and perennials such as Hellebores, Euphorbias, Echinacea and Phlomis as well as beans, tomatoes, squashes and peppers plus herb seeds such as dill, fennel, borage and parsley.
Bear in mind that seeds are often formed from the DNA of two plants which may be slightly different genetically - so the offspring may not exactly resemble the mother plant.
Divide bearded irises
They enter a dormant period during July and August. This is the ideal time to divide and replant them. Ideally, you should do this every four years or so so that the clump does not become too congested.