On a recent visit to New England I looked especially for what I could see people were growing in their gardens – being that kind of nosy person as I am when it comes to gardens..
Admittedly it was a particularly cold winter and spring was only just arriving – indeed we were told by a native that the snow had only just melted on his drive, but the range of plants seemed remarkably small.
There were lots of magnolias but only 3 varieties – soulangeana, a few nigra and white stellata. And there are some 200 plus varieties possible! Some varieties actually come from the US – mostly grandiflora – the ones that have shiny leaves, are non-deciduous and flower in the summer on a sunny wall site,; and the others mostly from South America. Though in a woodland garden my envy grew very green indeed as I spied several yellow magnolias in flower.
This is a standing gripe of mine – I once saw a yellow magnolia in flower at Kew and ever since wanted one for myself. Normally I don’t like yellow flowers much but I set my heart on a yellow magnolia.
When we reconfigured our front garden I set out to buy one for it. I had just the right space for a nice mid-sized tree. I scoured the Internet, asked Kew and the RHS – who did sell one but it wasn’t in stock and… In the end a Cornish nursery who specialised in rarer shrubs and from whom I had bought our pink ceanothus shrubs came up with one. A light yellow but still… we waited and it didn’t flower. But it was young and so another spring came round and lo one bud appeared, but a creamy white flower appeared… it’s young, next year maybe it will be yellow. Next spring came and more buds appeared, yes it was going to flower well. Lovely flowers opened but still pale cream. Yellow River wasn’t living up to its name at all! Could I encourage better yellow I asked the RHS? No, was the reply… and then, to cap it all, the nursery I had bought my tree from sent me a new catalogue with about a dozen yellow varieties to choose from! Ugh…
Our Yellow River is not quite as yellow as in this picture though… the other two magnolias are ours as they flowered this year.
So what else was growing in these New England gardens? Some small dwarf rhododendrons in purple, and one bright pink, no other colours despite many rhododendrons originating in the US. Lots of forsythia. Cherry trees. Judas trees. Daffodils – in standard sizes and colours – dwarfs, no whites no frills. A few tulips. Some grape hyacinth. A few pansies. And grass. Acres of grass. And yet more grass. No hedges with plots running into each other both in front of houses and in their back ‘yards’ or gardens. Sometimes some scrubby woodland but no woodland flowers.
We learnt what happens at the back from a friend who had lived in his house for over 20 years – since it was built in fact and yet he had only just started his first garden – the rest was grass – yes 5 acres of it. He had planted 3 small cherries and a small flower bed round his front door and was very proud of it as his neigh ours had nothing like it. Yet he had a stream running through the end of his garden which we would have loved to landscape.
We passed a few nurseries on the roads and they did seem very small and with few plants on display and really felt, that despite the winter temperatures – our friends said that they claimed that only conifers would grow – they had not explored the potential. It is true that my favourite winter clematis would not grow there but surely they could do better.
So here is where I started researching what they could have grown – looking initially at clematis of course. And then some others out of interest and to complement. I will be writing a special article about clematis in the US for a journal so I need not to pre-publish here…
The USA Horticultural Society publishes a zonal map of the USA which indicates what zone a place is in terms of hardiness of plants. This is very important as many plants will not survive very low winter or very high summer temperatures. There is both a heat zone map and a hardiness map to look at. So when purchasing a plant you need to consider both extremes. So for instance if you look at the hardiness rating you can purchase for Boston many of the same clematis as I have in my garden eg Westerplatte and Polish Spirit. For New York it is trickier as it will depend on where you are in the NY area, but generally it is the warmest rating similar to Boston where -15 C is the lowest temperature likely.
Now in our own garden we have had these types of winter temperatures occasionally so we could expect most clematis to survive the winters. However, as many people will have realised this summer, it is the heat and lack of water that can affect clematis, many of mine have had very short flowering seasons and have shrivelled up seedheads and started losing leaves without enough rain (here in my area of London we have missed just about every rain cloud in the last 2 months..).
So what could you grow in New England to supplement these few I saw…
Here are a few suggestions:
“Star magnolia is well known for its resistance to winter cold and grows well in USDA zones 4 through 8. Saucer varieties (M. x soulangeana) are also popular magnolia tree owing to their prolific flowering displays; they too are cold hardy and can be planted in USDA zones 4 through 9. In areas susceptible to late frosts, select the later-blooming cultivars “Lennei” or “Alexandrina.” Magnolia hybrids such as “Betty,” “Pinkie” and “Ricki,” created by crossing M. liliiflora with M. stellata, display cold resistance to USDA zone 5, and are also later bloomers, making them less susceptible to late frost damage. If you are set on planting a Southern magnolia (M. grandiflora) in a colder region, “Bracken’s Brown Beauty” is cold-hardy variety.” http://homeguides.sfgate.com/magnolia-trees-cold-temperature-65541.html
I have tried to find a clearer list of plants but mostly the sites just say to ‘look at the plant label’ in the nursery and I have tried search the US Horticultural Society too – interestingly they do not list a national clematis society so perhaps this is a plant that does not grown well on a national scale – or there is not a great deal of interest in it. All that I have managed to dredge up so far is a list of when you can expect the first frost in the year – and they are remarkably specific dates! Eg if you live in Baltimore you can expect your first frost on the 17th of November, but if you live in Charleston it will be on the 10th of December, but it will be the 11th if you live in Houston! Such specificity….
So failing in any details available from the USA itself I fall back on the RHS who have provided us with a hardiness rating for plants which goes down to minus 20. Not enough for all of the US but works in the UK!
So here are some plants that will survive -20: Cornus alba ‘Sibirica’, selections of Potentilla fruticosa, Erica carnea and Calluna vulgaris cultivars. Ginkgo biloba, Hosta, Lilium, Polemonium caeruleum, and Viburnum × burkwoodii are also likely to survive most cold temperatures.
My final search was in the plant finder offered by the RHS where I searched for the most cold, drought and wind resistant plants and found 149 that they could recommend – a lot were shrubby of course eg Berberis or from the pinus family but they also recommended some Geraniums, Lychnis, Japanese anemones, achillea, ferns, certain grasses eg stipa, papavers, aquilegia and campanula, and of course we must be reminded that tulips will not flower unless they are cold when in the bulb.
So what could you grow in the heat? The heat zone is defined as the number of days the area receives on average more than 30C. Boston and New York are around 100 days or 3 months plus.
Cold and heat together are tricky for plants of course but you can water and prepare plants for both through good planting, mulching and cold protection with sacking let alone fleece or a greenhouse! Don’t forget shading from the sun as this can help too. And check the micro-climates in your garden – we have at least three plus a frost passage n ours which means we plant differently in different areas and have now created a shaded passageway as well.
You can then look up for heat resistant plants of course and I would strongly recommend learning from nature here California and go to the stunning https://en.wikipedia.org/wiki/Ruth_Bancroft_Garden botanical garden in Walnut Creek and just see what you can grown in near drought conditions. When I visited I actually met Ruth very briefly as she was pottering around in the garden. We were taken around by a very knowledgeable docent and loved every minute of our visit. And as a result we grow several Agaves and Aloes in our hot spot and they are doing really well…