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Darwin Correspondence Project

From Peter S. Robertson    30 April 1867

Peter S. Robertson & Co. | Nurserymen | and | Seedsmen | at | 33 St. Andrew Square | and | Trinity Nursery. | Edinburgh

30 April 1867.

Ch. Darwin Esqr. | Down Bromley, Kent.

Sir,

My first attempt to cross the different varieties of Borecole was in 1859—1 for this purpose I planted near each other two plants each of the following Garden varieties, 1 Delaware, a purplish medium tall, curled sort— 2nd. Russian a very curled variety beautifully purple & not above 9 inches in height,

3d. Purple Scotch, a tall growing kind, with leaves nearly plain, greenish purple—

4th. Proliferous Purple,

5th. Perennial Kale, a purplish tall cut leaved suffruticose sort.

6th Pale Green triple curled German Greens

7 Plain Green German Greens very little curled—

On growing the seeds the following grew from each of these sorts— I found the seeds of No 5. germinate only about 10 per cent & not one of them seemed in any way different from the parent, only that they were weaker & did not survive the following winter

No 4. grew well, all the produce more or less proliferous but the colours were all shades from the Purple of the parent to nearly green & several were whitish, blanched like, & very unequal in size, there was no white Borecoles near them when the plants were in flower—*

No 2. The produce was very similar to the parent, only that about one tenth part were paler in colour or stronger as if crossed with No 1— or No 3.

No—1—3—6—&7. All produced a large proportion different from the parents, & appeared to have mutually affected each other greatly, a few plants in each kind were true to the type, & a great many plants were so different that one could hardly believe them to be Borecoles, some were nearly as plain as Cabbages, others had long narrow leaves like Brocoli but coarser looking—& a good many closed (hearted) like a Cabbage in autumn & seemed very like a new Garden sort called Cottagers Kale

I had about one acre of No 6. growing within a quarter of a mile of where these plants were planted for crossing & the whole produce of this acre was affected to the extent of about 1 per cent with monstrous crosses also— some grew a pretty dark purple.

I did not find a single proliferous plant grow from any of them but from No 4.

In 1861, I procured seeds of all the variegated & curious leaved kinds I could, & had them planted among each other in 1862 to see if they would cross & produce plants with white & purple on the same root, & I have twice since done the same thing, but have always found, that the varieties 6 & 7, sport into white or yellowish white & the Purple kinds into magenta, rose, or pale lilac, the variegated plants of both produce some selfs & I find that No 6. when grown of a very pure white ceased to produce seeds, only malformed siliquae with rudimentary seeds. I am of opinion that the whites & magentas do not cross.

I find that the plants do not show either their true colour or character till about November, during that month and December the young leaves produced are often very pure, delicate in texture & of intense beauty, both the magentas & whitish varieties stand winter frost & snow well, the colours being improved thereby—but in March & April the whitish varieties are very much sooner damaged by frost than the purples, and intense sunlight destroys the fine [tail] of both very quickly about the time they begin to throw up the seed stems—

In growing the seeds in spring in the open air I find that the coarser crosses most removed from the finest forms in appearance always grow strongest & first, so that parties cultivating them for the flower Garden should reject the strongest & carefully transplant the weakly plants, as from them the finest forms are got.—

I will be glad to write you any explanation you further require of these remarks—

I am—Sir | Your most obt Servant | Peter S. Robertson

*In successive growings of this variety it becomes quite destitute of leaves, nothing but the thread like ribs remain, which are very beautiful, & resemble some sea weeds.—

CD annotations

Top of letter: ‘Edinburgh’ pencil

Footnotes

No letter from CD to Robertson has been found, but one might have been inspired by a series of references in the Gardeners’ Chronicle to Robertson’s work on variegated kale or borecole (Gardeners’ Chronicle, 9 February 1867, p. 130; 9 March 1867, p. 236; 23 March, p. 294). In the issue for 23 March, Robertson was quoted as saying that white and magenta borecoles did not readily cross, but that one plant of either would ‘taint an acre of pure Green or common purple German greens’ (ibid., p. 294). A clipping from page 294 including this quote is associated with this letter in the Darwin Archive–CUL. CD discussed the cabbage family in Variation 1: 323–6, but did not cite Robertson.

Bibliography

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.

Summary

Describes his attempts to cross different varieties of borecole, and the results of the crosses.

Letter details

Letter no.
DCP-LETT-5519
From
Peter Skene Robertson
To
Charles Robert Darwin
Sent from
Edinburgh
Source of text
DAR 76: B49–51
Physical description
ALS 5pp †

Please cite as

Darwin Correspondence Project, “Letter no. 5519,” accessed on 29 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-5519.xml

Also published in The Correspondence of Charles Darwin, vol. 15

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