Winging it a little here, a hardness of 100 to nearly 200 PPM (parts per million) or 5.8 to 10.6 DH should be fine for gardneri.
1	Winging	wing	VERB	VBG	VerbForm=Ger	27	advcl	27:advcl	_
2	it	it	PRON	PRP	Case=Acc|Gender=Neut|Number=Sing|Person=3|PronType=Prs	1	obj	1:obj	_
3	a	a	DET	DT	Definite=Ind|PronType=Art	4	det	4:det	_
4	little	little	ADJ	JJ	Degree=Pos	1	obl:npmod	1:obl:npmod	_
5	here	here	ADV	RB	PronType=Dem	1	advmod	1:advmod	SpaceAfter=No
6	,	,	PUNCT	,	_	27	punct	27:punct	_
7	a	a	DET	DT	Definite=Ind|PronType=Art	8	det	8:det	_
8	hardness	hardness	NOUN	NN	Number=Sing	27	nsubj	27:nsubj	_
9	of	of	ADP	IN	_	14	case	14:case	_
10	100	100	NUM	CD	NumForm=Digit|NumType=Card	14	nummod	14:nummod	_
11	to	to	ADP	IN	_	13	case	13:case	_
12	nearly	nearly	ADV	RB	_	13	advmod	13:advmod	_
13	200	200	NUM	CD	NumForm=Digit|NumType=Card	10	nmod	10:nmod:to	_
14	PPM	ppm	NOUN	NN	Number=Sing	8	nmod	8:nmod:of	_
15	(	(	PUNCT	-LRB-	_	16	punct	16:punct	SpaceAfter=No
16	parts	part	NOUN	NNS	Number=Plur	14	appos	14:appos	_
17	per	per	ADP	IN	_	18	case	18:case	_
18	million	million	NOUN	NN	Number=Sing	16	nmod	16:nmod:per	SpaceAfter=No
19	)	)	PUNCT	-RRB-	_	16	punct	16:punct	_
20	or	or	CCONJ	CC	_	24	cc	24:cc	_
21	5.8	5.8	NUM	CD	NumForm=Digit|NumType=Card	24	nummod	24:nummod	_
22	to	to	ADP	IN	_	23	case	23:case	_
23	10.6	10.6	NUM	CD	NumForm=Digit|NumType=Card	21	nmod	21:nmod:to	_
24	DH	dh	NOUN	NN	Number=Sing	14	conj	8:nmod:of|14:conj:or	_
25	should	should	AUX	MD	VerbForm=Fin	27	aux	27:aux	_
26	be	be	AUX	VB	VerbForm=Inf	27	cop	27:cop	_
27	fine	fine	ADJ	JJ	Degree=Pos	0	root	0:root	_
28	for	for	ADP	IN	_	29	case	29:case	_
29	gardneri	gardnerus	NOUN	NNS	Number=Plur	27	obl	27:obl:for	SpaceAfter=No
30	.	.	PUNCT	.	_	27	punct	27:punct	_
